THE ROLE OF THE MEDIAL NUCLEUS OF AMYGDALA IN THE MATING-INDUCED ENHANCEMENT OF LORDOSIS IN FEMALE RATS - THE INTERACTION WITH LUTEINIZING-HORMONE-RELEASING HORMONE NEURONAL SYSTEM

The effect of bilateral lesion of the medial nucleus of amygdala (mAMY ) on the mating-induced enhancement of lordosis behavior in ovariectom ized (OVX) estrogen-primed rats was investigated. The enhancement of l ordosis following repeated coital stimulation was significantly reduce d in the mAMY-lesioned rats as compared with the sham-operated control s. Double labeling immunocytochemistry of the brain of the repeatedly mated females for Fos protein and luteinizing hormone-releasing hormon e (LHRH) revealed that a significantly lower percentage of the LHRH ne urons in the mAMY-lesioned females exhibited Fos immunoreactivity than the controls. This suggests that bilateral destruction of the mAMY su ppresses the activation of the LHRH neuronal system following repeated mating. Furthermore, the correlation between the number of Fos-positi ve LHRH neurons and lordosis-to-mount ratio in the sham-females was si gnificant, while a similar comparison in mAMY-lesioned females was not significant. Since LHRH is reported to enhance lordosis behavior in O VX estrogen-primed rats, it appears likely that the effects of mAMY on lordosis are mediated through the LHRH neuronal system. The results f urther support the involvement of the accessory olfactory system in th e mating-induced enhancement of lordosis behavior in female rats.