Ethanol-Taurine Interactions in the Brain: Mechanisms and Pathophysiological Implications

This chapter discusses the interactions of ethanol and taurine in the brain and the mechanisms and pathophysiology. Taurine is a nonproteinaceous sulfur amino acid present at high concentrations both in neurons and astrocytes in different brain regions. Taurine is a γ-aminobutyric acid_A (GABA_A) and glycine receptor agonist in distinct regions of cerebral cortex, cerebellum, and hypothalamus. Taurine is also readily released from and taken up by astrocytes and neurons: its intercellular redistribution upon hyper- or hyposomotic challenge suggests that taurine partici- pates in cell volume regulation. In the neuro-endocrine structures of the hypothalamus, taurine released from astrocytes in response to hypotonic stimulus acts on glycine receptors in the adjacent neurons, contributing to hypotonic inhibition of neurosecretion of oxytocin and vasopressin. Exogenously added taurine is neuroprotective by an anti-excitotoxic mechanism, involving direct interaction with GABA_A and/or ionotropic glutamate receptors, mostly of the N-methyl D-aspartate type. A plethora of stimuli trigger taurine release from astrocytes or neurons by mechanisms bypassing changes in the intracellular osmotic pressure, thus increasing the extracellular concentration of taurine and facilitating its neuromodulatory function. Ethanol and taurine share molecular targets in the brain.