Effect of urea on central nervous system activity in the cat

¹ Divisions of Neurosurgery and Neurology, School of Medicine, Western Reserve University, and University Hospitals of Cleveland, Cleveland, Ohio

Effects of i.v. infusion of urea were studied in 26 cats by recording spontaneous cortical activity and somatic afferent evoked potentials from the posteroventral lateral nucleus of the thalamus and periaqueductal midbrain reticular formation. Subsequent to the administration of a 20% solution of urea, spindling and seizure discharges appeared in the electrocorticogram. The evoked potentials from the posteroventral lateral nucleus of the thalamus and reticular formation remained unchanged. Control studies indicated that the operative procedure, including the insertion of subcortical electrodes, hydration incident to fluid administration, possible deterioration of the preparation and alteration of the osmolarity of the serum did not produce the observed results. It was demonstrated that urea administered intravenously, in amounts producing blood NPN values commensurate with those observed in patients with uremia, alters cortical activity and excitability.