Behavioural Brain Research 274 (2014) 118–127

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Research report

Ethological endophenotypes are altered by elevated stress hormone levels in both Huntington’s disease and wildtype mice Christina Mo a,b,∗ , Thibault Renoir a,∗∗,1 , Anthony J. Hannan a,b,1 a b

Florey Institute of Neuroscience and Mental Health, Kenneth Myer Building, University of Melbourne, Parkville, Australia Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Australia

h i g h l i g h t s • • • • •

Ethological phenotypes in HD mice may be altered by stress hormone treatment. CORT impaired olfactory function and hedonic response in female WT and HD mice. CORT treatment had no effect on hedonic response or nest-building in male mice. CORT transiently enhanced male vocalization responses to an estrus female mice. Olfactory and communicative behaviors are altered by CORT treatment regardless of the HD mutation.

a r t i c l e

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Article history: Received 18 July 2014 Received in revised form 24 July 2014 Accepted 26 July 2014 Available online 4 August 2014 Keywords: Neurodegenerative disease Corticosterone Stress hormone Gene–environment interactions Olfaction Ethological behavior Sexual behavior Tandem repeat disorder Vocalizations

a b s t r a c t Huntington’s disease (HD) is an autosomal dominant, neurodegenerative disorder with cognitive, psychiatric, motor, neuroendocrine and peripheral dysfunctions. Symptom onset and progression can be closely modeled in HD transgenic mice, which facilitate the search for therapeutics and environmental modulators. In the first investigation of chronic stress in HD, we have previously shown that administering a moderate dose of the stress hormone, corticosterone (CORT) had no effect on short-term memory in wildtype (WT) mice but accelerated the onset of the impairment in male R6/1 HD mice. We now extend this investigation to ethological dysfunctions in HD, which we hypothesized to be more susceptible to CORT treatment compared to the same functions in WT littermates. Both genotypes consumed similar doses of CORT dissolved in drinking water across 6–14 weeks of age and were assessed for olfactory sensitivity, nest-building, saccharin preference as well as vocal responses to sociosexual stimuli. In female HD and WT mice, olfactory sensitivity and saccharin preference were reduced by 2 and 4 weeks of CORT, respectively. In males, there was no effect of CORT on saccharin preference, however the number of vocalizations to a female mouse was transiently increased by CORT-drinking, regardless of genotype. Nest-building was severely impaired in HD mice at an early age, but was unaffected by CORT. Our results suggest that the presence of the HD mutation had no bearing on CORT-induced effects at this dose, suggesting that even moderately elevated stress hormone levels can impair ethological behaviors in both the HD and healthy brain. © 2014 Elsevier B.V. All rights reserved.

1. Introduction Huntington’s disease (HD) is a neurodegenerative disorder caused by a trinucleotide expansion in the HD gene [30].

∗ Corresponding author at: Florey Institute for Neuroscience and Mental Health, Kenneth Myer Building, University of Melbourne, VIC 3010, Melbourne, Australia. ∗∗ Corresponding author. E-mail addresses: [email protected], [email protected] (C. Mo), [email protected] (T. Renoir). 1 The authors contributed equally as joint senior authors. http://dx.doi.org/10.1016/j.bbr.2014.07.044 0166-4328/© 2014 Elsevier B.V. All rights reserved.

The length of the highly penetrant gene mutation determines the age of onset, but onset may also be modulated by environmental factors [79]. In light of ineffective pharmacological treatments, identification of such factors is a promising alternative to impeding disease progression. Physical and cognitive stimulation [19,27,39,55,60,63,64,73,74,80] and diet [20,44,45,69] have been suggested by clinical and animal studies as potential disease modifiers but other factors remain unidentified. There are limited investigations into the impact of stress on HD progression despite its high prevalence in HD gene-positive individuals [8,18]. An abnormal stress axis and elevated baseline levels of stress hormone have been reported in HD patients and mice

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[2,7,28,75]. Using the R6/1 transgenic mouse model, we have found that an acute forced swim triggered an exaggerated stress response [19], and depressive-like behavior [59] in female HD mice, but not WT littermates. Furthermore, a mild confinement stressor induced short-term memory deficits specifically in female HD mice [51]. We recently conducted the first investigation on the impact of chronic stress in HD by directly elevating stress hormone levels in HD transgenic mice to model repeated stress exposure. Oral treatment with corticosterone (CORT) accelerated the onset of a memory deficit in male R6/1 mice, but had no impact on WT mice at this dose (4.7 mg/kg/day) [49]. Taken together, the absence of effects on WT mice in these studies suggest that the HD mutation confers a vulnerability to stress. However, the impact on other dysfunctions in HD has not been investigated and can be difficult to model in rodents using the standard behavioral test battery. Behavioral assessments that are ethologically relevant to laboratory animals can improve the relevance of interpretations across species. Such tests in HD mice have revealed clinically relevant impairments [50]. For example, olfaction is critical for every day function in rodents and the olfactory deficit in R6/1 mice [50] recapitulates the impairment in HD patients [10,14,34,36,52,56]. Nest-building is crucial for thermoregulation and offspring welfare [35] and has been used as a measure of home-cage activity and general health in laboratory mice [23,53]. Nest quality shows early and progressive decline in HD mice [50]. Anhedonia is a depressive symptom experienced by HD patients [21] and modeled in HD mice using the saccharin preference test [65]. Sexual reward is also a hedonic stimulus and the ultrasonic vocalizations (USVs) to an estrus female or her urine can indicate sexual response [42,57]. Male R6/1 mice vocalize less to these stimuli [50], reflective of aberrant sexual behavior in HD patients [15,32,67]. There is little data on the impact of chronic stress on ethologically relevant behaviors, even in WT animals. Here we extend our work on the effects of elevated stress hormone in HD mice [49] by testing its impact on species-relevant behaviors: olfactory insensitivity, nest-building deficits, anhedonia and reduced sexual vocalizations. We hypothesized an exaggerated response to CORT treatment in HD mice and therefore chose a dose (25 mg/l) that moderately impacted long-term physiology [33] but also elevated circulating stress hormone levels during active drinking [24,71]. We hypothesized that oral CORT treatment would impair behaviors to a greater extent in HD mice compared to WT littermates.

