INCREASED SENSITIVITY TO COCAINE PLACE-PREFERENCE CONDITIONING BY SEPTAL-LESIONS IN RATS

Rats bearing electrolytic lesions of medial septum and sham-operated c ontrols were trained on cocaine place-preference in a 3-compartment ap paratus. Cocaine was paired with a white or a black compartment. An un biased design was used, in which cocaine was paired with the preferred side in half the animals and with the unpreferred side in the other h alf. Two low doses of cocaine HCl were used: 2.5 and 5.0 mg/kg. Only t wo pairings of drug with environment were used to minimize the influen ce of drug sensitization. Rats with septal lesions, but not controls, showed preference conditioning to the black side at 2.5 mg/kg; lesione d and control animals showed similar conditioning to the the black sid e at 5.0 mg/kg. Lesioned animals could not be conditioned to the white side at either dose. This was attributed to a drug-induced enhancemen t of a previously described increased reactivity to brightness followi ng septal lesions. Controls conditioned to either side at 5.0 mg/kg. I t was concluded that septal lesions lowered the cocaine dose required for preference conditioning, consistent with reports that such damage enhances some behavioral effects of psychostimulants.