- Email: [email protected]
Androgens and agonistic behavior in mice: Relevance to aggression and irrelevance to avoidance-of-attack
Physiology & Behavior, Vol. 15, pp. 695-699. Pergamon Press and Brain Research Pubi., 1975. Printed in the U.S.A.
Androgens and Agonistic Behavior in Mice: Relevance to Aggression and Irrelevance to Avoidance-of-Attack ' A L A N I. L E SH N ER A N D JOHN A. MOYER 2
Department o f Psychology, Bucknell Universi~, Lewisburg, PA 1 7837 (Received 30 January 1975)
LESHNER, A. I. AND J. A. MOYER. Androgens and agonistic behavior in mice: relevance to aggression and irrelevance to avoidance-of-attack. PHYSIOL. BEHAV. 15 (6) 695-699, 1975. - Two experiments were conducted to clarify the role of the androgens in determining the form and intensity of agonistic responses. Although varying androgen levels affected aggressiveness, changes in the levels of these gonadal hormones did not affect the tendency to avoid attack. Thus, although some hormones affect both the aggression and avoidance components of agonistic responding, the androgens affect only the aggression component. The implications of these findings for an understanding of the relationship among agonistie responses were considered. Agonistic behavior
Aggression
Avoidance-of-attack
Androgens
THE hormonal state of an individual influences both the form and the intensity of its responses to agonistic stimuli. For example, mice with either very low or very high levels of the pituitary-adrenocortical hormones react relatively nonaggressively to and readily avoid agonistic stimuli, whereas mice with intermediate levels of these hormones react quite aggressively to and do not readily avoid the same stimuli [7, 10, 15, 16]. Although it has been established that the androgens are important in the control of aggressive responding [4, 5, 12], little is known about the role of the androgens in the control of other agonistic responses, such as submissive responses. Because submissive responses are not emitted readily by naive animals [17,18], and because social experience effects might interfere with direct analysis of hormonal effects on submissive responding in experienced animals (e.g., [9]), it has been difficult to study directly the influence of hormonal states on submissiveness. We recently [ 15] studied the effects of pituitary-adrenocortical hormone manipulations on the avoidance component of submissive responding, avoidance-of-attack, by using a passive avoidance situation where the aversive stimulus was attack by a trained fighter. This passive avoidance procedure is used again in these studies to examine the role of the androgens in determining an animal's readiness to avoid attack. In this way we can begin to analyze at least indirectly the role of the androgens in determining an animal's readiness to become submissive. Experiment 1
Testosterone
Castration
examines the effects of withdrawal of the androgens and replacement therapy with a single androgen dosage on aggressive and avoidance responding, and Experiment 2 extends the findings of Experiment 1 by examining the effects of a wide range of androgen dosages on the avoidance behavior of castrated mice. The findings of these two studies also should further our understanding of the relationship between aggressiveness and the tendency to avoid in agonistic situations. Studies of intact animals [17, 18, 20] and animals with different pituitary-adrenocortical hormone levels [ I0, 15, 16] have suggested that aggressiveness and the tendency to avoid (fearfulness) are inversely correlated behavioral characteristics. If aggressiveness and the tendency to avoid agonistic stimuli are related in this way, Experiments 1 and 2 should show that androgen manipulations affect aggressive and avoidance behaviors oppositely. If the androgens do not affect these behaviors oppositely, however, aggressiveness and the tendency to avoid agonistic stimuli cannot be considered truly opposite response characteristics. EXPERIMENT 1 The first experiment examined the effects of castration and replacement therapy with testosterone propionate on aggressive and avoidance responses to agonistic stimuli. Aggression was assessed using a "standard o p p o n ent " test [6,8], and avoidance-of-attack was assessed uslng a passive
1Supported in part by Grant No. MH-23870 from NIMH. The authors thank M. Breen, R. Culberson, T. Gabrilovitch, B. Nock and J. Politch for their technical assistance, and D. Candland, O. Floody and R. M. Tarpy for their critical comments on an earlier version of this manuscript. 2Now at the Department of Psychology, Temple University. 695
696
LESHNER AND MOYER
avoidance situation where the aversive stimulus was attack by a trained fighter [15]. METHOD
Animals and Apparatus The animals in this study were 90 male, albino CFW mice, 6 weeks old at the time of surgery. They were housed singly in Wahmann home cages and were given free access to food and water throughout the experiment. The colony room was maintained on a 12 hr light/dark cycle, and the room temperature was controlled at 24 + I°C. The aggression testing arena was made of wood with a Plexiglas front panel and an opaque guillotine door that divided the chamber into halves. The arena measured 30.5 × 30.5 x 45.7 cm. The avoidance testing apparatus was two connected chambers that could be separated by a guillotine door. The start chamber measured 13.0 × 5.5 × 7.5 cm, and the attack chamber measured 23.5 × 30.3 × 29.0 cm.
