Repeated THC exposure during adulthood, more than adolescence, led to lasting increases in motivation and altered reward learning in rats.
Behavioral neuroscientists, addiction researchers, and endocannabinoid system researchers.
Age-dependent effectsadolescent vs. adult THC exposure had opposing effects on CB1-dependent motivation in rats
What the researchers found
Adult THC exposure enhanced instrumental contingency degradation learning and increased progressive ratio responding, while adolescent and adult THC had opposing effects on CB1 receptor-dependent motivation, decreasing and increasing rimonabant sensitivity respectively.
Why it matters
Understanding age-dependent effects of THC on reward processing and motivation has implications for both recreational cannabis use and therapeutic applications across different age groups.
The numbers in context
THC dose: 5 mg/kg/day for 14 days. Adult THC exposure augmented contingency degradation learning. Progressive ratio performance increased, more pronounced with adult exposure. Adolescent THC decreased and adult THC increased sensitivity to CB1 antagonist rimonabant.
How the study worked
Preclinical study with two experiments in rats. Repeated THC (5 mg/kg/day, 14 days) during adolescence or adulthood. Behavioral testing: reward devaluation, contingency degradation, hedonic feeding, and progressive ratio responding.
Who was studied
Male rats receiving repeated THC during adolescence or adulthood.
What this study cannot tell us
Rat reward processing may differ from humans. Single dose and duration of THC exposure. Food reward may not generalize to drug or other reward types.
How to read the evidence
Well-designed preclinical study with multiple behavioral measures and age comparisons, but limited to male rats and food reward.
When this study was published
Recent preclinical research on age-dependent THC effects.
The bigger picture
These findings suggest that cannabis exposure during different developmental periods creates distinct, lasting changes in how the brain processes and pursues rewards, with potential implications for understanding addiction vulnerability.
Replication
Male rats only; female and cross-reward type studies needed.
Funding
Not specified in abstract
Conflicts of interest
Not specified in abstract
Questions still open
- Do these age-dependent motivational changes translate to altered drug-seeking behavior?
- Could the opposing CB1 effects explain different addiction trajectories for adolescent vs. adult cannabis users?
Read the original research
Long-term effects of THC exposure on reward learning and motivated behavior in adolescent and adult male rats.
Psychopharmacology, 240(5), 1151-1167
Citation
Halbout, Briac; Hutson, Collin; Hua, Leann; Inshishian, Victoria; Mahler, Stephen V; Ostlund, Sean B. (2023). Long-term effects of THC exposure on reward learning and motivated behavior in adolescent and adult male rats.. Psychopharmacology, 240(5), 1151-1167. https://doi.org/10.1007/s00213-023-06352-4