Figure 1.

Effects of Δ⁹-THC and anandamide, alone (top) and in combination (bottom), in monkeys discriminating Δ⁹-THC (0.1 mg·kg⁻¹ i.v.) from vehicle. Abscissae: vehicle (V) or dose in mg·kg⁻¹ body weight. Ordinates: mean (±SEM) percentage of responding on the Δ⁹-THC lever. The composite additive line was determined from linear regression of all data from the individual dose–response curves (top panel) expressed as a function of the theoretically derived, combined total dose of Δ⁹-THC and anandamide (bottom panel, composite additive). The solid line in the bottom panel was determined from linear regression of the experimentally derived data produced by the combination of Δ⁹-THC and anandamide.