Brain Reseurch Bulktin,
0761.9?30/91 $3.00 + 00
Vol. 26, pp. 539-54,.1 ‘DPergamon Press plc, 1991. Printed in the U S A.
Reduction of Exploratory Behavior by Intraperitoneal Injection of Interleukin- 1 Involves Brain Corticotropin-Releasing Factor ADRIAN
Department
J. DUNN, MICHAEL
ANTOON
AND YVETTE
CHAPMAN
of Pharmacology
and Therapeutics, Louisiana Stute University Medical Center P.O. Box 33932, Shreveport, LA 71130-3932 Received
13 December
1990
AND Y. CHAPMAN. Reduction of explorntory behavior b! intruperironecd injection of inrerlrukin-l factor. BRAIN RES BULL 26(4) 539-542. 1991. -The behavior of mice was scored in a multicompartment chamber one hour following intraperitoneal injection of recombinant human interleukin- 1 (IL- 1). Both IL-I cr and IL-I p dose-dependently reduced the mean duration for which mice were in contact with novel stimuli without altering measures of locomotor activity. such as movements between the compartments or rears. These behavioral changes resemble those previously observed with prior restraint or intracerebroventricular (ICV) injection of corticotropin-releasing factor (CRF). Effective doses were in the range 0.1-10 ng for IL-la, and l-10 ng for IL-lp. The reduction in stimulus-contact times induced by I ng of IL-Ip was reversed by prior ICV injection of the CRF antagonist, alpha-helical CRF,,, , suggesting that IL-l causes secretion of brain CRF which in turn elicits the behavioral changes. These results indicate that peripheral administration of IL-la or IL-I p in low doses can alter behavior. They provide additional evidence that IL-l administration stimulates brain CRF secretion, and that brain CRF can modulate exploratory behavior. and thus reinforces the concept that IL-l administration can induce stress. DUNN. A. J., M. ANTOON invo/ve.s brain
Interleukin-
1
~orficorropin-re[easinR
Exploratory
behavior
Corticotropin-releasing
factor
Alpha-helical
CRF
tion of brain CRF.
PREVIOUS studies have indicated that prior restraint of rats or mice reduced the time for which mice and rats are in contact with stimuli in a novel multicompartment chamber [MCC: (2.4)]. We believe this behavioral change reflects a reduction in exploratory behavior. It can be mimicked by intracerebroventricular (ICV) application of low doses of corticotropin-releasing factor (CRF) in mice (4) and rats (24). Interleukin- 1 (IL- 1) is a cytokine produced by macrophages as an early step in the initiation of the immune response. IL-l administration to rodents can elicit a number of physiological and behavioral changes that occur following infections, such as fever (10). increased slow-wave sleep (16) and loss of appetite (7. 14, 17-19, 28, 29). It also elicits some physiological effects characteristic of stress, such as an activation of the HPA axis (3, 6. 11. 22, 27). of brain noradrenergic systems (11,15), and the sympathoadrenal system (20). The effect on the HPA axis in vivo appears to be mediated primarily by activation of secretion of CRF from hypothalamic neurons, because administration of antibody to CRF can antagonize or ablate the IL-l-induced increase in ACTH and corticosterone secretion (3, 22, 27). It was therefore of interest to determine whether peripheral administration of IL-l would cause reductions in exploratory behavior in the MCC resembling these observed following ICV CRF administration. and if so, whether these changes involved secre-
METHOD Materials
Recombinant human IL-la (hIL-la) was a gift from Dr P. Lomedico (Hoffmann-La Roche). hIL-1 p was a gift from Dr. Y. Hirai (Otsuka Pharmaceutical Co). The specific activity of the hIL-la (lot l/87) was 2.5 x lo9 Units/mg protein, that of hIL-1P (lot 871027) was 2 x 10’ Units/mg. Alpha-helical CRF,,, (ahCRF) was a gift from Dr. J. Rivier (Clayton Foundation for Peptide Biology, Salk Institute). ahCRF was dissolved in water at a concentration of 5 mg/ml and adjusted to 0.5% NaCl with crystalline NaCl. It was injected in a volume of 4 ~1 (2 ~1 into each cannula). Animals
Male VAF Plus CD-1 mice were obtained from Charles River (Raleigh-Durham facility). They were maintained on a 12-12 light-dark cycle (lights on 7 a.m.) with free access to food and water for at least one week prior to surgery and/or behavioral testing. At the time behavior was tested, they were 4-6 weeks old
539
DUNN. ANTOON ANI) CHAPMAN
540
(25-35 g). Mice were group-housed (5-6 per cage) until surgery, and individually
thereafter.
