Acute and chronic effects of beta9-tetrahydrocannabinol on seizures in the gerbil.

Beta9-THC was injected daily for 6 days into gerbils from our breeding colony that exhibit spontaneous epileptiform seizures. At a dose of 20 mg/kg no effect was seen on the latency, duration or severity of the seizures induced after 1 and 6 days of treatment. Delta9-THC (50 mg/kg) completely abolished the seizures after a single injection but tolerance developed to this effect so that no protection was afforded after 6 daily doses. Severe toxic signs were evident at the higher dose level with marked depression of spontaneous motor activity. The toxic effect increased progressively with chronic treatment and half the animals failed to survive.