Bruin Reseurch Bulletin, Vol. 4, pp. 131-133.Printed in the U.S.A.
Penile Reflexes and Copulatory Behavior in Male Rats Following Lesions in the Bed Nucleus of the Stria Terminalis’ RICHARD
Depurtment
J. VALCOURT
of Psychology,
AND BENJAMIN
University of Connecticut,
(Received
16 October
D. SACHS’
Storm, CT 06268
1978)
VALCOURT, R. J. AND B. D. SACHS. Penile rejlexes and copulatorybehavior in mule ruts following lesions in the bed nucleus of the striu terminuks. BRAIN RES. BULL. 4(l) 131-133, 1979.-Male rats with large lesions in the bed nucleus of the stria terminalis (BNST) had more intromissions preceding ejaculation (if they ejaculated at all), longer intervals between intromissions, and longer postejaculatory refractory periods than control animals. In tests for penile reflexes, BNST males were similar to control males in every respect. The copulatory deficits in BNST males are probably not mediated by a change in penile reflex potential. Copulation
Penile reflexes
Bed nucleus of stria terminalis
NEURAL control of male copulatory behavior is vested in both brain and spinal cord. Among other portions of the brain, the bed nucleus of the stria terminalis (BNST) and the corticomedial amygdala have been implicated in the achievement of ejaculation and, to some extent, the temporal patterning of copulation [2, 3, 6, 81. The male rat’s penile reflexes (erections, cups, and flips) are primarily spinally mediated, but are presumably controlled in part by the brain [ 1,4, 5,9]. Successful copulation occurs when these reflexes are smoothly integrated with the bodily movements of the animal. The loci of brain control of penile reflexes have not been identified, and we considered that some of the effects of BNST lesions upon copulatory behavior might be due to disruption of penile reflexes or their integration with mounting activity. We therefore inquired in this study whether BNST lesions would alter penile reflex potential. The disruptive effects of BNST lesions on copulation were confirmed, but these lesions did not alter sexual reflexes.
METHOD Thirty-five adult male Long-Evans rats from Charles River Breeding Laboratories were screened. Animals that copulated and showed reflexes during three of four weekly tests were included in the study. After screening, animals were randomly assigned to one of three groups: BNST Lesion (BNST, N=lO), Sham Operated (SHAM, N=6), and Unoperated Control (CONT, N=6). Surgery was performed under Chloropent anesthesia (0.3 ml/100 g body weight). Bilateral lesions were made by passing 8 mA radio frequency current for 15 set and then 9 mA for another 15 sec. Electrodes were No. 2 stainless steel insect pins insulated except
for 1 mm at the tip. Stereotaxic coordinates taken from Pellegrino and Cushman [7] were Anterior-Posterior +1.4, Medial-Lateral + 1.2, and Dorsal-Ventral -6.0. Bregma was the zero-point. Animals in the SHAM group received the same treatment except that the electrode was lowered 1 mm less ventrally and no current was passed. Beginning one week after surgery, weekly reflex and copulation tests were administered. For 3 weeks each male received a reflex test, followed 1 day later by a copulation test. For reflex testing the animal was placed on its back with its anterior portion contained in a plastic cylinder and a band wrapped snugly around its midsection. The experimenter further restrained the animal by gently gripping the hind legs. At the start of a test the penis was extruded from the penile sheath and held in place by applying light pressure at the base of the penis with a wooden applicator. Tests lasted for 15 min after the appearance of the first reflex, or for 30 min if no reflexes occurred. The reflexes were recorded on an event recorder which the experimenter operated with his toes. Three types of penile reflexes were scored. Erection is characterized by a swelling and extension of the penis, usually accompanied by a slight reddening. Cup was scored when the distal portion of the penis flared to become wider than the proximal portion. Cups can either appear immediately from the quiescent state or evolve out of an erection. In either event only the cup is recorded. AJlip is characterized by a quick dorsal flexion of the penis, which can either be erect or non-erect. Occasionally during a flip there is protrusion of the OS penis beyond the penile tip. From the event records the latency (the time from penis extrusion to first reflex), the number of erections, number of
‘Supported by research grants to BDS from NICHHD (HD-08933) and The University of Connecticut ‘To whom reprint requests should be addressed.
Copyright o 1979 ANKHO
Research Foundation.