2. Materials and methods 2.1. Mice R6/1 hemizygote males originally from the Jackson Laboratory (Bar Harbour, ME, USA) were bred with CBA × C57BL/6 (CBB6) F1 females to establish the R6/1 HD colony at the Florey Institute for Neuroscience and Mental Health. R6/1 offspring and their wildtype (WT) littermates were genotyped by polymerase chain reaction (PCR) from toe and tail biopsies. CAG repeat length sequencing showed a mean length of 136.4 ± 3.3 repeats. At 3–4 weeks of age, mice were randomly allocated to single-sex groups (n = 3–5) of mixed genotype. Standard housing consisted of laboratory cages (15 × 30 × 12 cm) with bedding and 2 facial tissues. Mice were maintained under a 12-hour light/dark cycle (7.00 am light on) with access to food and water ad libitum. behavioral testing was performed during the light phase. All experiments were approved and conducted in accordance with the guidelines of the Florey Institute Animal Ethics Committee and the National Health and Medical Research Council (NHMRC).

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2.2. Oral corticosterone treatment The stress hormone was passively administered by directly dissolving in the drinking water, a method which avoids injection stress, vehicle confounds [77] and elevates circulating levels at times relevant to the circadian rhythm [6]. Corticosterone (4pregnen-11-beta 21-diol-3 20-dione 21-hemisuccinate, Steraloids Inc., Rhode Island, USA) was prepared as per instructions [24]. The hemisuccinate powder was dissolved in tap water for 3–8 h at 4 ◦ C under basic conditions (pH > 12). After warming to room temperature, the pH was returned to neutral (7.1–7.3) using hydrochloric acid (10 M). Dissolved corticosterone (CORT) degrades over time so a new solution was prepared and administered every 72 h as recommended [24]. The dissolved solution was kept in the dark at all times and stored at 4 ◦ C when not in use. CORT was administered in place of drinking water from 6 to 14 weeks of age. We chose to begin the treatment during early adulthood, which is more clinically relevant and avoids confounds of the developing brain [76]. CORT consumption resulted in a similar dose to our previous study (4.7 mg/kg/day) [49] and no difference was found between the genotypes or sexes (Suppl Fig. 1).

2.3. Behavioral testing Mice were handled for 3 days prior to the first behavioral assessment. Animals were acclimatized to the testing room for 1 h unless otherwise indicated. Olfactory sensitivity was assessed at 8 weeks and 12 weeks of age only in female mice as performance was greatly impaired in male R6/1 mice by 8 weeks of age [50]. Separate cohorts at 8 weeks and 12 weeks of age were used for olfactory testing to control for the novelty of odor exposure. Nest-building was assessed in one cohort at all time points (6, 8, 10, 12 and 14 weeks of age) in both male and female mice. Saccharin preference testing occurred at 8 and 10 weeks of age in separate cohorts. The sexual vocalization testing is only available for male mice [42] and separate cohorts were used at each age of testing (8, 12 and 14 weeks of age).

2.4. Olfactory sensitivity test We determined the threshold for detecting a palatable odorant as previously described [50]. Briefly, mice were single-housed with two odorant vessels (3 ml graduated pipettes, Copan, USA) during acclimatization to the test room (2–3 h). For each testing trial (3 min), a dilution of whipped peanut butter (Kraft Foods Australia Ltd.) (10−1 , 10−2 or 10−3 ) was pipetted into one odorant vessel (500 ␮l) and water (500 ␮l) in the other. One dilution paired with water was presented per day for a total of three trials. The order of dilutions and the left-right positioning of water were randomized. A preference for sniffing peanut butter (PB) compared to water was regarded as a correct detection of the odorant: time spent sniffing [PB/(PB + Water)] × 100.

2.5. Nest-building test To test daily activity in the home cage [50], mice were singlehoused overnight in a fresh standard-housed cage with 8 grams of shredded paper (60 mm wide strips). The next morning, photos of each nest were taken for blinded scoring: 1 = undisturbed, 2 = flat nest, 3 = cup nest, 4 = dome nest, 5 = full dome nest. Quarter points (0.25) were also given for the number of sides of a nest (e.g. 3.5 for a cup nest with 2 sides). Mice were then returned to group housing.

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Fig. 1. Olfactory sensitivity was impaired by CORT treatment in female mice regardless of genotype.

2.6. Saccharin preference test Mice were allowed access to a solution of the non-caloric sweetener, saccharin to test for an anhedonic response. Mice were single-housed into new standard cages with two 10 ml glass pipettes equidistant apart and protruding at a ∼45◦ angle through the cage lid. For the water-drinking groups, one pipette was filled with water and the other with 0.1% saccharin in water. CORTdrinking groups were given CORT (25 mg/l) in one pipette and 0.1% saccharin in 25 mg/L CORT in the other. The left-right positioning of the saccharin pipette was counter-balanced across genotype and treatment groups. Overnight fluid consumption was recorded and animals were returned to group housing the next morning. 2.7. Ultrasonic vocalization recordings Male vocal responses to female mice and female urine exposure were measured as described previously [50]. Twelve hours prior to vocalization testing, the stage of estrous in experimentally naïve female WT littermates was identified by Diff-Quick staining (Thermo Fisher Scientific, Australia) of vaginal smears. Only females that were predicted to be in proestrous or estrous on the day of testing were used. Female mouse exposure: Exposure to an estrus female is a sexual and social interaction [61]. Male mice were single-housed under low lighting conditions (4 lux) and a female mouse was introduced for 5-min. Female-induced USVs were recorded using an ultrasound microphone (Avisoft UltraSoundGate CM16 condenser ultrasound microphone, Avisoft Bioacoustics, Germany). Time spent sniffing the female nose and anal region was scored blind to genotype and treatment. Female urine exposure: Male mice were exposed to estrus urine 1 h after female exposure. Five minutes prior to urine exposure, male mice were habituated to a cotton-tipped applicator (length: 15 cm) with its tip angled at nose height within the cage. The applicator was then switched for a new applicator dipped in fresh urine. Fresh urine was collected by either placing females in a standard cage lined with aluminium foil or by up-turning the tail and gently stroking the animal’s bladder [42]. Urine-induced USVs were recorded for 5 min. Females were alternated for urine collection to reduced stress. Time spent sniffing the applicator tip was recorded for later analysis. 2.8. Vocalization analyses USVs were recorded on Avisoft-RECORDER at a sampling rate at 250 kHz and 16-bit format. WAV files were then analyzed using