Procedure The animals were randomly assigned (preoperatively)to 1 of 6 groups formed according to a two-way (3 × 2) factorial design. There were 3 operation-hormone conditions: sham-castrated and placebo-treated (Sham), castrated and placebo-treated (Castr), and castrated and treated with 150 ~g/day testosterone propionate in 0.10 cc peanut oil (Castr + TP); and 2 sequences of testing: aggression-tested first and then avoidance-tested (A-F), and avoidance-tested first and then aggression-tested (F-A). The animals were anesthetized for surgery with a combination of sodium pentobarbital (40 mg/kg) and chloral hydrate (150 mg/kg). Castration and shamcastration were performed through incisions in the scrotum. Daily injections were begun immediately following surgery, and the animals were kept in isolation for 4 weeks prior to behavioral testing. The dosage of testosterone propionate used here (150 ug/day) was selected because it had been shown in earlier studies (e.g., [12,16]) to be effective in restoring the aggressiveness of castrated mice. Four weeks following surgery, the animals in the A-F testing sequence condition were aggression tested, and those in the F-A testing sequence condition were tested for avoidance-of-attack. One week following aggression testing the A-F animals were tested for avoidance-of-attack, and one week following avoidance-testing the F-A animals were tested for aggressiveness. Aggression testing was conducted once a day for 3 days. On each testing day, each animal received its appropriate injection 1 hr prior to testing. The animals were tested for aggressiveness against an unfamiliar olfactory bulbectomized mouse. This type of opponent has been shown to be nonaggressive, but to elicit high levels of aggressiveness from other mice [12,14]. Each experimental animal encountered a different opponent on each of the three testing days. Each test began with a 2 min adaptation period during which the experimental animal and the opponent were placed on opposite sides of the guillotine door of the aggression testing arena. Following this adaptation period, the door was lifted, and the animals were allowed to interact for a 5 min encounter period. During the encounter period, the latency to the first attack and the number of attacks, bites, chases of the opponent, tail rattles, and sniffs of the opponent were recorded for the experimental
animal. The chamber was cleaned thoroughly between encounters to remove residual odors. Aggressiveness was rated using a composite aggression score [20] according to which attacks and bites are weighted by a factor of 2, chases and tail rattles by a factor of 1, and sniffs by a factor of 1/2. These values were summed for each encounter, and the mean of each animal's scores in the three encounters was used as the measure of that animal's aggressiveness. Avoidance-of-attack was assessed using a passive avoidance task in which the aversive stimulus is attack by a trained fighter [15]. Passive avoidance conditioning was begun by placing the experimental animal in the start chamber, opening the guillotine door, and recording the latency for the test animal to enter the attack chamber. Immediately upon entering the attack chamber, the test animal was subjected to 5 sec of physical attack by the trained fighter. The animals then were separated and the experimental animal was returned to the start chamber. This procedure was repeated until the experimental animal remained in the start chamber without entering the attack chamber for 5 min (passive avoidance criterion). Twentyfour hours following acquisition of the avoidance response, the experimental animal was returned to the start chamber, the guillotine door was opened, and the latency to enter the attack chamber was recorded (retention test latency). The number of trials needed to achieve the passive avoidance criterion and the retention test latency were used as measures of avoidance responding (cf. 15). RESULTS There were no significant effects of the testing order on any of the measures. Therefore, the groups were combined for data presentation (n=30 in each case). Figure la presents the mean (-+ standard error)composite aggression score for the animals in each operationhormone condition. Analysis of variance revealed that castration significantly reduced aggressiveness below the levels of both the Sham and Castr + TP groups, which did not differ from each other, F(2,84) = 20.32, p<0.001. Figures lb and lc present the results of the avoidance test. Analyses of variance revealed no significant effect of the operation-hormone treatments on either the number of trials needed to achieve the passive avoidance criterion, F(2,84) = 2.26, p>0.05, or the retention test latency, F(2,84) = 1.36, p>0.05. EXPERIMENT 2 Experiment 1 showed that withdrawal of the androgens by castration leads to a reduction in aggressiveness, and that replacement therapy with testosterone propionate is capable of restoring the aggressiveness of castrated mice [4,5]. This study also showed that the tendency to avoid attack is not affected by changes in the level of the androgens. These two findings suggest that the level of the androgens is critical to one component of agonistic responding, aggressiveness, but irrelevant to another component, the tendency to avoid attack. Because of the potential importance of this latter finding to an understanding of the relationship between hormones and agonistic behavior, this study of the effects of androgens on avoidance-of-attack was repeated using a wider range of testosterone propionate dosages in order to examine more broadly the relationship of androgen levels to avoidance-responding in agonistic situations.
ANDROGENS AND AGONISTIC BEHAVIOR
697
(a)
uo ~n
(c)
(b)
I0-
50
40
t
o
m
o
a. 2 0 E o
_i
-
200
-
I
c o
. u
0
250
/
I
6-
150 -
t
tl
o
4~
¢-
Ill
o
O
I--
°~
4-
I00
-
¢p 4~
¢D
IX
O~
Ix
IX
I0
50-
2-
sham
I
I
costr.
castr, +TP
sham
Treatment
castr,
castr, +TP
sham.
