Possible role of dopamine in changes in LH and prolactin concentrations after experimentally induced hyperprolactinaemia in rats.
Nine-month-old female rats bearing an ectopic pituitary gland (from a litter-mate) under the right kidney capsule since day 30 of life and their sham-operated controls, were treated with a dopamine agonist (lysuride) or antagonist (metoclopramide). Plasma prolactin and LH levels were measured by double-antibody radioimmunoassays. Vaginal smears were taken before and during the treatment periods. Eight months after the operation, a significant (P less than 0.01) increase in basal prolactin levels together with a significant (P less than 0.05) reduction in LH values and permanent dioestrus occurred in the grafted animals when compared with controls. Lysuride treatment resulted in a marked reduction in plasma prolactin levels both in control and grafted rats over the whole 12 days of treatment, together with a partial restoration of plasma LH levels on day 1. From day 7 onwards a depression in LH values was again observed. Oestrous cycles were partially restored at the beginning of the treatment, but after 7 days dioestrus returned. Metoclopramide administration induced a significant (P less than 0.001) increase in basal prolactin levels in both grafted and control rats. Basal plasma LH values were unaffected in controls when compared with vehicle-treated animals. An increase could be seen in hyperprolactinaemic rats after 7 or 12 days of treatment however. The LH response to the administration of LH releasing hormone (LHRH) was greater in the experimental and control metoclopramide-treated rats when compared with vehicle-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D004298:Dopamine / Q000502:physiology*; D004873:Ergolines / Q000494:pharmacology*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D008090:Lisuride / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000097:blood*; D008787:Metoclopramide / Q000494:pharmacology*; D011388:Prolactin / Q000097:blood*; D051381:Rats; D011919:Rats, Inbred Strains; D014626:Vaginal Smears
D004873:Ergolines; D007987:Gonadotropin-Releasing Hormone; D011388:Prolactin; D007986:Luteinizing Hormone; D008090:Lisuride; D008787:Metoclopramide; D004298:Dopamine