Influence of Hypoglycemia and Hypothermia on Direct Current Potential During Cortical Spreading Depression in Rats

ABSTRACT

The object of this study was to investigate the influences of hypoglycemia and hypothermia on the direct current(DC) pontetial changes during cortical spreading depression(CSD) in rats. The induction of CSD was achieved by the application of KCI solution on the cortex of the frontal lobe. Hypoglycemia and hypothermia were induced respectively by insulin injection and the application of an ice pack. The DC potential changes during progressive hypoglycemia and hypothermia were measured with microelectrodes from the cortex of the parietal lobe of rats. Under contril condition, the rate of CSD was one per 5-10 min and the negative shift of DC potential was about 30 mV. The recovery time from negative shift to base line of DC potential was about 40 sec. In rats treated with insulin, the amplitude of DC potential shift was unaffected by hypoglycemia. The recovery time of DC shift was 40+/-2.26 sec at normoglycemia and it was delayed progressively as the blood glucose level lowered. The mean of it was 63+/-8.02 sec at 30 mg/dl and 77.1+/-22.0 sec with the blood glucose falling below 20 mg/dl. The same delay in the recovery time as seen in the hypogylcemia group was observed in rats treated with hypothermia. The recovery time of DC shift was 39.4+/-3.02 sec in normothermia(36.5degrees C), but it was delayed to 61.15+/-4.15 sec at 30degrees C and 96.67+/-14.92 sec at 26degrees C body temperature. This study suggested that each condition of profound hypoglycemia below 30 mg/dl and hypothermia below 30degrees C was to be harmful to the ion homeostasis and the integrity of the cell membrane and it may lead neurons to death.