Suppression of inflammatory events associated to intestinal ischemia-reperfusion by 5-HT1A blockade in mice

Intestinal ischemia and reperfusion (I/R) is a potentially life-threatening disease, ensuing from various clinical conditions. Experimentally, either protective or detrimental roles have been attributed to 5-HT in the functional and morphological injury caused by mesenteric I/R. Recently, we proved the involvement of 5-HT2A receptors in the intestinal dysmotility and leukocyte recruitment induced by 45min occlusion of the superior mesenteric artery (SMA) followed by 24h reperfusion in mice. Starting from these premises, the aim of our present work was to investigate the role played by endogenous 5-HT in the same experimental model where 45min SMA clamping was followed by 5h reflow. To this end, we first observed that ischemic preconditioning before I/R injury (IPC+I/R) reverted the increase in 5-HT tissue content and in inflammatory parameters induced by I/R in mice. Second, the effects produced by intravenous administration of 5-HT1A ligands (partial agonist buspirone 10mgkg(-1), antagonist WAY100135 0.5-5mgkg(-1)), 5-HT2A antagonist sarpogrelate (10mgkg(-1)), 5-HT3 antagonist alosetron (0.1mgkg(-1)), 5-HT4 antagonist GR125487 (5mgkg(-1)) and 5-HT re-uptake inhibitor fluoxetine (10mgkg(-1)) on I/R-induced inflammatory response were investigated in I/R mice and compared to those obtained in sham-operated animals (S). Our results confirmed the significant role played by 5-HT2A receptors not only in the late but also in the early I/R-induced microcirculatory dysfunction and showed that blockade of 5-HT1A receptors protected against the intestinal leukocyte recruitment, plasma extravasation and reactive oxygen species formation triggered by SMA occlusion and reflow. The ability of α7 nicotinic receptor (α7nAchR) antagonist methyllycaconitine (5mgkg(-1)) to counteract the beneficial action provided by buspirone on I/R-induced neutrophil infiltration suggests that the anti-inflammatory effect produced by 5-HT1A receptor antagonism could be partly ascribed to the indirect activation of α7nAch receptors.