Effect of crude rat hypothalamic extract on serum gonadotropin and prolactin levels in normal and orchidectomized male rats.

Abstract

Serum LH, FSH, and prolactin concentrations were determined by radioimmunoassay in etherized rats immediately prior to, and 8 min after, the iv injection of hypothalamic extract. There was a significant increase in serum LH in normal and in acute and chronic castrate animals injected with hypothalamic extract, whereas cerebral cortical extract failed to alter serum LH levels. Quantitatively the elevation of LH observed in chronic castrate rats following injection of hypothalamic extract was greater than that observed in normal or acute castrate animals. Hypothalamic extract produced a significant decrease in serum prolactin levels in normal rats, but failed to decrease serum prolactin in acute and chronic castrates to a statistically significant degree. There was a highly significant correlation between preinjection prolactin levels and the decrease of serum prolactin in all types of animals studied. An estimate of prolactin halftime was obtained from the preinjection and postinjection serum levels by ass...