Figure 3.

Bile acids (BA) activate receptors and ion channels. Nuclear receptors activated by BA include the farnesoid X receptor (FXR), pregnane X receptor (PXR), vitamin D receptor (VDR), liver X receptor (LXR), and glucocorticoid receptor (GR). Unconjugated BA might be able to cross the plasma membrane, and conjugated BA might cross the plasma membrane using transporters. Cell surface receptors activated by BA are Takeda G-protein receptor 5 (TGR5), sphingosine-1-phosphate receptor 2 (S1PR2), M2 and M3 muscarinic receptors, and formyl-peptide receptor (FPR). Bile acid-sensitive ion channel (BASIC), epithelial Na⁺ channel (ENaC), and large-conductance Ca²⁺- and voltage-activated K⁺ (BK) channels are ion channels that are activated by BA. These receptors and ion channels are expressed in the brain.