Avisoft-SASLab Pro, Version 5.2 (Avisoft Bioacoustics, Germany) at a threshold of −30 dB. Spectrograms were generated by a fast Fourier transformation (FFT-length 512, time window 100%, overlap 50%). The number of USVs at the 70 kHz range was counted during the first minute of exposure. 2.9. Statistical analyses Olfactory sensitivity and nest-building data were analyzed using 3-way repeated measures analysis of variance (ANOVA) in SPSS statistics Version 20 (IBM, Armonk, NY, USA). To assess homogeneity of variances, Mauchly’s test was used and the Greenhouse-Geisser correction was applied if sphericity was violated. Saccharin preference, USV and sniffing data were analyzed by 2-way ANOVA in GraphPad Prism 6 (GraphPad software, Inc. LA Jolla, CA). Bonferroni or LSD post-hoc tests were conducted when appropriate interactions were found. 3. Results 3.1. Olfactory sensitivity was impaired by CORT treatment in female mice In female mice at 8 weeks of age, analyses revealed no effect of genotype (F(1, 52) = 0.01, p = 0.920), or genotype × dilution interaction (F(1.76, 91.57) = 0.77, p = 0.731) indicating that female R6/1 mice showed olfactory performance similar to WT mice at 8 weeks of age (Fig. 1A). There was a main effect of CORT (F(1, 52) = 5.92, p = 0.018) but no genotype × CORT interaction (F(1, 52) = 0.05, p = 0.186) or dilution × CORT interaction (F(1.76, 91.57) = 0.78, p = 0.446). This shows that 2 weeks of CORT impaired overall olfactory sensitivity in both genotypes and regardless of dilution. There was also no significant dilution × genotype × CORT interaction (F(1.76, 91.57) = 1.35, p = 0.264). At 12 weeks of age (Fig. 1B), there was a main effect of genotype (F(1, 44) = 4.87, p = 0.033) and also a significant dilution × genotype interaction (dilution × genotype: F(2, 88) = 4.99, p = 0.009). Post-hoc comparisons showed a difference between WT and R6/1 mice preference for the 10−3 dilution (p = 0.002), but not the 10−1 (p = 0.362) or 10−2 (p = 0.462) dilutions. There was no main effect of CORT (F(1, 44) = 0.47, p = 0.495), or CORT × genotype interaction (F(1, 44) = 0.15, p = 0.704) (Fig. 1B). Detection of peanut butter odor in R6/1 female mice was intact at 8 weeks of age but impaired by 2 weeks of CORT-drinking regardless of genotype and dilution (A). Olfactory performance

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Fig. 2. Impaired nest-building in R6/1 mice is unaffected by chronic CORT treatment.

at 12 weeks of age was impaired in R6/1 females as indicated by an inability to detect the 10−3 dilution compared to WT mice (p = 0.002) (B). Performance at 12 weeks of age was not reduced by 6 weeks of CORT treatment in either genotype. Preference = [Time spent sniffing peanut butter/(time spent sniffing peanut butter + water)] × 100. Values represent means ± SEM of fold change relative to WT Water control. 8 weeks of age: n = 12–17, 12 weeks of age: n = 10–15 per group. (*) Indicates main effect of CORT, ** p < 0.01 indicates post-hoc analysis between WT and HD at 10−3 dilution.

3.2. Nest-building was not affected by CORT treatment Analyzing nest-building in female mice (Fig. 2A), we found main effects of genotype (F(1, 44) = 77.99, p < 0.000) and age (F(4, 176) = 3.62, p = 0.007) as well as a significant age × genotype interaction (F(4, 176) = 4.17, p = 0.003). LSD post-hoc analyses revealed that HD females (dashed lines) built lower quality nests compared to WT littermates (solid lines) at 6 weeks (p = 0.001), 8 weeks (p < 0.001), 10 weeks (p < 0.001), 12 weeks (p < 0.001) and 14 weeks (p < 0.001) of age. In addition, only HD mice showed a significant decline in nest score with age (6 weeks vs 12 weeks: p = 0.030, 6 weeks vs 14 weeks: p = 0.003). There was no main effect of CORT (F(1, 44) = 0.01, p = 0.905), although a significant CORT × genotype interaction was found (F(1, 44) = 5.47, p = 0.024). However, pairwise comparisons did not reach significance (WT water vs WT CORT: p = 0.084, HD water vs HD CORT: p = 0.129). Analyses of nest scores in male mice revealed a significant effect of age (F(4, 132) = 2.13, p = 0.080) and an age × genotype interaction (F(4, 132) = 2.61, p = 0.038) (Fig. 2B). LSD post-hoc tests showed that HD male mice built lower quality nests compared to WT littermates from 6 weeks of age (p = 0.001 and p < 0.001 for all other ages). There was a main effect of genotype (F(1, 33) = 77.99, p < 0.001) but no effect of CORT (F(1, 33) = 0.36, p = 0.552) or genotype × CORT interaction (F(1, 33) = 0.00, p = 0.996). Nest-building was impaired in female (A) and male (B) R6/1 mice (dashed lines) at the earliest age tested (6 weeks of age). Chronic CORT treatment did not significantly alter nest quality in either genotype. Overnight nests were scored blind to treatment, genotype and age. Values represent means ± SEM of fold change relative to WT Water control. Females: n = 10–16, Males: n = 8–10 mice per group. ** p < 0.01 for post-hoc genotype difference.

3.3. Chronic CORT treatment reduced saccharin preference in female mice In female mice there was no effect of genotype on saccharin preference at 8 weeks (F(1, 25) = 0.04, p = 0.847) or 10 weeks of age (F(1, 25) = 0.91, p = 0.350) (Fig. 3A, B). There was no effect of CORT after 2 weeks of treatment (F(1, 25) = 2.65, p = 0.116) (Fig. 3A), but 4 weeks of CORT reduced saccharin preference regardless of genotype (F(1, 25) = 8.74, p = 0.007) (Fig. 3B). In male mice, there was also no effect of genotype at 8 weeks (F(1, 33) = 0.18, p = 0.674) (Fig. 3E) or 10 weeks of age (F(1, 47) = 0.57, p = 0.454) (Fig. 3F). There was no effect of 2 weeks of CORT treatment (F(1, 33) = 0.70, p = 0.410) or 4 weeks of CORT treatment (F(1, 47) = 0.33, p = 0.567) on preference for saccharin solution. As expected, R6/1 mice consumed more fluid compared to WT littermates at both 8 weeks of age (females: F(1, 25) = 14.68, p = 0.001, males: F(1, 34) = 10.69, p = 0.003) (Fig. 3C, G) and 10 weeks of age (females: F(1, 25) = 12.41, p = 0.002, males: F(1, 47) = 26.91, p = 0.000) (Fig. 3D, H). Total fluid consumption was also affected by CORT in female mice after 4 weeks of treatment (F(1, 25) = 13.09, p = 0.001) (Fig. 3D) but not 2 weeks of treatment (F(1, 25) = 0.01, p = 0.919) (Fig. 3 C). In female mice, CORT had no effect on preference for saccharin solution after 2 weeks of treatment (A) but reduced saccharin preference after 4 weeks of treatment (B). This reduction after 4 weeks was accompanied with a reduction in overall volume of fluid consumed (D). Unexpectedly, female R6/1 mice did not show reduced preference for saccharin but fluid consumption was increased by the HD mutation at 8 weeks and 10 weeks of age (C, D). In male mice, saccharin preference was not affected by CORT treatment (E, F). Similar to female mice, there was a clear effect of genotype in total volume of fluid consumed with R6/1 males showing increased fluid intake (G, H). Values represent means ± SEM. Males 8 weeks: n = 9–10, 10 weeks: n = 11–14, Females 8 weeks: n = 6–8, 10 weeks: n = 6–8 mice per group. ## p < 0.01 for main effect of CORT, * p < 0.05, ** p < 0.01 and *** p < 0.001 for main effect of genotype.

