Effects of gastric distension and feeding on cardiovascular variables in the shorthorn sculpin (Myoxocephalus scorpius).

We have previously shown in rainbow trout (Oncorhynchus mykiss) that gastric distension induces an instantaneous alpha-adrenoceptor-mediated increase in the dorsal aortic blood pressure (P(da)), with no change in cardiac output (CO), gut blood flow (Q(cma)), or heart rate. To investigate if feeding habits affect these patterns and to compare the differences between gastric distension alone and feeding in the same experimental setting, we used the short-horn sculpin (Myoxocephalus scorpius), an inactive ambush predator with a capacity to eat large meals. An inflatable balloon was placed in the stomach of one group while another group was fed fish meat. When distending the stomach with a volume corresponding to a meal of 8-10% body weight, there is a profound and long-lasting increase in systemic (123 +/- 27%) and gastrointestinal (R(cma); 82 +/- 24%) vascular resistance, leading to an increase in P(da) (19%) without any change in CO or Q(cma). After force-feeding, there is a rapid transient increase in R(cma) (24 +/- 4%) and an even larger P(da) response (53%). There is also a subsequent increase in both CO (28 +/- 8%) and Q(cma) (27 +/- 9%) after 30 min. By 15 h, CO and Q(cma) increase further (41 +/- 11 and 63 +/- 14%, respectively), and this increase persists for up to 60 h. The increase in Q(cma) is mediated via both an increase in CO and a shunting of blood from the systemic circulation via a decrease in R(cma) (34 +/- 7%). In conclusion, the response to mechanical distension of the stomach is similar to what we have described in rainbow trout, and the postprandial gastrointestinal hyperemia is most likely chemically induced.