[The role of the dopaminergic system in the rat ovary]

Although many studies have been carried out on the dopaminergic system, little is known about the dopaminergic system in the ovary. The present study was undertaken to investigate the role of the dopamine (DA) system in ovarian function especially in steroidogenesis using rat ovaries. Ovarian cells from PMS-treated rats were incubated for 1 hour with or without DA or other drugs. DA, norepinephrine (NE) and isoproterenol (Iso) increased the levels of progesterone (P4) and cAMP in the media. D1 agonists (SKF38393, SKF82526-J, CY208-243) increased P4 secretion, whereas bromocriptine (D2 agonists) did not show any effect on the P4 level in the media. The effect of NE and Iso on P4 and cAMP levels was inhibited by propranolol (Pro; beta-blocker), while the increase of P4 and cAMP levels caused by DA or D1 agonists was suppressed by bulbocapnine (Bul; D1 antagonists). Propranolol (beta-blocker) or domperidone (D2 antagonists) did not affect the levels of P4 and cAMP. The presence of dopamine D1 receptor in the PMS-treated rat ovary was revealed by a kinetic study. The maximal number of binding sites (Bmax) of ovarian D1 receptor was 1.33fmol/mg tissue and the Kd value was 0.357nM. These results suggest that the DA system may physiologically play a role in the steroidogenesis in the ovary through D1 receptor.