Participation of the lower brain stem in induction of preovulatory gonadotropin surges in female rats.

Publisher Website
Google Scholar
Abstract
The role of the lower brain stem in controlling preovulatory gonadotropin surges was investigated in female rats under acute experimental conditions. Electrolytic lesions or diethyldithiocarbamate implantations in the ventrolateral part of the medulla oblongata (VLMO), which were carried out at 1100-1330 h on the day of proestrus, resulted in a blockade of the preovulatory surges of lutropin, FSH and prolactin subsequent ovulation. Such treatments in the dorsomedial part of the medulla oblongata did not affect gonadotropin surges or ovulation. By means of electrolytic lesions in the VLMO, norepinephrine concentrations were significantly reduced in the preoptic-anterior hypothalamic area at 1700-1800 h on proestrus, though they did not change in the mid-posterior hypothalamus. Electrochemical stimulations of the suprachiasmatic part of the preoptic area or norepinephrine injections into the 3rd ventricle at 1400-1500 h on proestrus in animals with VLMO lesions succeeded in inducing gonadotropin surges and ovulation. The lower brain stem apparently is involved in the induction of preovulatory gonadotropin surges, and the process may be mediated by the ascending noradrenergic system which originates in the VLMO.