Dissecting neuromuscular transmission in the gastrointestinal tract: from single cell RNA analysis to function and pharmacology.

Abstract

Gastrointestinal (GI) motility is coordinated by multiple neurotransmitter systems acting on distinct post-junctional cells within the smooth muscle-interstitial cell-PDGFRα⁺ (SIP) syncytium. This study integrates physiological, pharmacological, and single-cell transcriptomic data to define the cellular mechanisms underlying inhibitory and excitatory neuromuscular transmission in the human colon. Inhibitory signaling involves purinergic (P2Y₁) and adrenergic (α₁A) receptors, which activate SKCa channels in PDGFRα⁺ cells, while nitrergic (nitric oxide (NO)-soluble guanylate cyclase (sGC)-cGMP) pathways are primarily mediated by interstitial cells of Cajal (ICCs) and smooth muscle cells (SMCs). VIPergic signaling also contributes to relaxation through cAMP-dependent mechanisms possibly located in PDGFRα⁺ cells. Excitatory transmission is mainly driven by muscarinic M3 and M2 receptors expressed in ICCs and SMCs, leading to calcium-dependent contractions. Pharmacologically, hyoscine butylbromide (HBB) reduces acetylcholine (ACh)-induced contractions by blocking M2/M3 receptors, whereas neostigmine enhances cholinergic transmission to restore motility. Blockade of voltage-gated calcium channels (Cav1.2, CACNA1C) by agents such as otilonium bromide further contributes to spasmolytic effects. These findings provide an integrated framework linking receptor expression, cellular mechanisms, and drug actions that modulate GI motility.