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In the present chapter, we summarize much of the work on the taste avoidance drug discrimination procedure, presenting the logic for its initial introduction and the extension of the procedure in the investigation of the discriminative properties of various drugs. Results from these assessments parallel those from more traditional operant and maze designs in classifying and characterizing the discriminative properties of drug. At the same time, this design reveals a procedure that is sensitive in such assessments by indexing these stimulus properties more rapidly and at lower doses than in the more traditional procedures (in some cases for drugs heretofore resistant in their detection). Importantly, much remains to be learned about the taste avoidance procedure in that the nature of such learning remains unknown and the specific parameters under which it can be established and generalized and its neurochemical and neuroanatomical bases are largely unexplored. The application of drug discrimination learning to human drug abuse continues to be an important consideration for this specific design (as well as that of drug discrimination procedures in general), and recent parallels between drug use and food intake in terms of its regulation by interoceptive stimuli suggests a possible role of the loss of stimulus control in drug escalation and addiction (with possible therapeutic implications via the modulation of these interoceptive cues).

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RationaleΔ9‐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. In this context, previous studies have examined the effect of THC history on the aversive and rewarding effects of THC. However, such assessments have been made in different animals under different experimental procedures, making it difficult to assess the relative contribution of either affective property to abuse vulnerability.MethodsIn the present experiment, male Sprague‐Dawley rats were administered six pre‐exposure injections (3.2 mg/kg THC) over 12 days. This was followed 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). Changes in preferences and aversions for the drug‐paired stimuli were evaluated in final place and taste conditioning tests.ResultsRelative to control subjects, THC produced robust taste avoidance, but did not induce place conditioning. Pre‐exposure to THC attenuated THC‐induced taste avoidance and had no effect on place conditioning with THC.ConclusionsSimilar to prior work, THC induced robust and dose‐dependent taste avoidance. The failure to see THC‐induced 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 (as evidenced in the attenuated taste avoidance), some avoidance was still evident (THC‐injected animals drank less than controls). This suggests that the failure to see a change in THC‐induced place preferences following THC pre‐exposure was a function of its residual aversive effects limiting its 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.Support or Funding InformationThis research was supported by a grant from the Mellon Foundation to Anthony Riley