Calcitonin gene-related peptide in neural tissues: a phylogenetic study

A heterologous radioimmunoassay using a rabbit antiserum raised against human calcitonin gene-related peptide (CGRP) was used to measure levels of immunoreactive CGRP (IR-CGRP) in the brain, pituitary, and spinal cord in species representing all classes of vertebrates from cyclostomes to mammals, except amphibians. All the brain extracts except those from the trout, goldfish, and iguana demonstrated the presence of IR-CGRP. Pituitary extracts from all animals, except the ratfish, goldfish and trout, contained IR-CGRP. CGRP was present in all classes of animals tested and seems to be highly conserved in the nervous system, where it may act as a neurotransmitter or neuromodulator.