3-PPP, over .5 to 4.5 micromoles/kg, produced a dose-dependent decrease in locomotor activity, presumably by inhibiting the basal activity of ascending dopamine neurons. There was little difference between the groups treated chronically with saline or cocaine in terms of their response to 3-PPP. It appears, therefore, that there is no behavioral evidence for the presence of dopamine auto receptor subsensitivity following chronic cocaine.
