Abstract
Many US adolescents are regularly exposed to Δ9-tetrahydrocannabinol (THC) via the smoking and more recently, vaping, of cannabis and cannabis extracts. Growing legalization of cannabis for medical and recreational purposes, and decreasing perceptions of harm, make it increasingly important to determine the consequences of frequent adolescent exposure.
Male and female Wistar rats were implanted with radio-telemetry devices to monitor body temperature and exposed to twice daily 30 minute inhalation of THC vapor, or the propylene glycol (PG) vehicle, from post-natal day (PND) 35-39 and PND 42-45 using an e-cigarette based system. Responses to THC were re-determined from PND 86-94 and chow intake was assessed in mid adulthood. Blood samples were obtained from additional groups following THC inhalation on PND 31, on PND 39 after a week of twice daily exposure, and during early adulthood. Additional groups of male rats exposed repeatedly to THC or PG during adolescence were evaluated for intravenous self-administration of oxycodone as adults.
Female, but not male, adolescents developed tolerance to the hypothermic effects of THC inhalation in the first week of repeated exposure despite similar plasma THC levels. Each sex exhibited tolerance to THC hypothermia in adulthood after repeated adolescent THC with THC exhibiting greater potency in females. Repeated-THC male rats consumed more food than their PG treated control group, in the absence of a significant bodyweight difference, but male rats did not differ in oxycodone self-administration.
This study confirms that repeated THC vapor inhalation in adolescence results in lasting consequences observable in adulthood.