Prostaglandins play an important role in diurnal changes of tuberoinfundibular dopaminergic neuronal activity and prolactin secretion in ovariectomized, estrogen-treated rats

Intracerebroventricular injection of prostaglandins (PGs) has long been sho wn to stimulate the secretion of prolactin (PRL). The action of specific PG and the underlying mechanism, however, remain inconclusive, In this study, we evaluated the involvement of PGs in the diurnal changes of the tuberoin fundibular dopaminergic (TIDA) neurons and PRL secretion in ovariectomized (OVX) rats treated with estrogen (E-2). Prior treatment of indomethacin (50 mg/kg, subcutaneous) for 24 h significantly prevented the afternoon decrea se of TIDA neuronal activity and blocked the PRL surge. Intracerebroventric ular injection of PGE(1) (5 mug/3 mul/rat) at 1000 h significantly lowered the activity of TIDA neurons, while similar treatment of PGE, was without e ffect. In OVX + E-2 rats pretreated with indomethacin, PGE, given at 15, bu t not 30 or 180 min before decapitation at 1500 h significantly reversed th e effects of indomethacin on TIDA neuronal activity, while the blocked PRL surge was not reversed. The PGs also exhibited a stimulatory effect on nigr ostriatal dopamine IDA) neurons with PGE, being the most effective agent. T hese results indicate that endogenous PGs play a significant role in the co ntrol of central DA neurons, especially the diurnal changes of TIDA neurona l activity and PRL secretion in OVX + E-2 rats. (C) 2001 Elsevier Science I nc.