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 ovariectomized (OVX) estrogen-primed rats was investigated. The enhancement of lordosis following repeated coital stimulation was significantly reduced in the mAMY-lesioned rats as compared with the sham-operated controls. Double labeling immunocytochemistry of the brain of the repeatedly mated females for Fos protein and luteinizing hormone-releasing hormone (LHRH) revealed that a significantly lower percentage of the LHRH neurons in the mAMY-lesioned females exhibited Fos immunoreactivity than the controls. This suggests that bilateral destruction of the mAMY suppresses the activation of the LHRH neuronal system following repeated mating. Furthermore, the correlation between the number of Fos-positive LHRH neurons and lordosis-to-mount ratio in the sham-females was significant, while a similar comparison in mAMY-lesioned females was not significant. Since LHRH is reported to enhance lordosis behavior in OVX estrogen-primed rats, it appears likely that the effects of mAMY on lordosis are mediated through the LHRH neuronal system. The results further support the involvement of the accessory olfactory system in the mating-induced enhancement of lordosis behavior in female rats.