The presence of bile acids in the brain during normal physiological conditions was reported in several studies in rats,mice and humans (Higashi et al. 2017; Huang et al. 2015;Mano et al. 2004a; Pan et al. 2017; Zheng et al. 2016) raisingthe question as to the role(s) of these intestinal surfactantsin the brain. As in the liver, the bile acid composition inthe brain is highly complex, consisting of several bile acidspecies. These include both primary (unconjugated and conjugated) and secondary (unconjugated and conjugated) BAs