Effects of 7,8-dihydroxyflavone on rat jejunal dynamics subjected to ischaemia-reperfusion injury.

It is known that 7,8-dihydroxyflavone (7,8-DHF), a synthetic agonist specific for TrkB, promotes intestinal cholinergic contraction. However, after intestinal ischaemia-reperfusion (IR) injury, how 7,8-DHF affects intestinal contractile dynamics is unknown. In this study, an IR injury model was prepared with rats subjected to 45 minutes clamping of the superior mesenteric artery. The IR injury decreased postoperative food intake and body weight, delayed defecation time, lowered intestinal propulsive rate and decreased cholinergic contraction of jejunal muscle strips, indicating the occurrence of injured jejunal contraction after IR. Feeding rats with 7,8-DHF improved these intestinal activities injured by IR, which exhibited the in vivo effect of 7,8-DHF. To explore its molecular mechanism, the expression and phosphorylation of TrkB, PLC γ1, Akt, and ERK1/2 in the jejunal strips were examined with western blots. The IR injury significantly decreased the expression and phosphorylation levels of all factors studied here. However, 7,8-DHF feeding specifically enhanced the phosphorylation of TrkB, PLC γ1 and Akt factors in both sham- and IR-operated rats, indicating that 7,8-DHF may have activated TrkB which then activated its downstream PLC γ1 and Akt. Finally, we found that 7,8-DHF augmented cholinergic receptor M3 expression somehow. These results imply a possibility that 7,8-DHF might be capable of alleviating the jejunal contractile damage caused by IR through activation of TrkB and augmentation of M3 expression.