Abstract
Noradrenergic innervation of the cerebral arteries has been histochemically and electronmicroscopically established. However, the direct evaluation of its function has never been attempted yet.
Recently we succeeded in demonstrating the action potentials directly from the cerebral arterial walls of the cat. Discharges of the action potentials increased during induced hypotension and decreased during induced hypertension. These responses of the action potentials were affected by the intravenous administration of various agents such as a ganglion blocking agent (hexamethonium bromide), a dopamine-β-hydroxylase inhibitor (fusaric acid), a false neurotransmitter (5-hydroxydopamine) and an axonal conduction inhibitor (tetrodotoxine).
The purpose of the present study was to investigate the effects of cervical sympathectomy on the action potentials and their responses to changes in blood pressure.
Twenty adult cats were anesthetized with 1.0% a-chloralose and 10% urethane followed by artificial respiration. Superior cervical ganglionectomy and preganglionectomy were performed in 7 and 13 cats, respectively.
Action potentials from the pial arterial walls were recorded by means of fine bipolar platinum electrodes, high sensitive. preamplifiers, band-pass filters and a data analyzing computer. Mass discharges of the action potentials were analyzed using a program of pulse density variation.
Preganglionectomy did not abolish the normal responses of the action potentials to changes in blood pressure ( : an increase of the discharges during induced hypotension and a decrease during induced hypertension) in 6 out of 7 cats for acute experiments. The normal response was maintained even three weeks after the operation in 5 out of 6 cats for chronic experiments.
Immediately after the superior cervical ganglionectomy the normal response of action potentials to changes in blood pressure was maintained in all cats except one. On the other hand, three weeks after the operation the response was completely abolished on the side of the operation in all 4 cats, although the response on contralateral side was remained intact.
In conclusion, the response of the discharges directly recorded from the pial arterial walls was abolished in the chronic cats with superior cervical ganglionectomy, which suggests that the superior cervical ganglion plays some role on the action potentials from the pial arterial walls.
