The effect of environmental temperature on the electrocortical activity of cats immobilized by neuromuscular blocking agents

Abstract

1. 1. The effect of environmental temperature on the electric activity of the brain of cats immobilized by neuromuscular blocking agents was studied systematically. Gallamine triethiodide (Flaxedil) was mainly used but succinylcholine and d-tubocurarine chloride were also sometimes administered as neuromuscular blocking agents. Electrocortical effects of the different drugs were similar. 2. 2. When the environmental temperature which had been much lower than the normal body temperature of the animal was elevated gradually, the low voltage fast neocortical activity began to be replaced by spindle and slow activity as the environmental temperature became higher than 25°C. The hippocampal electrical activity also showed a change parallel to the neocortical activity. When the environmental temperature became very close to or even higher than the body temperature, the synchronized neocortical activity returned to the low voltage fast pattern again. 3. 3. When the environmental temperature was much lower (20–25°C) than the body temperature and the neocortical electrogram showed low voltage fast pattern, the application of a hot water bag (45°C) to the animal had a remarkable electrocortical synchronizing effect similar to that of the elevation of the environmental temperature. The application of a cold water bag, on the other hand, desynchronized the electrocortical activity. 4. 4. Desynchronization of the neocortical activity corresponded to an elevation of the systolic blood pressure and the synchronization to its fall. 5. 5. Partial transection of the ventrolateral part or total transection of the neuraxis at the level of C-1 abolished the electrocortical modifying effect of both the alteration of environmental temperature and application of hot and cold water bags. These results suggest that the electrocortical activity of the immobilized cat might be modified mainly by alteration of afferent impulses originating, probably, in the peripheral thermoceptor. 6. 6. The activated sleep period could not be identified in the cat during immobilization with neuromuscular blocking agents.