3.4. Female-induced vocalizations were transiently enhanced by CORT treatment During exposure to a female mouse at 8 weeks of age, analyses of the number of vocalizations showed no main effect of CORT treatment (F(1, 20) = 0.63, p = 0.437) or an effect of genotype (F(1, 20) = 3.35, p = 0.082) (Fig. 4A). At 12 weeks of age, there was

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Fig. 4. Chronic CORT treatment transiently enhanced male vocalization response to a female mouse.

no effect of genotype (F(1, 22) = 0.07, p = 0.794) but a significant effect of CORT (6 weeks of treatment) (F(1, 22) = 6.42, p = 0.019) (Fig. 4B). In contrast, at 14 weeks of age, there was a significant effect of genotype (F(1, 32) = 46.04, p < 0.001) but no effect of CORT (F(1, 32) = 0.03, p = 0.863) (Fig. 4C). No interactions were found at all ages. In analyses of time spent sniffing the female mouse, there was no main effect of genotype (F(1, 20) = 0.96, p = 0.340) or CORT treatment (F(1, 20) = 0.60, p = 0.448) at 8 weeks of age (Fig. 4D). At 12 weeks of age, there was a significant effect of genotype (F(1, 23) = 21.00, p = 0.001), indicating that HD male mice spent less time sniffing the female compared to WT littermates (Fig. 4E). However, there was no main effect of CORT (F(1, 23) = 1.24, p = 0.277) or genotype × CORT interaction (F(1, 23) = 0.75, p = 0.395). At 14 weeks of age, male HD mice again spent less time sniffing compared to WT mice (F(1, 30) = 10.38, p = 0.003) but there was no effect of 8 weeks of CORT treatment (F(1, 30) = 1.84, p = 0.186) or interaction (F(1, 30) = 0.08, p = 0.780) (Fig. 4F). As expected, the number of vocalizations in response to a female mouse was similar between genotypes at 8 and 12 weeks of age (A, B) but was dramatically reduced in HD male mice at 14 weeks of age compared to WT littermates (C). There was no effect of 2 weeks of CORT treatment (8 weeks of age), however 6 weeks of CORT enhanced the number of vocalizations in males, regardless of genotype. The effect did not persist to 8 weeks of CORT treatment. Time spent sniffing the female mouse at 8 weeks of age was no different between genotypes (D) but as expected, HD male mice spent less time sniffing the female mouse at 12 and 14 weeks of age (E, F). Sniffing was defined as the male nose within 0.5 cm of the oral or anal region of the female mouse. Values represent means ± SEM of fold change relative to WT Water control. 8 weeks: n = 4–8, 12 weeks: n = 5–8, 14 weeks: n = 8–10 mice per group. ** p < 0.01, *** p < 0.001 for main effect of genotype, $ p < 0.05 for main effect of CORT.

3.5. Sexually-induced vocalizations were unaffected by CORT treatment When presented with estrus urine at 8 weeks of age, there was no significant effect of genotype (F(1, 20) = 0.30, p = 0.588) or effect of CORT (F(1, 20) = 0.21, p = 0.655) on the number of vocalizations emitted (Fig. 5A). Similarly, at 12 weeks of age, there was no main effect of genotype (F(1, 23) = 0.74, p = 0.397) (Fig. 5B). By 14 weeks of age, there was a significant effect of genotype (F(1, 31) = 47.27, p < 0.001), indicating that HD mice emit less vocalizations in response to urine compared to WT controls (Fig. 5C). However, there was again no main effect of CORT treatment (F(1, 31) = 2.72, p = 0.109). At 8 weeks of age, analyses of time spent sniffing estrus urine revealed no significant effect of CORT (F(1, 20) = 0.03, p = 0.859) but a trend for an effect of genotype (F(1, 20) = 3.86, p = 0.063). At 12 weeks of age, there was an effect of genotype (F(1, 23) = 9.54, p = 0.005), however, there was no significant effect of CORT (F(1, 23) = 0.48, p = 0.500) and no genotype × CORT interaction (F(1, 20) = 0.37, p = 0.548). Analyses at 14 weeks of age show that the higher sniffing time in HD mice persists with age (effect of genotype: F(1, 32) = 10.42, p = 0.003). No other effects or interactions were found. The number of vocalizations in response to urine did not differ between R6/1 and WT mice at 8 weeks or 12 weeks of age (A, B). However, as expected at 14 weeks of age, a deficit in response was evident in HD mice compared to WT mice (C). Time spent sniffing urine was no different between genotypes at 8 weeks of age (D) but in line with previously published results, was higher in HD males at 12 and 14 weeks of age compared to WT controls (E, F). Chronic CORT treatment did not affect the number of vocalizations or sniffing time in either genotype. Sniffing was defined as the male nose within 0.5 cm of the oral or anal region of the female mouse. Values represent fold change relative to WT Water control. 8 weeks: n = 4–8, 12 weeks: n = 5–8, 14 weeks: n = 8–10 mice per group. ** p < 0.01, *** p < 0.001 for main effect of genotype.

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Fig. 5. Urine-induced vocalizations from male mice were unaffected by chronic CORT treatment.

