The suppressive effects of intraperitoneal cocaine are augmented when evaluated in nondeprived rats

Rats suppress intake of a saccharin conditioned stimulus (CS) when paired w ith all drugs of abuse tested including morphine, cocaine, heroin, amphetam ine, and ethanol. Although most of these drugs suppress intake when adminis tered via a range of routes, the efficacy of cocaine is an exception. Speci fically, cocaine-induced suppression of saccharin intake is much greater wh en administered subcutaneously than when administered intraperitoneally. Th e subcutaneous route of administration of cocaine, however, is somewhat pro blematic because, unless diluted, can cause stark necrosis. The present stu dy, then, reexamined the effectiveness of intraperitoneal cocaine using les s restrictive deprivation regimens that are known to facilitate the express ion of the phenomenon. The results showed that, while only a 10- and 20-mg/ kg dose of cocaine suppressed intake of the saccharin CS when evaluated in moderately water-deprived rats, all doses tested (i.e., 5, 10, and 20 mg/kg ) significantly reduced CS intake when saccharin-cocaine pairings were eval uated in rats maintained on food and water ad libitum. Taken together, thes e data show that rats will readily avoid intake of a saccharin cue when pai red with the intraperitoneal administration of cocaine and that the magnitu de of the effect is augmented when examined in a need-free state. (C) 2001 Elsevier Science Inc. All rights reserved.