Role of periaqueductal grey prostaglandin receptors in formalin-induced hyperalgesia.

In this study we have investigated the role of periaqueductal grey prostaglandin receptors in formalin-induced hyperalgesia in mice. Glutamate and GABA release changes have been monitored by in vivo microdialysis. Intra-periaqueductal grey microinjections of misoprostol, a non-selective prostaglandin receptor agonist, increased nociceptive responses in the formalin test only during the late phase.

Differential roles of mGlu8 receptors in the regulation of glutamate and gamma-aminobutyric acid release at periaqueductal grey level.

We investigated the role of group III metabotropic glutamate (mGlu) receptors on glutamate and GABA releases at the periaqueductal grey (PAG) level by using in vivo microdialysis in rats. Intra-PAG perfusion of either L-(+)-2-amino-4-phosphonobutyric acid (L-AP4, 100-300 microM), (RS)-4-phosphonophenylglycine ((RS)-PPG, 100-300 microM) selective agonists of group III mGlu receptors, or (S)-3,4-dicarboxyphenylglycine ((S)-3,4-DCPG, 50-100 microM), a selective agonist of mGlu8 receptor, increased glutamate and decreased GABA extracellular concentrations. (RS)-alpha-methylserine-O-phosphate (MSOP, 0.

Metabotropic glutamate receptor 5 and dorsal raphe serotonin release in inflammatory pain in rat.

In this study, we evaluated the effects of 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a selective antagonist of metabotropic glutamate subtype 5 receptors (mGlu(5)), delivered through different paths on dorsal raphe serotonin (5-HT) and on thermoceptive responses in rats with inflammatory pain. Intraplantar formalin and carrageenan increased 5-HT (137+/-11% and 212+/-6% of pre-injection baseline, respectively) and reduced nociceptive threshold (23+/-7% and 19+/-3% of pre-injection baseline, respectively). MPEP (2 mg/kg i.