The CB2 Cannabinoid Receptor Was Required for Nicotine's Rewarding Effects but Not Withdrawal | Research

The takeaway

Mice lacking CB2 cannabinoid receptors did not develop nicotine place preference, and a CB2 antagonist blocked nicotine reward, but CB2 played no role in nicotine withdrawal or acute effects.

Read this if you are interested in the biological overlap between the cannabinoid and nicotine systems.

CB2 receptors played opposite roles in nicotine reward (required) vs. cocaine reward (inhibitory)

What the researchers found

Using both pharmacological (drug) and genetic (knockout mice) approaches, researchers found that CB2 receptors are essential for nicotine's rewarding effects. Nicotine-induced conditioned place preference was completely blocked by the CB2 antagonist SR144528 and was absent in CB2 knockout mice.

Conversely, the CB2 agonist O-1966, when combined with a sub-threshold nicotine dose, produced place preference. Interestingly, for cocaine the pattern was opposite: the CB2 agonist blocked cocaine reward, while CB2 knockout mice showed normal cocaine reward. CB2 receptors played no role in nicotine withdrawal symptoms or acute somatic effects like hypothermia and pain reduction.

Why it matters

This study revealed that CB2 receptors, previously thought to be mainly peripheral immune receptors, play a critical role in nicotine reward. The opposing roles in nicotine versus cocaine reward suggest sophisticated and substance-specific cannabinoid modulation of addiction.

The numbers in context

Nicotine CPP blocked by SR144528 (3 mg/kg). Absent in CB2 knockout mice. CB2 agonist O-1966 (1-20 mg/kg) + subthreshold nicotine = CPP. O-1966 (20 mg/kg) blocked cocaine CPP. CB2 knockout: normal cocaine CPP, normal nicotine withdrawal.

How the study worked

Conditioned place preference paradigm in wild-type mice with CB2 antagonist/agonist, and in CB2 knockout mice. Nicotine withdrawal precipitated with mecamylamine in nicotine-dependent mice. Acute nicotine effects (hypothermia, hypoalgesia) tested in CB2 knockout mice.

What this study cannot tell us

Mouse conditioned place preference may not fully model human addiction. Genetic knockout creates lifelong absence, which may cause compensatory changes. Only one pharmacological antagonist and agonist were tested. The mechanism by which CB2 mediates nicotine reward was not identified.

How to read the evidence

Animal study with complementary pharmacological and genetic approaches; preliminary but well-controlled evidence.

When this study was published

Published in 2013. CB2 receptor involvement in addiction has become an emerging research area.

The bigger picture

The finding that CB2 receptors play opposite roles in nicotine and cocaine reward adds complexity to our understanding of how the endocannabinoid system modulates addiction. It suggests that CB2-targeted medications for addiction would need to be substance-specific.

Questions still open

Could CB2-targeted drugs help treat nicotine addiction in humans? Why do CB2 receptors play opposite roles for nicotine versus cocaine? Where in the brain are CB2 receptors mediating nicotine reward?

Common questions

How are the cannabinoid and nicotine systems connected?

This study showed that CB2 cannabinoid receptors are required for nicotine to produce its rewarding effects in mice. Without functional CB2 receptors, nicotine did not create a place preference. This means the endocannabinoid system is directly involved in processing nicotine's rewarding signal, though the exact brain circuits involved remain to be identified.

Could cannabis-related drugs help people quit smoking?

This study suggests CB2 receptor manipulation could theoretically affect nicotine reward. A CB2 antagonist blocked nicotine place preference. However, the opposite effect on cocaine (CB2 agonist blocked cocaine reward) shows these interactions are substance-specific and complex. Much more research is needed before any clinical applications could be developed.

Read the original research

The cannabinoid CB2 receptor is necessary for nicotine-conditioned place preference, but not other behavioral effects of nicotine in mice.

Psychopharmacology, 229(4), 591-601

View on PubMed ↗Publisher’s paper ↗

Citation

Ignatowska-Jankowska, Bogna M; Muldoon, Pretal P; Lichtman, Aron H; Damaj, M Imad. (2013). The cannabinoid CB2 receptor is necessary for nicotine-conditioned place preference, but not other behavioral effects of nicotine in mice.. Psychopharmacology, 229(4), 591-601. https://doi.org/10.1007/s00213-013-3117-6