Physiology & Behavior, Vol. 17, pp. 297--301. Pergamon Press and Brain Research Publ., 1976. Printed in the U.S.A.
Pituitary-Adrenal Effects on Avoidance-of-Attack in Mice: Separation of the Effects of ACTH and Corticosterone I JOHN A. MOYER 2 AND ALAN I. LESHNER 3
Department o f Psychology, Bucknell University, Lewisburg PA 17837 (Received 18 August 1975) MOYER, J. A. AND A. I. LESHNER. Pituitary.adrenal effects on avoidance.of-attack in mice: separation of the effects of ACTH and corticosterone. PHYSIOL. BEHAV. 17(2) 297-301, 1976. - Two experiments were conducted to separate the effects of ACTH and corticosterone on avoidance-of-attack. In Experiment 1, treatment with corticosterone restored the avoidance performance of hypophysectomized mice to normal levels. In Experiment 2, ACTH treatment increased the avoidance retention of intact mice but did not affect the avoidance responding of mice which were adrenalectomized and treated with a replacement dosage of corticosterone (controlled-corticosterone condition). These two studies suggest that corticosterone is the critical hormone of the pituitary-adrenal axis in the control of avoidance responding in agonistic situations. In addition, these studies demonstrate that (I) ACTH and corticosterone affect avoidance-of-attack differently from the way they have been shown to affect avoidance responding in shock-mediated situations, and (2) different hormones of the pituitary-adrenal axis are involved in the control of aggressivenessand avoidance-of-attack. Agonistic behavior Hypophysectomy
Avoidance-of-attack Adrenalectomy
Pituitary
Adrenals
AN animal's hormonal state appears to influence both the form and intensity of its agonistic responses [10, 12, 13, 14, 15]. Although much has been learned about the role of hormonal factors in the control of aggressive behaviors, relatively little is known about the role of endocrine factors in other components of agonistic responding, such as submissive or avoidance reactions. We recently [ 15] studied the effects of some pituitaryadrenocortical manipulations on the avoidance component of agonistic behavior using a passive avoidance procedure (avoidance-of-attack) in which the aversive stimulus is attack by a trained fighter. Those studies showed that both decreases and increases in pituitary-adrenocortical activity levels lead to increased tendencies to avoid attack. The designs used in our earlier studies, however, did not permit a separation of the effects of ACTH from those of corticosterone. Therefore, we designed these two studies to separate the effects of ACTH and corticosterone on avoidance-of-attack. We used combinations of experimental manipulations through which we could maintain the level of one hormone constant while varying the level of the other hormone.
ACTH
Corticosterone
EXPERIMENT 1 In our earlier studies [15], varying ACTH levels had a biphasic effect o n avoidance-of-attack in hypophysectomized mice: both low and high ACTH levels increased the retention of this avoidance response. In this experiment, we treated hypophysectomized mice with a range of corticosterone dosages and observed their avoidance responding. If corticosterone treatment is ineffective in restoring the avoidance responding of hypophysectomized mice, then ACTH must be necessary for the maintenance of normal avoidance responding in this agonistic situation. On the other hand, if increasing corticosterone levels without altering ACTH levels produces effects similar to those observed in our earlier study, then ACTH is not necessary; changes in corticosterone levels alone can account for pituitary-adrenal effects on avoidance-of-attack. METHOD
Animals and Apparatus The animals used in this study were 86 male, albino
1This research was a portion of a master's thesis completed by the first author. Supported in part by Grants No. MH-23870 from NIMH and No. BMS-75-08120 from NSF. Steroid suspending vehicle was generously provided by Drug Research and Development Chemotherapy, N.C.I. The authors thank M. Breen, A. Dempster, B. Neck, J. Politch, and T. Robinson for their technical assistance, and D. Candland, O. Floody and R. Tarpy for their critical comments on an earlier version of this manuscript. 2Now at the Department of Psychology, Temple University. 3Address reprint requests to: Alan I. Leshner, Department of Psychology, BuckneUUniversity, Lewisburg, PA 17837. 297
298
MOYER AND LESHNER
CD-1 mice, 6 weeks old at the time surgery. The mice were housed singly in Wahmann home cages with free access to food and water for 2 weeks prior to testing. All animals were maintained on a 5% sucrose solution postoperatively [11]. The colony room was maintained on a 12 hr light/dark cycle, and the room temperature was controlled at 24 +- I°C. The avoidance testing apparatus was 2 connected chambers that could be separated by a guillotine door. One chamber (start chamber)measured 13.0 × 5.5 × 7.5 cm, and the other chamber (attack chamber) measured 23.5 × 30.3 x 29.0 cm. The animals were randomly assigned to 1 of 5 experimental conditions or one control condition. The experimental animals all were hypophysectomized (hypox) and received either 0.0 (n = 14), 75 (n = 15), 150 (n = 13), 225 (n = 16), or 300 (n -- 14) mcg/day corticosterone (Nutritional Biochemicals, Corp.) subcutaneously in 0.10 cc steroid suspending vehicle. The control animals were all sham-hypophysectomized and treated daily with a 0.10 cc steroid suspending vehicle placebo (Sham-Placebo). All injections were administered for 1 week prior to testing and until the termination of the experiment. All surgical
procedures were carried out by the supplier, Charles l~iver Mouse Farms, Wilmington, Mass. Avoidance-of-attack was assessed using a passive avoidance situation in which the aversive stimulus was attack by a trained fighter. Fighters were trained according to the procedure outlined by Scott and Frederics0n [17]. Passive avoidance conditioning was conducted by placing the experimental animals into the start chamber, opening the guillotine door, and recording the latency for the test animal to enter the attack chamber. Immediately on entering the attack chamber, the trained fighter was released from a small restraining cage and the test animal was subjected to 5 sec of physical attack. The animals were then separated and the test animal was returned to the start chamber. This procedure was repeated until the test animal remained in the start chamber for 5 rnin (passive avoidance criterion). Twenty-four hr following acquisition of the avoidance response, the test animal was returned to the start chamber, the guillotine door was opened, and the latency for the test animal to enter the attack chamber was recorded (retention test latency). The number of trials required to achieve the passive avoidance criterion and the
(a)
12
(b)
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150
225
300
Cort. Dosage ( mcg/day)
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150
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225
300
Cort. Dosage (mcg/day)
FIG. 1. The effects of corticosterone on mean +_standard error (a) trials needed to achieve the passive avoidance criterion and (b) retention test latency of hypophysectomized mice.
