Ovulation delay induced by blockade of the cholinergic system on dioestrus-1, is related to changes in dopaminergic activity of the preoptic anterior-hypothalamic area of the rat

One hour after the injection of 100 mg/kg of atropine-sulphate at 1300 h of dioestrus-l, there was an abrupt increase of 17 beta -oestradiol plasma le vel and a significant increase in dopaminergic neural activity in preoptic anterior-hypothalamic area, without changes in luteinizing hormone serum le vel, in comparison with the saline injected group, Animals injected with at ropine-sulphate showed a second increase in dopaminergic neural activity in the preoptic anterior-hypothalamic at 1100 of dioestrus-2 (atropine-sulpha te 0.471 +/- 0.7 vs. saline 0.241 +/- 0.03, p < 0.01), In this group of ani mals, the preovulatory surges of 17<beta>-oestradiol and luteinizing hormon e occurred simultaneously at 1700 h of the expected day of oestrus; spontan eous ovulation was delayed until the expected day of dioestrus-l. Present r esults suggest that during dioestrus-l there is a functional relationship b etween the cholinergic and dopaminergic systems in preoptic anterior-hypoth alamic area, regulating the release of luteinizing hormone resulting in ovu lation, (C) 2001 Elsevier Science Inc.