Studies on the hypotensive action of alpha-methyldopamine.
1. Intraventricular alpha-methyldopamine (50-200 mug) produced a dose-related fall in blood pressure in conscious spontaneously hypertensive rats. Pretreatment with intraventricular 6-hydroxydopamine prevented this hypotensive effect of alpha-methyldopamine. 2. The hypotensive effect of alpha-methyldopamine was prevented by intraventricular injection of phentolamine or desmethylimipramine, but not by intraperitoneal injection of haloperidol. 3. Pretreatment with U-14,624, a selective central dopamine-beta-hydroxylase inhibitor, prevented the hypotensive effect of alpha-methyldopamine. 4. Alpha-methyldopamine was considerably less potent than noradrenaline as a pressor agent in the pithed rat, but noradrenaline and alpha-methylnoradrenaline were found to be equipotent. 5. Alpha-methyldopamine (1-5 mg i.c.v.) reduced pressor responses elicited by electrical stimulation of the midbrain reticular formation in cats anaesthetized with chloralose. 6. It is concluded that the hypotensive action of alpha-methyldopamine in conscious animals involves intact central alpha-adrenergic neurones and a central adrenergic uptake mechanism for the formation of alpha-methylnoradrenaline.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002415:Cats; D003846:Deoxyepinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D003864:Depression, Chemical; D003891:Desipramine / Q000494:pharmacology; D004298:Dopamine / Q000031:analogs & derivatives*; D004347:Drug Interactions; D004558:Electric Stimulation; D005260:Female; D006220:Haloperidol / Q000494:pharmacology; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D008771:Nordefrin / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D012154:Reticular Formation / Q000502:physiology; D013997:Time Factors
D006220:Haloperidol; D003846:Deoxyepinephrine; D008771:Nordefrin; D003891:Desipramine; D004298:Dopamine; D009638:Norepinephrine; D010646:Phentolamine