Nuclear receptor estrogen complex in the pineal gland. Modulation by sympathetic nerves

Abstract

Pineal nuclear receptor estradiol complex determined by the 3H-estradiol exchange assay exhibited a Kd = 0.42 nM. Its concentration was maximal at proestrus and after administering 2-20 microgram of estradiol to spayed rats. It was also detected in 6-day-old rats, before full maturation of pineal sympathetic nerves is attained. Superior cervical ganglionectomy caused nuclear receptor estrogen complexes (NREC) to decrease by 48 and 65% 5 and 14 days later; estradiol administration brought about increases of complex levels (1.9-2.3-fold) which were significantly smaller than in control or decentralized rats (3.4-3.9-fold). The time course of accumulation and retention of nuclear complexes was not affected by ganglionectomy. Isoproterenol restored the basal levels of NREC, but inhibited the effects of estradiol on complex accumulation; propranolol, administered simultaneously with estradiol also inhibited estrogen effects on the pineal. Estradiol incubation in vitro increased pineal nuclear receptor hormone levels and enhanced the conversion of serotonin into melatonin and 5-methoxytryptophol; no changes in hydroxyindole-O-methyl transferase (HIOMT) activity were detected. These data support the conclusion that accumulation and retention of pineal NREC are under partial dependence upon sympathetic nerves.