Treatment
castr,
castr. +TP
Treatment
FIG. 1. The effects of androgen manipulations on mean +-standard error (a) aggressiveness, (b) trials needed to achieve the passive avoidance criterion, and (c) retention test latencies. METHOD
Animals and Apparatus The animals in this study were 59 male, albino CFW mice, 6 weeks old at the time of surgery. The mice were housed singly in Wahmann home cages and were given free access to food and water throughout the experiment. 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 the same as in Experiment 1.
Procedure The animals were randomly assigned (preoperatively)to 1 of 4 experimental groups or one control group. The animals in the control group (n=l 1) were sham-castrated and treated once a day with a 0.10 cc peanut oil placebo. All animals in experimental groups were castrated, and they were treated with I of 4 dosages of testosterone propiohate: 0 (n = 13), 75 (n = 13), 150 ( n = 13), or 225 ( n = 9) t~g/day. All injections were begun immediately following surgery. Three weeks following surgery, the mice were avoidance-tested as described in Experiment 1. RESULTS Figure 2a presents the mean (-+ standard error) number
of trials needed to achieve the passive avoidance criterion for each group, and Fig. 2b presents the mean (+ standard error) retention test latency for each group. Analyses of variance revealed no significant differences among the groups on either measure (for trials measure: F(4,54) = 0.69, p>0.05; for retention test latency measure: F(4,54) = 1.67, p> 0.05).
DISCUSSION These two experiments show that although the level of the androgens is important to aggressive responding (cf. [4, 5, 12]), the level of these hormones is irrelevant to the tendency to avoid attack. Specifically, Experiments 1 and 2 showed that manipulating the levels of the androgens does not affect either the rate of acquisition or the retention of a passive avoidance response for which the motivating stimulus is attack by a trained fighter. Adult androgen levels also have been shown to be irrelevant to avoidance responding in shock-mediated situations. Castration in adulthood has no effect on shuttle-box avoidance [2], Sidman avoidance [ 19], jump-up avoidance [21], and step-down passive avoidance behaviors [13]. On the other hand, prepubertal castration does affect avoidance responding [13,21], and the sex difference in avoidance learning and performance is modified by changes in the perinatal androgen environment [ 3 ]. Therefore, a more
698
LESHNER AND MOYER
(a)
JO,~-
25C
(b)
-
200 -
I
t'0 ° ~
t
g J
L--
Im
c
0 e,-
0
Go
100
° m
Ix
Ix 50
2-
,t.
I
I
I
I
s h a m ee
0
75
150
225
TP Dosage (mcg~lay)
t~
,
I
I
I
s h ~ 13 ~ t
0
75
150
225
TO Dosage (mcg/day)
FIG. 2. The effects of androgen levels on mean ± standard error (a) trials needed to achieve the passive avoidance criterion and (b) retention test latencies. complete understanding of the role of the androgens in avoidance-of-attack requires an examination of the effects of perinatal and prepubertal androgen manipulations on adult avoidance responding in agonistic situations. The findings of these two studies help clarify the role of endocrine factors in determining the form and intensity of agonistic responses. Earlier studies [ 15,16] have shown that the pituitary-adrenocortical hormones affect both the aggression and avoidance components of agonistic behavior. Animals with either very low or very high levels of the pituitary-adrenocortical hormones are predisposed to react relatively nonaggressively to and with a heightened tendency to avoid agonistic stimuli. Experiments 1 and 2, however, suggest that the androgens affect only one component of agonistic responding, the aggression component. Thus, an animal with low androgen levels should be relatively nonaggressive but need not be submissive or avoid readily, and, therefore, should react relatively blandly to agonistic stimuli. The findings of Barfield, Busch and Wallen's [ 1] study of the agonistic behavior of castrated rats supports this expectation. They found that although castrated rats typically are nonaggressive, they are not readily submissive, and will fight back successfully if provoked. Thus, the pituitary-adrenocortical hormones affect the form and intensity of both the aggression and avoidance components of agonistic responding, but the
androgens affect only the intensity of aggressive responses and do not affect avoidance responses to agonistic stimuli. The findings of these two studies also clarify the relationship between aggressiveness and the tendency to avoid attack (fearfulness) in agonistic situations. Earlier studies of intact animals [ 17, 18, 20] and animals with different levels of the pituitary-adrenocortical hormones [15] have suggested that aggressiveness and avoidance tendencies are inversely correlated: the more aggressive an animal the less it avoids, and the reverse. Experiment 1 shows, however, that aggressiveness and avoidance tendencies are not inversely related across differences in androgen levels. Although castrated mice are less aggressive than intact mice, they do not avoid agonistic stimuli more readily. Thus, aggression and avoidance probably are relatively independent components of agonistic behavior that interact at high levels of aggressiveness (as in the intact animal [20]) or at extremely high levels of avoidance tendencies (as in submissive animals [ 17,18 ] and those with very high or very low levels of pituitary-adrenocortical activity [15]). At low levels of aggressiveness, however, aggressiveness and the tendency to avoid are not always inversely correlated. If nonaggressiveness is induced by altering pituitary-adrenocortical activity levels, the animal will tend to avoid agonistic stimuli readily. If nonaggressiveness is induced by reducing androgen levels, however, the
ANDROGENS AND AGONISTIC BEHAVIOR
699
a n i m a l will n o t avoid readily. T h u s , highly aggressive animals p r o b a b l y d o n o t avoid readily a n d t h o s e t h a t avoid readily are n o t very aggressive, b u t nonaggressive a n i m a l s
n e e d n o t avoid readily. W h e t h e r or n o t nonaggressive animals will avoid agonistic stimuli readily d e p e n d s on t h e way in w h i c h nonaggressiveness has b e e n i n d u c e d .
