Effects of prostaglandins on the internal and external carotid blood flow in the monkey

Internal and external carotid blood flow was measured simultaneously by the use of a recently described electromagnetic flowmeter technique. Intracarotid prostaglandin E₁ (PGE₁) markedly increased external carotid flow and reduced internal carotid flow, possibly because of “steal” from the internal carotid artery. lntracarotid PGF_2a constricted both the internal and external carotid artery, whereas PGF_1a had a minimal constrictor effect only on the external carotid artery. Based on the experimental findings, it is hypothesized that the characteristic cranial flow changes of migraine headache may be caused by a single biochemical agent that has a differential effect on external and internal carotid flow to cause simultaneous dilation of the external carotid vasculature and steal of blood from the internal carotid system.