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-1, there was an abrupt increase of 17beta-oestradiol plasma level and a significant increase in dopaminergic neural activity in preoptic anterior-hypothalamic area, without changes in luteinizing hormone serum level, in comparison with the saline injected group. Animals injected with atropine-sulphate showed a second increase in dopaminergic neural activity in the preoptic anterior-hypothalamic at 1100 of dioestrus-2 (atropine-sulphate 0.471 +/- 0.7 vs. saline 0.241 +/- 0.03, p < 0.01). In this group of animals, the preovulatory surges of 17beta-oestradiol and luteinizing hormone occurred simultaneously at 1700 h of the expected day of oestrus; spontaneous ovulation was delayed until the expected day of dioestrus-1. Present results suggest that during dioestrus-1 there is a functional relationship between the cholinergic and dopaminergic systems in preoptic anterior-hypothalamic area, regulating the release of luteinizing hormone resulting in ovulation.