Characterization of muscarinic acetylcholine receptors on the rat pancreatic gastrin-producing cell line B6 RIN

The mechanisms of cholinergic stimulation of gastrin cells were studied in the rat pancreatic cell line B6 RIN. Carbachol induced an increase in intracellular Ca²⁺ and stimulated gastrin release in a dose-dependent manner over the range 10^?5-10^?3 M. These effects were completely abolished by atropine, suggesting the implication of muscarinic cholinergic receptors. The binding properties of these receptors were investigated. N-Methyl-³H]scopolamine (³h]nms) binding on cell homogenates was time-dependent, saturable and consistent with a single high-affinity binding class (K_d = 39.5 pM, and B_max = 7.9 fmol/mg DNA). Carbachol competitively inhibited ³H]NMS binding. The potency of inhibition of ³H]NMS binding by subtype selective antagonists was hexahydrodifenidol> pirenzepine> AF-DX 116. These results suggest the M₃, muscarinic receptors may be involved in the carbachol-induced gastrin release from B6 RIN cells.