Tamoxifen administration alters gastrointestinal motility in mice

Abstract Background Tamoxifen is widely used for Cre‐estrogen receptor‐mediated genomic recombination in transgenic mouse models to mark cells for lineage tracing and to study gene function. However, recent studies have highlighted off‐target effects of tamoxifen in various tissues and cell types when used for induction of Cre recombination. Despite the widespread use of these transgenic Cre models to assess gastrointestinal (GI) function, the effect of tamoxifen exposure on GI motility has not been described. Methods We examined the effects of tamoxifen on GI motility by measuring total GI transit, gastric emptying, small intestinal transit, and colonic contractility in wild‐type adult mice. Key Results We observed a significant delay in total GI transit in tamoxifen‐treated mice, with unaltered gastric emptying, accelerated small intestinal transit, and abnormal colonic motility. Conclusion Our findings highlight the importance of considering GI motility alterations induced by tamoxifen when designing protocols that utilize tamoxifen as a Cre‐driver for studying GI function.