The P2Y₁ receptor in the colonic myenteric plexus of rats and its correlation with opioid-induced constipation

This study was designed to explore the expression changes of P2Y₁ receptors in the distal colonic myenteric layer of rats. An opioid induced constipation(OIC) rat model was generated by intraperitoneal (i.p) injection of loperamide. At 7 days post-treatment, the model rats were assessed by calculating the fecal water content and the gastrointestinal transit ratio. The immunofluorescence (IF)-based histochemical study was used to observe the distribution of P2Y₁ receptors in the distal colonic myenteric plexus. Western blotting (WB) was performed to evaluate the expression changes of P2Y₁ proteins in the myenteric layer, and the electrophysiological approaches were carried out to determine the regulatory roles of P2Y₁ receptors on distal colonic motor function. IF showed that P2Y₁ receptors are co-expressed MOR in the enteric nerve cells of the distal colonic myenteric plexus. Moreover, the WB revealed that the protein levels of P2Y₁ were significantly decreased in the distal colonic myenteric layer of OIC rats. In vitro tension experiments exhibited that the P2Y₁ receptor antagonist MRS2500 enhanced the spontaneous contraction amplitude, adding EM2 and β-FNA did not have any effect on MRS2500. Therefore, P2Y₁ receptor expression could be associated with the occurrence of OIC in this rat model and the regulation of colonic motility by MOR may be related to the release of purine neurotransmitters such as ATP in the colonic nervous system.