4. Discussion Based on previous work revealing a vulnerability to stress hormone treatment in HD mice [49], we hypothesized that the same treatment would also impair ethological behaviors in HD to a greater extent than in WT mice. Chronic CORT treatment impaired olfactory detection and induced anhedonia in female mice but enhanced social vocalization responses in male animals. Nest quality was not altered by CORT treatment in either genotype. Therefore, contrary to our hypothesis, moderate CORT treatment impacted on these behaviors regardless of the HD mutation, suggesting that ethological functions are sensitive to stress hormone even in healthy animals.

learning and report negative effects [11,38,43,62,68]. For example, mild stress through bright light and sound exposure impaired the acquisition of odor memory in rats [43]. On the other hand, odor discrimination in mice was not affected by prenatal stress [5] or chronic physical confinement [31]. Glucocorticoid elevations through wheel running [9] and prenatal stress [5] increased and reduced hippocampal neurogenesis, respectively but had no effect on olfactory bulb neurogenesis. While the impacts of CORT treatment on the hippocampus are well studied [12,24,25], to our knowledge this is the first evidence that CORT can impair olfactory detection in mice. This is consistent with reports of decreased plasticity markers in the piriform cortex after chronic CORT [54]. Olfaction is not only of high ethological importance to our experimental animal but is also relevant to many psychiatric and neurodegenerative disorders [17,29,78].

4.1. Olfactory insensitivity in female mice was impaired by CORT treatment 4.2. No impact of CORT treatment on nest-building Olfaction is important for foraging, navigation and social interaction in rodents [16]. Olfactory detection is impaired in R6/1 mice [50], reflective of the insensitivity in HD patients [14,52,56]. Stress hormone treatment from 6 weeks to 8 weeks of age worsened olfactory detection in R6/1 females, but also impaired performance in WT females (Fig. 1A). Further treatment up until 12 weeks of age did not have an effect (Fig. 1B). Reduced preference for the odor was unlikely due to general anhedonia since saccharin preference was unaffected by 2 weeks of CORT treatment (Fig. 3A). These data suggest that there is not a vulnerability of the HD olfactory system to CORT at the dose used in the present study. The use of other doses and treatment in late-stage R6/1 mice with reduced olfactory plasticity [36] may prove otherwise. The novel and more general finding is that stress hormone treatment in female mice can impair a highly important sensory function. There is little literature on the behavioral effects of stress on olfaction. Such studies focus on the impact of stress on olfactory

The quality of a nest is a reflection of general health [23] and a source of daily stimulation modeling ‘activities of daily living’ for a laboratory mouse [4,50]. Male and female R6/1 mice show a robust, early impairment and subsequent decline in nest-building compared to WT littermates [50]. CORT treatment had no effect in WT or R6/1 mice of either sex, paralleling as absence of CORT effects on motor coordination and weight gain in our previous study [49]. Interventions such as hippocampal lesions [13], glutamatergic receptor mutations [3] and pharmacological agents [37] have disrupted nest-building but investigations on the effects stress on nest quality are limited. Thermal stress has been shown to stimulate nest-building [22,41] and both acute injection of corticosterone and restraint stress increased the time that mice spent within a nest [72]. Although here we report no impact of the present dose of CORT, higher doses can severely impair WT cognitive, affective and motor functions [40,47,70]. Such doses could potentially mask

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any genotype differences (our hypothesis) due to a ‘floor effect’. At a dose of CORT that impairs female olfactory detection and hedonic responses (see following sections), nest-building appears a robust ethological behavior that remained uninterrupted by elevated stress hormone treatment. 4.3. CORT treatment reduced saccharin preference only in female mice Previous work in rodents has shown that chronic CORT treatment can induce anhedonia, the reduced experience of pleasure [70]. However, male mice are often exclusively used [24,26,82]. In our present study we found that CORT treatment reduced saccharin preference in female, but not in male animals (Fig. 3). This sex-specific result supports the notion that female mice are more sensitive in emotional measures to stress compared to males [1]. Furthermore, 4 weeks of CORT treatment was required, whereas 2 weeks of treatment was insufficient. In corroboration with this, 3 weeks of treatment reduced saccharin preference in another oral CORT study [24]. The increased consumption of fluid in HD animals at 8 and 10 weeks of age corroborates with previously published work in the R6/1 [65] and R6/2 [81] mouse models (but did not affect CORT consumption as shown in Suppl Fig. 1). However, the anhedonic phenotype in female R6/1 mice [65] was not replicated in the present study (Fig. 3A, B). The longer period of single housing used by Renoir and colleagues (4 nights vs 1 night in the present study) may be necessary to induce depressive-like behaviors in R6/1 female mice [46]. 4.4. Social, but not sexual communication is transiently enhanced in male mice Ultrasonic vocalizations (USVs) can reflect particular behavioral states of mice [66]. Vocalizations to estrus urine have been associated with sexual behaviors and the activation of reward-related circuitry, representing a hedonic response [42,57]. We quantified the vocalizations emitted from male mice as an indicator of sociosexual interaction (estrus female exposure) and sexual arousal (estrus urine exposure). We replicated previous results [50] that male R6/1 mice emitted less vocalizations at 14 weeks of age compared to WT littermates (Fig. 4, 5). HD patients experience sexual dysfunction and reduced drive [67] and the genotype result is discussed in a previous publication [50]. Stress hormone treatment over 6 weeks increased the number of USVs emitted by WT and HD males in the sociosexual context (female mouse exposure) (Fig. 4B). Two weeks of CORT was insufficient and the effect was not found after 8 weeks of treatment. This transient enhancement of male communication was not accompanied by an increase in the level of physical interest (sniffing) of the female mouse (Fig. 4D) and CORT treatment did not impact on the frequency or amplitude of vocalizations (data not shown). In response to the sexual stimulus alone (estrus urine), vocalization and sniffing levels were not affected by CORT-drinking in either genotype (Fig. 5). The increased interest in female urine by R6/1 male mice is discussed in a previous publication [50]. The dose of CORT used in the present study (25 mg/l) is comparatively moderate [33,49] so we cannot rule out that higher doses may induce more dramatic effects. Indeed, a more severe stressor, repeated foot shock, reduced time spent sniffing estrus urine, but not vocalizations to urine in WT males [42]. Together, the results suggest that chronic CORT had a subtle enhancing effect on male communication to a female mouse, and it was the social, rather than sexual aspect of this interaction that was affected. An absence of CORT effect after 8 weeks of age may be due to the progressive

