Effects of lesions of putative LHRH-containing pathways and midbrain nuclei on lordotic behavior and luteinizing hormone release in ovariectomized rats.

Lordotic behavior and LH release were measured in ovariectomized rats after radiofrequency lesions of the midbrain central gray (MCG), interpeduncular nucleus (IPN), mammillary bodies (MMM), stria medullaris (SM), or fasciculus retroflexus (FR), areas which are reported to contain immunoactive luteinizing hormone-releasing hormone (LHRH), a hypothalamic decapeptide which has been implicated in the neuroendocrine control of lordosis. SM and FR lesions increased lordotic behavior after estrone-priming. IPN lesions reversed an increase in lordotic behavior seen in IPN sham-lesioned animals treated with estrone. MCG lesions decreased lordotic behavior after estrone-priming, while MMM lesions had no effect. None of the lesions significantly altered lordotic responsiveness when animals were repeatedly mated or were treated with estrone + progesterone. There was a slight decrease in serum LH levels in SM animals. Results are interpreted in terms of the role of LHRH in control of lordosis, and of midbrain mechanisms for influencing lordotic behavior.