International Inc.-0361-9230/79/010131-03$00.80/O
VALCOURT
132
TABLE MEAN RESULTS
OF THE COPULATION
AND SACHS
1
TESTS. TEMPORAL
MEASURES
ARE IN SECONDS
Group Copulation Test
BNST SHAM CONT Postop 2 Postop 3 Postop 2 Postop 3 Postop 2 Postop 3
N Number of Mounts Number of Intromissions Hit Rate Mean Interintromission Interval Ejaculation Latency Postejaculatory Interval
4 16.0 17.5 0.55 55.0* 974.5* 685.8$
4 42.8t 19.5* 0.33* 95.lf 1819.8$ 703.2t
6 8.8 10.2 0.56 26.8 287.8 351.5
6 10.7 11.5 0.56 27.6 336.2 366.2
6 7.7 10.2 0.69 36.5 380.3 388.8
6 8.3 10.2 0.58 35.0 379.8 387.8
*p
Penile Reflexes and Copulatory Behavior in Male Rats Following Lesions in the Bed Nucleus of the Stria Terminalis’ RICHARD
Depurtment
J. VALCOURT
of Psychology,
AND BENJAMIN
University of Connecticut,
(Received
16 October
D. SACHS’
Storm, CT 06268
1978)
VALCOURT, R. J. AND B. D. SACHS. Penile rejlexes and copulatorybehavior in mule ruts following lesions in the bed nucleus of the striu terminuks. BRAIN RES. BULL. 4(l) 131-133, 1979.-Male rats with large lesions in the bed nucleus of the stria terminalis (BNST) had more intromissions preceding ejaculation (if they ejaculated at all), longer intervals between intromissions, and longer postejaculatory refractory periods than control animals. In tests for penile reflexes, BNST males were similar to control males in every respect. The copulatory deficits in BNST males are probably not mediated by a change in penile reflex potential. Copulation
Penile reflexes
Bed nucleus of stria terminalis
NEURAL control of male copulatory behavior is vested in both brain and spinal cord. Among other portions of the brain, the bed nucleus of the stria terminalis (BNST) and the corticomedial amygdala have been implicated in the achievement of ejaculation and, to some extent, the temporal patterning of copulation [2, 3, 6, 81. The male rat’s penile reflexes (erections, cups, and flips) are primarily spinally mediated, but are presumably controlled in part by the brain [ 1,4, 5,9]. Successful copulation occurs when these reflexes are smoothly integrated with the bodily movements of the animal. The loci of brain control of penile reflexes have not been identified, and we considered that some of the effects of BNST lesions upon copulatory behavior might be due to disruption of penile reflexes or their integration with mounting activity. We therefore inquired in this study whether BNST lesions would alter penile reflex potential. The disruptive effects of BNST lesions on copulation were confirmed, but these lesions did not alter sexual reflexes.
METHOD Thirty-five adult male Long-Evans rats from Charles River Breeding Laboratories were screened. Animals that copulated and showed reflexes during three of four weekly tests were included in the study. After screening, animals were randomly assigned to one of three groups: BNST Lesion (BNST, N=lO), Sham Operated (SHAM, N=6), and Unoperated Control (CONT, N=6). Surgery was performed under Chloropent anesthesia (0.3 ml/100 g body weight). Bilateral lesions were made by passing 8 mA radio frequency current for 15 set and then 9 mA for another 15 sec. Electrodes were No. 2 stainless steel insect pins insulated except
for 1 mm at the tip. Stereotaxic coordinates taken from Pellegrino and Cushman [7] were Anterior-Posterior +1.4, Medial-Lateral + 1.2, and Dorsal-Ventral -6.0. Bregma was the zero-point. Animals in the SHAM group received the same treatment except that the electrode was lowered 1 mm less ventrally and no current was passed. Beginning one week after surgery, weekly reflex and copulation tests were administered. For 3 weeks each male received a reflex test, followed 1 day later by a copulation test. For reflex testing the animal was placed on its back with its anterior portion contained in a plastic cylinder and a band wrapped snugly around its midsection. The experimenter further restrained the animal by gently gripping the hind legs. At the start of a test the penis was extruded from the penile sheath and held in place by applying light pressure at the base of the penis with a wooden applicator. Tests lasted for 15 min after the appearance of the first reflex, or for 30 min if no reflexes occurred. The reflexes were recorded on an event recorder which the experimenter operated with his toes. Three types of penile reflexes were scored. Erection is characterized by a swelling and extension of the penis, usually accompanied by a slight reddening. Cup was scored when the distal portion of the penis flared to become wider than the proximal portion. Cups can either appear immediately from the quiescent state or evolve out of an erection. In either event only the cup is recorded. AJlip is characterized by a quick dorsal flexion of the penis, which can either be erect or non-erect. Occasionally during a flip there is protrusion of the OS penis beyond the penile tip. From the event records the latency (the time from penis extrusion to first reflex), the number of erections, number of
‘Supported by research grants to BDS from NICHHD (HD-08933) and The University of Connecticut ‘To whom reprint requests should be addressed.
Copyright o 1979 ANKHO
Research Foundation.
International Inc.-0361-9230/79/010131-03$00.80/O
VALCOURT
132
TABLE MEAN RESULTS
OF THE COPULATION
AND SACHS
1
TESTS. TEMPORAL
MEASURES
ARE IN SECONDS
Group Copulation Test
BNST SHAM CONT Postop 2 Postop 3 Postop 2 Postop 3 Postop 2 Postop 3
N Number of Mounts Number of Intromissions Hit Rate Mean Interintromission Interval Ejaculation Latency Postejaculatory Interval
4 16.0 17.5 0.55 55.0* 974.5* 685.8$
4 42.8t 19.5* 0.33* 95.lf 1819.8$ 703.2t
6 8.8 10.2 0.56 26.8 287.8 351.5
6 10.7 11.5 0.56 27.6 336.2 366.2
6 7.7 10.2 0.69 36.5 380.3 388.8
6 8.3 10.2 0.58 35.0 379.8 387.8
*p
