Distribution and chromatographic characterisation of CGRP-like immunoreactivity in the brain and gut of the rat.

Radioimmunoassay, chromatography and immunocytochemistry were used to study the occurrence of calcitonin gene-related peptide in the brain and gastrointestinal tract of the rat. In the brain, the highest concentrations of the peptide were found in the medulla oblongata (58.3 +/- 6.8 pmol/g) where immunocytochemistry showed the presence of immunoreactive cell bodies. Significant concentrations were also found in the pancreas and throughout the gastrointestinal tract, the highest levels occurring in the pyloric sphincter (48.0 +/- 6.0 pmol/g). CGRP-like immunoreactivity in the gastrointestinal tract was restricted to nerve fibers. Chromatographic analysis of the CGRP-like immunoreactivity occurring in these tissues showed that at least 70% was indistinguishable from the synthetic peptide. However, there was also evidence of a number of smaller cross-reacting molecular species.