THE UPTAKE AND RELEASE OF [3H]‐2‐AMINO‐6,7‐DIHYDROXY1,2,3,4‐TETRAHYDRONAPHTHALENE (ADTN) BY STRIATAL NERVE TERMINALS

Abstract

1 A study has been made of the uptake and release of [G-³H]-2-amino 6,7-dihydroxy-1, 2,3,4-tetra-hydronaphthalene (ADTN) by crude striatal synaptosomes of the rat. 2 Uptake was rapid, temperature-dependent and could be suppressed by a variety of metabolic inhibitors. 3 The Michaelis-Menten kinetics indicated the presence of two distinct transport systems in the striatum which were of much higher capacity than those found in the cerebellum, which lacks dopaminergic innervation. 4 Uptake of [³H]-ADTN was strongly inhibited by dopamine and the two potent dopamine-uptake inhibitors, benztropine and nomifensine, but only weakly by imipramine and amphetamine (the latter in non-reserpine-treated animals). 5 Accumulated [³H]-ADTN could be released from striatal slices by elevated K⁺. A similar release was evoked upon the addition of the ionophore, A23187. 6 The most potent releaser of [³H]-ADTN was (+)-amphetamine. This effect occurred at concentrations inactive against ADTN uptake. The neuroleptic ris-flupenthixol produced an inhibition of the spontaneous release. 7 It is concluded that [³H]-ADTN is accumulated preferentially into areas of the rat brain rich in dopamine. The pharmacological specificity of the uptake suggests that it is a good substrate for the dopamine carrier. Following uptake, [³H]-ADTN may be released by K⁺ and a calcium ionophore, which raises the possibility that ADTN might act as a false transmitter.