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decline of this function in HD mice, abolishing any impact of CORT treatment. 4.5. Gene–environment interactions–HD mutation and stress In this study, we have further elucidated the impact of stress in HD using ethological behaviors relevant to the experimental species. Contrary to our hypothesis, we found no gene–environment interactions for chronic CORT and the treatment perturbed species-specific functions in both WT and HD mice. This suggests that (1) in healthy mice, ethological behaviors compared to motor and memory functions [49] may be more sensitive to CORT effects. Using ethologically-salient, rather than standard stimuli for tests (e.g. olfaction rather than vision) improved efficiency of learning in rodents [58] and offer more relevant measures for experimental outcomes. Using other stressors and speciesspecific behaviors (e.g. foraging, burying and home cage locomotor activity) are required to test if ethological measures are indeed more sensitive to stress compared to the standard test battery. And (2) the influence of CORT on WT mice may have masked any vulnerability of ethological functions in HD and a shorter exposure or a ‘washout’ period may be required. Our results suggest that elevated stress hormone levels can impair important functions in HD, but also in healthy controls. This is not dissimilar to enrichment and exercise in that these interventions improve specific behaviors in HD mice but also benefit their WT littermates [60,74]. In the context of HD symptomatology, collective data suggests a preferential impact of stressors on the memory, depression-related and olfactory phenotypes compared to the motor, nest-building and sexual impairments [19,49,51]. More work involving stressors of different type and severity (currently underway) as well as in replication in other models of HD will likely reveal varying effects on the range of HD dysfunctions. The evidence so far suggests that stress is an important player in gene–environment interactions in HD progression and a clinical study may substantiate the importance of lifestyle management in HD gene-positive carriers. 5. Conclusion Tests of species-typical behaviors in laboratory animals are currently under-utilized and incorporating ethological tests into the test battery will improve animal modeling and their translational capacity. Using this ethological approach we showed that olfactory sensitivity and hedonic responses were altered by stress hormone treatment in both WT and HD female mice, providing further evidence that stress can modulate selective phenotypes in HD. However, the HD mutation did not impart an additional vulnerability to the present stress protocol in these functions. Acknowledgements This work was funded by an ARC FT3 Future Fellowship (FT100100835) to AJH. AJH is an Honorary NHMRC Senior Research Fellow. CM is a University of Melbourne Australian Postgraduate Award Scholar. TR is supported by an ARC Discovery Early Career Research Award. The Florey Institute of Neuroscience and Mental Health acknowledges the support from the Victorian Government’s Operational Infrastructure Support Grant. The authors have no conflict of interest to declare. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.bbr.2014.07.044.

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References [1] Autry AE, Adachi M, Cheng P, Monteggia LM. Gender-specific impact of brain-derived neurotrophic factor signaling on stress-induced depression-like behavior. Biol Psychiatry 2009;66:84–90. [2] Aziz NA, Anguelova GV, Marinus J, Lammers GJ, Roos RAC. Sleep and circadian rhythm alterations correlate with depression and cognitive impairment in Huntington’s disease. Parkinsonism Relat Disord 2010;16:345–50. [3] Ballard TM, Pauly-Evers M, Higgins GA, Ouagazzal A-M, Mutel V, et al. Severe impairment of NMDA receptor function in mice carrying targeted point mutations in the glycine binding site results in drug-resistant nonhabituating hyperactivity. J Neurosci 2002;22:6713–23. [4] Barnett SA, Hocking WE. Are nests built for fun? Effects of alternative activities on nest-building by wild house mice. Behav Neural Biol 1981;31:73–81. [5] Belnoue L, Grosjean N, Ladevèze E, Abrous DN, Koehl M. Prenatal stress inhibits hippocampal neurogenesis but spares olfactory bulb neurogenesis. PLoS ONE 2013;8:e72972. [6] Birt DF, Duysen E, Wang W, Yaktine A. Corticosterone supplementation reduced selective protein kinase C isoform expression in the epidermis of adrenalectomized mice. Cancer Epidemiol Biomarkers Prev 2001;10:679–85. [7] Bjorkqvist M, Petersen A, Bacos K, Isaacs J, Norlen P, et al. Progressive alterations in the hypothalamic-pituitary-adrenal axis in the R6/2 transgenic mouse model of Huntington’s disease. Hum Mol Genet 2006;15:1713–21. [8] Bombard Y, Palin J, Friedman JM, Veenstra G, Creighton S, et al. Beyond the patient: the broader impact of genetic discrimination among individuals at risk of Huntington disease. Am J Med Genet Part B: Neuropsychiatric Genet 2012;159B:217–26. [9] Brown J, Cooper-Kuhn CM, Kempermann G, Van Praag H, Winkler J, et al. Enriched environment and physical activity stimulate hippocampal but not olfactory bulb neurogenesis. Eur J Neurosci 2003;17:2042–6. [10] Bylsma F, Moberg P, Doty R, Brandt J. Odor identification in Huntington’s disease patients and asymptomatic gene carriers. J Neuropsychiatry Clin Neurosci 1997;9:598–600. [11] Colas-Zelin D, Light KR, Kolata S, Wass C, Denman-Brice A, et al. The imposition of, but not the propensity for, social subordination impairs exploratory behaviors and general cognitive abilities. Behav Brain Res 2012;232: 294–305. [12] Conrad CD, McLaughlin KJ, Harman JS, Foltz C, Wieczorek L, et al. Chronic glucocorticoids increase hippocampal vulnerability to neurotoxicity under conditions that produce CA3 dendritic retraction but fail to impair spatial recognition memory. J Neurosci 2007;27:8278–85. [13] Deacon RMJ, Croucher A, Rawlins JNP. Hippocampal cytotoxic lesion effects on species-typical behaviours in mice. Behav Brain Res 2002;132:203–13. [14] Delmaire C, Dumas EM, Sharman MA, van den Bogaard SJA, Valabregue R, et al. The structural correlates of functional deficits in early huntington’s disease. Hum Brain Mapp 2013;34:2141–53. [15] Dewhurst K, Oliver JE, McKnight AL. Socio-psychiatric consequences of huntington’s disease. Brit J Psychiatry 1970;116:255–8. [16] Doty R. Odor-guided behavior in mammals. Experientia 1986;42:257–71. [17] Doty RL. Olfactory dysfunction in Parkinson disease. Nat Rev Neurol 2012;8:329–39. [18] Downing N, Smith M, Beglinger L, Mills J, Duff K, et al. Perceived stress in prodromal Huntington disease. Psychol Health 2012;27:196–209. [19] Du X, Leang L, Mustafa T, Renoir T, Pang TY, Hannan AJ. Environmental enrichment rescues female-specific hyperactivity of the hypothalamicpituitary-adrenal axis in a model of Huntington’s disease. Transl Psychiatry 2012;2:e133. [20] Duan W, Guo Z, Jiang H, Ware M, Li X, Mattson M. Dietary restriction normalizes glucose metabolism and BDNF levels, slows disease progression, and increases survival in huntingtin mutant mice. Proc Natl Acad Sci U S A 2003:100. [21] Folstein SE, Folstein MF. Psychiatric features of Huntington’s disease: recent approaches and findings. Psychiatr Dev 1983;1:193–205. [22] Gaskill BN, Gordon CJ, Pajor EA, Lucas JR, Davis JK, Garner JP. Heat or insulation: behavioral titration of mouse preference for warmth or access to a nest. PLoS ONE 2012;7:e32799. [23] Gaskill BN, Karas AZ, Garner JP, Pritchett-Corning KR. Nest building as an indicator of health and welfare in laboratory mice. J Visual Exp 2013:e51012. [24] Gourley SL, Kiraly DD, Howell JL, Olausson P, Taylor JR. Acute hippocampal brain-derived neurotrophic factor restores motivational and forced swim performance after corticosterone. Biol Psychiatry 2008;64:884–90. [25] Gourley SL, Swanson AM, Koleske AJ. Corticosteroid-induced neural remodeling predicts behavioral vulnerability and resilience. J Neurosci 2013;33:3107–12. [26] Gourley SL, Taylor JR. Recapitulation and reversal of a persistent depressionlike syndrome in rodents in current protocols in neuroscience. John Wiley & Sons Inc.; 2009. [27] Harrison DJ, Busse M, Openshaw R, Rosser AE, Dunnett SB, Brooks SP. Exercise attenuates neuropathology and has greater benefit on cognitive than motor deficits in the R6/1 Huntington’s disease mouse model. Exp Neurol 2013;248:457–69. [28] Heuser IJE, Chase TN, Maral Mouradian M. The limbic-hypothalamicpituitary-adrenal axis in Huntington’s disease. Biol Psychiatry 1991;30: 943–52. [29] Huckins L, Logan D, Sánchez-Andrade G. Olfaction and olfactory-mediated behaviour in psychiatric disease models. Cell Tissue Res 2013;354: 69–80.

