Antinociceptive Effects of H-3 (R-Methylhistamine) and GABA(B) (Baclofen)-Receptor Ligands in an Orofacial Model of Pain in Rats

作者：Nowak Przemyslaw^*; Kowalinska Kania Magdalena; Nowak Damian; Kostrzewa Richard M; Malinowska Borowska Jolanta

来源：Neurotoxicity Research, 2013, 24(2): 258-264.

DOI：10.1007/s12640-013-9385-4

• H-3 receptor
• GABA(B) receptor
• Orofacial pain
• Formalin test
• Rats

The present study explored the antinociceptive effects of H-3 (R-alpha-methylhistamine) and GABA(B) (baclofen) receptor ligands in an orofacial model of pain in rats. Orofacial pain was induced by subcutaneous injection of formalin (50 mu l, 5 %) in the upper lip region, and the number of jumps and time spent face rubbing was recorded for 40 min. Formalin produced a marked biphasic pain response; first phase, 0-10 min (jumps), and second phase, 15-40 min, (rubbing). Baclofen (50 mu g) injected into the rat wiskerpad 5 min before formalin administration suppressed both phases of pain whereas R-alpha-methylhistamine (12.5 mu g) abolished the first phase only. Brains were taken immediately after behavioral testing was completed. HPLC/ED analysis showed that 5-hydroxytryptamine (5-HT) turnover was increased in hippocampus, thalamus, and brain stem of all formalin groups, excepting the baclofen group in which the balance of 5-HT metabolism was restored to control values. These findings demonstrate that GABA(B) receptors represent peripheral targets for analgesia. Consequently, locally administered baclofen may be a useful approach in treating inflammatory trigeminal pain.

• 出版日期2013-8