Correspondence
Mechanisms of Drug Addiction
N Engl J Med 2003; 349:2365December 11, 2003
- Article
To the Editor:
Camí and Farré (Sept. 4 issue)1 provide a comprehensive review of the neuronal and behavioral mechanisms involved in drug addiction. Their information on the potential for abuse of cannabinoids, however, is outdated. The authors claim that, in contrast to results obtained with opioids, cocaine, amphetamines, ethanol, and nicotine, “laboratory animals cannot be taught to self-administer Δ9-tetrahydrocannabinol.” It has been shown that persistent self-administration behavior is maintained with intravenous Δ9-tetrahydrocannabinol in animals, with patterns similar to those reported for cocaine given at doses comparable to those present in marijuana smoke inhaled by humans.2 Justinova and colleagues recently demonstrated that even animals that have not previously been exposed to other psychoactive drugs can be taught to self-administer Δ9-tetrahydrocannabinol.3 Those reports suggest that marijuana has as much potential for abuse as other drugs of abuse. It does not necessarily mean that the health or social consequences of marijuana use are similar to those of cocaine or heroin use or that marijuana has no therapeutic potential. The addictive properties of Δ9-tetrahydrocannabinol and other abused drugs, however, appear to be similar.
3 ReferencesPatrik Munzar, M.D.
2417 Hastings Dr., Belmont, CA 94002
patrikmunzar@yahoo.com 1
Cami J ,Farre M . Drug addiction. N Engl J Med 2003;349:975-986
Full Text | Web of Science | Medline2
Tanda G ,Munzar P ,Goldberg SR . Self-administration behavior is maintained by the psychoactive ingredient of marijuana in squirrel monkeys. Nat Neurosci 2000;3:1073-1074
CrossRef | Web of Science | Medline3
Justinova Z ,Tanda G ,Redhi GH ,Goldberg SR . Self-administration of delta9-tetrahydrocannabinol (THC) by drug naive squirrel monkeys. Psychopharmacology (Berl) 2003;169:135-140
CrossRef | Web of Science | Medline
Author/Editor Response
Dr. Munzar states that the data we cite in our review regarding the potential for abuse of cannabinoids are outdated. His argument is based on two previous experimental studies in which squirrel monkeys self-administered Δ9-tetrahydrocannabinol by the intravenous route. However, the evidence provided by Tanda et al.1 was not obtained from naive animals: the authors reported maintenance of Δ9-tetrahydrocannabinol self-administration in four monkeys previously trained to self-administer cocaine. Previous experience with cocaine or other drugs of abuse may induce long-term neurobiologic adaptations, facilitating subsequent acquisition and maintenance of Δ9-tetrahydrocannabinol self-administration. In fact, the functional state of reward circuits in the brain in naive monkeys differs from that in monkeys that self-administer.2 The recent observation that three drug-naive squirrel monkeys self-administered Δ9-tetrahydrocannabinol, reported by Justinova et al.,3 was not available when we wrote our article. This work is an important contribution, but the scientific evidence from the animal model needs further study.
3 ReferencesJordi Camí, M.D., Ph.D.
Magí Farré, M.D., Ph.D.
Institut Municipal d'Investigació Mèdica, 08003 Barcelona, Spain
jcami@imim.es 1
Tanda G ,Munzar P ,Goldberg SR . Self-administration behavior is maintained by the psychoactive ingredient of marijuana in squirrel monkeys. Nat Neurosci 2000;3:1073-1074
CrossRef | Web of Science | Medline2
Maldonado R . Study of cannabinoid dependence in animals. Pharmacol Ther 2002;95:153-164
CrossRef | Web of Science | Medline3
Justinova Z ,Tanda G ,Redhi GH ,Goldberg SR . Self-administration of delta9-tetrahydrocannabinol (THC) by drug naive squirrel monkeys. Psychopharmacology (Berl) 2003;169:135-140
CrossRef | Web of Science | Medline
