Brief exposure to female odors "emboldens" male mice by reducing predator-induced behavioral and hormonal responses

In rodents, where chemical signals play a particularly important role in de termining intersexual interactions, various studies have shown that male be havior and physiology is sensitive to female odor cues. Here we examined th e effects of brief (I min) and more prolonged (60 min) preexposure to the o dors of a novel estrous female on the behavioral and hormonal responses of sexually experienced and inexperienced male mice, Mus musculus, to subseque nt predator (cat and weasel) odor exposure and potential predator risk. Bri ef, but not prolonged, preexposure to the odors of an estrous female decrea sed the aversion and avoidance responses of male mice to cat odor in a Y-ma ze preference test, with the extent of responses being affected by a males prior sexual experience. Similarly, brief, but not prolonged, preexposure t o female odors markedly attenuated the analgesic responses elicited in male mice by weasel odor. Brief exposure to a novel estrous female by itself ha d no significant immediate effects on either corticosterone or testosterone levels in the males. However, brief, but not prolonged, preexposure to the odors of an estrous female attenuated the marked increase in corticosteron e and decrease in testosterone that were induced in males by exposure to we asel odor. The decreases in aversive responses to, and effects of, predator odor exposure that are induced by brief exposure to a novel estrous female may reflect a greater risk taking and boldness in males that could directl y facilitate access to an immediately, and possibly transiently, available novel sexually receptive female. (C) 2001 Elsevier Science.