Salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, SAL) is a dopamine-derived tetrahydroisoquinoline, first identified in the urine of a Parkinson's disease patienttreated with L-DOPA. SAL is generated endogenouslyvia bothenzymatic and non-enzymatic Pictet-Spenglercondensation of dopamine with acetaldehyde. It is also found indietary sourcessuchas bananas, mushrooms, and cocoa, as well as in certain microbes. SALhas been detected in cerebrospinal fluid and various brain regions. SAL acts as a neuroactive compound implicated in ethanol's reinforcing effects and has been proposed as an endogenous prolactin-releasing factor. Its structural similarity to the neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) haslong provokedsuspicions that SAL may inducedopaminergic neurodegeneration throughgeneration ofreactive oxygen species and subsequent activation ofcell death pathways. However, recent in vitro and in vivo studies reveal a biphasic profile: at low concentrations, SAL exerts neuroprotective effects, whereas at higher concentrations, it becomes neurotoxic. This review therefore summarizes differential pathophysiological roles of SAL based onexperimental and clinicalfindings, highlighting its context-specific, dose-dependent actions in the centralnervous system.