Heterotypic sexual behavior in male rats after lesions in different amygdaloid nuclei.

Previous studies showed that different amygdaloid nuclei are involved in the control of lordosis behavior in female rats. The objective of the present study was to determine whether these nuclei played a role in the control of lordosis behavior in the male rat. Lesions were placed into different amygdaloid nuclei in male rats castrated as adults and primed with ovarian hormones. Lesions in the corticomedial amygdaloid nucleus completely suppressed lordosis behavior as expressed by the number of animals displaying lordosis responses to male mounts. By contrast extended lesions placed into the lateral amygdaloid nucleus (LN) remained without effects. Lesions placed in the very posterior part of the LN produced "hypersexuality" with a rise in the number of animals displaying lordosis responses and high LQ values. Lesions in the anterior part of the LN induced a decrease in the number of animals showing lordosis responses. The amygdala was then concluded to represent a functionally heterogeneous structure with different regions exerting opposite effects on the display of lordosis behavior in the male rat.