GASP1 Disruption Spared Some Cannabinoid Tolerance While Temperature Tolerance Remained
Disrupting the receptor-sorting protein GASP1 reduced several forms of tolerance to WIN55,212-2 in mice, but it did not prevent temperature tolerance. That exception limits a claim that one receptor-trafficking mechanism explains all cannabinoid adaptation.
Receptor sorting was experimentally altered
Researchers compared male GASP1-knockout and wild-type mice during acute and repeated synthetic-cannabinoid dosing. They measured nociception, coordination, activity and temperature, alongside CB1 receptor-binding assessments. WIN55,212-2 was the tested agonist, not THC.
Several behavioral comparisons supported the mechanism
Wild-type mice developed tolerance to repeated WIN effects on antinociception, motor coordination and reduced activity. Knockout mice showed much less adaptation on those measures, with changes reduced below statistical significance in key comparisons. The accompanying receptor results supported a role for post-endocytic sorting and downregulation.
The temperature exception must remain visible
Both genotypes developed similar hypothermic tolerance. Thus, the absence of significant receptor downregulation in the knockout group did not mean every functional response remained unchanged. The authors also noted that nonsignificant behavioral changes could still contain some tolerance; they did not prove an exact zero effect.
What cannot be inferred about cannabis users
A genetically modified mouse receiving an experimental agonist is not a test of a person’s cannabis history or impairment. Other proteins, brain regions and drug-specific mechanisms may contribute. The study provides evidence for a receptor-trafficking contribution to selected outcomes, while arguing against a universal mechanism or a clinical strategy that would remove every consequence of repeated THC exposure.
Related analysis: Cannabis Tolerance Claims: Questions to Ask Before Relying on Expert Testimony.
Primary research
Differential regulation of behavioral tolerance to WIN55,212-2 by GASP1. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology (2010). DOI: 10.1038/npp.2010.6.
