3H]Spiperone binding in the rat striatum during the development of physical dependence on phencyclidine and after withdrawal

Binding of [3H]spiperone to dopamine D2 receptors was measured in the striatum of male rats that were infused with phencyclidine (PCP, 45 mg/kg per day) or vehicle (saline) via an intrajugular cannula for 1, 3.5, or 7 days. The 7-day PCP infusion, which was shown previously to induce physical dependence, produced a significant 30% decrease in receptor density (Bmax). Two days after termination of the 7-day PCP infusion, Bmax values were no longer significantly lower than those of saline-infused controls. The acute administration of PCP (20 mg/kg, i.p.) did not alter receptor density 45 min later.