DARP-36aa selectively promotes survival and morphological development of cultured mesencephalic neurons

We examined the effects of DARP-36aa on the survival and morphological development of embryonic rat mesencephalic neurons. Treatment of mesencephalic cultures with DARP-36aa, a synthetic peptide corresponding to the N terminal of dopamine-releasing protein (DARP), resulted in a 1.8-fold increase in neuron survival. Morphological analysis revealed that DARP-36aa-treated neurons contained 48% more branching points per neuron compared with controls. DARP-36aa selectively affected mesencephalic cultures; diencephalic and C6 glioma cells were not affected by DARP-36aa treatments. Mesencephalic cultures were also incubated with polyclonal antibodies against DARP-36aa (anti-DARP-36aa) to assess the effect of immunoneutralization of endogenous DARP on these cells. Mesencephalic cultures treated with anti-DARP-36aa contained 43% fewer neurons, and the number of branching points per neuron was decreased by nearly twofold compared with cultures grown with medium alone. Similar to cultures treated with DARP-36aa, immunoneutralization of DARP had no effect on any parameters examined in primary diencephalic and C6 glioma cultures. Mesencephalic cultures maintained in the presence of DARP-36aa had a 3.2-fold increase in the number of tyrosine hydroxylase (TH)-immunoreactive neurons, whereas anti-DARP-36aa incubations decreased TH-immunoreactive neurons by 40% compared with control cultures. Finally, coincubation of the specific tyrosine kinase inhibitor genistein with DARP-36aa resulted in a complete attenuation of DARP-36aa-mediated neuron survival and development in mesencephalic cultures. The findings indicate that DARP-36aa is a novel neurotrophic peptide that selectively promotes the survival and development of mesencephalic neurons.