The source of an aggression-promoting olfactory cue, released by alpha-melanocyte stimulating hormone, in the male mouse.

Earlier experiments demonstrated that the injection of alpha-melanocyte stimulating hormone into one mouse of a male pair results, 15 minutes later, in the release of an olfactory cue which increases the aggressive behavior of its partner. Because the preputial gland, whose activity is dependent upon testosterone and alpha-MSH, produces an odor which stimulates aggressive behavior, its relationship with the MSH response was investigated. Preputialectomy failed to prevent the release of the odor by an MSH-treated subordinate mouse of a pair, although preputialectomy of one mouse of a naive pair resulted in it later displaying higher levels of aggression than its intact partner, which then became subordinate. Swabs taken from the perineal region of alpha-MSH-injected subordinates, contained more aggression-promoting factor than swabs taken from saline injected subordinates. It is concluded that the short-term effects of alpha-MSH upon aggression are probably via a product of glandular or urinary origin other than the preputial gland and that the latter is more involved in long-term aggression-promoting cues.