PT - JOURNAL ARTICLE AU - J R Strader AU - P A Gwirtz AU - C E Jones TI - Comparative effects of alpha-1 and alpha-2 adrenoceptors in modulation of coronary flow during exercise. DP - 1988 Aug 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 772--778 VI - 246 IP - 2 4099 - http://jpet.aspetjournals.org/content/246/2/772.short 4100 - http://jpet.aspetjournals.org/content/246/2/772.full SO - J Pharmacol Exp Ther1988 Aug 01; 246 AB - During submaximal exercise, an alpha adrenergic vasoconstriction that opposes metabolic dilation exists in the coronary circulation. Fifteen dogs were given i.c. injections of prazosin (0.5 mg) or yohimbine (0.7 mg) to determine the participation of alpha 1 and alpha 2 adrenoceptors in the vasoconstriction during exercise. All dogs were chronically instrumented to measure left circumflex blood flow, heart rate, regional left ventricular function and global left ventricular function. The experimental protocol consisted of a graded exercise regimen during which, at the highest level of exercise an alpha antagonist was given i.c. Exercise significantly increased heart rate, left ventricular pressure, dP/dt, systolic shortening and rate of shortening, and coronary blood flow. After the prazosin injection there was an increase in circumflex blood flow (25 +/- 3%) as well as regional (38 +/- 6%) and global (20 +/- 3%) contractile function. However, there was no change in circumflex blood flow or myocardial function after yohimbine. These data indicate that during exercise the sympathetic constrictor tone in the coronary circulation is mediated primarily by alpha 1 adrenoceptors, with little or no involvement from alpha 2 adrenoceptors.