The Effects of Delta-9-Tetrahydrocannabinol (THC) History on THC-induced Taste and Place Conditioning

Delta-9-tetrahydrocannabinol (THC) produces both aversive and rewarding effects in animal models. Given that the balance between a drug's affective properties is thought to underlie its abuse potential, it is important to consider these properties of THC and how they (and their balance) are impacted by various factors. Previous studies have examined the effect of THC history on the aversive and rewarding effects of THC, yet these assessments have been made in different animals under different experimental procedures. The present experiment examined the effect of THC history (3.2 mg/kg) on the affective properties of THC (1 or 3.2 mg/kg) as assessed by a combined taste avoidance/place preference procedure in which a novel saccharin solution and environment were paired with THC (0, 1 or 3.2 mg/kg). THC produced robust taste avoidance, but did not induce place conditioning. Pre-exposure to THC attenuated taste avoidance but had no effect on place conditioning. The failure to see place preferences is likely due to the aversive effects of THC masking its rewarding properties. Although THC pre-exposure weakened the aversive effects of THC, avoidance was still evident. The failure to see a change in THC place conditioning with a drug history may be a function of these residual aversive effects limiting THC's relatively weak rewarding properties. These findings support the view that the interaction of reward and aversion is important in behavioral displays of the affective properties of abused drugs.