DISCRIMINATIVE STIMULUS-FIELD AND OPEN-FIELD EFFECTS OF THE ENANTIOMERS OF 11-HYDROXY-DELTA-8-TETRAHYDROCANNABINOL IN PIGEONS AND GERBILS

The cannabimimetic activity of the two enantiomers of 11-hydroxy-delta -8-tetrahydrocannabinol (11-OH-delta-8-THC) was evaluated in pigeons t rained to discriminate between the presence and absence of (-)-delta-9 -tetrahydrocannabinol [(-)-delta-9-THC]. (-)-11-OH-Delta-8-THC exhibit ed cannabimimetic activity with a potency (ED(50), 0.17 mg/kg) similar to that of delta-9-THC. The duration of action for (-)-11-OH-delta-8- THC was shorter than that observed for delta-9-THC. No cannabimimetic activity was seen after administrations of(+)-11-OH-delta-8-THC, indic ating enantiomeric selectivity for the discriminable effects. A dose-r elated decrease in response rate occurred with (-)-11-OH-delta-8-THC, but not with (+)-11-OH-delta-8-THC; the latter compound produced an in crease in responding at 3 mg/kg. Open-field behavior in Mongolian gerb ils indicated marked suppression of rearing (vertical activity) after treatments with (-)-delta-9-THC and (-)-11-OH-delta-8-THC; this did no t occur after (+)-11-OH-delta-8-THC. The results support the notion of cannabimimetic enantiospecificity.