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Cannabinoid receptor‐independent actions of the aminoalkylindole WIN 55,212‐2 on trigeminal sensory neurons
Author(s) -
Price Theodore J,
Patwardhan Amol,
Akopian Armen N,
Hargreaves Kenneth M,
Flores Christopher M
Publication year - 2004
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0705778
Subject(s) - capsazepine , trpv1 , calcitonin gene related peptide , chemistry , cannabinoid , trigeminal ganglion , endocrinology , cannabinoid receptor , medicine , cannabinoid receptor agonists , agonist , nociceptor , capsaicin , receptor , pharmacology , neuropeptide , transient receptor potential channel , neuroscience , biology , sensory system , nociception , biochemistry
The prototypical aminoalkylindole cannabinoid WIN 55,212‐2 (WIN‐2) has been shown to produce antihyperalgesia through a peripheral mechanism of action. However, it is not known whether WIN‐2 exerts this action directly via cannabinoid receptors located on primary afferents or if other, perhaps indirect or noncannabinoid, mechanisms are involved. To address this question, we have examined the specific actions of WIN‐2 on trigeminal ganglion (TG) neurons in vitro by quantifying its ability to modulate the evoked secretion of the proinflammatory neuropeptide CGRP as well as the inflammatory mediator‐induced generation of cAMP. WIN‐2 evoked CGRP release from TG neurons in vitro (EC 50 =26 μ M ) in a concentration‐ and calcium‐dependent manner, which was mimicked by the cannabinoid receptor‐inactive enantiomer WIN 55,212‐3 (WIN‐3). Moreover, WIN‐2‐evoked CGRP release was attenuated by the nonselective cation channel blocker ruthenium red but not by the vanilloid receptor type 1 (TRPV1) antagonist capsazepine, suggesting that, unlike certain endogenous and synthetic cannabinoids, WIN‐2 is not a TRPV1 agonist but rather acts at an as yet unidentified cation channel. The inhibitory effects of WIN‐2 on TG neurons were also examined. WIN‐2 neither inhibited capsaicin‐evoked CGRP release nor did it inhibit forskolin‐, isoproteranol‐ or prostaglandin E 2 ‐stimulated cAMP accumulation. On the other hand, WIN‐2 significantly inhibited (EC 50 =1.7 μ M ) 50 m M K + ‐evoked CGRP release by approximately 70%. WIN‐2 inhibition of 50 m M K + ‐evoked CGRP release was not reversed by antagonists of cannabinoid type 1 (CB1) receptor, but was mimicked in magnitude and potency (EC 50 =2.7 μ M ) by its cannabinoid‐inactive enantiomer WIN‐3. These findings indicate that WIN‐2 exerts both excitatory and inhibitory effects on TG neurons, neither of which appear to be mediated by CB1, CB2 or TRPV1 receptors, but by a novel calcium‐dependent mechanism. The ramifications of these results are discussed in relation to our current understanding of cannabinoid/vanilloid interactions with primary sensory neurons.British Journal of Pharmacology (2004) 142 , 257–266. doi: 10.1038/sj.bjp.0705778