[30] Huntington’s Disease Collaborative Research Group. A novel gene containing a trinucleotide repeat that is expanded and unstable on Huntington’s disease chromosomes. Cell 1993;72:971–83. [31] Jeong YH, Park CH, Yoo J, Shin KY, Ahn S-M, et al. Chronic stress accelerates learning and memory impairments and increases amyloid deposition in APPV717I-CT100 transgenic mice, an Alzheimer’s disease model. FASEB J 2006:05–4265. [32] Jhanjee A, Anand K, Bajaj B. Hypersexual features in Huntington’s disease. Singapore Med J 2011;25:e131–3. [33] Karatsoreos IN, Bhagat SM, Bowles NP, Weil ZM, Pfaff DW, McEwen BS. Endocrine and physiological changes in response to chronic corticosterone: a potential model of the metabolic syndrome in mouse. Endocrinology 2010;151:2117–27. [34] Larsson M, Lundin A, Robins Wahlin T. Olfactory functions in asymptomatic carriers of the Huntington disease mutation. J Clin Exp Neuropsychol 2006;28:1373–80. [35] Latham N, Mason G. From house mouse to mouse house: the behavioural biology of free-living Mus musculus and its implications in the laboratory. Appl Anim Behav Sci 2004;86:261–89. [36] Lazic SE, Goodman AOG, Grote HE, Blakemore C, Morton AJ, et al. Olfactory abnormalities in Huntington’s disease: Decreased plasticity in the primary olfactory cortex of R6/1 transgenic mice and reduced olfactory discrimination in patients. Brain Res 2007;1151:219–26. [37] Li X, Morrow D, Witkin JM. Decreases in nestlet shredding of mice by serotonin uptake inhibitors: comparison with marble burying. Life Sci 2006;78: 1933–9. [38] Li X, Yu F, Guo A. Sleep deprivation specifically impairs short-term olfactory memory in drosophila. Sleep 2009;32:1417–24. [39] López-Sendón JL, Royuela A, Trigo P, Orth M, Lange H, et al. What is the impact of education on Huntington’s disease? Mov Disord 2011;26:1489–95. [40] Luine VN, Spencer RL, McEwen BS. Effects of chronic corticosterone ingestion on spatial memory performance and hippocampal serotonergic function. Brain Res 1993;616:65–70. [41] Lynch C, Hegmann J. Genetic differences influencing behavioral temperature regulation in small mammals II. Genotype-environment interactions. Behav Genet 1973;3:145–54. [42] Malkesman O, Scattoni ML, Paredes D, Tragon T, Pearson B, et al. The female urine sniffing test: a novel approach for assessing reward-seeking behavior in rodents. Biol Psychiatry 2010;67:864–71. [43] Manella LC, Alperin S, Linster C. Stressors impair odor recognition memory via an olfactory bulb-dependent noradrenergic mechanism. Front Integrat Neurosci 2013:7. [44] Marder K, Gu Y, Eberly S, et al. Relationship of mediterranean diet and caloric intake to phenoconversion in huntington disease. JAMA Neurol 2013;70:1382–8. [45] Marder K, Zhao H, Eberly S, Tanner CM, Oakes D, et al. Dietary intake in adults at risk for huntington disease: analysis of PHAROS research participants. Neurology 2009;73:385–92. [46] Martin AL, Brown RE. The lonely mouse: verification of a separationinduced model of depression in female mice. Behav Brain Res 2010;207: 196–207. [47] Metz GA, Jadavji NM, Smith LK. Modulation of motor function by stress: a novel concept of the effects of stress and corticosterone on behavior. Eur J Neurosci 2005;22:1190–200. [49] Mo C, Pang TY, Ransome MI, Hill RA, Renoir T, Hannan AJ. High stress hormone levels accelerate the onset of memory deficits in male Huntington’s disease mice. Neurobiol Dis 2014;69:248–62. [50] Mo C, Renoir T, Hannan AJ. Novel ethological endophenotypes in a transgenic mouse model of Huntington’s disease. Behav Brain Res 2014. [51] Mo C, Renoir T, Pang TYC, Hannan AJ. Short-term memory acquisition in female Huntington’s disease mice is vulnerable to acute stress. Behav Brain Res 2013;253:318–22. [52] Moberg P, Doty R. Olfactory function in huntington’s disease patients and atrisk offspring. Int J Neurosci 1997;89:133–9. [53] Moretti P, Bouwknecht JA, Teague R, Paylor R, Zoghbi HY. Abnormalities of social interactions and home-cage behavior in a mouse model of Rett syndrome. Human Mol Genet 2005;14:205–20. [54] Nacher J, Pham K, Gil-Fernandez V, McEwen BS. Chronic restraint stress and chronic corticosterone treatment modulate differentially the expression of molecules related to structural plasticity in the adult rat piriform cortex. Neuroscience 2004;126:503–9. [55] Nithianantharajah J, Barkus C, Murphy M, Hannan AJ. Gene-environment interactions modulating cognitive function and molecular correlates of synaptic plasticity in Huntington’s disease transgenic mice. Neurobiol Dis 2008;29:490–504. [56] Nordin S, Paulsen JS, Murphy C. Sensory- and memory-mediated olfactory dysfunction in Huntington’s disease. J Int Neuropsychol Soc 1995;1: 281–90. [57] Nyby J. Ultrasonic vocalizations during sex behavior of male house mice (Mus musculus): A description. Behav Neural Biol 1983;39:128–34. [58] Olsson IAS, Nevison CM, Patterson-Kane EG, Sherwin CM, Van de Weerd HA, Würbel H. Understanding behaviour: the relevance of ethological approaches in laboratory animal science. Appl Anim Behav Sci 2003;81: 245–64. [59] Pang TYC, Du X, Zajac MS, Howard ML, Hannan AJ. Altered serotonin receptor expression is associated with depression-related behavior in the R6/1

