Cannabinoid CB1 receptor-mediated inhibition of glutamate release from rat hippocampal synaptosomes

Eur J Pharmacol. 2003 May 23;469(1-3):47-55. doi: 10.1016/s0014-2999(03)01734-5.

Abstract

Cannabinoid receptors are widely expressed in the brain and have been shown to regulate synaptic transmission through a presynaptic mechanism. Using synaptosomal preparation, I show here that 2,3-dihydro-5-methyl-3-(4-morpholinyl-methyl)-pyrrolo-1,4-benzoxazin-6-yl-1-naphthalenylmethanone (WIN 55212-2) strongly depressed 4-aminopyridine-evoked glutamate release in a concentration-dependent manner, and this effect was reversed by the selective cannabinoid CB(1) receptor antagonist 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide (AM 281). The inhibitory modulation by WIN 55212-2 was not due to a decrease in synaptosomal excitability or a direct effect on the release machinery because WIN 55212-2 did not alter 4-aminopyridine-mediated depolarization and ionomycin-induced glutamate release. In addition, the WIN 55212-2-mediated inhibition of glutamate release was blocked by the G(i)/G(o) protein inhibitor pertussis toxin, but not by the protein kinase A inhibitor 2,3,9,10,11,12-Hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo-benzodiazocine-10-carboxylic acid, hexyl ester (KT 5720). Furthermore, this inhibitory effect was associated with a decrease in 4-aminopyridine-evoked Ca(2+) influx, which could be completely prevented in synaptosomes pretreated with the N- and P/Q-type Ca(2+) channel blockers. Together, these observations indicate that activation of cannabinoid CB(1) receptors inhibit 4-aminopyridie-evoked glutamate release from hippocampal synaptosomes through a inhibitory G protein to suppress N- and P/Q-type Ca(2+) channel activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Benzoxazines
  • Cannabinoids / metabolism
  • Cannabinoids / pharmacology
  • Glutamic Acid / metabolism*
  • Hippocampus / drug effects
  • Hippocampus / metabolism*
  • Male
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Morpholines / pharmacology
  • Naphthalenes / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Cannabinoid, CB1 / agonists
  • Receptor, Cannabinoid, CB1 / antagonists & inhibitors
  • Receptor, Cannabinoid, CB1 / metabolism*
  • Synaptosomes / drug effects
  • Synaptosomes / metabolism*

Substances

  • Benzoxazines
  • Cannabinoids
  • Morpholines
  • Naphthalenes
  • Receptor, Cannabinoid, CB1
  • Glutamic Acid
  • Win 55212-2