聴覚性誘発電位(AEP)および脳波に対するcaffeineの効果

We studied the effects of caffeine on the central nervous system by auditory evoked potentials (AEP) with 25 healthy male subjects (T-group: 24-44 y.o., mean caffeine consumption: 251.4 mg/day). According to the DSM-IV criteria for caffeine intoxication, T-group were devided into the light (L-group: 11 subjects, ≦250 mg/ day) and heavy consumer group (H-group: 14 subjects, >250 mg/ day), and into caffeine (CAF-group) and placebo administration group (PLA-group) according to a double-blind cross-over design. EEG containing AEP was recorded through the two deviations (monopolar : Cz→A1+2, bipolar : Cz→T5); before and 30, 60 and 90 min after the oral administration of caffeine or placebo (3 mg/kg of B.W.). Consecutive changes of the latencies and amplitudes in group mean AEP were studied. Those of individual AEP were subjected to the component analysis, and to the statistical assessment with reference to the EEG power % changes.
1. After the administration of caffeine, CAF-group had a significant decrease in N 4 (= N 1, latency : 95-125 msec) and P 5 (=P 2, latency : 160-200 msec) latencies of long latency components, followed by a decrease in N 4-P 5 amplitudes of AEP, which indicated that there was a post-exciting inhibitory effect in CAF(H)-group. In EEG, α power % significantly increased, whereas δ, θ and β power % significantly decreased. These findings indicated that caffeine might have a sedative effect as well as the exciting effects on the primary and secondary auditory cortex.
2. CAF(H)-group had significant changes in latencies of AEP and EEG only 30 min after the administration of caffeine, whereas CAF(L)-group had these changes over 60 min after that, suggesting the hypersensitivity to caffeine by the interruption of caffeine consumption.
3. These changes seemed to be assciated with the effects of caffeine as an adenosine A1 receptor antagonist in the cerebral cortex, although further investigation on the neurotransmitters related to caffeine should be expected.