The researchers, in an article published in Science journal, said they found a naturally occurring hormone in the brain that spontaneously blocks the experience triggered by THC, Radio France Internationale reported Friday.
By studying rats and mice that ingested marijuana, the scientists said they found the steroid hormone pregnenolone suppressed the activity of a brain molecule called the type-1 cannabinoid receptor.
As the rodents felt the effects of THC, their pregnenolone levels increased by 1,500 percent and blocked THC's effects on the brain.
"If your [brain] is exposed to very high levels of marijuana, this natural mechanism is triggered and protects you from cannabis exposure," lead author Pier Vincenzo Piazza of the French Institute of Health and Medical Research in Paris told RFI.
Piazza said his team looked into what the hormone blocked.
"The high, the loss of memory, the sedative effect, but also the relaxation of pain or the induction of eating," Piazza told RFI. "So this hormone blocked either the bad or the good effect of THC."
He said the research was intended to discover possible treatments for marijuana intoxication and addiction.
He said researchers hope to begin clinical trials of a derivative of the hormone in 18 months.