Neurons of the guinea pig IMG are surrounded by nerve fibers containing CGRP-like immunoreactivity (LI). The purpose of this study was to determine whether colonic distension releases CGRP-LI in the IMG and whether opioid peptides and neurotensin(8-13) [NT(8-13)] modulate its release. Colonic distension released CGRP-LI. Methionine-enkephalin acted through mu and/or delta receptors to block release. NT(8-13) had no effect on release of CGRP-LI. Capsaicin pretreatment reduced the content of CGRP-LI in the IMG by 37%. Colonic distension did not release CGRP-LI from capsaicin-insensitive fibers. The data suggest that colonic distension releases CGRP-LI material from capsaicin-sensitive nerves and that enkephalins modulate release of CGRP-LI.
- Calcitonin gene-related peptide
- Dorsal root ganglion
- Guinea pig
- Inferior mesenteric ganglion
- Prevertebral ganglia
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience