Repeated Δ9-tetrahydrocannabinol exposure in adolescent monkeys: persistent effects selective for spatial working...

Area of Science:

• Neuroscience
• Developmental Psychology
• Pharmacology

Background:

• Adolescents may be more susceptible to persistent cognitive impairments from cannabis use.
• Human studies face confounds, limiting causal inference on adolescent cannabis use and working memory deficits.

Purpose of the Study:

• To investigate the causal relationship between repeated Δ9-tetrahydrocannabinol (THC) exposure and working memory in adolescent non-human primates.
• To assess the impact of THC on spatial and object working memory during a critical developmental window.

Main Methods:

• Seven pairs of adolescent male rhesus monkeys received daily intravenous THC or vehicle for six months.
• Spatial and object working memory tasks were administered 23 and 71 hours post-administration.
• Acute effects were assessed at the study's start and end.

Main Results:

• Repeated THC exposure impaired spatial working memory improvement in a delay-dependent manner compared to controls.
• No significant differences were observed in object working memory task improvements between groups.
• No evidence of THC sensitivity or tolerance emerged after six months of exposure.

Conclusions:

• Persistent cognitive effects of THC are more pronounced when exposure occurs during active neural circuit maturation.
• Spatial working memory, which matures later, showed greater vulnerability to THC exposure during adolescence.