Effects of Ischemia and Reperfusion on P2X^sub 2^ Receptor Expressing Neurons of the Rat Ileum Enteric Nervous System

We investigated the effects of ischemia/reperfusion in the intestine (I/R-i) on purine receptor P2X^sub 2^-immunoreactive (IR) neurons of the rat ileum. The superior mesenteric artery was occluded for 45 min with an atraumatic vascular clamp and animals were sacrificed 4 h later. Neurons of the myenteric and submucosal plexuses were evaluated for immunoreactivity against the P2X^sub 2^ receptor, nitric oxide synthase (NOS), choline acetyl transferase (ChAT), calbindin, and calretinin. Following I/R-i, we observed a decrease in P2X^sub 2^ receptor immunoreactivity in the cytoplasm and surface membranes of neurons of the myenteric and submucosal plexuses. These studies also revealed an absence of calbindin-positive neurons in the I/R-i group. In addition, the colocalization of the P2X^sub 2^ receptor with NOS, ChAT, and calretinin immunoreactivity in the myenteric plexus was decreased following I/R-i. Likewise, the colocalization between P2X^sub 2^ and calretinin in neurons of the submucosal plexus was also reduced. In the I/R-i group, there was a 55.8% decrease in the density of neurons immunoreactive (IR) for the P2X^sub 2^ receptor, a 26.4% reduction in NOS-IR neuron, a 25% reduction in ChAT-IR neuron, and a 47% reduction in calretinin-IR neuron. The density of P2X^sub 2^ receptor and calretinin-IR neurons also decreased in the submucosal plexus of the I/R-i group. In the myenteric plexus, P2X^sub 2^-IR, NOS-IR, ChAT-IR and calretinin-IR neurons were reduced in size by 50%, 49.7%, 42%, and 33%, respectively, in the I/R-i group; in the submucosal plexus, P2X^sub 2^-IR and calretinin-IR neurons were reduced in size by 56% and 72.6%, respectively. These data demonstrate that ischemia/reperfusion of the intestine affects the expression of the P2X^sub 2^ receptor in neurons of the myenteric and submucosal plexus, as well as density and size of neurons in this population. Our findings indicate that I/R-i induces changes in P2X^sub 2^-IR enteric neurons that could result in alterations in intestinal motility.[PUBLICATION ABSTRACT]