ACTIVITY OF PEPTIDERGIC NEURONS IN THE AMYGDALA DURING SEXUAL-BEHAVIOR IN THE MALE-RAT

The medial amygdaloid nucleus (AME) occupies a central position in the circuitry that organizes sexual behavior in the male rat. It receives a projection from olfactory structures that are activated by pheromon al cues indicating receptivity in the female and projects in turn to l imbic and hypothalamic structures that are thought to organize aspects of coitus. Electrical stimulation of the AME elicits a behavioral sta te that is indistinguishable by several measures from the post-ejacula tory interval. We used chronic single-unit recording techniques to det ermine the behavioral conditions in which the AME is normally active. We found that the cells indeed fired selectively during the presence o f a receptive female, but that the discharge considerably anticipated copulation in time. We propose that sexual behavior in the male rat is a reaction chain of fixed action patterns, each one acting as a relea ser for the next. The AME mediates an early event in the reaction chai n, namely recognition of the receptive female, but electrical activati on of the AME causes the reaction chain to proceed to its culminating behavior, the post-ejaculatory interval.