Role of the anterior hypothalamus-preoptic area in the regulation of courtship behavior in the male Canadian red-sided garter snake (Thamnophis sirtalis parietalis): lesion experiments.

Lesions of the medial preoptic area and/or the ventromedial hypothalamus resulted in an abrupt and immediate decline in courtship behavior in adult male Canadian red-sided garter snakes (Thamnophis sirtalis parietalis). Lesions of the more anterior portions of the preoptic area resulted in a more gradual, delayed decline in courtship behavior. Male snakes sustaining lesions dorsal, ventral, or caudal to the anterior hypothalamus-preoptic area exhibited no change in courtship behavior relative to controls. Measurements of testis size, spermatogenic stage, and circulation levels of androgens revealed no differences between any of the groups. There were marked differences in the change in hematocrit over time between the groups. These results indicate that the anterior hypothalamus-preoptic area is involved in the control of courtship behavior in the adult male red-sided garter snake. Moreover, it is suggested that the stimulus affecting the anterior hypothalamus-preoptic area to activate courtship is temperature related.