P2Y(1) receptors mediate purinergic relaxation in the equine pelvic flexure.
Authors: Mas M, Mañé N, Fernández F, Gallego D, Pumarola M, Jiménez M
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: P2Y₁ Receptors and Equine Pelvic Flexure Motility Understanding the neurochemical basis of large intestinal function is essential for developing targeted treatments for equine colic and other motility disorders. Using tissue samples from six horses, researchers employed electrophysiology and organ bath contractility studies to characterise how the pelvic flexure's circular muscle relaxes and contracts in response to nerve stimulation, revealing that purinergic signalling via P2Y₁ receptors and nitric oxide pathways mediate distinct phases of muscle relaxation. Electrical field stimulation reduced pelvic flexure contractions to 3% of baseline; blocking P2Y₁ receptors (with MRS2500) or inhibiting nitric oxide synthesis (with L-NNA) individually reduced this relaxation significantly, but blocking both pathways simultaneously abolished the relaxant response entirely, indicating these mechanisms work in parallel rather than sequentially. The findings also confirmed that cholinergic pathways drive contraction, mirroring the neuromuscular organisation observed in human colonic tissue. These results suggest that P2Y₁ receptors represent a viable pharmacological target for managing equine motility disorders, potentially offering an alternative or complementary approach to existing treatments for conditions characterised by reduced intestinal propulsion.
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Practical Takeaways
- •P2Y1 receptors represent a novel pharmacological target for treating equine colonic motility disorders, potentially offering therapeutic options beyond current standard treatments
- •The equine colon uses the same relaxation mechanisms (purinergic and nitrergic pathways) as humans, suggesting human colonic treatments may have translational potential for equine practice
- •Understanding that purinergic signaling mediates colonic relaxation could guide future drug development for colic management and post-operative ileus prevention
Key Findings
- •P2Y1 receptor antagonist MRS2500 abolished fast inhibitory junction potentials (IJPf) in equine pelvic flexure smooth muscle (P<0.001)
- •Electrical field stimulation reduced rhythmic contractions to 3.0±2.5% of baseline, with P2Y1 blockade reducing this to only 6.0±2.8% inhibition (P<0.05)
- •Nitric oxide synthase inhibition reduced EFS-induced relaxation to 24.4±11.3% of baseline, indicating dual purinergic and nitrergic pathways
- •Combined P2Y1 antagonism and nitric oxide synthase inhibition completely reversed EFS-induced relaxation, demonstrating these are the primary inhibitory mechanisms