Hypertonic urea: Its effects on cortical and subcortical evoked potentials in cat

Abstract

The effects of urea and concomitant cerebral dehydration on potentials evoked in the cerebral cortex, midbrain reticular formation, and cerebellar cortex by somatic stimulation were studied in the cat. Urea (1.5 g/kg i.v.) typically augmented the negative and late positive phases of triphasic positive-negative-positive evoked cerebral cortical responses recorded monopolarly. This change began about 15 min after urea administration. It paralleled the onset of cerebral shrinkage and was maximal after about 1 h. These evoked potential changes persisted for 5 to 7 h in most cases, but sometimes returned to control levels after about 2 h. Resumption of the original cortical volume was not essential for return to baseline amplitudes.