The effects of acute temperature change on smooth muscle contractility of rainbow trout (Oncorhynchus mykiss Walbaum) intestine

Abstract

The effects of altered temperature in vivo on in vitro smooth muscle contractility of rainbow trout intestine were investigated. Initial analysis of the data revealed a seasonal variation in the maximal tension of intestinal smooth muscle attainable with 5-hydroxytryptamine (serotonin), carbachol, KCl, and transmural stimulation in vitro. Peaks occurred in spring and troughs in autumn. There was no seasonal cycling of the potency of the stimulants. All data regarding the efficacy of the stimulants were subsequently corrected for seasonal variation. The response of smooth muscle depends on the temperature of the water in which the fish are placed (2°C-20°C). There was a marked linear increase in efficacy and a slight increase in potency of the stimulants with increasing temperature. Changes in responsiveness of the intestinal smooth muscle occurred within 30 min of moving the fish between tanks. Smooth muscle reactivity returned to pretreatment values by 48h. Any changes in responsiveness with regards to time were unlikely to be as a consequence of water temperature, but may have been a result of handling stress.

Changes in smooth muscle contractility of rainbow trout (Oncorhynchus mykiss Walbaum) intestine during acclimation to altered temperature

“…Fish were removed at days 2, 4, and 8 for testing. Twelve additional fish, time-matched with the test animals to correct for seasonal variability (Burka et al 1993), were removed from the holding tank and used immediately to establish concentration-response relationships to 5-hydroxytryptamine (5-HT), carbachol, and KCI and frequency-response relationships to TMS (see below).…”

“…The intestine was removed from the fish within 3 min of netting, washed, and suspended in KrebsHenseleit solution (maintained at the temperature to which the fish were acclimated) in isolated organ baths as previously reported (Burka et al 1993).…”

“…The cited studies utilized fish which had been temperature acclimated (4-20°C) for 6 to 8 weeks prior to experimentation. The contractility of rainbow trout gastrointestinal smooth muscle in vitro also depends on temperature (Burka et al 1990(Burka et al , 1993. Those studies showed a marked linear increase in efficacy and a slight increase in potency to the smooth muscle contractile agonists, 5-hydroxytryptamine (5-HT; serotonin) and carbachol, the depolarizing agent, KCI, and transmural electrical stimulation (TMS) of the muscle with increasing temperature.…”

“…Those studies showed a marked linear increase in efficacy and a slight increase in potency to the smooth muscle contractile agonists, 5-hydroxytryptamine (5-HT; serotonin) and carbachol, the depolarizing agent, KCI, and transmural electrical stimulation (TMS) of the muscle with increasing temperature. Changes in contractility occur within 30 min of moving the fish between tanks and part of the change may be a consequence of handling stress (Burka et al 1993).…”

“…Because altered smooth muscle reactivity returns to normal levels within 48 hrs following handling stress (Burka et al 1993), an extended temperature adaptation regimen was employed to reduce the combined stress of handling and acute temperature change. The present protocol was able to demonstrate some intrinsic changes in gastrointestinal motility that occur during acclimation to modified ambient temperatures.…”