Central nervous system effect of enflurane.

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Experiments were performed in cats and rats. In cats anesthetized with enflurane(2-5%), eeg seizures were not induced by hypocapnia(PaCO2;20mmHg), while with stimulation(tapping forelimb), seizures were induced either at normocapnia or hypocapnia when enflurane was above 3.5%. The stimulation required to induce seizures was dose-dependently decreased. Unilateral excision of cerebral cortex did not change EEG in the thalamus. Cortical EEG was not also affected by a destruction of ventrobasal complex(VB) in the thalamus and of the hippocampus. Stimulation required to induce seizures was not affected by a hippocampal destruction but was increased by a VB destruction. Somatosensory evoked petentials in the cortex and thalamus by an electrical stimulation of sciatic nerve during enflurane anesthesia were dose-dependently suppressed, and were not affected by cortical excision.Enflurane, on the other hand, increased threshold of electrically induced seizures and dose-dependently suppressed th … More e seizures induced by drugs (pentylenetetrazol, kainic acid, penicillin). Furthermore, deep enflurane anesthesia abolished the increase of glucose consumption in the VB, cerebral cortex, corpus callosum and internal capsule produced by intracortical injection of penicillin despite enflurane(4%) alone produced characteristic increase in these areas in rats. The increase in glucose consumption in the corpus callosum and hippocampal CA3 was not observed in cats even when seizures were induced by forelimb tapping. Local cerebral blood flow was markedly increased during 4% enflurane anesthesia, which was decreased by hypocapnia, possibly producing uncoupling between metabolism and flow.In summary, somatosensory stimulation induces seizures during deep enflurane anesthesia, while electrically or drug-induced seizures are suppressed, suggesting epileptogenic and antiepileptic properties of enflurane. The results also demonstrated the species difference in cerebral cortical and intercortical activities during enflurane anesthesia. Less