PARASYMPATHETIC INNERVATION OF CEPHALIC ARTERIES IN RABBITS - COMPARISON WITH SYMPATHETIC AND SENSORY INNERVATION

We investigated the distribution of parasympathetic, sympathetic, and sensory perivascular nerve fibers in rabbit cephalic arteries supplyin g the brain, exocrine glands, nasal mucosa, masseter muscles, tongue, and skin in the face and also examined cranial autonomic and sensory g anglia. NADPH diaphorase (NADPHd)-positive and vasoactive intestinal p eptidelike immunoreactive (VIP-LI) neurons were located in the cranial parasympathetic ganglia. Neuropeptide Y (NPY)-LI neurons occurred mai nly, and dopamine beta-hydroxylase (DBH)-LI neurons occurred exclusive ly, in the superior cervical (sympathetic) ganglion. Substance P (SP)- LI and calcitonin gene-related peptide (CGRP)-LI neurons occurred only in the trigeminal (sensory) ganglion. Therefore, it was assumed that; NADPHd-positive and VIP-LI perivascular nerve fibers in cephalic arte ries were parasympathetic, all DBH-LI and most NPY-LI fibers were symp athetic, and SP-LI and CGRP-LI fibers were sensory in nature. In the c erebral arteries, NADPHd-positive and VIP-LI varicose fibers were more numerous in the rostral than in the caudal half of the Circle of Will is. In the extracranial arteries, NADPHd-positive and VIP-LI fibers we re most abundant in the lingual, lacrimal, and supraorbital arteries; sparse in the parotid and submandibular arteries; and absent in the ea r artery. There was an obvious proximal-to-distal density gradient alo ng individual cephalic arterial trees. In contrast, DBH-LI, NPY-LI, SP -LI, and CGRP-LI varicose nerve fibers were similar in density in all cephalic arteries and their branches. These neuroanatomical findings s uggest that differential parasympathetic innervation in cephalic arter ies may play a role in the partitioning of blood flow between differen t cephalic tissues. (C) 1997 Wiley-Liss, Inc.