Hypothalamic serotoninergic receptors in negative feed-back regulation of pituitary-testicular axis in rats.

Complete deafferentation of mediobasal hypothalamus did not prevent a decrease of testosterone level in plasma of male rats after a hemicastration. From this finding a conclusion on a relative autonomy of hypophysiotropic area of hypothalamus in regulating the blood testosterone level by a negative feed-back mechanism was drawn. However, the administration of serotonin (200 micrograms in 10 microliters) into the lateral ventricle in rat males bearing a complete deafferentation of mediobasal hypothalamus resulted in a blocking of compensatory increase of testosterone level in plasma after a hemicastration as compared to either intact or just deafferented animals in which the level of testosterone reached the initial value at 72 h after a hemicastration. Finally, the experiments with the injections of serotonin (2.5 micrograms in 2 microliters) into various areas of mediobasal hypothalamus showed that the site of inhibitory effect of stimulated serotoninergic receptors on the mechanism of negative feed-back in pituitary-testicular system may be located in arcuate nuclei.