Binding sites for calcitonin gene-related peptide in distinct areas of rat brain.

Calcitonin gene-related peptide (CGRP) binding sites were localized in rat brain and spinal cord by an in vitro labeling light microscopic technique using [125I]rCGRP as radioligand. Specific rCGRP binding with a dissociation constant (Kd) of 0.53 nM to membrane preparations from rat brain cortex was characterized. The presence and the selective distribution of specific high affinity CGRP binding sites in the central nervous system suggest a role for this recently predicted peptide as a neurotransmitter.