Electrophysiological Study of the Influence of Subcortical Structures on the Photo-evoked Eyelid, Microvibration

Part 1: Electrical Stimulation and Destruction

Abstract

The mechanism of photo-evoked eyelid microvibration (MV) was studied in unanesthetized rabbits by giving a series of electrical stimulation on the subcortical structures (such as caudate nucleus, globus pallidus, putamen, amygdaloid nucleus, hippocampus and ventrolateral nucleus of thalamus) or by destroying them electrically.
1. Five components were observed in the MV in response to the photic stimulation. They were named MV₁, MV₂, MV₃, MV₄ and MV₅and their peak latencies were 33.1,44.1,57.3,70.0 and 83.0 msec respectively.
2. The influence on the amplitude of MV by electrical stimulation of subcortical structures was studied with frequencies of 3Hz and 100 Hz. Stimulation of the caudate nucleus with 100 Hz suppressed MV to a greater degree than with 3 Hz.
3. Stimulation of the putamen with 3 Hz suppressed MV to a greater degree than with 100 Hz.
4. Stimulation of the globus pallidus with 3 Hz and 100 ', Hz potentiated MV, and the Potentiation was stronger with 100 Hz.
5. Stimulation of amygdaloid nucleus had either facilitatory or inhibitory effect on MV, depending on the site of stimulation. Inhibitory effect was often observed with stimula t i on of the ventral part of the amygdaloid nucleus.
6. MV was depressed by stimulation of the hippocampus with both frequencies, especially with 100 Hz.
7. Stimulation of the ventrolateral nucleus of the thalamus suppressed MV. Its effect was not dependent on the difference in freqency.
8. MV either increased or decreased in amplitude with stimulation of the internal capsule. In the same animal, the effect on MV was the same with the two diffenent frequencies o f stimulation. In the potentiated case, stimulation of the internal capsule with 100 H z increased to a greater extent than with 3 Hz.
9. MV was recorded 10,60 and 120 minutes after generating a electrical lesion in the caudate nuclei. MV slowly increased step by step after destruction of the bilateral cauda t e nuclei, while MV gradually decreased after destruction of the globus pallidus.
10. MV increased after destruction of the putamen and the maximal response was usually obtained at 60 minutes. In some cases, MV either increased or decreased at 10 min u tes.
11. Destruction of the amygdaloid nucleus markedly potentiated MV, especially, at a later time.
12. Potentiation of MV was observed at both 60 and 120 minutes after widespread destruction of the hippocampus, while some cases, MV decreased at 10 minutes.
13. MV decreased at 10 minutes after damage of the ventrolateral nucleus of the thalamus, whereas it increased at both 60 and 120 minutes after destruction.
14. Destruction of the internal capsule resulted in different effects on MV at 10 minutes, though MV tended to decrease at both 60 and 120 minutes.
15. Intravenous injection of barbiturate (5mg/kg) markedly suppressed MV.
16. The effect of electrical stimulation of the subcortical structures was frequently reversed by the prior application of barbiturate.