Drug discrimination learning with naloxone: An assessment of the role of precipitated withdrawal

Abstract

Recently, it has been reported that the opiate antagonist naloxone hydrochloride could serve as a discriminative cue in drug discrimination learning (DDL) within a conditioned taste aversion (CTA) design. Given that the animals were chronically exposed to saccharin and that naloxone has been shown to precipitate withdrawal in animals with such exposure, it was possible that the cue to which these animals attended was that of naloxone-precipitated withdrawal. To test this possibility, in the present study animals were chronically exposed to saccharin for 14 days prior to the pairing of saccharin with a naloxone injection in a procedure that paralleled the parameters of the DDL study within a CTA design. The present findings did not demonstrate a potentiation of a naloxone-induced aversion in animals chronically preexposed to saccharin (i.e., there was no evidence of naloxone-precipitated withdrawal). The failure of chronic saccharin exposure to potentiate a naloxone aversion in the present study, under the procedure that supported naloxone DDL, suggests that naloxone-precipitated withdrawal was not likely the discriminative cue in the previous study.