Regional effects of hypoxia and hypothermia on rebound excitation in large intestine of piebald mouse model for Hirschsprung's disease

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Abstract
Effects of hypoxia and hypothermia on the poststimulus rebound contractile response (PSRR) were studied in the circular muscle coat of the large intestine of the piebald mouse model for Hirschsprung's disease. The PSRR in the terminal segment of the normal large intestine, which corresponds to the aganglionic segment of the piebald mice, was found to be much more resistant to hypoxia than more proximal regions of the bowel. Effects of hypoxia on the PSRR of megacolonic preparations from piebald mice were essentially the same as for the proximal and midcolon of normal mice. The exception was an increase in latency for the PSRR in the intestine of diseased animals that did not occur in the preparations from normal littermates. Effects of hypothermia, unlike hypoxia, were not markedly different in the proximal and distal large intestine. The latency and duration of the PSRR were increased during hypothermia while the amplitude decreased in all ganglionated regions of large intestinal preparations from both piebald mice and their normal siblings. This was interpreted to result from suppression of inhibitory neuronal activity. The results suggest that the capacity for anerobic metabolism within the neuromuscular apparatus responsible for the PSRR is greater in the terminal large intestine than in the proximal and midcolon.