COCAINE CONDITIONING AND COCAINE SENSITIZATION - WHAT IS THE RELATIONSHIP

With repeated cocaine use, cocaine conditioned behavior develops to as sociated stimuli, and in addition, sensitization can occur to the unco nditioned stimulant affects of cocaine. To investigate the relationshi p between the conditioned and unconditioned behavioral effects of repe ated cocaine use. two groups of rats (n = 7) were given five daily pai red cocaine treatments (10 mg/kg i.p.) immediately before a 20-min pla cement in an open-field environment. (Other groups received either sal ine before testing or cocaine unpaired which n:as administered 30 min after resting in the homecage. When tested in the open-field with sali ne for conditioned effects, the two cocaine paired groups selectively exhibited substantial and equivalent cocaine conditioned responses. On e of these groups n:as subjected to an extinction procedure which was effective in eliminating the cocaine conditioned responses. Subsequent ly, all the rats which had received cocaine in the first phase of the experiment. paired and unpaired, along with a subset of saline animals were given a cocaine (10 mg/kg i.p.) challenge test. The paired cocai ne animals exhibited an earlier onset of the cocaine induced behaviora l response (sensitization) as compared with the saline and the unpaire d cocaine animals. Critically, the sensitization effects were unaffect ed by extinction, and in addition, the conditioned response did not co ntribute to the sensitization effect. It is suggested that the cocaine drug response occludes the cocaine conditioned response. Subsequent t o this sensitization test, the animals were retested for conditioning. In this test, the paired cocaine animals which had not been subjected to the extinction procedure still exhibited a conditioned cocaine res ponse, whereas, the paired cocaine group subjected to extinction was i ndistinguishable from saline controls. Although the present results sh ow that Pavlovian conditioned responses to exteroceptive contextual cu es do not directly contribute to cocaine induced behavioral sensitizat ion effects, the sensitization effects were context-specific, and ther efore, were tied to associative processes. It is suggested that contex t specificity is mediated by a compound stimulus complex comprised of exteroceptive stimuli and interoceptive cocaine drug cues. Furthermore , these exteroceptive and interoceptive cues associated with cocaine e ffectively expedice the onset of cocaine effects, and thereby, facilit ate the addictive potency of cocaine. (C) 1998 Elsevier Science B.V. A ll rights reserved.