REFERENCES 1. Barfield, R. J., D. E. Busch and K. Wallen. Gonadal influence on agonistic behavior in the male domestic rat. Hormones Behav. 3: 247-259, 1972. 2. Beatty, W. W. and P. A. Beatty. Hormonal determinants of sex differences in avoidance behavior and reactivity to electric shock in the rat. J. comp. physiol. Psychol. 73: 4 4 6 - 4 5 5 , 1970. 3. Beatty, W. W. and P. A. Beatty. Effects of neonatal testosterone on the acquisition of an active avoidance response in genotypically female rats. Psychon. Sci. 19: 315-316, 1970. 4. Beeman, E. A. The effect of male hormone on aggressive behavior in mice. Physiol. Zool. 20: 373-405, 1947. 5. Bevan, J. M., W. Bevan and B. F. Williams. Spontaneous aggressiveness in young castrate C3H mice treated with three dose levels of testosterone. Physiol. Zool. 31: 2 8 4 - 2 8 8 , 1958. 6. Brain, P. F. and N. W. NoweU. Some observations of intermale aggression testing in albino mice. Communs Behav. Biol. 5: 7 - 1 7 , 1970. 7. Brain, P. F., N. W. Nowell and A. Wouters. Some relationships between adrenal function and the effectiveness of a period of isolation in inducing intermale aggression in albino mice. Physiol. Behav. 6: 2 7 - 2 9 , 1971. 8. Brain, P. F. and A. Poole. Some studies on the use of "standard opponents" in intermale aggression testing in TT albino mice. Behaviour 50: 100-110, 1974. 9. Burge, K. G. and D. A. Edwards. The adrenal gland and the pre- and post-castration aggressive behavior of male mice. Physiol. Behav. 7: 885-888, 1971. 10. Candland, D. K. and A. I. Leshner. A model of agonistic behavior: endocrine and autonomic correlates. In: Limbic and Autonomic Nervous Systems Research, edited by L. V. DiCara. New York: Plenum, 1974, pp. 137-163. 11. Denenberg, V. H., E. Gaulin-Kremer, R. Gandelman and M. X. Zarrow. The development of standard stimulus animals for mouse (Mus musculus) aggression testing by means of olfactory bulbectomy. Anim. Behav. 21: 590-598, 1973.
12. Edwards, D. A. Early androgen stimulation and aggressive behavior in male and female mice. Physiol. Behav. 4: 333-338, 1969. 13. Klemm, W. R. ECS effects on one-trial avoidance behavior in intact and gonadectomized male rats. Communs Behav. Biol. 4: 5 5 - 5 8 , 1969. 14. Leshner, A. I. and A. E. Johnson. Effects of adrenalectomy on the aggressiveness of neonataUy androgenized female mice. Physiol. Behav. 13: 703-705, 1974. 15. Leshner, A. I., J. A. Moyer and W. A. Walker. Pituitaryadrenocortical activity and avoidance-of-attack in mice. Physiol. Behav. 15: 6 8 9 - 6 9 3 , 1975. 16. Leshner, A. I., W. A. Walker, A. E. Johnson, J. S. Kelling, S. J. Kreisler and B. B. Svare. Pituitary adrenocortical activity and intermale aggressiveness in isolated mice. Physiol. Behav. 11: 705-711, 1973. 17. Seward, J. P. Aggressive behavior in the rat I. General characteristics; age and sex differences. J. comp. Psychol. 38: 175-197, 1945. 18. Seward, J. P. Aggressive behavior in the rat IV. Submission as determined by conditioning, extinction and disuse. J. comp. Psychol. 39: 5 1 - 7 6 , 1946. 19. Stenn, P. G. and I. Barofsky. Testosterone and acquisition of Sidman avoidance in male rats. Paper presented at meetings of Eastern Psychological Association, New York, 197 I. 20. Svare, B. B. and A. I. Leshner. Behavioral correlates of intermale aggression and grouping in mice. J. comp. physiol. Psychol. 85: 203-210, 1973. 21. Telegdy, G., J. Hadnagy and K. Liss~ik. The effects of gonads on conditioned avoidance behaviour of rats. Acta physiol. hung. 33: 4 3 9 - 4 4 6 , 1968.
