RESUMO
The present study was designed to analyze the effects of drugs th at interfere with sympathetic transmission on the external carotid vasodilator response induced by the 5-HT1A receptor agonist, indorenate, in pentobarbital-anesthetized dogs. Intracarotid (i.c.) infusions of indorenate (1000 µg/lmin) produced an increase in external carotid blood flow (external C.B.F.) without modifying mean arterial blood pressure or heart rate. This effect of indorenate was dose-dependently antagonized by intravenous (i.v.) administration of the Ó1-adrenoceptor antagonist, prazosin (1, 3.1, 10, 31 and 100 µg/kg), the ganglionic blocking agent, mecamylamine (0.31, 0.1, 0.31, 1, 3.1 and 10 mg/kg) or the 5-HT2 receptor and Ó1-adrenoceptor antagonist, ketanserin (10, 31 and 100 µ/kg). It is concluded that indorenate.induced increase in canine external C.B.F. is dependent on the vascular neurogenic tone