Fig. 6. Pooled summary data of study 2. (Top ) Mean values ± SD of net increases of peak neuronal discharge frequency (Fn) at the 1/2 D40Hzand D40HzN -methyl-d-aspartic acid (NMDA) dose rates for 0–minimum alveolar concentration (MAC), 1 MAC, and 0 MAC end-control for 13 neurons. Halothane, 1 MAC, caused a small reduction in the D40Hznet increase from 40 Hz to 38.7 ± 15.4 Hz. (Bottom ) Normalized 1/2 D40Hz and D40Hz net response data for the same 13 neurons show that the postsynaptic glutamatergic excitatory response was not significantly depressed by the anesthetic.