Peripheral glutamate receptors participate in interleukin-1β-induced mechanical allodynia in the orofacial area of rats

The present study was performed to examine peripheral cytokine-induced mechanical allodynia in the orofacial area and to investigate whether peripheral excitatory amino acids participate in the cytokine-induced mechanical allodynia. Experiments were carried out on male Sprague-Dawley rats. After interleukin-1β (IL-1β) was applied subcutaneously to the orofacial area, we examined withdrawal responses produced by air puffs applied to the IL-1β injection site. The threshold of air puffs that produced withdrawal behavioral responses decreased significantly in a dose-dependent manner after injection of IL-1β. Pretreatment with an IL-1 receptor antagonist abolished the decrease in the threshold of air puffs. Pretreatment with DL-2-amino-5-phosphonvaleric acid, an N-methyl-D-aspartic acid (NMDA) receptor antagonist, did not affect IL-1β-induced mechanical allodynia. However, pretreatment with 6,7-dinitroquinoxaline-2,3-dione, a non-NMDA receptor antagonist, abolished the decrease in the threshold of air puffs. These results suggest that peripheral cytokine can produce mechanical allodynia in the orofacial area and that excitatory amino acids can modulate IL-1β-induced mechanical allodynia via non-NMDA receptors.