Temporomandibular-evoked jaw muscle reflex: role of brain stem NMDA and non-NMDA receptors

This study investigated the possible involvement of brain stem excitatory a mino acid receptor mechanisms and the trigeminal subnucleus caudalis (Vc) i n temporomandibular joint (TMJ)evoked reflex jaw muscle activity. Glutamate injected into the TMJ of anesthetized rats reflexly evoked activity in the jaw muscles. Application of lidocaine, but not saline, to the surface of t he caudal brainstem overlying Vc significantly suppressed TMJ-evoked jaw mu scle activity, while application of NMDA or non-NMDA receptor antagonists a lso significantly attenuated jaw muscle activity. These results provide evi dence that Vc is a critical relay in the TMJ-evoked reflex activation of th e jaw muscles, and that both NMDA and non-NMDA receptor mechanisms may cont ribute to these effects. NeuroReport 12: 1875-1878 (C) 2001 Lippincott Will iams & Wilkins.