Relative potency of tetrahydrocannabinol derivatives on tonic immobility in chickens.

Chickens were given varying dosages of delta 3-, delta 8-, and delta 9-THC and tested for duration of tonic immobility (TI). Although all derivatives had a profound facilitation effect, delta 9-THC was the most potent. These results are unusual in that TI is a well documented fear-potentiated reaction and THC generally has tranquilization-like effects.