NRG1 and Parkinson disease: Recently, it has been found that injection of NRG1 in the dorsal vicinity of the SN causes a dopamine overflow in the striatum [65] and systemic injection of a portion of the extracellular NRG1 domain-known to cross the blood-brain barrier- protects dopaminergic neurons in a mouse model of Parkinson's disease and produces an increase of striatal DA in a matter of days [66].