ROLE OF HYPOTHALAMIC DOPAMINERGIC RECEPTORS IN THE CONTROL OF LORDOSIS BEHAVIOR IN THE FEMALE RAT

The role of hypothalamic dopaminergic receptors in lordotic behavior was studied by infusing dopaminergic agents into either the medial preoptic area (MPOA), arcuate-ventromedial area (ARC-VM) or lateral hypothalamic area (LHA). Dopaminergic receptor stimulants, dopamine (DA) and apomorphine (APO), enhanced sexual receptivity when infused into the MPOA or ARC-VM in ovariectomized (OVX) rats primed with low doses of estrone. Under these conditions of low preinfusion receptivity (mean preinfusion L M=0.159), haloperidol (HALO), a dopaminergic receptor blocker, had no statistically significant effect upon lordotic behavior. Infusions of DA, APO, or HALO into the LHA also had no effect upon lordotic behavior in this model. A second experiment, in which OVX rats were primed with higher doses of estrone to maintain high preinfusion receptivity (mean preinfusion L M=0.869), was used to evaluate the effects of dopaminergic receptor blockade upon elevated sexual behavior. Using the second protocol, dopaminergic blockers, HALO and α flupenthixol, were observed to significantly depress lordotic behavior when infused into the MPOA and ARC-VM. In this model no alterations in sexual behavior were observed following MPOA or ARC-VM infusions of APO or the inactive stereoisomer of α flupenthixol, β fluqenthixol. Thus, the hypothalamic activation of dopaminergic receptors was shown to be stimulatory upon lordotic behavior. A third experiment was designed to evaluate the effects of dopaminergic receptor blockade upon luteinizing hormone-releasing hormone (LRH) enhanced lordotic behavior. In this protocol comparisons were made among the lordotic responses to MPOA and ARC-VM infusions of LRH, LRH with HALO and vehicle. Infusions of LRH into the MPOA and ARC-VM significantly enhanced lordotic behavior, whereas the addition of HALO to the LRH infusates abolished this response. It was proposed that hypothalamic dopaminergic receptor activation may contribute to the stimulatory effects of LRH upon lordotic behavior. © 1979.