Lack of Tolerance to Δ9-Tetrahydrocannabinol in Chimpanzees

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Science  02 Feb 1973:
Vol. 179, Issue 4072, pp. 490-492
DOI: 10.1126/science.179.4072.490


Five chimpanzees were given Δ9-tetrahydrocannabinol (Δ9THC): 1.0 milligram per kilogram of body weight for 21 days and 4.0 milligrams per kilogram of body weight for 42 days. Although accuracy and speed of performance on a delayed matching-to-sample task were significantly affected by both doses, tolerance to Δ9THC did not develop. No long-term behavioral effects of Δ9THC were observed after termination of the drug regimens.