Assessment of the Cardiohemodynamic Effects of Ibopamine, an Orally-Active Dopamine Analogue, in the Anesthetized Open-Chest Guinea Pig and the Isolated Gu nea Pig Atria

Abstract

In the anesthetized open-chest guinea pig, ibopamine (10-300 fig/kg, i.v.), epinine (10-100 /cg/kg, i.v.) and dopamine (10-300 itg/kg, i.v.) produced dose-related increases in heart rate (prevented by 20 itg/kg pindolol, i.v.), left ventricular dP/dt max and aortic flow. Ibopamine produced pressor effects (pre vented by 0.5 mg/kg phentolamine, i.v.), while dopamine produced a slight de pressor effect. A biphasic response (the pressor phase followed by a depressor) was observed after epinine, although the depressor phase was not significant. Calculated total peripheral resistance (TPR) tended to be increased after ibopamine and epinine (initial phase), while it was decreased after dopamine. Pindolol potentiated the increase in TPR produced by ibopamine and epinine, while the increase in TPR was converted to the decrease after phentolamine.Decreases in TPR produced by epinine and the highest dose of dopamine were inhibited by pindolol.In the isolated guinea pig atria, ibopamine (10-6-10-4 M) increased the atrial rate and the developed tension in a concentration-related manner. The positive chronotropic and inotropic effects of ibopamine were of the same order as those of epinine.