Smooth muscle in the gastrointestinal tract

Smooth muscle in the gastrointestinal tract refers to the involuntary, non-striated muscle layer responsible for peristalsis and coordinated contraction-relaxation cycles that propel and mix luminal contents. Contraction is primarily regulated by intracellular calcium signaling and neurotransmitters, especially acetylcholine acting on muscarinic acetylcholine receptors of the M2 and M3 subtypes. M3 receptors mainly mediate contraction via Gq-protein-coupled mechanisms leading to calcium release and actin-myosin interaction, while M2 receptors modulate contraction by inhibiting cAMP production. Gastrointestinal smooth muscle contains a wide array of receptors and ion channels and is the target tissue for numerous drugs used to treat motility disorders, spasms, and pain[2][3][4][5][6][7]. Note: It is more appropriate to define specific molecular targets (such as "Muscarinic acetylcholine receptor M2" or "Myosin-11" or "Voltage-dependent L-type calcium channel") than the tissue type itself when discussing canonical drug targets[1][2][3][4][5][6][7].

Other names

Gastrointestinal smooth muscleGI smooth muscle

Muscarinic antagonists inhibit cholinergic (parasympathetic) stimulation, leading to smooth muscle relaxation and reduced GI motility (e.g., antispasmodics) [1][4][5]. Muscarinic agonists stimulate muscarinic receptors, increasing smooth muscle contraction and motility[4][5]. Calcium channel blockers inhibit calcium influx needed for contraction[7]. K⁺ channel modulators affect muscle excitability and tone[6].