Effects of Calcium Channel Blockers on Cold-Induced Vasodilatation and Elevated Sympathetic Tone in the Canine Internal Maxillary Artery Bed

Abstract

This study was concerned with the interactive effects of cold-induced vasodilatation, blockade of voltage-sensitive Ca²⁺ channels and sympathetic nerve stimulation in the nasal vascular bed of anesthetized dogs. To estimate the distribution of the internal maxillary artery blood flow to capillaries and to arteriovenous anastomoses (AVA), the microsphere technique in combination with electromagnetic flowmetry was used. Intraarterial infusion of verapamil resulted in a dose-dependent vasodilatation and a redistribution of the internal maxillary artery blood flow in favor of the capillary fraction, at the expense of the AVA fraction. Cold exposure of the nasal and facial tissues was followed (as a result of a marked dilatation of the AVA) by a prompt increase in internal maxillary artery blood flow. Simultaneously applied electrical stimulation of the cervical sympathetic trunk resulted in a significant fall in blood flow, caused mainly by a decrease in capillary flow. Verapamil infusion combined with cold exposure led to a simultaneous elevation of the AVA and capillary flows. When electrical stimulation of the cervical sympathetic trunk was also applied, the AVA and capillary flows were affected in different manners, depending on the sequence of the stimulations. Analysis of capillary flow data in the various nasal and facial tissue compartments indicates that cold exposure, blockade of the voltage-dependent Ca²⁺ channels and an elevated sympathetic tone modify the local nutritive blood flow.

The relationship between subjective and objective measures of nasal function

“…The function of these interesting papillae is not known but they may have a role as thermoreceptors as there is some evidence that cooling causes a change in blood flow through the capillary circulation (19).…”