Lesions of the accessory olfactory bulb decrease lordotic responsiveness and reduce mating-induced c-fos expression in the accessory olfactory system.

The effect of bilateral lesion of the accessory olfactory bulb (AOB) on the mating-induced enhancement of sexual receptivity was investigated in ovariectomized (OVX) female rats. Lesions of the AOB significantly reduced the lordosis-to-mount (L/M) ratio in mating tests conducted 20 to 50 days after the lesion but L/M ratios at earlier (10 days) and later (51-90 days) time periods were not affected. The decrease in L/M was accompanied by a reduction in the number of c-fos immunopositive cells in the medial amygdala (mAMYG) and bed nucleus of the stria terminalis (BNST) measured after 3 h of repetitive mating. In the mAMYG, the reduction in c-fos immunoreactivity was correlated to the L/M ratio as well as to the number of intromissions received during the mating tests. The results suggest that information processed from the AOB to the mAMYG and the BNST is important for facilitation of lordosis behavior, and that the mAMYG may integrate information from the AOB with ascending input activated during copulatory behavior to regulate receptivity.