Surgery
For ICV injection, mice were implanted bilaterally with polyethylene cannulae in the lateral ventricles (Clay Adams PE-50 tubing) according to the method of Guild and Dunn (13) using pentobarbital anesthesia (65 mgkg). They were allowed to recover housed individu~ly for IO-14 days before behavioral testing. After the behavioral obse~ation period a solution of methyiene blue dye was injected Pugh the cannttlae, and the brain excised five minutes later to verify the cannula placements. Behavioral Testing
The behavioral apparatus and testing procedure have been described previously (1, 4, 23). The apparatus consisted of a chamber (38 X 38 x 23 cm) divided into nine interconnecting compartments. Each compartment contained a one inch hole in the floor. In each hole slightly below floor level a wire-mesh sphere (ca. 1 inch diameter) was rigidly mounted to serve as a novel stimulus. Observations were commenced immediately after placement in the central compartment of the apparatus for a period of 25 min. Behaviors scored included measures of locomotor activity: the number of comp~ments entered, and the number and duration of rears, as well as periods of inactivity; the number and duration of contacts with the stimuli, and the frequency of grooming and scratching. Contacts with the stimuli normally involved nose contact (sniffing), and occasionally licking or biting. The number of movements between compartments and of rears were used as measures of locomotor activity to assess nonspecific sedative or stimulant effects. Scoring was enabled by an NEC i3201A lap-top computer modified for use as an event recorder by S & K Computer Products Ltd. (Buffalo, NY). Each mouse was tested only once in the apparatus, and this occurred between 9 a.m. and 4 p.m.
Saline
0.1 ng
Dose
’ ng
10 ng
IL-l
FIG. 1. The effect of P IL-la on stimulus-contact times in the MCC. Mice were injected with saline or IL-la at doses of 0.1, 1.Oor 10 ng one hour before placement in the MCC. The data presented are the combined results of two experiments (n = 8), one of which included saline and the 10 ng dose of IL-la, and the other saline and 0.1 and 1 ng doses of lIla. The IL-la-induced reductions of s~m~us-contact times were significantly different from saline [Dunnett’stest: 0.1 ng: $21) = 3.0, ~~0.01, 1 ng; $21)=4.0, p
0761.9?30/91 $3.00 + 00
Vol. 26, pp. 539-54,.1 ‘DPergamon Press plc, 1991. Printed in the U S A.
Reduction of Exploratory Behavior by Intraperitoneal Injection of Interleukin- 1 Involves Brain Corticotropin-Releasing Factor ADRIAN
Department
J. DUNN, MICHAEL
ANTOON
AND YVETTE
CHAPMAN
of Pharmacology
and Therapeutics, Louisiana Stute University Medical Center P.O. Box 33932, Shreveport, LA 71130-3932 Received
13 December
1990
AND Y. CHAPMAN. Reduction of explorntory behavior b! intruperironecd injection of inrerlrukin-l factor. BRAIN RES BULL 26(4) 539-542. 1991. -The behavior of mice was scored in a multicompartment chamber one hour following intraperitoneal injection of recombinant human interleukin- 1 (IL- 1). Both IL-I cr and IL-I p dose-dependently reduced the mean duration for which mice were in contact with novel stimuli without altering measures of locomotor activity. such as movements between the compartments or rears. These behavioral changes resemble those previously observed with prior restraint or intracerebroventricular (ICV) injection of corticotropin-releasing factor (CRF). Effective doses were in the range 0.1-10 ng for IL-la, and l-10 ng for IL-lp. The reduction in stimulus-contact times induced by I ng of IL-Ip was reversed by prior ICV injection of the CRF antagonist, alpha-helical CRF,,, , suggesting that IL-l causes secretion of brain CRF which in turn elicits the behavioral changes. These results indicate that peripheral administration of IL-la or IL-I p in low doses can alter behavior. They provide additional evidence that IL-l administration stimulates brain CRF secretion, and that brain CRF can modulate exploratory behavior. and thus reinforces the concept that IL-l administration can induce stress. DUNN. A. J., M. ANTOON invo/ve.s brain
Interleukin-
1
~orficorropin-re[easinR
Exploratory
behavior
Corticotropin-releasing
factor
Alpha-helical
CRF
tion of brain CRF.
