The Changes of Cortical Spreading Depression During Hypothermia and Rewarming in Rat

ABSTRACT

The present study was carried out to evaluate the effect of hypothermia and rewarming on the pattern of Cortical Spreading Depression(CSD) and predict the resultant vulnerability of the brain. Thirty four Sprague-Dawley rats, either sex, weighing 250-350gm, were used. They were devided into 4 groups, according to the degree of hypothermia and speed of rewarming, Profound Hypothermia & Slow Rewarming(G I), Profound Hypothermia & Rapid Rewarming(G II), Moderate Hypothermia & Slow Rewarming(G III), Moderate Hypothermia & Rapid Rewarming(G IV). CSD was elicited by local application of KC1 and identified by Direct Current Potential(DCP). We estimated the Frequency of DCP, Recovery time of negative shift of DCP, Area of negative shift of DCP according to the change of body temperature. The frequencies of DCP increased after rewarming compared with the normothermic state in all groups, statistical significance(P<0.05) was specially evident in Group II(Profound Hypothermia & Rapid Rewarming group), 5.1+/-0.3/30min.(mean+/-standard error) in normothermic state, while 9.3+/-0.8/30min in rewarming state. Recovery time(width) of DCP was delayed with hypothermia but decreased with rewarming but delayed state compared with normothermic state in all groups, i.e. 34.7+/-1.0sec at normothermic state, 59.9+/-4.3sec at 27.5 degrees C, 40+/-1.4sec at rewarming state in Group II. We can predict that the vulnerability of the brain tissue may be increased during the rewarming state following hypothermia in all groups. Such evidence is more significant in Group II(Profound Hypothermia & Rapid Rewarming) during the period of certain time(30-60min) after rewarming.