Myoelectric bowel activity in ischemia/reperfusion damage. Role of sensory neurons

The present knowledge indicates that afferent sensory neurons (C-fibres) play an important role in the relationship between intestinal myoelectric activity (IMA) and blood flow (LDBF). The aim of this study was to evaluate the role of C-fibers in myoelectric activity of small intestine during its ischemia and reperfusion. A neurotoxin-capsaicin (CAP) was used to induce functional ablation of afferent sensory neurons. Experiments were performed on 6 groups of anesthetized rats. In the I, II, III group of rats IMA and LDBF were recorded during 100% ischemia induced by AMA 15, 30 and 60 min total occlusion and during 60 min reperfusion period. In group V and VI, IMA and LDBF were registered after intrajejunal placement of 1% CAP. In group IV we measured effects of intraluminal instillation of CAP alone. Intraluminal placement of CAP induced an early increase in slow wave amplitude SWA and slow wave frequency SWF by 35+/-11% and 19+/-10% (p<0.05) with the subsequent decrease in both by 25+/-6 and 24+/-8% (p<0.05) respectively. Short 15 min lasting ischemia induced by 100% occlusion of AMA evoked only a slight increase of SWA. During reperfusion period SWA and SWF returned to the baseline values after 15 min. Total 30 min occlusion decreased SWA and SWF by 25+/-9 and 24+/-6% (p<0.05) respectively. During reperfusion period recovery of IMA parameters to preocclusion values were slower. Intestinal hyperemia was smaller than in previous group. After 60 min lasting intestinal ischemia SWA and SWF were decreased by 58+/-7 and 40+/-6% (p<0.01) respectively. There was no return of IMA parameters to control values. These data demonstrated that intestinal ischemia induces typical changes in the bowel myoelectric activity. These changes possess their own electrical characteristics which can be used in clinical practice for evaluation of the degree ischemically-induced intestinal injury. Capsaicin pretreatment significantly decreased SWA and SWF and LDBF in comparison with those observed in group II and III during 30 and 60 min occlusion and reperfusion period. We conclude that afferent neurons C activated during mesenteric ischemia/reperfusion play an important role in protecting ischemic bowel viability.