PITUITARY-ADRENAL EFFECTS ON AVOIDANCE retention test latency were used as indices of avoidance responding. RESULTS Figure la presents the mean (+- standard error) number of trials required to achieve the passive avoidance criterion for each group. A one-way analysis of variance revealed no significant differences among the groups (F(5,79) = 1.85, p>0.05). Thus neither hypox nor treatment of hypox mice with corticosterone at any dosage level affected acquisition performance. Figure l b presents the mean (-+ standard error) retention test latency for each group. A one-way analysis of variance revealed a significant difference among the groups (F(5,79) = 2.81, p 0 . 0 5 ; ACTH vs Placebo: F(1,59) = 0.78, p>0.05; and Controlled-Corticosterone x ACTH interaction: F(1,59) = 1.30, p>0.05. Thus, none of the experimental manipulations affected acquisition performance. Figure 2b presents the mean (_+ standard error) retention test latencies for each group. Two-way analysis of variance revealed a significant two-way interaction of the major factors, Controlled-Corticosterone x ACTH ( F ( 1 , 5 9 ) = 5.21, p
Pituitary-Adrenal Effects on Avoidance-of-Attack in Mice: Separation of the Effects of ACTH and Corticosterone I JOHN A. MOYER 2 AND ALAN I. LESHNER 3
Department o f Psychology, Bucknell University, Lewisburg PA 17837 (Received 18 August 1975) MOYER, J. A. AND A. I. LESHNER. Pituitary.adrenal effects on avoidance.of-attack in mice: separation of the effects of ACTH and corticosterone. PHYSIOL. BEHAV. 17(2) 297-301, 1976. - Two experiments were conducted to separate the effects of ACTH and corticosterone on avoidance-of-attack. In Experiment 1, treatment with corticosterone restored the avoidance performance of hypophysectomized mice to normal levels. In Experiment 2, ACTH treatment increased the avoidance retention of intact mice but did not affect the avoidance responding of mice which were adrenalectomized and treated with a replacement dosage of corticosterone (controlled-corticosterone condition). These two studies suggest that corticosterone is the critical hormone of the pituitary-adrenal axis in the control of avoidance responding in agonistic situations. In addition, these studies demonstrate that (I) ACTH and corticosterone affect avoidance-of-attack differently from the way they have been shown to affect avoidance responding in shock-mediated situations, and (2) different hormones of the pituitary-adrenal axis are involved in the control of aggressivenessand avoidance-of-attack. Agonistic behavior Hypophysectomy
Avoidance-of-attack Adrenalectomy
Pituitary
Adrenals
AN animal's hormonal state appears to influence both the form and intensity of its agonistic responses [10, 12, 13, 14, 15]. Although much has been learned about the role of hormonal factors in the control of aggressive behaviors, relatively little is known about the role of endocrine factors in other components of agonistic responding, such as submissive or avoidance reactions. We recently [ 15] studied the effects of some pituitaryadrenocortical manipulations on the avoidance component of agonistic behavior using a passive avoidance procedure (avoidance-of-attack) in which the aversive stimulus is attack by a trained fighter. Those studies showed that both decreases and increases in pituitary-adrenocortical activity levels lead to increased tendencies to avoid attack. The designs used in our earlier studies, however, did not permit a separation of the effects of ACTH from those of corticosterone. Therefore, we designed these two studies to separate the effects of ACTH and corticosterone on avoidance-of-attack. We used combinations of experimental manipulations through which we could maintain the level of one hormone constant while varying the level of the other hormone.