C. Mo et al. / Behavioural Brain Research 274 (2014) 118–127

[60]

[61]

[62]

[63]

[64]

[65]

[66]

[67] [68]

[69]

[70]

transgenic mouse model of Huntington’s disease. Hum Mol Genet 2009;18: 753–66. Pang TYC, Stam NC, Nithianantharajah J, Howard ML, Hannan AJ. Differential effects of voluntary physical exercise on behavioral and brain-derived neurotrophic factor expression deficits in huntington’s disease transgenic mice. Neuroscience 2006;141:569–84. Pietropaolo S, Delage P, Cayzac S, Crusio WE, Cho YH. Sex-dependent changes in social behaviors in motor pre-symptomatic R6/1 mice. PLoS ONE 2011;6:e19965. Raˇceková E, Lievajová K, Danko J, Martonˇcíková M, Fleˇsárová S, et al. Maternal separation induced alterations of neurogenesis in the rat rostral migratory stream. Cell Mol Neurobiol 2009;29:811–9. Renoir T, Chevarin C, Lanfumey-Mongredien L, Hannan A. Effect of enhanced voluntary physical exercise on brain levels of monoamines in Huntington disease mice. PLOS Currents Huntington Dis 2011:3. Renoir T, Pang TYC, Mo C, Chan G, Chevarin C, et al. Differential effects of early environmental enrichment on emotionality related behaviours in Huntington’s disease transgenic mice. J Physiol 2013;591:41–55. Renoir T, Zajac MS, Du X, Pang TY, Leang L, et al. Sexually dimorphic serotonergic dysfunction in a mouse model of huntington’s disease and depression. PLoS ONE 2011;6:e22133. Scattoni ML, Crawley J, Ricceri L. Ultrasonic vocalizations: a tool for behavioural phenotyping of mouse models of neurodevelopmental disorders. Neurosci Biobehav Rev 2009;33:508–15. Schmidt EZ, Bonelli RM. Sexuality in Huntington’s disease. WMW Wiener Medizinische Wochenschrift 2008;158:78–83. Scotto-Lomassese S, Strambi C, Strambi A, Aouane A, Augier R, et al. Suppression of adult neurogenesis impairs olfactory learning and memory in an adult insect. J Neurosci 2003;23:9289–96. Simonin C, Duru C, Salleron J, Hincker P, Charles P, et al. Association between caffeine intake and age at onset in Huntington’s disease. Neurobiol Dis 2013;58:179–82. Sterner EY, Kalynchuk LE. Behavioral and neurobiological consequences of prolonged glucocorticoid exposure in rats: Relevance to depression. Progr Neuro-Psychopharmacol Biol Psychiatry 2010;34:777–90.

127

[71] Stone EA, Lin Y. An anti-immobility effect of exogenous corticosterone in mice. Eur J Pharmacol 2008;580:135–42. [72] Stone EA, Quartermain D. Alpha-1-noradrenergic neurotransmission, corticosterone, and behavioral depression. Biol Psychiatry 1999;46:1287–300. [73] Trembath K, Horton Z, Tippett L, Hogg V, Collins V, et al. A retrospective study of the impact of lifestyle on age at onset of Huntington disease. Mov Disorders 2010;58:179–82. [74] van Dellen A, Blakemore C, Deacon R, York D, Hannan AJ. Delaying the onset of Huntington’s in mice. Nature 2000;404:721–2. [75] van Duijn E, Selis MA, Giltay EJ, Zitman FG, Roos RAC, et al. Hypothalamic–pituitary–adrenal axis functioning in Huntington’s disease mutation carriers compared with mutation-negative first-degree controls. Brain Res Bull 2010;83:232–7. [76] Veenit V, Cordero MI, Tzanoulinou S, Sandi C. Increased corticosterone in peripubertal rats leads to long-lasting alterations in social exploration and aggression. Front Behav Neurosci 2013:7. [77] Waters P, McCormick C. Caveats of chronic exogenous corticosterone treatments in adolescent rats and effects on anxiety-like and depressive behavior and hypothalamic-pituitary-adrenal (HPA) axis function. Biol Mood Anxiety Disorders 2011;1:4. [78] Wesson DW, Levy E, Nixon RA, Wilson DA. olfactory dysfunction correlates with amyloid-␤ burden in an alzheimer’s disease mouse model. J Neurosci 2010;30:505–14. [79] Wexler NS, Lorimer J, Porter J, Gomez F, Moskowitz C, et al. Venezuelan kindreds reveal that genetic and environmental factors modulate Huntington’s disease age of onset. Proc Natl Acad Sci U S A 2004;101:3498–503. [80] Wood NI, Glynn D, Morton AJ. Brain training” improves cognitive performance and survival in a transgenic mouse model of Huntington’s disease. Neurobiol Dis 2011;42:427–37. [81] Wood NI, Goodman AOG, van der Burg JMM, Gazeau V, Brundin P, et al. Increased thirst and drinking in Huntington’s disease and the R6/2 mouse. Brain Res Bull 2008;76:70–9. [82] Wu T-C, Chen H-T, Chang H-Y, Yang C-Y, Hsiao M-C, et al. Mineralocorticoid receptor antagonist spironolactone prevents chronic corticosterone induced depression-like behavior. Psychoneuroendocrinology 2013;38:871–83.