The calcitonin family of peptides, which includes calcitonin, two calcitonin-related gene peptides (CGRPs), adrenomedullin, and amylin, share a disulfide-bonded loop, an amphipathic a-helix, and an amidated C-terminus. The peptides influence a variety of physiological effects, including vascular tone, food intake and bone metabolism. The biological effects of the peptides are mediated by two class B GPCRs, CT receptor (calcitonin receptor) and CL receptor (calcitonin receptor-like receptor) (Poyner et al., 2002). The pharmacology of the CT and CL receptors is strongly influenced by their association with a family of three receptor activity modifying proteins (RAMPs), which are 14-17 kD single pass transmembrane proteins. CGRP (calcitonin gene-related peptide) induces vasodilation, and its activity is primarily mediated by CGRP1, composed of CL in complex with RAMP1 (Hasbak et al., 2003). As a consequence of its role as a vasodilator, CGRP acting via CGRP1 appears to play an important role in hypertension (Deng and Li, 2005). Millipore's CGRP1 membrane preparations are crude membrane preparations made from our proprietary stable recombinant cell lines to ensure high-level of GPCR surface expression; thus, they are ideal HTS tools for screening of antagonists of CGRP1 interactions with CGRP. The membrane preparations exhibit a Kd of 1.1-1.7 nM for [125I]-hCGRP. With 5 µg/well CGRP1 Membrane Prep and 1 nM [125I]-hCGRP, a greater than 15-fold signal-to-background ratio was obtained.