Effect of blockade of dopaminergic receptors on acetylcholine (Ach)-induced alterations of plasma gonadotropin and prolactin (Prl) in conscious ovariectomized rats.
The participation of acetylcholine (Ach) in the control of gonadotropin and prolactin (Prl) release was evaluated in intact or pimozide-treated conscious, ovariectomized (OVX) rats bearing indwelling 3rd ventricular and jugular venous cannulae by measuring plasma hormone levels by radioimmunoassay (RIA). Third ventricular injection of 20 or 100 microgram of atropine sulfate (2 microliter) significantly lowered plasma LH and Prl levels. Intraventricular injection of 20 microgram Ach (2 microliter) induced a significant elevation in plasma LH and suppression of Prl within 5 min of injection, whereas FSH was elevated only at 30 min. Intraventricular atropine blocked the action of Ach to elevate FSH and LH and to lower Prl. Intravenous pulse injection of atropine at a dose of 5 mg/kg suppressed plasma LH and Prl. Blockade of dopamine (DA) receptors with pimozide prevented the FSH- and LH-releasing and Prl-lowering effects of intraventricular Ach. The atropine-induced suppression of LH release was reversed and an elevation occurred in animals which were pretreated with the DA receptor blocker. Atropine injection had no effect on already elevated Prl levels in pimozide-pretreated animals. The results provide further evidence for cholinergic stimulation of gonadotropin and inhibition of Prl release and indicate that cholinergic control may be mediated via the tuberoinfundibular dopaminergic neurons.
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002369:Castration; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood*; D007276:Injections, Intraventricular; D007986:Luteinizing Hormone / Q000097:blood*; D010868:Pimozide / Q000494:pharmacology; D011388:Prolactin / Q000097:blood*; D011863:Radioimmunoassay; D051381:Rats; D011954:Receptors, Dopamine / Q000187:drug effects*
D011954:Receptors, Dopamine; D010868:Pimozide; D001285:Atropine; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D000109:Acetylcholine