AMPHETAMINE-INDUCED WITHDRAWAL RESPONDING - EFFECTS OF REPEATED DRUG ADMINISTRATION

The first purpose of this research was to assess withdrawal haloperido l-appropriate lever responding 24 h after a single administration of 0 .35, 0.75, and 1.00 mg/kg amphetamine. Rats were trained to discrimina te among 0.35 mg/kg amphetamine (AM), distilled water (DW), and 0.033 mg/kg haloperidol (HA) in a three-lever drug discrimination task. An i ncrease in HA-appropriate lever responding occurred following the 1.00 mg/kg dose of AM but not after either of the lower doses. The second purpose was to determine the effect of repeated administration of 0.75 mg/kg AM. Two groups of animals were given five administrations of dr ug, one at an interdose interval (IDI) of 24 h and the other at an IDI of 48 h. Control animals were given injections of DW. Increased HA-ap propriate lever responding occurred in both of the AM-treated groups. The magnitude of this effect tended to be less in the 48-h IDI group. Thus, even though HA-lever responding was not evident 24 h after a sin gle administration of 0.75 mg/kg AM, it was produced by repeated admin istration of this dose, even at 48-h intervals.