Specific and Nonspecific Multiple Unit Activities During the Onset of Pentylenetetrazol Seizures. II. Acute Lesions Interrupting Nonspecific System Connections

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Abstract
Nonspecific cortical, thalamic, mesencephalic and pontine multiple unit activities (MUA) and changes in EEG and MUA of the sciatic nerve after threshold pentylenetetrazol activation were studied in 3 groups of animals [cat] in which neuronal connections were interrupted at 3 different levels of the CNS: spinal, mesencephalic and prethalamic. Maximal increments of nonspecific MUA and maximal increments and maximal decrements of sciatic MUA after pentylenetetrazol from each group of lesioned animals were statistically compared with those observed in intact animals. Pentylenetetrazol threshold for producing cortical tonic-clonic EEG discharges was increased in animals with mesencephalic and prethalamic lesioned animals, whereas thalamic MUA maximal increment was significantly decreased in mesencephalic and significantly increased in prethalamic lesioned animals. Pontine MUA maximal increment was significantly increased in spinal, mesencephalic and prethalamic lesioned animals, and mesencephalic MUA maximal increment was not significantly modified in either prethalamic lesioned or in spinal transected animals. Sciatic MUA maximal increment and maximal decrement were significantly decreased in spinal transected animals, whereas only maximal increment was significantly decreased in mesencephalic and only maximal decrement was significantly decreased in prethalamic lesioned animals. Under normal conditions the development of generalized seizures induced by threshold pentylenetetrazol injection is apparently highly dependent upon the neuronal interactions between nonspecific structures at different levels of the CNS. The possible nature of these neuronal interactions in the intact animals was discussed.