Release of vasoactive peptides from autonomic and sensory nerves.

Release of specific vasoactive peptides occurs upon activation of perivascular parasympathetic (vasoactive intestinal polypeptide and peptide histidine isoleucine), sympathetic (neuropeptide Y) and sensory (calcitonin gene-related peptide and tachykinins) nerves. These peptides may serve as cotransmitters with acetylcholine and noradrenaline with interactions both at the pre- and postjunctional levels. Some long-lasting nonadrenergic, noncholinergic vascular effects upon nerve activation may thus be peptide-mediated. Strong activation seems to be necessary for peptidergic transmission in the parasympathetic and sympathetic system while local sensory mechanisms may occur even at single impulses.