Effect of Hibernation on the Enteric Nervous System of Thirteen-lined Ground Squirrel Colon

Kathryn Ann Thompson

Abstract


The enteric nervous system is the intrinsic nervous system within the gut that controls gastrointestinal motility, ion secretion, and local blood flow. During hibernation, gastrointestinal motility is slowed down. The study aims to investigate the changes in the enteric nervous system that may contribute to the lowered level of gastrointestinal motility. Summer active, winter torpor, and interbout arousal thirteen-lined ground squirrels were used. Immunofluorescence staining was used to examine the changes in neurochemical codes in the enteric nervous system of the colon. Cell counts were carried out to obtain the number of cell bodies immunoreactive to choline acetyltranferase (ChAT), a marker for cholinergic neurons, nitric oxide synthase (NOS), an enzyme which catalyzes the synthesis of the inhibitory neurotransmitter nitric oxide, and substance P (SP), a marker for a subset of excitatory motor neurons. There was a significant decrease in the number of ChAT-immunoreactive (IR) neurons in the myenteric plexus of winter torpor ground squirrels.  In the summer active group, there were 14.17 ± 1.45 ChAT-IR neurons/myenteric ganglion. In the winter torpor group, there were 8.48 ± 1.14 ChAT-IR neurons/myenteric ganglion (P < 0.05, n = 5). In the interbout arousal group, there were 11.38 ± 1.44 ChAT-IR neurons/myenteric ganglion (P > 0.05, n = 5). There was no significant difference in expression of NOS or of SP between summer active, winter torpor, and interbout arousal ground squirrels. Selective downregulation of ChAT in the myenteric plexus of the ground squirrel colon may contribute to gut hypomotility during winter torpor.


Keywords


Hibernation, gastrointestinal motility, enteric nervous system, thirteen-lined ground squirrel

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