Trigeminalectomy modifies pial arteriolar responses to hypertension or norepinephrine.

The responses of pial precapillary vessels were examined bilaterally using a closed cranial-window preparation in 11 anesthetized cats after chronic unilateral section of the trigeminal ganglia. During increases or decreases in arterial PCO2 or hypoxia, vasoconstrictor and vasodilator responses were symmetrical and appropriate on the two sides. The superfusion of vessels with norepinephrine (10 micrograms/ml) constricted large and small pial arterioles to a greater extent on the denervated side, and this difference persisted even after washing (P less than 0.02). After severe hypertension, small and large arterioles dilated on both sides, although to a greater extent on the innervated side. In 8 of 10 acutely hypertensive animals, extravasation of intravenously administered iodinated albumin was greater in the intact than deafferented hemisphere. These results suggest that the trigeminal nerve can modify the responses of cerebral arterioles and participate in the regulation of the cerebral vasculature.