To see if they could shed light on this grey area, researchers from the University of East Anglia and the University Pompeu Fabra began conducting behavioral studies on rodents that they exposed to THC, such as exposing their paws to hot plates and examining their reactions. Using mice designed to lack one of the serotonin receptors, they found that the pain-relieving and amnesic effects of THC are independent of each other. So while these mutant mice didn’t lose their memories on THC, the drug still acted as a pain-reliever in them.