視覚性誘発電位(VEP)および脳波へのinsulin低血糖の影響

The effects of insulin-induced hypoglycemia on central nervous system were studied by visual flash evoked potential (VEP), with 8 schizophrenic patients (31~47 y.o.), during the 'Kleine Insulinbehandlung'. In the three experimental sessions on different days, human regular insulin were injected subcutaneously to each patient, whose consciousness level were lowered to the stage of somnolence and recovered after intake of a solution of glucose (100 g). EEG containing VEPs evoked by flash stimuli once every 5 seconds were derived from the two derivations (2 nd ch : O1→A1+2, 5 th ch : O1→Cz). In the experimental session, EEG containing VEPs were recorded before and 20, 40, 60, 80, 100 and 120 min after the injection of insulin, and 20 min after intake of glucose. Consecutive changes of group mean VEP were studied. Individual VEPs were subjected to the component analysis, and to the statistical assessment together with EEG power%. The following results were obtained.
1. The long latency components of VEP significantly increased in latency and significantly deceased in peak-to-peak amplitude in the early stage after the injection of insulin. These findings indicate the inhibitory effects of insulin-induced hypoglycemia on the cerebral cortex in the early stage.
2. The short latency components of VEP significantly increased in the latency of N2 and significantly decreased in the peak-to-peak amplitude of P2-N2 in the latter stage. In EEG, the power% of δ and θ frequency bands significantly increased and that of α 1~β 2 significantly decreased in the latter stage. These findings indicate the inhibitory effects on the lateral geniculate body due to the decline of the brainstem activity, in the latter stage of insulin-induced hypoglycemia.