Postprandial changes in enteric electrical activity and gut blood flow in rainbow trout (Oncorhynchus mykiss) acclimated to different temperatures

Enteric electrical activity, cardiac output and gut blood flow were measured in rainbow trout (Oncorhynchus mykiss) acclimated to either 10 degrees C or 16 degrees C. Enteric electrical activity showed, in both the fasted and postprandial state, a distinct pattern with clusters of burst-like events interspersed by silent periods. The frequency of electrical events increased postprandially for both acclimation groups. Event frequency increased from 3.0+/-0.5 to 9.6+/-1.4 events min(-1) and from 5.9+/-0.9 to 11.8+/-2.0 events min(-1) in the 10 degrees C and 16 degrees C groups, respectively. Similarly, the number of events per cluster increased postprandially for both acclimation groups. Gut blood flow, cardiac output and heart rate increased after feeding. The gut blood flow significantly increased in both groups and peaked at 257+/-19% and 236+/-22% in the 10 degrees C and 16 degrees C groups, respectively. There was a strong correlation between the number of events and gut blood flow at both temperatures. Comparison between the two groups showed that fish acclimated to 16 degrees C may have an increased cost of sustaining the basal activity of the gut compared with the group acclimated to 10 degrees C. In conclusion, we have for the first time measured enteric electrical activity in vivo in a fish species and we have also demonstrated a strong correlation between gut blood flow and enteric electrical activity in fasted and postprandial fish.