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5-HT(1B) receptors inhibit glutamate release from primary afferent terminals in rat medullary dorsal horn neurons.

AbstractBACKGROUND AND PURPOSE:
Although 5-HT(1B) receptors are expressed in trigeminal sensory neurons, it is still not known whether these receptors can modulate nociceptive transmission from primary afferents onto medullary dorsal horn neurons.
EXPERIMENTAL APPROACH:
Primary afferent-evoked EPSCs were recorded from medullary dorsal horn neurons of rat horizontal brain stem slices using a conventional whole-cell patch clamp technique under a voltage-clamp condition.
KEY RESULTS:
CP93129, a selective 5-HT(1B) receptor agonist, reversibly and concentration-dependently decreased the amplitude of glutamatergic EPSCs and increased the paired-pulse ratio. In addition, CP93129 reduced the frequency of spontaneous miniature EPSCs without affecting the current amplitude. The CP93129-induced inhibition of EPSCs was significantly occluded by GR55562, a 5-HT(1B/1D) receptor antagonist, but not LY310762, a 5-HT(1D) receptor antagonist. Sumatriptan, an anti-migraine drug, also decreased EPSC amplitude, and this effect was partially blocked by either GR55562 or LY310762. On the other hand, primary afferent-evoked EPSCs were mediated by the Ca(2+) influx passing through both presynaptic N-type and P/Q-type Ca(2+) channels. The CP93129-induced inhibition of EPSCs was significantly occluded by ω-conotoxin GVIA, an N-type Ca(2+) channel blocker.
CONCLUSIONS AND IMPLICATIONS:
The present results suggest that the activation of presynaptic 5-HT(1B) receptors reduces glutamate release from primary afferent terminals onto medullary dorsal horn neurons, and that 5-HT(1B) receptors could be, at the very least, a potential target for the treatment of pain from orofacial tissues.
AuthorsI-S Choi, J-H Cho, C-H An, J-K Jung, Y-K Hur, J-K Choi, I-S Jang
JournalBritish journal of pharmacology (Br J Pharmacol) Vol. 167 Issue 2 Pg. 356-67 (Sep 2012) ISSN: 1476-5381 [Electronic] England
PMID22462474 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Copyright© 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.
Chemical References
  • Pyridines
  • Pyrroles
  • Receptor, Serotonin, 5-HT1B
  • 3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo(3,2-b)pyrid-5-one
  • Glutamic Acid
Topics
  • Action Potentials
  • Afferent Pathways (metabolism)
  • Animals
  • Electrophysiological Phenomena
  • Glutamic Acid (metabolism)
  • Posterior Horn Cells (physiology)
  • Pyridines (pharmacology)
  • Pyrroles (pharmacology)
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Serotonin, 5-HT1B (metabolism)

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