AUTORADIOGRAPHIC STUDIES ON THE UPTAKE OF H-3 DOPAMINE BY NEURONS ANDASTROCYTES IN EXPLANT AND PRIMARY CULTURES OF RAT CNS - EFFECTS OF UPTAKE INHIBITORS

The cellular localization of the uptake of H-3-dopamine was studied in explant and primary cultures from various regions of rat central nerv ous system by means of autoradiography. In explant cultures of substan tia nigra, H-3-dopamine was taken up by cell bodies and processes of m any neurons. In cultures from striatum, cerebellum and spinal cord, ne uronal cell bodies were not labelled, whereas outgrowing nerve fibres revealed intense uptake of the monoamine. Uptake of H-3-dopamine by ne urons was Na+- and temperature-dependent, suggesting an active uptake mechanism. In explant cultures, astrocytes did not accumulate H-3-dopa mine, whereas in primary cultures, which were prepared from the same r egions of rat central nervous system as the explant cultures, astrocyt es also revealed uptake of this monoamine. The intensity of labelling was dependent on the incubation time. Little uptake of H-3-dopamine wa s observed after an incubation time of 5 min and only after 10-15 min did the astrocytes show moderate labelling. Uptake of H-3-dopamine by astrocytes was not Na+- and temperature-dependent, indicating that gli al cells do not possess an active uptake mechanism for this monoamine. This is consistent with biochemical investigations by other laborator ies, demonstrating that astrocytes accumulate H-3-dopamine by a facili tated diffusion system. Addition of the uptake inhibitors nomifensine or GBR 12909 to explant cultures markedly reduced or inhibited uptake of H-3-dopamine by neurons at a concentration of 10(-6) M. In contrast , accumulation of H-3-dopamine by astrocytes in primary cultures was o nly slightly affected by nomifensine at 10(-6) M. At the highest conce ntration used (10(-5) M), nomifensine also blocked the uptake of H-3-d opamine by astrocytes. Our finding that GBR 12909 almost completely in hibited the uptake of H-3-dopamine by astrocytes already at 10(-6) M s uggests that this compound is a more potent inhibitor of the glial upt ake of dopamine than nomifensine.