Differentiative effects of dopamine on striatal neurons involve stimulation of the cAMP/PKA pathway.

The neurotransmitter dopamine (DA) stimulates neurite outgrowth and growth cone formation in cultures of embryonic rat striatum through activation of D1 but not D2 receptors. We show here that neurite outgrowth could be stimulated to a similar extent by elevating cellular cAMP levels. Second, the neuritotrophic effect of DA was completely abolished by inhibiting adenylate cyclase or protein kinase A (PKA) but not protein kinase C (PKC). Third, double staining of cultures with antibodies against growth-associated protein-43 (GAP-43) and the phosphorylated form of the cAMP response element binding protein (pCREB) showed that pCREB was nearly exclusively associated with GAP-43-positive, i.e., actively growing, neurons. Again, this effect depended on D1 receptor and PKA activation. Although cross-talk with other signaling pathways needs to be studied further, we conclude that DA promotes the differentiation of striatal neurons via stimulation of D1 receptors and the cAMP/PKA signal transduction pathway.