Norepinephrine: the next therapeutics frontier for Parkinson's disease.

Tissue concentrations of norepinephrine (NE) are markedly decreased in various regions of the Parkinson's disease (PD) brain. As in the substantia nigra pars compacta, neuronal dropout and Lewy bodies are prominent changes affecting the locus coeruleus, which is the source of ascending NErgic projections. Despite the major roles of NE throughout the brain, there has been only minimal exploration of pharmacological intervention with NErgic neurotransmission. Cognitive operations, "freezing" of gait, tremor, dyskinesia, REM sleep regulation, and other aspects of brain function are tied into signaling by NE, and there is also evidence that it may have a role in the neurodegenerative process itself. This article reviews the reported pharmacological experience in PD therapeutics.