At a dose as low as 1 microgram per kilogram of body weight, lysergic acid diethylamide (LSD) significantly decreased the suppressive effect of electric shock on licking behavior of the rat. Attenuation of punishment was also obtained with mescaline, but neither dimethyltryptamine nor Δ 9 -tetrahydrocannabinol was active in this test. Cyproheptadine and α-propyldopacetamide, drugs that...