Psychotomimetic Cannabinoid Hyperlocomotion Involves GSK-3β Signaling at Striatopallidal Neurons in Male Mice

Hyperlocomotion induced by psychotomimetic agents is considered a proxy for positive psychotic-like symptoms and is used in antipsychotic drug screenings with rodents. Cannabinoids are psychotomimetic drugs in humans, and low doses of cannabinoid CB₁ receptor (CB1R) agonists induce hyperlocomotion in rodents. However, the cellular and molecular mechanisms underlying this effect remain unexplored so far.

We used a combination of pharmacological and genetic manipulations in cultured cells and adult male mouse models, together with an intracellular signaling detection method. Our multidisciplinary approach included locomotor activity (n = 10-12 mice/group), alphaLISA technology (n = 4-12 mice/group), transfection of the β-arrestin 1 protein in STHdh ^Q7/Q7 cells (n = 4-6/group) and a viral strategy in transgenic lines to selectively block GSK-3β (glycogen synthase kinase-3β) phosphorylation (n = 8-10 mice/group). We also used fluorescence in situ hybridization, real-time quantitative and droplet digital polymerase chain reaction, and tandem mass spectrometry.

We showed that the hyperlocomotion induced by a low dose (0.3 mg/kg) of cannabinoid Δ⁹-tetrahydrocannabinol depends on the activation of plasma membrane CB1R located on dopamine D₂ receptor-positive striatopallidal projecting neurons. This activation regulates the β-arrestin 1/Akt/GSK-3β signaling pathway, which is required for the hyperlocomotor effect. The signaling-specific CB1R inhibitors, pregnenolone and its clinically developed analog, AEF0117, prevent GSK-3β-dependent psychomotor stimulation induced by THC.

This work highlights an intracellular mechanism of CB1R expressed by a selective key neuronal pathway mediating the psychotomimetic effect of THC and, by extension, low-dose cannabis consumption. This discovery will likely aid the development of unprecedented therapeutic modalities for the treatment of psychotic conditions.