Ventromedial hypothalamic lesions and cholinergic control of female sexual behavior

Ovariectomized female rats received bilateral electrolytic or sham lesions of the ventromedial nucleus of the hypothalamus (VMNH). They were tested for sexual receptivity in response to estrogen (EB) and progesterone (P) treatment. Following this they were treated with a small dose of EB and tested for their response to intraventricular microinjection of a muscarinic cholinergic agonist or a vehicle solution. Those animals with lesions involving almost the entire extent of the VMNH displayed an impaired response to EB and P and to the agonist. Lesions which spared 30-50% of the anterior portion of the VMNH did not result in an impairment to EB and P or to the agonist. It is suggested that the disruption of the cholinergic induction of receptivity by such lesions was due either to destruction of estrogen receptors located in cell bodies in the VMNH which send projections to extrahypothalamic cholinergic neurons or to estrogen- and cholinergic-responsive cells intrinsic to the VMNH which are critical for the expression of sexual receptivity.