Donoso MV, Hermosilla D, Navarrete C, Álvarez P, Lillo JG, Huidobro-Toro JP. Reciprocal sympatho-sensory control: functional role of nucleotides and calcitonin gene-related peptide in a peripheral neuroeffector junction.
Neuroscience 2011;
203:216-29. [PMID:
22178987 DOI:
10.1016/j.neuroscience.2011.11.067]
[Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 11/25/2011] [Accepted: 11/28/2011] [Indexed: 11/24/2022]
Abstract
The rat vas deferens has scattered sensory afferens plus a dense network of sympathetic motor efferens; these fibers are not known to interact functionally. We ascertained whether sensory fibers modulate the release of sympathetic transmitters through the release of calcitonin gene-related peptide (CGRP) and reciprocally assessed whether sympathetic transmitters modulate the overflow of ir-CGRP from sensory fibers. The tissue overflow of electrically evoked sympathetic co-transmitters (ATP/metabolites, noradrenaline (NA), and immunoreactive neuropeptide tyrosine (ir-NPY)) and the motor responses elicited were quantified following either exogenous CGRP or capsaicin application to elicit peptide release. Conversely, the outflow of ir-CGRP was examined in the presence of sympathetic transmitters. Exogenous CGRP reduced in a concentration-dependent manner the electrically evoked outflow of ATP/metabolites, NA, and ir-NPY with EC(50) values of 1.3, 0.18, and 1.9 nM, respectively. CGRP also reduced the basal NA overflow. The CGRP-evoked modulation was blocked by CGRP8-37 or H-89. Release of endogenous CGRP by capsaicin significantly reduced the basal overflow of NA, ir-NPY, and the electrically evoked sympathetic transmitter release. ADP, 2-methylthioadenosine-5'-O-diphosphate (2-MeSADP), or UTP decreased the electrically evoked ir-CGRP overflow, whereas clonidine, α,β-methyleneadenosine 5'-triphosphate (α,β-mATP), or adenosine (ADO) were inactive. CGRP acting postjunctionally also reduced the motor responses elicited by exogenous NA, ATP, or electrically evoked contractions. We conclude that CGRP exerts a presynaptic modulator role on sympathetic nerve endings and reciprocally ATP or related nucleotides influence the release of ir-CGRP from sensory fibers, highlighting a dynamic sympatho-sensory control between sensory fibers and sympathetic nerve ending. Postjunctional CGRP receptors further contribute to reduce the tissue sympathetic motor tone implying a pre and postjunctional role of CGRP as a sympathetic tone modulator.
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