The major goal of these studies is to examine the molecular control of calcitonin gene4""""""""elated peptide (CGRP) activity in the trigeminovascular system. CGRP from trigeminal ganglia neurons is one of the most potent vasodilator mechanisms in the cercbral circulation. The importance of CGRP is highlighted by its involvement in subarachnoid hemorrhage, hypertension, and migraine. We have recently shown that viral delivery of CGRP is capable of preventing vasospasm after subarachnoid hemorrhage. To understand the mechanisms of CGRP action, we now propose to study the CGRP receptor regulatory subunits. Both presynaptic and postsynaptic receptors on the trigeminal ganglia neurons and cerebral vessels have been reported. However, the molecular mechanisms that define CGRP receptor activity are only recently becoming known. The CGRP receptor is a trimer of the calcitonin receptor-like receptor (CRLR) and two regulatory subunits called receptor activity-modifying protein 1 (RAMP1) and receptor component protein (RCP). RAMP1 is required for ligand binding activity and RCP is required for full signaling activity. We propose to test the hypothesis that gene transfer of CGRP receptor subunits can increase CGRP activity in the trigeminovascular system. Specifically, we will ask whether the RAMP1 and RCP proteins can regulate presynaptic and postsynaptic CGRP receptor function in trigeminal ganglia neurons and vascular muscle. The approach will be to use primary cell cultures and transgenic mice. First, the CGRP receptor proteins will be tested in cultured trigeminal neurons and vascular muscle. Second, CGRP-induced vasorelaxation will be measured in vitro using large arteries from RAMP1 and RCP transgenic mice and vasomotor responses will be studied in cerebral microvessels in vivo. Third, relaxation of the basilar artery will be compared in wildtype and transgenic mice in combination with CGRP gene transfer. This project builds on and continues our past studies on effects of CGRP and CGRP gene transfer in the cerebrovasculature. By coupling receptor studies with our adenoviral vector encoding CGRP we expect to lay the foundation for a combined approach of CGRP gene delivery and CGRP receptor modulation. The project will bring together expertise in cerebral circulation (Faraci and Heistad), CGRP expression (Russo), and CGRP receptor function (Dickerson). The significance of this project is that it will provide a new understanding of mechanisms of CGRP action and a potentially new perspective on therapeutic strategies for vascular disorders.
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