Blood flow increases in common carotid artery, lower lip and palate elicited by lingual nerve stimulation in anesthetized cats.

The purpose of the present study was to examine whether changes in blood flow in the common carotid artery (CCA) reflect those in individual extracranial tissues (lower lip and palate). Changes were evoked at the three sites simultaneously using a somato-parasympathetic reflex activation method in urethane-alpha-chloralose anesthetized, vago-sympathectomized cats. Somato-parasympathetic reflex activation was induced by electrical stimulation of the central cut end of the ipsilateral lingual nerve. The blood flow changes evoked in CCA, lower lip and palate changed in parallel when the stimulus to the blood vessels was changed (by changing the stimulus applied to the afferents or by blocking the efferent pathway). However, when drugs were given intravenously which would act directly on receptors in the blood vessels (including the endothelium) or alter the systemic blood pressure level, the evoked responses in CCA reacted in a quantitatively different manner from those evoked in lower lip and palate. These results suggest that evoked changes in CCA blood flow cannot be regarded as an accurate reflection of changes occurring simultaneously in individual extracranial tissues, at least when examining the effect of such drugs on parasympathetic mediated vasodilation.