Regional pharmacologic responses of the vertebral and internal carotid arteries.

Simultaneous measurements were made of the effects upon blood flow within the internal carotid and vertebral arteries during induced hypercapnea, hypocapnea, hypoxia, intravenous administration of β-ethyl-β-methylglutaramide, epinephrine, l -norepinephrine, papaverine, histamine and acetylcholine in the rhesus monkey. Electromagnetic flowmeters were used for measurements. No different effect on flow or regional vascular resistance was produced by hypocapnea, hypercapnea, anoxia, epinephrine or norepinephrine. Differences in regional vascular resistance and flow patterns were observed during bemegride-induced seizures and the administration of papaverine, histamine and acetylcholine. Regional metabolic effects on cerebral blood flow caused by seizures are considered. The importance of diversion of cervical internal carotid and vertebral artery flow into the blood supplying the extracerebral tissues is discussed as a possible explanation for differences in the regional pharmacologic effects of papaverine, histamine and acetylcholine.