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

Gastrointestinal (GI) motility is coordinated by multiple neurotransmitter systems acting on distinct postjunctional cells within the smooth muscle-interstitial cell-platelet derived growth factor receptor alpha-positive (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 small-conductance calcium-activated potassium channels in PDGFRα+ cells, whereas nitrergic [nitric oxide (NO)-soluble guanylate cyclase-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 reduces acetylcholine-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.NEW & NOTEWORTHY In this manuscript, we correlate data from single-cell RNA analysis with previously published physiological findings. Based on this correlation, we discuss the mechanisms of action of clinically relevant drugs and reevaluate their effects within the context of the smooth muscle, interstitial cells, and PDGFRα+ cell (SIP) syncytium. This work also has translational relevance, providing clinicians with a more comprehensive understanding of drug mechanisms of action.