EFFECTS OF HYPERGLYCEMIA ON GASPING AND AUTORESUSCITATION IN NEWBORN RATS

The aim of this study was to test the effects of glucose on the gaspin g ability and survival in a rat pup model during acute anoxia. Newborn rat pups of both 1 and 8 days of age were given glucose (30 and 60 mg /animal) or saline intraperitoneally and subsequently subjected to ano xia (100% N-2). Glucose supplement induced hyperglycemia. Respiration was recorded by barometric plethysmography. The rat pups responded to acute anoxia with a robust sequence of respiratory pattern: hyperpnea, primary apnea, hypoxic gasping and secondary apnea. During anoxia the 1-day-old rats gasped much longer than the 8-day-old rats (23.4 +/- 1 .0 vs. 6.1 +/- 0.5 min, p < 0.001). No difference was found in gasping duration between the saline control and the glucose-supplemented 1-da y-old rat pups. The 8-day-old supplemented rats gasped much longer(9.3 +/- 0.5 min) than the control rats (6.1 +/- 0.5 min, p < 0.01). The a nimals autoresuscitated when they received oxygen (100%) during the ga sping period. When oxygen was given after the gasping period, the surv ival rate was 33.3% in control and 0% in supplemented 1-day-old rats, and 100% in control and 50% in glucose-supplemented 8-day-old rats (p < 0.02). Further controlled experiments for a fixed period of anoxia t o 13.5 min resulted in survival rates of 50.0% for controls and 28.6% for supplemented animals, respectively. The overall survival rate was then 85.2% in control and 52.9% in supplemented 8-day-old rats (p < 0. 05). Lactate concentration in blood rapidly increased in the first 6 m in of anoxia and thereafter gradually increased to 22.1 mmol/l around the last gasp in the 1-day-old rats. Hyperglycemia did not cause furth er accumulation of lactate despite a transient elevation over the cont rol rats at 6 min of anoxia. In the 8-day-old supplemented animals the lactate level was only modestly increased, probably due to the prolon ged gasping period. In conclusion, we found that gasping performance w as well preserved in the 8-day-old glucose-supplemented rats, whereas the autoresuscitation mechanism after the last gasp might be altered d ue to hyperglycemia. In addition, the accumulation of lactate in the b lood did not affect the gasping performance and the mechanisms of auto resuscitation.