Frequent Δ9- tetrahydrocannabinol exposure during adolescence impairs sociability in adult mice exposed to an aversive painful stimulus.

Early-life exposure to Δ9-tetrahydrocannabinol (Δ9-THC), the intoxicating constituent of cannabis, may produce enduring neurochemical changes in brain structures involved in the regulation of sociality but it is still unclear how such changes influence social behavior later in life. In the present study, we exposed male mice to moderate daily doses of Δ9-THC (5 mg/kg, intraperitoneal) during adolescence (postnatal day, PND, 30 to 43) and, when animals reached adulthood (PND70), we assessed their performance in the three-chamber social interaction task before and 3 weeks after injection of the chemical irritant formalin (1 % vol, intraplantar), which produces both immediate and persistent pain-related behaviors in mice. Prior Δ9-THC treatment did not alter social interaction in control adult mice but disrupted it in animals that developed lasting sensory abnormalities following formalin injection. The findings suggest that frequent exposure to Δ9-THC during adolescence causes in male mice a dormant dysfunction in social behavior which can be unmasked in adulthood when the animals experience an aversive state.