Figure 8.

Exogenous glutamate application at the trigeminal motor pool potently increases masseter muscle tone during all behavioral states except tonic REM sleep. A, A typical example showing that perfusion of glutamate into the left trigeminal motor pool potently increases left masseter muscle (LM) tone during both alert waking and during NREM sleep. Remarkably, glutamate application is unable to overcome the atonia of tonic REM sleep; however, it does increase the number of muscle twitches during phasic REM. B, Group data (n = 6) demonstrating that exogenous glutamate application significantly increased left masseter muscle tone in waking and NREM sleep (p < 0.002), without changing levels of motor tone during tonic REM sleep (p = 0.916). C, D, Perfusion of glutamate into the left trigeminal motor pool also increased the number of muscle twitches during phasic REM sleep, but there was no change in the amplitude of muscle twitches after glutamate application (p = 0.099). All values are means ± SEM; *p < 0.05 and **p < 0.002; A.U., arbitrary units.