Localization of CGRP receptor components and receptor binding sites in rhesus monkey brainstem: A detailed study using in situ hybridization,immunofluorescence, and autoradiography |
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| Authors: | Sajedeh Eftekhari Renee C. Gaspar Rhonda Roberts Tsing‐Bau Chen Zhizhen Zeng Stephanie Villarreal Lars Edvinsson Christopher A. Salvatore |
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| Affiliation: | 1. Department of Clinical Sciences, Division of Experimental Vascular Research, Lund University, Lund, Sweden;2. Department of Neuroscience, Merck Research Laboratories, West Point, Pennsylvania;3. Department of Imaging, Merck Research Laboratories, West Point, Pennsylvania;4. Department of Pain and Migraine Research, Merck Research Laboratories, West Point, Pennsylvania |
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| Abstract: | Functional imaging studies have revealed that certain brainstem areas are activated during migraine attacks. The neuropeptide calcitonin gene–related peptide (CGRP) is associated with activation of the trigeminovascular system and transmission of nociceptive information and plays a key role in migraine pathophysiology. Therefore, to elucidate the role of CGRP, it is critical to identify the regions within the brainstem that process CGRP signaling. In situ hybridization and immunofluorescence were performed to detect mRNA expression and define cellular localization of calcitonin receptor–like receptor (CLR) and receptor activity–modifying protein 1 (RAMP1), respectively. To define CGRP receptor binding sites, in vitro autoradiography was performed with [3H]MK‐3207 (a CGRP receptor antagonist). CLR and RAMP1 mRNA and protein expression were detected in the pineal gland, medial mammillary nucleus, median eminence, infundibular stem, periaqueductal gray, area postrema, pontine raphe nucleus, gracile nucleus, spinal trigeminal nucleus, and spinal cord. RAMP1 mRNA expression was also detected in the posterior hypothalamic area, trochlear nucleus, dorsal raphe nucleus, medial lemniscus, pontine nuclei, vagus nerve, inferior olive, abducens nucleus, and motor trigeminal nucleus; protein coexpression of CLR and RAMP1 was observed in these areas via immunofluorescence. [3H]MK‐3207 showed high binding densities concordant with mRNA and protein expression. The present study suggests that several regions in the brainstem may be involved in CGRP signaling. Interestingly, we found receptor expression and antagonist binding in some areas that are not protected by the blood–brain barrier, which suggests that drugs inhibiting CGRP signaling may not be able to penetrate the central nervous system to antagonize receptors in these brain regions. J. Comp. Neurol. 524:90–118, 2016. © 2015 Wiley Periodicals, Inc. |
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| Keywords: | CGRP CLR RAMP1 CGRP receptor antagonists brainstem primate RRID:AB_2336928 RRID:AB_142672 RRID:AB_2314535 RRID:AB_2238799 |
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