Functional evidence for the involvement of multiple transmitters in the efferent functions mediated by the capsaicin-sensitive sensory neurons at visceral level.

It is well known that endogenous CGRP is co-released with SP from both central and peripheral terminals of capsaicin-sensitive sensory neurons. However, the functional counterpart of peptide co-existence is largely unknown. In some tissues, one of these peptides is almost devoid of postjunctional effects, while in others CGRP potentiates the effects of SP. We present evidence of a third possible interaction, that implies a physiological antagonism. Further studies are needed to define the ability of natural stimuli to induce functional changes in the different organs, at the light of: I) tissue levels of sensory neuropeptides, II) relative amounts released by natural stimuli at various intensities, and III) postjunctional responsiveness to neuropeptides.