The neutral CB1 receptor antagonist PIMSR reduced cocaine self-administration, motivation to seek cocaine, and cue-triggered relapse in rodents through dopamine-dependent mechanisms, without being rewarding or aversive itself.
Addiction researchers and pharmaceutical scientists developing treatments for cocaine use disorder.
Reduced cocaine seeking without being rewarding or aversive itself
What the researchers found
PIMSR dose-dependently inhibited cocaine self-administration, shifted the dose-response curve downward, decreased motivation to seek cocaine, and reduced cue-induced reinstatement. PIMSR was neither rewarding nor aversive. It attenuated cocaine-enhanced brain reward stimulation and the effects of THC and a CB1 agonist, confirming CB1 receptor involvement.
Why it matters
Rimonabant, a previous CB1 antagonist, failed in clinical trials due to severe psychiatric side effects (it was an inverse agonist). PIMSR, as a neutral antagonist, may avoid these issues while still treating cocaine addiction.
The numbers in context
PIMSR inhibited cocaine self-administration under FR5 (not FR1), reduced progressive-ratio breakpoints, and attenuated cue-induced reinstatement. Effects confirmed through CB1 knockout mice and receptor antagonism.
How the study worked
Multiple preclinical behavioral assays in rats and transgenic mice: cocaine self-administration (FR1, FR5, progressive ratio), place conditioning, intracranial self-stimulation (electrical and optogenetic), and receptor antagonist studies.
What this study cannot tell us
Preclinical study only. PIMSR also inhibited sucrose self-administration, suggesting potential effects on natural reward. Human pharmacokinetics and safety are unknown.
How to read the evidence
Comprehensive preclinical characterization with mechanism confirmation, but no human data available.
When this study was published
Published in 2022.
The bigger picture
The distinction between neutral antagonists (which block the receptor without changing baseline activity) and inverse agonists (which reduce baseline activity) may be critical for developing CB1-targeting medications without the psychiatric side effects that sank rimonabant.
Questions still open
- Would PIMSR's effect on natural reward (sucrose) cause appetite or motivation problems in humans? Can neutral CB1 antagonism treat other substance use disorders?
Common questions
How is PIMSR different from rimonabant?
Did it completely stop cocaine use in animals?
Read the original research
Therapeutic potential of PIMSR, a novel CB1 receptor neutral antagonist, for cocaine use disorder: evidence from preclinical research.
Translational psychiatry, 12(1), 286
Citation
Galaj, Ewa; Hempel, Briana; Moore, Allamar; Klein, Benjamin; Bi, Guo-Hua; Gardner, Eliot L; Seltzman, Herbert H; Xi, Zheng-Xiong. (2022). Therapeutic potential of PIMSR, a novel CB1 receptor neutral antagonist, for cocaine use disorder: evidence from preclinical research.. Translational psychiatry, 12(1), 286. https://doi.org/10.1038/s41398-022-02059-w
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