adolescent rats were exposed to tetrahydrocannabinol (THC), the active molecule in cannabis. After all the THC had cleared from the rats’ bodies, Hurd’s team allowed the test subjects to mate with untreated rats. The resulting pups were given to foster mothers with no previous THC exposure, in case the drug had affected the biological mothers’ parenting skills. When the pups matured, they were introduced to a system that required them to exert physical effort to self-administer heroin. Rats with a parent that had been exposed to THC were willing to put in more effort to obtain the drug.
