Jf. Burka et al., CHANGES IN SMOOTH-MUSCLE CONTRACTILITY OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS WALBAUM) INTESTINE DURING ACCLIMATION TO ALTERED TEMPERATURE, Fish physiology and biochemistry, 12(4), 1993, pp. 347-355
The effects of altered water temperature in vivo on in vitro smooth mu
scle contractility of rainbow trout intestine were investigated. Tempe
rature has a significant effect on receptor-mediated intestinal smooth
muscle contractility in the rainbow trout. The efficacy of 5-HT, carb
achol, and transmural stimulation increased with temperatures above 10
-degrees-C, with an optimal increase at 15-degrees-C. There was also a
modest increase in the potency of 5-HT and carbachol within 2 days of
establishing trout at 20-degrees-C. By day 8, most of these changes h
ad either stabilized or were returning to control values, suggesting t
hat acclimation changes in membranes and enzyme activities were taking
effect. However, the contractile responses to carbachol and transmura
l stimulation were still increasing at this time. This may imply that
the muscarinic receptors are more resistant to membrane acclimation ch
anges and may take longer to adapt. Because these experiments were con
trolled for handling stress and seasonal changes that affect contracti
lity, we have been able to demonstrate some early changes in smooth mu
scle contractility that occur during acclimation to altered temperatur
e.