Title & Introduction
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Offense, Defense & Patrol/Marking
Page 2
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Neural Circuitry & Motivational Mechanisms
Page 3
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How Circulating Hormones May Affect Behavior
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Pregnancy and Lactation
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ACTH, etc.
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Reproductive States
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Conclusion
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References
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ACTH AND CORTICOSTEROIDS
Activation of the pituitary-adrenal axis and their hormones ACTH and corticosteroids have been implicated in the increased submissiveness and decreased offense shown by male muroid rodents after repeated defeat. Leshner and colleagues performed a series of experiments from which they concluded that the effects on offense are due to ACTH and those on submission are due to corticosteroids. Leshner, Walker, Johnson, Kelling, Kreisler, and Svare (1973) reported that supranormal levels of ACTH reduce the frequency of intermale fighting (i.e., offense) of mice despite manipulations that hold constant other hormones, including androgens and corticosteroids. The effect of ACTH on offense is complex, however, being facilitative when acute and inhibitory when chronic (Brain & Evans, 1977; Matte, 1979). Corticosteroids have been reported to increase the passive avoidance by a mouse of a previously victorious opponent (Moyer & Leshner, 1976) and to increase the rate of submissive upright posture in response to attack (Nock & Leshner, 1976). The effect is not due to ACTH, since there is no effect if ACTH levels are altered and corticosteroid levels are kept constant (Moyer & Leshner, 1976). The effects are also not due to altered levels of androgens (Leshner & Moyer, 1975).
The site of action of corticosteroids and ACTH on the neural substrates of submission and offense have not been directly investigated. Corticosteroids are taken up by neurons in the hippocampus, septum, amygdala, and pyriform and cingulate cortex (Stumpf & Sar, 1976). These are the structures that have been implicated by lesion and brain stimulation studies in the control of submissive behavior (Figure 2 in Adams, 1979a). ACTH, on the other hand, does not seem to cross the blood-brain barrier at normal concentrations in the circulation (Krieger & Liotta, 1979), so the mechanism of its effects on the neural substrate of offense is problematic.
It appears likely that the pituitary-adrenal hormones do not affect the neural substrates of defense, except insofar as the behavior of a subordinate animal is shifted from defense to submission in confrontation with a conspecific, as noted above. In a situation that does not involve a con specific opponent, the novel open-field test situation, the suppression of pituitary-adrenal activity by hypothalamic implants of hydrocortisone does not affect freezing behavior in rats (Stern, Erskine, & Levine, 1973).
In summary, it is possible to account for most of the data regarding the affects of normal levels of ACTH and corticosteroids on agonistic behavior by supposing that corticosteroids facilitate the consociate modulator and/or neural structures that project to it.
EPINEPHRINE AND NOREPINEPHRINE
Since epinephrine and norepinephrine are secreted by the adrenal medulla in response to various motivating stimuli of defense - including handling and transfer to a strange cage, painful shock, and anticipation of painful shock (McCarty & Kopin, 1978) and fighting, defeat, and stimuli associated with defeat (Hucklebridge & Nowell, 1974) - it might be expected that these hormones would facilitate defense or submissive behaviors. As far as I know, however, there are no studies investigating this question in social interactions. Instead, there are indirect data from studies on avoidance or escape from shock, indicating that these behaviors may be enhanced by the hormones of the adrenal medulla. Removal of the adrenal medulla retards active avoidance (Conner & Levine, 1969) and injection of epinephrine may enhance active avoidance (Conner & Levine, 1969), escape (Kamano, 1968), or passive avoidance (Leventhal & Killackey, 1968).
In cold-blooded vertebrates, the hormones of the adrenal medulla may have a critical facilitative effect on offense and defense mediated by a rise in body temperature. It is possible that the secretion of hormones from the adrenal medulla into the peripheral circulation may contribute to the rapid and dramatic rise in body temperature that makes a cold-blooded animal ready for effective flight or attack (Engbretson & Livezey, 1972).
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