Androgens and Agonistic Behavior in Mice: Relevance to Aggression and Irrelevance to Avoidance-of-Attack ' A L A N I. L E SH N ER A N D JOHN A. MOYER 2
Department o f Psychology, Bucknell Universi~, Lewisburg, PA 1 7837 (Received 30 January 1975)
LESHNER, A. I. AND J. A. MOYER. Androgens and agonistic behavior in mice: relevance to aggression and irrelevance to avoidance-of-attack. PHYSIOL. BEHAV. 15 (6) 695-699, 1975. - Two experiments were conducted to clarify the role of the androgens in determining the form and intensity of agonistic responses. Although varying androgen levels affected aggressiveness, changes in the levels of these gonadal hormones did not affect the tendency to avoid attack. Thus, although some hormones affect both the aggression and avoidance components of agonistic responding, the androgens affect only the aggression component. The implications of these findings for an understanding of the relationship among agonistie responses were considered. Agonistic behavior
Aggression
Avoidance-of-attack
Androgens
THE hormonal state of an individual influences both the form and the intensity of its responses to agonistic stimuli. For example, mice with either very low or very high levels of the pituitary-adrenocortical hormones react relatively nonaggressively to and readily avoid agonistic stimuli, whereas mice with intermediate levels of these hormones react quite aggressively to and do not readily avoid the same stimuli [7, 10, 15, 16]. Although it has been established that the androgens are important in the control of aggressive responding [4, 5, 12], little is known about the role of the androgens in the control of other agonistic responses, such as submissive responses. Because submissive responses are not emitted readily by naive animals [17,18], and because social experience effects might interfere with direct analysis of hormonal effects on submissive responding in experienced animals (e.g., [9]), it has been difficult to study directly the influence of hormonal states on submissiveness. We recently [ 15] studied the effects of pituitary-adrenocortical hormone manipulations on the avoidance component of submissive responding, avoidance-of-attack, by using a passive avoidance situation where the aversive stimulus was attack by a trained fighter. This passive avoidance procedure is used again in these studies to examine the role of the androgens in determining an animal's readiness to avoid attack. In this way we can begin to analyze at least indirectly the role of the androgens in determining an animal's readiness to become submissive. Experiment 1
Testosterone
Castration
examines the effects of withdrawal of the androgens and replacement therapy with a single androgen dosage on aggressive and avoidance responding, and Experiment 2 extends the findings of Experiment 1 by examining the effects of a wide range of androgen dosages on the avoidance behavior of castrated mice. The findings of these two studies also should further our understanding of the relationship between aggressiveness and the tendency to avoid in agonistic situations. Studies of intact animals [17, 18, 20] and animals with different pituitary-adrenocortical hormone levels [ I0, 15, 16] have suggested that aggressiveness and the tendency to avoid (fearfulness) are inversely correlated behavioral characteristics. If aggressiveness and the tendency to avoid agonistic stimuli are related in this way, Experiments 1 and 2 should show that androgen manipulations affect aggressive and avoidance behaviors oppositely. If the androgens do not affect these behaviors oppositely, however, aggressiveness and the tendency to avoid agonistic stimuli cannot be considered truly opposite response characteristics. EXPERIMENT 1 The first experiment examined the effects of castration and replacement therapy with testosterone propionate on aggressive and avoidance responses to agonistic stimuli. Aggression was assessed using a "standard o p p o n ent " test [6,8], and avoidance-of-attack was assessed uslng a passive
1Supported in part by Grant No. MH-23870 from NIMH. The authors thank M. Breen, R. Culberson, T. Gabrilovitch, B. Nock and J. Politch for their technical assistance, and D. Candland, O. Floody and R. M. Tarpy for their critical comments on an earlier version of this manuscript. 2Now at the Department of Psychology, Temple University. 695
696
LESHNER AND MOYER
avoidance situation where the aversive stimulus was attack by a trained fighter [15]. METHOD
Animals and Apparatus The animals in this study were 90 male, albino CFW mice, 6 weeks old at the time of surgery. They were housed singly in Wahmann home cages and were given free access to food and water throughout the experiment. The colony room was maintained on a 12 hr light/dark cycle, and the room temperature was controlled at 24 + I°C. The aggression testing arena was made of wood with a Plexiglas front panel and an opaque guillotine door that divided the chamber into halves. The arena measured 30.5 × 30.5 x 45.7 cm. The avoidance testing apparatus was two connected chambers that could be separated by a guillotine door. The start chamber measured 13.0 × 5.5 × 7.5 cm, and the attack chamber measured 23.5 × 30.3 × 29.0 cm.
