Effects of temperature on control mechanisms of gut motility in fish

Abstract

Gut motility is essential for digestion, nutrient absorption and thus overall health of animals. The present study investigated how temperature affects stimulatory pathways controlling gut motility in two teleost species, rainbow trout (Oncorhynchus mykiss) and shorthorn sculpin (Myoxocephalus scorpius), focusing mainly on autonomic nerve control involving the excitatory neurotransmitter acetylcholine, and the interstitial cells of Cajal (ICC). Contractile force of smooth muscle preparations from cardiac stomach and proximal intestine were recorded in vitro at 10, 15 and 20°C. In both species, increased temperature reduced the maximal force generated by the tissues when the cholinergic agonist carbachol was added. At the same time, tissues showed increased sensitivity to carbachol at increased temperatures, reflected by lower log EC50 values, at least in the shorthorn sculpin. Blocking the ICC activity with blockers of Ano1 channel did not affect the response to carbachol at 10°C, however it caused a rightward shift on the concentration response curve at the elevated temperatures, particularly in the rainbow trout, suggesting involvement of ICC in mediation of the cholinergic signal. In addition, inhibition of ICC caused in most samples a decrease in the basal tension, particularly at higher temperatures, suggesting that ICC play an important role in maintaining gastrointestinal excitability and basal tone. The effects of Ano1 blockers differed between organs and species, indicating regional and species-specific differences in ICC-related mechanisms. Overall, the results demonstrate that elevated temperature alters gastrointestinal motility control in teleost fish by affecting both smooth muscle responsiveness and ICC-associated mechanisms. These findings contribute to the understanding of how warming environmental conditions may influence digestive physiology in ectothermic vertebrates and may have implications for both conservation biology and aquaculture.