Smooth muscle cells, interstitial cells and neurons in the gallbladder (GB): Functional syncytium of electrical rhythmicity and GB motility (Review)

The motility of the gallbladder (GB) involves the storage, concentration and delivery of bile. GB motor functions are controlled by multiple complex factors, such as extrinsic and intrinsic innervation, humoral factors and neuropeptides. GB emptying results from coordinated contractions of the muscular layers of the GB wall. Depolarization of GB smooth muscle (GBSM) depends on the activation of the regular depolarization‑repolarization potential, referred to as slow waves (SWs). These rhythmic SWs of GBSM contraction are mediated by several cell types, including smooth muscle cells (SMCs), GB neurons, telocytes (TC) and specialized pacemaker cells called interstitial cells of Cajal (ICC). The present article introduced a new GB motor unit, the SMC‑TC‑ICC‑neuron (STIN) syncytium. In GB, STIN cells provide pacemaker activity, propagation pathways for SWs, transduction of inputs from motor and sensory neurons and mechanosensitivity. The present review provided an overview of STIN cells, mechanisms generating GBSM contractile behavior and GB motility, and discussed alterations of STIN cell function under different disease conditions.