Procedure The animals were randomly assigned (preoperatively)to 1 of 6 groups formed according to a two-way (3 × 2) factorial design. There were 3 operation-hormone conditions: sham-castrated and placebo-treated (Sham), castrated and placebo-treated (Castr), and castrated and treated with 150 ~g/day testosterone propionate in 0.10 cc peanut oil (Castr + TP); and 2 sequences of testing: aggression-tested first and then avoidance-tested (A-F), and avoidance-tested first and then aggression-tested (F-A). The animals were anesthetized for surgery with a combination of sodium pentobarbital (40 mg/kg) and chloral hydrate (150 mg/kg). Castration and shamcastration were performed through incisions in the scrotum. Daily injections were begun immediately following surgery, and the animals were kept in isolation for 4 weeks prior to behavioral testing. The dosage of testosterone propionate used here (150 ug/day) was selected because it had been shown in earlier studies (e.g., [12,16]) to be effective in restoring the aggressiveness of castrated mice. Four weeks following surgery, the animals in the A-F testing sequence condition were aggression tested, and those in the F-A testing sequence condition were tested for avoidance-of-attack. One week following aggression testing the A-F animals were tested for avoidance-of-attack, and one week following avoidance-testing the F-A animals were tested for aggressiveness. Aggression testing was conducted once a day for 3 days. On each testing day, each animal received its appropriate injection 1 hr prior to testing. The animals were tested for aggressiveness against an unfamiliar olfactory bulbectomized mouse. This type of opponent has been shown to be nonaggressive, but to elicit high levels of aggressiveness from other mice [12,14]. Each experimental animal encountered a different opponent on each of the three testing days. Each test began with a 2 min adaptation period during which the experimental animal and the opponent were placed on opposite sides of the guillotine door of the aggression testing arena. Following this adaptation period, the door was lifted, and the animals were allowed to interact for a 5 min encounter period. During the encounter period, the latency to the first attack and the number of attacks, bites, chases of the opponent, tail rattles, and sniffs of the opponent were recorded for the experimental
animal. The chamber was cleaned thoroughly between encounters to remove residual odors. Aggressiveness was rated using a composite aggression score [20] according to which attacks and bites are weighted by a factor of 2, chases and tail rattles by a factor of 1, and sniffs by a factor of 1/2. These values were summed for each encounter, and the mean of each animal's scores in the three encounters was used as the measure of that animal's aggressiveness. Avoidance-of-attack was assessed using a passive avoidance task in which the aversive stimulus is attack by a trained fighter [15]. Passive avoidance conditioning was begun by placing the experimental animal in the start chamber, opening the guillotine door, and recording the latency for the test animal to enter the attack chamber. Immediately upon entering the attack chamber, the test animal was subjected to 5 sec of physical attack by the trained fighter. The animals then were separated and the experimental animal was returned to the start chamber. This procedure was repeated until the experimental animal remained in the start chamber without entering the attack chamber for 5 min (passive avoidance criterion). Twentyfour hours following acquisition of the avoidance response, the experimental animal was returned to the start chamber, the guillotine door was opened, and the latency to enter the attack chamber was recorded (retention test latency). The number of trials needed to achieve the passive avoidance criterion and the retention test latency were used as measures of avoidance responding (cf. 15). RESULTS There were no significant effects of the testing order on any of the measures. Therefore, the groups were combined for data presentation (n=30 in each case). Figure la presents the mean (-+ standard error)composite aggression score for the animals in each operationhormone condition. Analysis of variance revealed that castration significantly reduced aggressiveness below the levels of both the Sham and Castr + TP groups, which did not differ from each other, F(2,84) = 20.32, p<0.001. Figures lb and lc present the results of the avoidance test. Analyses of variance revealed no significant effect of the operation-hormone treatments on either the number of trials needed to achieve the passive avoidance criterion, F(2,84) = 2.26, p>0.05, or the retention test latency, F(2,84) = 1.36, p>0.05. EXPERIMENT 2 Experiment 1 showed that withdrawal of the androgens by castration leads to a reduction in aggressiveness, and that replacement therapy with testosterone propionate is capable of restoring the aggressiveness of castrated mice [4,5]. This study also showed that the tendency to avoid attack is not affected by changes in the level of the androgens. These two findings suggest that the level of the androgens is critical to one component of agonistic responding, aggressiveness, but irrelevant to another component, the tendency to avoid attack. Because of the potential importance of this latter finding to an understanding of the relationship between hormones and agonistic behavior, this study of the effects of androgens on avoidance-of-attack was repeated using a wider range of testosterone propionate dosages in order to examine more broadly the relationship of androgen levels to avoidance-responding in agonistic situations.
ANDROGENS AND AGONISTIC BEHAVIOR
697
(a)
uo ~n
(c)
(b)
I0-
50
40
t
o
m
o
a. 2 0 E o
_i
-
200
-
I
c o
. u
0
250
/
I
6-
150 -
t
tl
o
4~
¢-
Ill
o
O
I--
°~
4-
I00
-
¢p 4~
¢D
IX
O~
Ix
IX
I0
50-
2-
sham
I
I
costr.
castr, +TP
sham
Treatment
castr,
castr, +TP
sham.
