RESUMO
This study was designed to investigate a possible interaction between 17ßestradiol and glutamate receptors of the paragigantocellularis lateralis (LPGi) nucleus on pain coping behavior using the formalin test in ovariectomized (OVX) rats. The results showed that intraLPGi injection of 17ßestradiol declined flexing behavior in both phases of the formalin test. Still, it only diminished the late phase of licking behavior in the OVX rats. NMDA receptor antagonist, AP5, reversed the analgesic effect of 17ßestradiol on flexing behavior in both phases of the formalin test in the OVX rats. The 17ßestradiolinduced antinociceptive effect on the flexing duration was prevented by CNQX (AMPA receptor antagonist) only in the early phase of the formalin test in the OVX rats. AP5 and CNQX reduced the antinociceptive effect of 17ßestradiol in the late phase, but not the early phase of licking response in the OVX rats. These results suggested: (i) The intraLPGi injection of 17ßestradiol is satisfactory in producing modest analgesia on the formalininduced inflammatory pain in the OVX rats; (ii) Cotreatment of glutamate receptors (NMDA and AMPA) antagonists and 17ßestradiol in the LPGi nucleus decrease the analgesic effect of 17ßestradiol in the OVX rats; (iii) There is a possible association between 17ßestradiol and glutamate receptors of the LPGi nucleus on pain coping behavior in the OVX rats.