Jf. Burka et al., THE EFFECTS OF ACUTE TEMPERATURE-CHANGE ON SMOOTH-MUSCLE CONTRACTILITY OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS WALBAUM) INTESTINE, Fish physiology and biochemistry, 12(1), 1993, pp. 53-60
The effects of altered temperature in vivo on in vitro smooth muscle c
ontractility of rainbow trout intestine were investigated. Initial ana
lysis of the data revealed a seasonal variation in the maximal tension
of intestinal smooth muscle attainable with 5-hydroxytryptamine (sero
tonin), carbachol, KCl, and transmural stimulation in vitro. Peaks occ
urred in spring and troughs in autumn. There was no seasonal cycling o
f the potency of the stimulants. All data regarding the efficacy of th
e stimulants were subsequently corrected for seasonal variation. The r
esponse of smooth muscle depends on the temperature of the water in wh
ich the fish are placed (2-degrees-C-20-degrees-C). There was a marked
linear increase in efficacy and a slight increase in potency of the s
timulants with increasing temperature. Changes in responsiveness of th
e intestinal smooth muscle occurred within 30 min of moving the fish b
etween tanks. Smooth muscle reactivity returned to pretreatment values
by 48h. Any changes in responsiveness with regards to time were unlik
ely to be as a consequence of water temperature, but may have been a r
esult of handling stress.