Treatment
castr,
castr. +TP
Treatment
FIG. 1. The effects of androgen manipulations on mean +-standard error (a) aggressiveness, (b) trials needed to achieve the passive avoidance criterion, and (c) retention test latencies. METHOD
Animals and Apparatus The animals in this study were 59 male, albino CFW mice, 6 weeks old at the time of surgery. The mice were housed singly in Wahmann home cages and were given free access to food and water throughout the experiment. 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 the same as in Experiment 1.
Procedure The animals were randomly assigned (preoperatively)to 1 of 4 experimental groups or one control group. The animals in the control group (n=l 1) were sham-castrated and treated once a day with a 0.10 cc peanut oil placebo. All animals in experimental groups were castrated, and they were treated with I of 4 dosages of testosterone propiohate: 0 (n = 13), 75 (n = 13), 150 ( n = 13), or 225 ( n = 9) t~g/day. All injections were begun immediately following surgery. Three weeks following surgery, the mice were avoidance-tested as described in Experiment 1. RESULTS Figure 2a presents the mean (-+ standard error) number
of trials needed to achieve the passive avoidance criterion for each group, and Fig. 2b presents the mean (+ standard error) retention test latency for each group. Analyses of variance revealed no significant differences among the groups on either measure (for trials measure: F(4,54) = 0.69, p>0.05; for retention test latency measure: F(4,54) = 1.67, p> 0.05).
DISCUSSION These two experiments show that although the level of the androgens is important to aggressive responding (cf. [4, 5, 12]), the level of these hormones is irrelevant to the tendency to avoid attack. Specifically, Experiments 1 and 2 showed that manipulating the levels of the androgens does not affect either the rate of acquisition or the retention of a passive avoidance response for which the motivating stimulus is attack by a trained fighter. Adult androgen levels also have been shown to be irrelevant to avoidance responding in shock-mediated situations. Castration in adulthood has no effect on shuttle-box avoidance [2], Sidman avoidance [ 19], jump-up avoidance [21], and step-down passive avoidance behaviors [13]. On the other hand, prepubertal castration does affect avoidance responding [13,21], and the sex difference in avoidance learning and performance is modified by changes in the perinatal androgen environment [ 3 ]. Therefore, a more
698
LESHNER AND MOYER
(a)
JO,~-
25C
(b)
-
200 -
I
t'0 ° ~
t
g J
L--
Im
c
0 e,-
0
Go
100
° m
Ix
Ix 50
2-
,t.
I
I
I
I
s h a m ee
0
75
150
225
TP Dosage (mcg~lay)
t~
,
I
I
I
s h ~ 13 ~ t
0
75
150
225
TO Dosage (mcg/day)
FIG. 2. The effects of androgen levels on mean ± standard error (a) trials needed to achieve the passive avoidance criterion and (b) retention test latencies. complete understanding of the role of the androgens in avoidance-of-attack requires an examination of the effects of perinatal and prepubertal androgen manipulations on adult avoidance responding in agonistic situations. The findings of these two studies help clarify the role of endocrine factors in determining the form and intensity of agonistic responses. Earlier studies [ 15,16] have shown that the pituitary-adrenocortical hormones affect both the aggression and avoidance components of agonistic behavior. Animals with either very low or very high levels of the pituitary-adrenocortical hormones are predisposed to react relatively nonaggressively to and with a heightened tendency to avoid agonistic stimuli. Experiments 1 and 2, however, suggest that the androgens affect only one component of agonistic responding, the aggression component. Thus, an animal with low androgen levels should be relatively nonaggressive but need not be submissive or avoid readily, and, therefore, should react relatively blandly to agonistic stimuli. The findings of Barfield, Busch and Wallen's [ 1] study of the agonistic behavior of castrated rats supports this expectation. They found that although castrated rats typically are nonaggressive, they are not readily submissive, and will fight back successfully if provoked. Thus, the pituitary-adrenocortical hormones affect the form and intensity of both the aggression and avoidance components of agonistic responding, but the
androgens affect only the intensity of aggressive responses and do not affect avoidance responses to agonistic stimuli. The findings of these two studies also clarify the relationship between aggressiveness and the tendency to avoid attack (fearfulness) in agonistic situations. Earlier studies of intact animals [ 17, 18, 20] and animals with different levels of the pituitary-adrenocortical hormones [15] have suggested that aggressiveness and avoidance tendencies are inversely correlated: the more aggressive an animal the less it avoids, and the reverse. Experiment 1 shows, however, that aggressiveness and avoidance tendencies are not inversely related across differences in androgen levels. Although castrated mice are less aggressive than intact mice, they do not avoid agonistic stimuli more readily. Thus, aggression and avoidance probably are relatively independent components of agonistic behavior that interact at high levels of aggressiveness (as in the intact animal [20]) or at extremely high levels of avoidance tendencies (as in submissive animals [ 17,18 ] and those with very high or very low levels of pituitary-adrenocortical activity [15]). At low levels of aggressiveness, however, aggressiveness and the tendency to avoid are not always inversely correlated. If nonaggressiveness is induced by altering pituitary-adrenocortical activity levels, the animal will tend to avoid agonistic stimuli readily. If nonaggressiveness is induced by reducing androgen levels, however, the
ANDROGENS AND AGONISTIC BEHAVIOR
699
a n i m a l will n o t avoid readily. T h u s , highly aggressive animals p r o b a b l y d o n o t avoid readily a n d t h o s e t h a t avoid readily are n o t very aggressive, b u t nonaggressive a n i m a l s
n e e d n o t avoid readily. W h e t h e r or n o t nonaggressive animals will avoid agonistic stimuli readily d e p e n d s on t h e way in w h i c h nonaggressiveness has b e e n i n d u c e d .
