Pharmacological studies with endogenous enhancer substances: beta-phenylethylamine, tryptamine, and their synthetic derivatives.

The discovery of enhancer regulation in the mesencephalon and the concept that it plays a key role in the operation of innate and acquired drives [Neurochem. Res. 28 (2003) 1187] sets the trace amines (TAs) in their true physiological perspective. The regulation is defined as the existence of enhancer-sensitive neurons in the brain capable of working in a split-second on a high activity level due to endogenous enhancer substances. For the time being, only beta-phenylethylamine (PEA) and tryptamine are the experimentally analyzed examples. (-)-Deprenyl (selegiline), widely used in Parkinson's disease and Alzheimer's disease today, and known as the first selective monoamine oxidase (MAO) type-B inhibitor for decades, was identified as a PEA-derived synthetic mesencephalic enhancer substance. An important and convincing confirmation of the enhancer concept was the recent development of a highly specific and potent tryptamine-derived synthetic mesencephalic enhancer substance, (-)-1-(benzofuran-2-yl)-2-propylaminopentane [(-)-BPAP]. This substance, which is specific and hundreds of times more potent than selegiline, is now the best experimental tool to study the enhancer regulation in the mesencephalon and a promising candidate to significantly surpass the therapeutic efficiency of selegiline in depression, Parkinson's disease, and Alzheimer's disease.