THE EFFECTS OF EPININE ON ARTERIAL BLOOD-PRESSURE AND REGIONAL VASCULAR RESISTANCES IN ANESTHETIZED RATS

1. We carried out experiments in anesthetized rats to study the hemody namic effects of intravenous injections of epinine. 2. Epinine (1-320 mu g/kg) produced a biphasic effect on mean arterial blood pressure (n =30), At doses lower than 40 mu g/kg, arterial blood pressure decrease d (by as much as 21.5+/-3.4%), though at higher doses it increased dos e dependently (by as much as 73.2+/-14.5%). Epinine also produced brad icardia in a dose-dependent manner (by as much as 26.4+/-4.9%). Sulpir ide (100 mu g/kg) suppressed the hypotensive effect of epinine but did not change the hypertensive effect. In the presence of prazosin (1,00 0 mu g/kg), arterial blood pressure remained significantly decreased a t all doses of epinine. Neither sulpiride nor prazosin changed the bra dycardic effect of epinine. 3. Prazosin produced a significant decreas e in renal vascular resistance. Epinine (5 mu g/kg) after prazosin rev erted the effects of prazosin in renal vascular resistance, without an y significant modification in the renal blood flows. However, 20 mu g/ kg epinine increased the renal vascular resistances and, moreover, pro duced a significant decrease in the blood flows of both kidneys. Neith er prazosin nor epinine produced modifications in the intestinal vascu lar bed. 4. Although epinine possesses significant dopamine and alpha- adrenergic activities that are involved in the biphasic effect of the agent on mean arterial blood pressure in anesthetized rats, in the pre sence of prazosin, it is not possible to manifest dopaminergic activit y involved in the increase in renal or mesenteric blood flow; this may be due to the low tone of the vascular wall induced by the alpha-adre nergic antagonist, though an alpha(2)-activity cannot be discarded. (C ) 1998 Elsevier Science Inc.