Resting State Brain Networks under Inverse Agonist versus Complete Knockout of the Cannabinoid Receptor 1.

Area of Science:

• Neuroscience
• Pharmacology
• Genetics

Background:

• The cannabinoid receptor 1 (CB₁) is a key target for THC and is implicated in various conditions.
• Suppression of CB₁ is explored for therapeutic purposes, but its whole-brain effects are not fully understood.
• Previous studies have shown unanticipated psychological side effects from CB₁ suppression.

Purpose of the Study:

• To investigate the whole-brain effects of complete CB₁ gene knockout versus short-term CB₁ suppression.
• To examine white matter structure and brain network activity in mice lacking the CB₁ gene (cnr1).
• To compare the effects of chronic CB₁ loss with acute suppression using the inverse agonist rimonabant.

Main Methods:

• In vivo imaging was performed on cnr1 knockout mice and mice treated with the CB₁ inverse agonist rimonabant.
• White matter structural changes were analyzed.
• Brain network activity and functional directional uniformity were assessed.

Main Results:

• cnr1 mice exhibited altered white matter and functional directional uniformity (males), with largely unchanged network activity.
• Rimonabant treatment altered cortical network activity but not functional directional uniformity.
• Rimonabant did not affect brain regions impacted by chronic cnr1 loss or previous behavioral studies.

Conclusions:

• Chronic loss of CB₁ function leads to subtle brain rewiring while largely preserving network activity.
• Short-term CB₁ suppression (rimonabant) affects network activity differently than chronic gene knockout.
• Results highlight significant differences between chronic CB₁ loss and acute suppression, urging further preclinical research for CB₁-targeting drugs.