Comparative responses of the carotid and vertebral arterial systems of rhesus monkeys to betahistine.

A newly developed photoelectric method was used in 5 rhesus monkeys to measure the mean transit time of blood through the carotid and vertebral arteries, together with measurement of the blood flow through the tissues of the fronto-parietal area supplied by the carotid artery and of the cerebellar tonsil supplied by the vertebral artery. Following intravenous administration of betahistine mesylate, a histamine analog, the mean transit times of blood through the 2 arteries were equally shortened by 10%, despite a 20% decrease in the mean arterial blood pressure (P less than 0.05). The cerebral tissue and cerebellar tissue blood flow was increased by betahistine, from 70.4 to 81.4 ml/100g/min and from 73.2 to 84.0 ml/100g/min, respectively. Since histamine has been reported to produce a decrease in cardiac output, the increase in cerebral blood flow confirmed that betahistine is a selective cerebral vasodilating agent. However, by comparing the hemodynamic data for the two cerebral arterial systems, it can be concluded that the responses of the carotid and vertebral arterial systems to the vasodilating action of betahistine were essentially the same in extent.