Drug Cues and Self-Administration Answered Different Questions in a Cannabinoid Animal Review

A cannabinoid-like drug cue did not automatically establish that animals would self-administer the drug. A 2002 review described discrimination and reinforcement experiments as different approaches to studying cannabinoid effects and dependence.

Drug discrimination tested a learned internal cue

Maldonado’s review abstract describes cross-discrimination among natural and synthetic cannabinoid agonists. In such work, a trained response indicates that a test drug shares features of a previously learned drug cue. This is an animal behavioral assay of stimulus effects. It does not directly measure a person’s subjective experience, diagnose intoxication in a driver or establish that two substances have identical effects.

Reinforcement required separate evidence

The review also addressed place conditioning, intracranial self-stimulation and drug self-administration. Its abstract reports that experimental conditions were important: many THC self-administration attempts had been unsuccessful, while positive results were reported with a synthetic agonist in mice and THC in monkeys with prior cocaine self-administration experience. These are historical descriptions of the literature summarized in 2002, rather than a statement that THC cannot reinforce behavior under other conditions.

One positive assay cannot stand in for all the others

A compound can share a learned cue without the same evidence for maintaining drug-taking behavior. Conversely, an unsuccessful self-administration procedure does not establish absence of abuse potential in people. The review’s different paradigms therefore should retain their species, training history and actual outcomes when cited. For a scientific opinion, identify whether the evidence concerns stimulus similarity, reward-related behavior, reinforcement or withdrawal. Combining those terms into a single claim of addiction would discard the distinctions the experiments were designed to examine.

Related analysis: later THC reinforcement experiments in drug-naive squirrel monkeys.

Research cited

Maldonado (2002). Study of cannabinoid dependence in animals. Review abstract.