THE EFFECT OF HYPERTONIC UREA SOLUTION ON ELECTROSHOCK SEIZURE THRESHOLD AND ELECTROLYTE DISTRIBUTION IN RATS’

The role of water and electrolyte metabolism in clinical epilepsy and experimental convul-sions has been studied intermittently during the past several decades. However, the exact rela-tion between alterations in water and electro-lyte levels and changes in central nervous sys-tem (CNS) excitability is still not completely clear. While investigating the effect of hyper-tonic urea solutions on brain water content, cerebrospinal fluid (CSF) pressure, and urea uptake by the cerebral cortex (Reed and Woodbury, 1962a,b), we observed that ne-phrectomized rats which had received urea, 2 g/kg intraperitoneally (i.p.) as a 50 % solution, appeared to be less susceptible to spontaneous seizures than were control nephrectomized rats. About this time, Carter (1962) reported his favorable experience with the use of hyper-tonic urea solution in the treatment of status epilepticus. In view of the foregoing and the fact that hypertonic urea solution has been used clinically to reduce brain volume and CSF pressure, the work reported here was under-taken in an attempt to establish the effect of hypertonic urea solution on CNS excitability and to study the relation between CNS excita-bility, brain water content, and brain electro-h’te concentrations. METHODS. Male Sprague-Dawley rats, initial body weight 150 to 175 g, were used as experi-mental animals. Water and food were available ad libitnno throughout the experiments. Two series of experiments were conducted. In the first series 160 rats were divided into 10 groups of 16 animals each. Prior to testing the effect of hypertonic urea solution on the electroshock seizure threshold (EST), each animal was shocked and the average EST of each group wa.s determined on 2 occasions