Fig. (1).

Schematic representation of nigrostriatal dopamine pathway in healthy people (a) and Parkinsonian patients before (b) and after treatment with a neurorestorative agent (c). Dopamine neurons in healthy patients receive trophic support from neurotrophic factors (shown with dark red dots). In Parkinsonian patients, axons of dopamine neurons in the putamen are either lost or degenerated (dotted line) and the number of dopamine neuron bodies in substantia nigra pars compacta is reduced. Treatment of PD patients with growth factors (or their mimetics) stimulates regrowth and arborization of dopamine axons in the putamen (c), thus restoring the dopamine balance and abolishing motor symptoms. (The color version of the figure is available in the electronic copy of the article).