Effects of Hibernation on gastrointestinal transit

Abstract

Hibernating animals experience dramatic changes in the structure and function of their digestive system, along with other organ systems. Gut motility mixes food with digestive enzymes and propels it from the stomach to the more distal regions of the digestive tract for further processing. During the inter-digestive state, gut motility helps to clean out the indigestible matter and prevent bacteria overgrowth in the intestine. Despite its importance, changes in gut motility during hibernation have received minimal attention. The purpose of this study was to investigate the effects of hibernation on gut motility and its neuronal regulation. Thirteen-lined ground squirrels in summer active, winter torpor, and interbout arousal states were used in the study. Gastrointestinal transit was measured using a charcoal meal method. Immunofluorescence was used to measure the expression of neurotransmitter synthetic enzymes in the enteric nervous system of the stomach. Gastrointestinal transit was significantly slowed during torpor, but returned to normal level during interbout arousal. Choline acetyltransferase is an enzyme used in the synthesis of acetylcholine, a major excitatory neurotransmitter in the enteric nervous system. Nitric oxide synthase is an enzyme used in the synthesis of nitric oxide, a major inhibitory neurotransmitter in the enteric nervous system. There was no significant change in the number of neurons expressing choline acetyltransferase or nitric oxide synthase in the myenteric plexus of the stomach among arousal states. Further studies are needed to explore the changes of other neurotransmitters in the enteric nervous system during hibernation. Understanding the mechanisms responsible for the changes in gut motility during hibernation may provide insights into the basis of gastrointestinal motility disorders in humans.