Comparison of typical responses evoked in the jaw muscles as a result of local application of MO and EAA receptor agonists to the TMJ region. Data points indicate the mean EMG (n = 6) relative to preinjection baseline EMG activity. Error bars indicate SE. Solid arrows below each curve indicate the time of application. Application of MO to the TMJ region resulted in a characteristic increase in the electromyographic activity of jaw muscles both ipsilateral and contralateral to the injection site (Yu et al., 1995, 1996). Application of the EAAs to the TMJ region evoked activity in the ipsilateral jaw muscles that was similar to that evoked by MO. The above data suggest that activation of either NMDA or non-NMDA EAA receptors within the TMJ region may provide sufficient stimulation to evoke reflex jaw muscle activity. Ipsi. Dig., Ipsilateral digastric muscle; Ipsi. Mass., ipsilateral masseter muscle; Cont. Mass., contralateral masseter Muscle; Cont. Dig., contralateral digastric muscle.