Prostaglandins may participate in opioidergic and cholinergic control of the diurnal changes of tuberoinfundibular dopaminergic neuronal activity andserum prolactin level in ovariectomized, estrogen-treated rats

The roles of prostaglandins (PGs) involved in opioidergic, cholinergic, and serotonergic regulation of the diurnal changes of tuberoinfundibular dopam inergic (TIDA) neuronal activities were investigated in ovariectomized, est rogen-treated rats, Treatment with naloxone [10 mg/kg, intraperitoneal (i.p .)], atropine (5 mg/kg, i.p.), or ketanserin (10 mg/kg, i.p.) at either 120 0 or 1400 h prevented the afternoon decrease of TIDA neuronal activity and the prolactin (PRL) surge. Intracerebroventricular (i.c.v.) injection of PG E(1) (5 mug/3 mul/rat) at 1500 h significantly reversed the effects of nalo xone and atropine, but not that of ketanserin. In ovariectomized, estrogen- primed rats pretreated with indomethacin, i.c.v. injection of either nicoti ne (10 ng/rat) or fentanyl (10 ng/rat) failed to suppress the TIDA neuronal activity and to stimulate the PRL secretion. These data suggest that PG ma y be involved in opioidergic and cholinergic control of the diurnal changes of TIDA neuronal activity and the PRL secretion in ovariectomized (OVX) E-2 rats. (C) 2001 Elsevier Science Inc.