The acute effects of diazepam (DZP) and sodium valproate (VPA) on somatosensory evoked potential (SEP) were studied with 16 healthy male subjects (26~43 y. o.). In the two experimental sessions on different days, DZP (0.1 mg/kg) or VP A (5 mg/kg) was orally administered for each subjects. EEGs containing SEPs evoked by electric stimuli once every 5 sec were derived from the two derivations (monopolar : C3'→A1+2, bipolar : C3'→F3') and recorded into magnetic tape, before and 30, 60, and 90 min after the administration of these drugs. Reproducing the tape, SEPs with 1024 msec of analysis time were obtained by averaging 100 responses, and EEGs were subjected to the frequency analysis. Consecutive changes of group mean SEP were studied. Individual SEPs were subjected to the component analysis, and to the statistical assessment together with EEG. The following results were obtained.
1. After the administration of DZP, amplitudes of middle and long latency compenent significantly decreased and continued from early stage. The latencies were significantly increased and recovered for the middle latency component (P3~N4), while decreased for those of long latency component (N5~) later. After administration of DZP, in EEG, the power % were significantly increased for not only drug induced β but also δ and θ, and they had significant positive correlation with the latencies of middle latency component. These results suggest that DZP has the transient inhibitory effect to brainstem reticular formation, thalamus and hypothalamus, and continuous inhibitory effect to cerebral gray matter from early stage, and might facilitate transmission in cerebral white matter through GABA neuron system.
2. After the administration of VPA, the latencies did not significantly change for latencies of middle latency component, but increased for these of long latency component (P6~). Amplitudes of middle and long latency components decreased significantly. In EEG, the power % were significantly increased for α1 and decreased for β2. These results suggest that VPA has no or weak effect to brainstem reticular formation, thalamus and hypothalamus, while it has the inhibitory effect to cerebral gray matter through GABA neuron system