PREVIOUS studies have indicated that prior restraint of rats or mice reduced the time for which mice and rats are in contact with stimuli in a novel multicompartment chamber [MCC: (2.4)]. We believe this behavioral change reflects a reduction in exploratory behavior. It can be mimicked by intracerebroventricular (ICV) application of low doses of corticotropin-releasing factor (CRF) in mice (4) and rats (24). Interleukin- 1 (IL- 1) is a cytokine produced by macrophages as an early step in the initiation of the immune response. IL-l administration to rodents can elicit a number of physiological and behavioral changes that occur following infections, such as fever (10). increased slow-wave sleep (16) and loss of appetite (7. 14, 17-19, 28, 29). It also elicits some physiological effects characteristic of stress, such as an activation of the HPA axis (3, 6. 11. 22, 27). of brain noradrenergic systems (11,15), and the sympathoadrenal system (20). The effect on the HPA axis in vivo appears to be mediated primarily by activation of secretion of CRF from hypothalamic neurons, because administration of antibody to CRF can antagonize or ablate the IL-l-induced increase in ACTH and corticosterone secretion (3, 22, 27). It was therefore of interest to determine whether peripheral administration of IL-l would cause reductions in exploratory behavior in the MCC resembling these observed following ICV CRF administration. and if so, whether these changes involved secre-
METHOD Materials
Recombinant human IL-la (hIL-la) was a gift from Dr P. Lomedico (Hoffmann-La Roche). hIL-1 p was a gift from Dr. Y. Hirai (Otsuka Pharmaceutical Co). The specific activity of the hIL-la (lot l/87) was 2.5 x lo9 Units/mg protein, that of hIL-1P (lot 871027) was 2 x 10’ Units/mg. Alpha-helical CRF,,, (ahCRF) was a gift from Dr. J. Rivier (Clayton Foundation for Peptide Biology, Salk Institute). ahCRF was dissolved in water at a concentration of 5 mg/ml and adjusted to 0.5% NaCl with crystalline NaCl. It was injected in a volume of 4 ~1 (2 ~1 into each cannula). Animals
Male VAF Plus CD-1 mice were obtained from Charles River (Raleigh-Durham facility). They were maintained on a 12-12 light-dark cycle (lights on 7 a.m.) with free access to food and water for at least one week prior to surgery and/or behavioral testing. At the time behavior was tested, they were 4-6 weeks old
539
DUNN. ANTOON ANI) CHAPMAN
540
(25-35 g). Mice were group-housed (5-6 per cage) until surgery, and individually
thereafter.
Surgery
For ICV injection, mice were implanted bilaterally with polyethylene cannulae in the lateral ventricles (Clay Adams PE-50 tubing) according to the method of Guild and Dunn (13) using pentobarbital anesthesia (65 mgkg). They were allowed to recover housed individu~ly for IO-14 days before behavioral testing. After the behavioral obse~ation period a solution of methyiene blue dye was injected Pugh the cannttlae, and the brain excised five minutes later to verify the cannula placements. Behavioral Testing
The behavioral apparatus and testing procedure have been described previously (1, 4, 23). The apparatus consisted of a chamber (38 X 38 x 23 cm) divided into nine interconnecting compartments. Each compartment contained a one inch hole in the floor. In each hole slightly below floor level a wire-mesh sphere (ca. 1 inch diameter) was rigidly mounted to serve as a novel stimulus. Observations were commenced immediately after placement in the central compartment of the apparatus for a period of 25 min. Behaviors scored included measures of locomotor activity: the number of comp~ments entered, and the number and duration of rears, as well as periods of inactivity; the number and duration of contacts with the stimuli, and the frequency of grooming and scratching. Contacts with the stimuli normally involved nose contact (sniffing), and occasionally licking or biting. The number of movements between compartments and of rears were used as measures of locomotor activity to assess nonspecific sedative or stimulant effects. Scoring was enabled by an NEC i3201A lap-top computer modified for use as an event recorder by S & K Computer Products Ltd. (Buffalo, NY). Each mouse was tested only once in the apparatus, and this occurred between 9 a.m. and 4 p.m.
Saline
0.1 ng
Dose
’ ng
10 ng
IL-l
FIG. 1. The effect of P IL-la on stimulus-contact times in the MCC. Mice were injected with saline or IL-la at doses of 0.1, 1.Oor 10 ng one hour before placement in the MCC. The data presented are the combined results of two experiments (n = 8), one of which included saline and the 10 ng dose of IL-la, and the other saline and 0.1 and 1 ng doses of lIla. The IL-la-induced reductions of s~m~us-contact times were significantly different from saline [Dunnett’stest: 0.1 ng: $21) = 3.0, ~~0.01, 1 ng; $21)=4.0, p
