Chronic Dopamine D2 Receptor Activation Does Not Affect Survival and Differentiation of Cultured Dopaminergic Neurons: Morphological and Neurochemical Observations

Abstract: Primary cultures of rat ventral mesencephalon were used to elucidate the role of chronic stimulation of dopamine (DA) D₂ autoreceptors in the development of fetal dopaminergic neurons in vitro. Cultured dopaminergic neurons, as visualized by tyrosine hydroxylase immunocytochemistry, became more differentiated in the course of cultivation time and exhibited specific high-affinity uptake for ³H]DA. In rat striatal tissue, activation of D₂ receptors has been shown to inhibit the release of DA. Previously accumulated ³H]DA was released from the cultures upon depolarization in a Ca²⁺-dependent manner. K⁺-evoked ³H]DA release could be inhibited by the selective D₂ receptor agonists LY 171555 and N0437 in a concentration-dependent manner. The inhibitory effects of LY 171555 and N0437 were antagonized by the selective DA D₂ receptor antagonist sulpiride. These observations are indicative for the expression of functional D₂ receptors in the cultures. Daily treatment of these cultures for 7 days with LY 171555 or sulpiride did not lead to any change in protein content, the number of tyrosine hydroxylase-immunoreactive neurons, or the uptake capacity for ³_H]DA. Our data demonstrate that chronic stimulation of DA D₂ receptors does not impair survival or differentiation of cultured fetal dopaminergic neurons.