Ibotenic Acid-Induced Lesions of the Medial Zona Incerata Decrease Lordosis Behavior in the Female Rat

In order to examine the role of the medial zona incerta in female sexual behavior, ovariectomized estrogen and progesterone treated female rats were tested for sexual receptivity following bilateral injections of the selective neurotoxin, ibotenic acid (3 ugjO.3 ul dissolved in phosphate-buffered saline) directly into the medial zona incerta. These injections produced a significant attenuation of lordosis behavior in highly receptive females when compared to saline injected controls (shams). This decrease in sexual receptivity was also reflected in a significant increase of rejections of male mount attempts. Additionally, the frequency of hopping, darting and ear wiggling was significantly decreased in ibotenic injected females when compared to saline injected controls. Consistent with previous studies these lesions produced a transient impairment of drinking behavior (hypodipsia) typical of rats with large electrolytic lesions of the ZI. This is the first report to demonstrate that mZI neurons playa role in mediating sexual receptivity fn the female rat. Collectively, these results suggest that the functional integrity of the mZI is of crucial importance for the VM H-MCG mediated expression of sexual receptivity in the female rat. Ibotenic acid induced lesions of the medial zona incerta, however, did not abolish sexual behavior.