Simultaneous evaluation by a double labelling method of drug-induced uptake inhibition and release of dopamine in synaptosomal preparation of rat striatum.

Crude synaptosomal preparations from corpora striata of rat were preloaded with [14C]DA, rinsed, and then incubated with [3H]DA and the drug to be tested. During the 5 min of the second incubation, DA uptake and release rates were time- and temperature-dependent. On this double labelling test, nomifensine, cocaine, benztropine and amphetamines displayed IC50 and release curves similar to those obtained from separate uptake and release studies. In the presence of high concentrations of iprindole, amitriptyline and butriptyline (greater than 3 X 10(-6) M), a [14C]DA release was observed which closely coincided with an apparent inhibition of [3H]DA uptake. This double labelling test allows the determination of the participation of the releasing effect of drugs in their apparent inhibition of DA uptake.