Electrophysiological studies on the effect of stimulation of the nucleus ventralis anterior (VA)and nucleus reticularis (RET) of the thalamus were conducted in the rabbit. The following results were obtained.
1) The ave rage spike and wave pattern appearing in the cerebral cortical EEG on stimulation of the VA with 3 Hz and that induced by a similar stimulation of the RET was calculated by use of the digital computor (Nihon Kohden ATAC-201) and a comparison of the patterns showed that spikes predominated when the VA is stimulated and waves predominated when the RET is stimulated.
2) Late components N6 and N7 of the average evoked potential appearing in the cerebral cortex on stimulation of the sciatic nerve are suppressed by 3Hz stimulation of the VA and intensified by stimulation of the RET.
3) Late components HN5 and H N6 of the average evoked potential of the hippocampus elicited by stimulation of the sciatic nerve are at times intensified by stimulation of the VA and RET with 3 Hz and suppressed at other times but a trend for intensification was greater with stimulation of the RET.
4) The integratin g value of the evoked muscular discharge, appearing in the fore-and hindlimbs on stimulation of the cerebral cortex, increased or decreased with stimulation of VA (3,8Hz) and RET (3,8 Hz) but a greater trend for decrease was observed with VA atimulation compared to RET stimulation.
5) The integratin g value of the evoked muscular discharge, appearing in the fore- and hindlimbs on stimulation of the hippocampus, increased or decreasad with stimulation of VA (3,8 Hz) and RET (3,8 Hz).
6) A trend for decrease in the carotid blood flow was noted on stimulation of the VA (3,100Hz) but there was little change on RET stimulation (3,100 Hz).
7) The frequency of spontaneous discharges of the cervical sympathetic trunk increased with VA stimulation (3,100 Hz) but decreased with RET stimulation (3,100 Hz).
8) The arrest reaction in the behavior of the rabbit with both VA stimulatio n (3,100 Hz)and RET stimulation (3,100 Hz) but a trend for a lower threshold was noted with VA stimulation.
9) The effect of drugs (morphine, barbiturate, chlorpromazine, tridion) on the spike and wave pattern elicited by 3 Hz VA and 3 Hz RET stimulation was studied using the digital computor (ATAC-201) and it was found that tridion had a suppressive action on the spike induced by stimulation of both VA and RET.
The findings suggest that VA is involv ed in the appearance of petit mal symptoms and spikes are more closely related than waves. It can also be said that drugs like tridion, which show a suppressive action on spikes rather than on waves, will be more effective in the petit mal patient.
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