ACTH
Corticosterone
EXPERIMENT 1 In our earlier studies [15], varying ACTH levels had a biphasic effect o n avoidance-of-attack in hypophysectomized mice: both low and high ACTH levels increased the retention of this avoidance response. In this experiment, we treated hypophysectomized mice with a range of corticosterone dosages and observed their avoidance responding. If corticosterone treatment is ineffective in restoring the avoidance responding of hypophysectomized mice, then ACTH must be necessary for the maintenance of normal avoidance responding in this agonistic situation. On the other hand, if increasing corticosterone levels without altering ACTH levels produces effects similar to those observed in our earlier study, then ACTH is not necessary; changes in corticosterone levels alone can account for pituitary-adrenal effects on avoidance-of-attack. METHOD
Animals and Apparatus The animals used in this study were 86 male, albino
1This research was a portion of a master's thesis completed by the first author. Supported in part by Grants No. MH-23870 from NIMH and No. BMS-75-08120 from NSF. Steroid suspending vehicle was generously provided by Drug Research and Development Chemotherapy, N.C.I. The authors thank M. Breen, A. Dempster, B. Neck, J. Politch, and T. Robinson for their technical assistance, and D. Candland, O. Floody and R. Tarpy for their critical comments on an earlier version of this manuscript. 2Now at the Department of Psychology, Temple University. 3Address reprint requests to: Alan I. Leshner, Department of Psychology, BuckneUUniversity, Lewisburg, PA 17837. 297
298
MOYER AND LESHNER
CD-1 mice, 6 weeks old at the time surgery. The mice were housed singly in Wahmann home cages with free access to food and water for 2 weeks prior to testing. All animals were maintained on a 5% sucrose solution postoperatively [11]. The colony room was maintained on a 12 hr light/dark cycle, and the room temperature was controlled at 24 +- I°C. The avoidance testing apparatus was 2 connected chambers that could be separated by a guillotine door. One chamber (start chamber)measured 13.0 × 5.5 × 7.5 cm, and the other chamber (attack chamber) measured 23.5 × 30.3 x 29.0 cm. The animals were randomly assigned to 1 of 5 experimental conditions or one control condition. The experimental animals all were hypophysectomized (hypox) and received either 0.0 (n = 14), 75 (n = 15), 150 (n = 13), 225 (n = 16), or 300 (n -- 14) mcg/day corticosterone (Nutritional Biochemicals, Corp.) subcutaneously in 0.10 cc steroid suspending vehicle. The control animals were all sham-hypophysectomized and treated daily with a 0.10 cc steroid suspending vehicle placebo (Sham-Placebo). All injections were administered for 1 week prior to testing and until the termination of the experiment. All surgical
procedures were carried out by the supplier, Charles l~iver Mouse Farms, Wilmington, Mass. Avoidance-of-attack was assessed using a passive avoidance situation in which the aversive stimulus was attack by a trained fighter. Fighters were trained according to the procedure outlined by Scott and Frederics0n [17]. Passive avoidance conditioning was conducted by placing the experimental animals into the start chamber, opening the guillotine door, and recording the latency for the test animal to enter the attack chamber. Immediately on entering the attack chamber, the trained fighter was released from a small restraining cage and the test animal was subjected to 5 sec of physical attack. The animals were then separated and the test animal was returned to the start chamber. This procedure was repeated until the test animal remained in the start chamber for 5 rnin (passive avoidance criterion). Twenty-four hr following acquisition of the avoidance response, the test animal was returned to the start chamber, the guillotine door was opened, and the latency for the test animal to enter the attack chamber was recorded (retention test latency). The number of trials required to achieve the passive avoidance criterion and the
(a)
12
(b)
300
250
:~ 200 (,.) E
i-o
_1 "~_
~
6
15C
E
o
o
,.e-, ~0
"-" lOC
i-
I--
I
r~
50
~, ShamPlacebo
i
l
I
I
I
0
75
150
225
300
Cort. Dosage ( mcg/day)
l;
ShamPlacebo
!
,
0
75
,
150
I
!
225
300
Cort. Dosage (mcg/day)
FIG. 1. The effects of corticosterone on mean +_standard error (a) trials needed to achieve the passive avoidance criterion and (b) retention test latency of hypophysectomized mice.
PITUITARY-ADRENAL EFFECTS ON AVOIDANCE retention test latency were used as indices of avoidance responding. RESULTS Figure la presents the mean (+- standard error) number of trials required to achieve the passive avoidance criterion for each group. A one-way analysis of variance revealed no significant differences among the groups (F(5,79) = 1.85, p>0.05). Thus neither hypox nor treatment of hypox mice with corticosterone at any dosage level affected acquisition performance. Figure l b presents the mean (-+ standard error) retention test latency for each group. A one-way analysis of variance revealed a significant difference among the groups (F(5,79) = 2.81, p 0 . 0 5 ; ACTH vs Placebo: F(1,59) = 0.78, p>0.05; and Controlled-Corticosterone x ACTH interaction: F(1,59) = 1.30, p>0.05. Thus, none of the experimental manipulations affected acquisition performance. Figure 2b presents the mean (_+ standard error) retention test latencies for each group. Two-way analysis of variance revealed a significant two-way interaction of the major factors, Controlled-Corticosterone x ACTH ( F ( 1 , 5 9 ) = 5.21, p
