Effect of hypothermia on motor function of adult rats after neonatal hyperthermic hypoxic-ischemic brain insult.

Regarding therapeutic hypothermia for human neonatal hyperthermic hypoxic-ischemic encephalopathy (HIE), we investigated the motor function of a neonatal hyperthermic HIE rat model, and also performed systemic hypothermia using the model. Forty-two neonatal Wistar rats at 7-days-old were used in this study. The left common carotid artery of 34 neonatal rats was ligated under isoflurane anesthesia. We also established a sham group (S group, n = 8). After 1-h recovery, all rats were exposed to 8% oxygen at an ambient temperature (T (a)) of 40 degrees C for 15 min. Following insult, 16 rats were placed in a chamber at a T (a) of 30 degrees C (H group) and the other 18 rats at a T (a) of 37 degrees C after arterial ligation (N group), and all rats in the S group were placed in a chamber at a T (a) of 37 degrees C for 12 h. A Rota-Rod test was performed involving all rats at 8 weeks old. The rod was rotated at 5, 5, and 7 rpm on three consecutive days, respectively. Rats in the N group stayed on the rotating rod for a significantly shorter period than those in S and H groups only on the second day of measurement. The width of the insulted hemisphere in N group rats was significantly smaller than those in S and H groups. There was no significant correlation between S and H groups regarding the motor function and anatomy. These results suggest that neonatal hyperthermic hypoxic-ischemic insult impairs the motor function, which may be rescued by systemic hypothermia after insult.