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Brain Res. 2015 Mar 10;1600:93-109. doi: 10.1016/j.brainres.2014.11.031. Epub 2014 Nov 20.

Localization of CGRP, CGRP receptor, PACAP and glutamate in trigeminal ganglion. Relation to the blood-brain barrier.

Author information

1
Department of Clinical Sciences, Division of Experimental Vascular Research, Lund University, BMC A13, Sölvegatan 17, SE-22184 Lund, Sweden. Electronic address: Sajedeh.Eftekhari@med.lu.se.
2
Department of Pain and Migraine Research, Merck Research Laboratories, West Point, PA, USA.
3
Department of Clinical Experimental Research, Glostrup Research Institute, Glostrup Hospital, Glostrup, Denmark.
4
Department of Imaging, Merck Research Laboratories, West Point, PA, USA.
5
Department of Clinical Sciences, Division of Experimental Vascular Research, Lund University, BMC A13, Sölvegatan 17, SE-22184 Lund, Sweden; Department of Clinical Experimental Research, Glostrup Research Institute, Glostrup Hospital, Glostrup, Denmark.

Abstract

Calcitonin gene-related peptide (CGRP) receptor antagonists have demonstrated anti-migraine efficacy. One remaining question is where do these blockers act? We hypothesized that the trigeminal ganglion could be one possible site. We examined the binding sites of a CGRP receptor antagonist (MK-3207) and related this to the expression of CGRP and its receptor in rhesus trigeminal ganglion. Pituitary adenylate cyclase-activating polypeptide (PACAP) and glutamate were examined and related to the CGRP system. Furthermore, we examined if the trigeminal ganglion is protected by the blood-brain barrier (BBB). Autoradiography was performed with [(3)H]MK-3207 to demonstrate receptor binding sites in rhesus trigeminal ganglion (TG). Immunofluorescence was used to correlate binding and the presence of CGRP and its receptor components, calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein 1 (RAMP1), and the distribution of PACAP and glutamate in rhesus and rat TG. Evans blue was used to examine large molecule penetration into the rat TG. High receptor binding densities were found in rhesus TG. Immunofluorescence revealed expression of CGRP, CLR and RAMP1 in trigeminal cells. CGRP positive neurons expressed PACAP but not glutamate. Some neurons expressing CLR and RAMP1 co-localized with glutamate. Evans blue revealed that the TG is not protected by BBB. This study demonstrates CGRP receptor binding sites and expression of the CGRP receptor in rhesus and rat TG. The expression pattern of PACAP and glutamate suggests a possible interaction between the glutamatergic and CGRP system. In rat the TG is outside the BBB, suggesting that molecules do not need to be CNS-penetrant to block these receptors.

KEYWORDS:

CGRP; CGRP receptor antagonists; CLR; Evans blue; RAMP1; Trigeminal ganglion

PMID:
25463029
DOI:
10.1016/j.brainres.2014.11.031
[Indexed for MEDLINE]

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