REFERENCES 1. Barfield, R. J., D. E. Busch and K. Wallen. Gonadal influence on agonistic behavior in the male domestic rat. Hormones Behav. 3: 247-259, 1972. 2. Beatty, W. W. and P. A. Beatty. Hormonal determinants of sex differences in avoidance behavior and reactivity to electric shock in the rat. J. comp. physiol. Psychol. 73: 4 4 6 - 4 5 5 , 1970. 3. Beatty, W. W. and P. A. Beatty. Effects of neonatal testosterone on the acquisition of an active avoidance response in genotypically female rats. Psychon. Sci. 19: 315-316, 1970. 4. Beeman, E. A. The effect of male hormone on aggressive behavior in mice. Physiol. Zool. 20: 373-405, 1947. 5. Bevan, J. M., W. Bevan and B. F. Williams. Spontaneous aggressiveness in young castrate C3H mice treated with three dose levels of testosterone. Physiol. Zool. 31: 2 8 4 - 2 8 8 , 1958. 6. Brain, P. F. and N. W. NoweU. Some observations of intermale aggression testing in albino mice. Communs Behav. Biol. 5: 7 - 1 7 , 1970. 7. Brain, P. F., N. W. Nowell and A. Wouters. Some relationships between adrenal function and the effectiveness of a period of isolation in inducing intermale aggression in albino mice. Physiol. Behav. 6: 2 7 - 2 9 , 1971. 8. Brain, P. F. and A. Poole. Some studies on the use of "standard opponents" in intermale aggression testing in TT albino mice. Behaviour 50: 100-110, 1974. 9. Burge, K. G. and D. A. Edwards. The adrenal gland and the pre- and post-castration aggressive behavior of male mice. Physiol. Behav. 7: 885-888, 1971. 10. Candland, D. K. and A. I. Leshner. A model of agonistic behavior: endocrine and autonomic correlates. In: Limbic and Autonomic Nervous Systems Research, edited by L. V. DiCara. New York: Plenum, 1974, pp. 137-163. 11. Denenberg, V. H., E. Gaulin-Kremer, R. Gandelman and M. X. Zarrow. The development of standard stimulus animals for mouse (Mus musculus) aggression testing by means of olfactory bulbectomy. Anim. Behav. 21: 590-598, 1973.
12. Edwards, D. A. Early androgen stimulation and aggressive behavior in male and female mice. Physiol. Behav. 4: 333-338, 1969. 13. Klemm, W. R. ECS effects on one-trial avoidance behavior in intact and gonadectomized male rats. Communs Behav. Biol. 4: 5 5 - 5 8 , 1969. 14. Leshner, A. I. and A. E. Johnson. Effects of adrenalectomy on the aggressiveness of neonataUy androgenized female mice. Physiol. Behav. 13: 703-705, 1974. 15. Leshner, A. I., J. A. Moyer and W. A. Walker. Pituitaryadrenocortical activity and avoidance-of-attack in mice. Physiol. Behav. 15: 6 8 9 - 6 9 3 , 1975. 16. Leshner, A. I., W. A. Walker, A. E. Johnson, J. S. Kelling, S. J. Kreisler and B. B. Svare. Pituitary adrenocortical activity and intermale aggressiveness in isolated mice. Physiol. Behav. 11: 705-711, 1973. 17. Seward, J. P. Aggressive behavior in the rat I. General characteristics; age and sex differences. J. comp. Psychol. 38: 175-197, 1945. 18. Seward, J. P. Aggressive behavior in the rat IV. Submission as determined by conditioning, extinction and disuse. J. comp. Psychol. 39: 5 1 - 7 6 , 1946. 19. Stenn, P. G. and I. Barofsky. Testosterone and acquisition of Sidman avoidance in male rats. Paper presented at meetings of Eastern Psychological Association, New York, 197 I. 20. Svare, B. B. and A. I. Leshner. Behavioral correlates of intermale aggression and grouping in mice. J. comp. physiol. Psychol. 85: 203-210, 1973. 21. Telegdy, G., J. Hadnagy and K. Liss~ik. The effects of gonads on conditioned avoidance behaviour of rats. Acta physiol. hung. 33: 4 3 9 - 4 4 6 , 1968.