Abstract

Dose-response curves were determined for the effects of some Cannabis sativa constituents on pigeons conditioned to peck a key under a multiple fixed-ratio, fixed-interval (mult FR FI) schedule of food presentation, or under a schedule that required the spacing of pecks 20 to 24 seconds apart, and on rats conditioned to press a lever for water under a mult FR FI schedule. l-Δ⁹- and l-Δ⁸-trans-tetrahydrocannabinol (Δ⁹- and Δ⁸-THC) caused dose-dependent decreases in the rates of key pecking under both components of the mult FR FI schedule in pigeons. Cannabinol, in doses up to 180 mg/kg, had no effect on key pecking of pigeons under the mult FR FI schedule. Under the temporally-spaced responding schedule Δ⁹- and Δ⁸-THC decreased the rate of responding, disrupted the temporal pattern of responding and increased the frequency of long interresponse times of the pigeons. Δ⁹-THC decreased the rate of lever pressing of rats under both components of the mult FR FI schedule. The decreases in response rates lasted as long as 24 hours after the highest doses of the THC's in the pigeons and the rats. Increases in the rate of responding were not observed under any schedule in either species.