Reinstatement of vaginal cycles in aged female rats.
Old constant estrous and young cycling control rats were injected with L-dopa, 200 mg/kg, for a period of 14 days. L-Dopa reinstated vaginal cycling in the old rats and it did not affect the vaginal cycling in young rats. Likewise, 200 mg/kg of L-tyrosine reinstated vaginal cycling. The effect of L-dopa on old rats was blocked by pimozide, by high doses of MK-486 and Ro 4-4602, and by fusaric acid. High doses of phenoxybenzamine or L-propranolol did not alter the L-dopa effect on old rats. A low dose of MK-486 or Ro 4-4602 increased the efficacy of L-dopa in reinstating vaginal cycling. These results suggest that L-dopa reinstates vaginal cycling in old rats by stimulating dopamine receptors. The possibility that a simultaneous stimulation of norepinephrine alpha and beta receptors and/or a decrease of central nervous system serotonin is necessary for this effect is discussed.
D000375:Aging / Q000187:drug effects*; D000818:Animals; D001545:Benserazide / Q000008:administration & dosage / Q000494:pharmacology; D002230:Carbidopa / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004971:Estrus / Q000187:drug effects*; D005260:Female; D005669:Fusaric Acid / Q000008:administration & dosage / Q000494:pharmacology; D007016:Hypophysectomy; D007980:Levodopa / Q000008:administration & dosage / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D010868:Pimozide / Q000008:administration & dosage / Q000494:pharmacology; D011247:Pregnancy; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D014443:Tyrosine / Q000494:pharmacology; D014621:Vagina / Q000166:cytology / Q000187:drug effects*
D010643:Phenoxybenzamine; D010868:Pimozide; D014443:Tyrosine; D007980:Levodopa; D001545:Benserazide; D011433:Propranolol; D005669:Fusaric Acid; D002230:Carbidopa