Behavioral and EEG alterations with brain stem compression and effect of thyrotropin-releasing hormone (TRH) in chronic cats

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Abstract
Behavioral and EEG changes induced by brain stem compression and the effect of TRH were studied. The compression was given for 1-6 min by inflating a balloon chronically implanted on the dorsal surface of the cat brain stem in the 4th ventricle via cisterna magna. Within 10-36 s after the start of the compression, the cats turned sideways and became motionless in a spastic extension of 4 legs; thereafter all reverted to a normal position, after 45-120 min, although slight movements or head-up position was seen in some animals. The cortical EEG patterns seen after the compression were initially a brief rush of low multitude-fast waves (EEG arousal) followed by a flattened and/or spike pattern, and subsequently these shifted to high amplitude-slow waves with or without an accompanying EEG arousal. The behavioral and EEG changes were remarkably improved by i.v. administration of TRH as follows: 8 of 12 cats with 1 mg/kg and 1 of 4 cats with 0.5 mg/kg promptly changed from the lateral to a crouching or abdominal position, and never turned sideways again. Partial recovery such as movements of forelegs, struggling or head-up in the lateral position, rolling or slight shift of position was seen within several min in 3 cats with 1 mg/kg and in 2 cats with 0.5 mg/kg. TRH induced a dose dependent, persistent EEG arousal in all cats. Apparently TRH ameliorates deterioration in behavior and the EEG, this deterioration was similar to clinical states of consciousness disturbance induced by brain stem compression.