Effects of therapeutic hypothermia after hypoxic-ischemic insults in neonatal rats assessed by motor function using rotor rod test

Abstract

Effects of therapeutic hypothermia soon after hypoxic-ischemic (HI) insults in infants is now receiving attention in perinatology. Although the neonatal HI rat model is established in the experimental study, effects of therapeutic hypothermia in rats' actual motor activity has rarely been tested. In this study, we investigated the effects of therapeutic hypothermia in motor function of HI neonatal rat model using rotor rod test. We ligated the left common carotid artery in ten seven-day-old rats under inspired isoflurane anesthesia, then exposed the rats to 8% oxygen at 40 degrees for 15 min. Therapeutic hypothermia was induced in 5 of the rats (hypothermia group) immediately after the insult by maintaining the rats' body temperature at 30 degrees for 12 hrs. In the other the rats' body temperature was maintained around 36 degrees (normothermia group). Rotor rod test was performed two months after the HIE insults. On the 1st day of experiments, all rats fell from the rod rotating at 5 rpm within 60 sec. On the 2nd day, all rats in the hypothermia group stayed on the rotating rod for 60 sec, although all rats in the normothermia group again fell within 60 sec. On the 3rd day, all the rats stayed on the rod at 7 rpm for 60 sec. Hypothermia soon after HI insult may improve motor function compared to normothermia. [J Physiol Sci. 2006;56 Suppl:S227]