Calcitonin gene-related peptide: novel neuropeptide.

Calcitonin gene-related peptide (CGRP) is a 37 amino acid peptide encoded in the calcitonin gene. Its expression is dependent on tissue-specific alternative RNA processing: mRNA for CGRP predominates in the brain, whilst calcitonin (CT) mRNA predominates in thyroid C cells. The existence of this hitherto unsuspected peptide was predicted by mRNA analysis and demonstrated using antibodies raised against a synthetic peptide corresponding to the predicted C-terminal sequence of CGRP. The distribution of CGRP in the central and peripheral nervous system and its co-localization in some neurons with substance P (SP) or acetylcholine suggests several possible roles in autonomic, sensory and motor functions. Its actions appear to depend on the existence of specific CGRP receptors in target tissues, distinct from the receptors for CT but bearing some resemblance to them.