LACK OF DOPAMINE-RECEPTOR AGONISTS EFFECT ON STRIATAL DOPAMINE TRANSPORTER BINDING-SITES

Depending on experimental conditions, chronic cocaine exposure can ind uce an increase in binding to the dopamine transporter (DAT). One poss ible mechanism for the cocaine-induced-upregulation in DAT binding sit es is through stimulation of presynaptic D-2 receptors by excess synap tic dopamine. To test this hypothesis, the present experiment examined in rats the effect of chronic quinpirole and apomorphine treatments o n striatal DAT binding sites. Rats were chronically injected subcutane ously with either: quinpirole, 0.7 mg/kg body weight, apomorphine, 2.0 mg/kg body weight, or vehicle. Striatal DAT binding was then examined autoradiographically using the DAT-selective cocaine congeners [I-125 ]RTI-121 and [H-3]WIN 35428. Analysis of the results indicated that qu inpirole and apomorphine administration did not alter DAT cocaine bind ing sites.