Abstract
Neonates sometimes suffer from severe brain damage by hypoxic-ischemic (HI) insults such as cord compression during delivery. Brain hypothermia soon after the HI insult might relieve HI encephalopathy (HIE) but this has not been fully examined. In this study, the effect of brain hypothermia was examined using a simple behavioral method. For the study of neonatal HIE, rat HIE models were produced by ligation of the left or right carotid artery in 7-day-old rats followed by exposure to a hypoxic environment of 8% oxygen for 15 minutes. We made five groups of rats; NRG (n=8) and NLG (n=7) groups had the right and left carotid artery ligated, respectively, and were returned to their mother. HRG (n=6) and HLG (n=6) groups were placed in hypothermic conditions of 33 °C for 12 hr after right or left carotid ligation. A sham group (SG, n=3) was also established. We performed a swimming test using 4- to 7-week-old rats. The rat was placed in the center of a circlular pool (diameter 150cm, depth 15cm) and swam in a clockwise or counterclockwise direction until it arrived at the pool wall. NLG tended to turn counterclockwise, but NRG tended to turn clockwise. However, SG, HLG and HRG tended to turn equally clockwise and counterclockwise. The ratios of operated/contralateral cerebrum hemisphere were 1.00, 0.87, 0.81, 1.00, 0.94 in SG, NLG, NRG, HLG and HRG, respectively. Brain hypothermia soon after HI insult may improve physical function in HIE rats. [J Physiol Sci. 2007;57 Suppl:S191]
