Expression of receptor-activity modifying protein (RAMP) mRNAs in the mouse brain

Receptor activity modifying proteins (RAMPs) comprise a family of accessory proteins for G protein-coupled receptors (GPCRs). They function as receptor modulators that determine the ligand specificity of receptors for calcitonin gene-related peptide (CGRP), amylin and adrenomedullin (ADM). Here we demonstrate for the first time the characteristic distributions of the RAMP family mRNAs in the brain. Northern blot analysis revealed that mRAMP 1 and 3 mRNAs were intensely expressed in the brain, but mRAMP2 mRNA less abundantly. In situ hybridization studies showed the heterogenous and unique distributions of mRAMP mRNAs; RAMP1 mRNA was widely expressed throughout the brain including the cerebral cortex, caudate putamen, amygdaloid complex, hippocampus, cerebellum and ependyma, mRAMP2 was most abundant in the hippocampus, cerebellum, pia mater and blood vessels, while mRAMP3 was specifically distributed in a variety of thalamic nuclei and the cerebellum. In addition, RAMP1 and -3 genes were also detected in the subfornical organ and area postrema, which are members of circumventricular organs lacking blood-brain barrier. The present results help in understanding the diversification and regulation of receptor functions for calcitonin family peptides, and potentially other GPCRs in the brain.