Different levels of immunoreactivity for synaptosomal-associated protein of 25 kDa in vasoconstrictor and vasodilator axons of guinea-pigs

Immunoreactivity (IR) for synaptosomal-associated protein of 25 kDa (SNAP-2 5) was examined in axons of autonomic vasoconstrictor and vasodilator neuro ns innervating the lingual and uterine arteries of guinea-pigs. Polyacrylam ide gel electrophoresis and immunoblotting of protein extracts demonstrated a SNAP-25-IR band at 25 kDa in both arteries. Quantitative confocal micros copy demonstrated significantly higher levels of SNAP-25-IR in varicosities with IR for vasoactive intestinal peptide (VIP) than in adjacent axons wit h IR for tyrosine hydroxylase (TH). Levels of SNAP-25-IR in TH-IR axons, re lative to adjacent VIP-IR axons, were significantly higher in the lingual a rtery than the uterine artery. These differences in IR for SNAP-25, a prote in considered essential for calcium-dependent exocytosis of neurotransmitte rs, raise the possibility that mechanisms of transmitter release may vary b etween different classes of autonomic neurons. (C) 2000 Elsevier Science Ir eland Ltd. All rights reserved.