Effects of new‐generation inhibitors of the calcium‐activated chloride channel anoctamin 1 on slow waves in the gastrointestinal tract

Background and Purpose High‐throughput screening of compound libraries using genetically encoded fluorescent biosensors has identified several second‐generation. low MW inhibitors of the calcium‐activated chloride channel anoctamin 1 (CaCC/Ano1). Here we have (i) examined the effects of these Ano1 inhibitors on gastric and intestinal pacemaker activity; (ii) compared the effects of these inhibitors with those of the more classical CaCC inhibitor, 5‐nitro‐2‐(3‐phenylpropylalanine) benzoate (NPPB); (ii) examined the mode of action of these compounds on the waveform of pacemaker activity; and (iii) compared differences in the sensitivity between gastric and intestinal pacemaker activity to the Ano1 inhibitors. Experimental Approach Using intracellular microelectrode recordings of gastric and intestinal muscle preparations from C57BL/6 mice, the dose‐dependent effects of Ano1 inhibitors were examined on spontaneous electrical slow waves. Key Results The efficacy of second‐generation Ano1 inhibitors on gastric and intestinal pacemaker activity differed significantly. Antral slow waves were more sensitive to these inhibitors than intestinal slow waves. CaCC inh ‐A01 and benzbromarone were the most potent at inhibiting slow waves in both muscle preparations and more potent than NPPB. Dichlorophene and hexachlorophene were equally potent at inhibiting slow waves. Surprisingly, slow waves were relatively insensitive to T16A inh ‐A01 in both preparations. Conclusions and Implications We have identified several second‐generation Ano1 inhibitors, blocking gastric and intestinal pacemaker activity. Different sensitivities to Ano1 inhibitors between stomach and intestine suggest the possibility of different splice variants in these two organs or the involvement of other conductances in the generation and propagation of pacemaker activity in these tissues.