Male scent-induced analgesia in the deer mouse, Peromyscus maniculatus: involvement of benzodiazepine systems.

Exposure to bedding taken from the soiled home cage of an isolated male resident elicited a significant increase in the nociceptive responses of male deer mice, Peromyscus maniculatus artemisiae, from mixed sex pairs. The analgesia induced by exposure to the male scent was insensitive to the opiate antagonist, naloxone, and was blocked by either pre- or post-olfactory exposure injections of the benzodiazepine antagonist, Ro 15-1788, or agonist, diazepam. This non-opioid analgesia was of brief duration (15-30 min) and rapid onset, being evident after 1 min of exposure to the olfactory cues. Bedding treated with the novel odor of peppermint also induced analgesia in the deer mice. This analgesia was opioid mediated, being blocked by naloxone and insensitive to the benzodiazepine manipulations. Exposure to either fresh bedding, or the soiled bedding of another mixed sex pair of deer mice, had no significant effect on nociception. These results indicate that exposure of male deer mice to the olfactory cues associated with a potentially threatening individual (dominant/aggressive isolated male) elicits an analgesic response that involves alterations in the activity of benzodiazepine systems.