Effects of delta-9-THC and a water soluble ester of delta-9-THC on schedule-controlled behavior.

delta-9-Tetrahydrocannabinol (delta-9-THC) and one of its water soluble esters (SP-111) decreased the rates of responding by pigeons working under a variable interval 3-min schedule of food presentation, or a multiple fixed-ratio 30, fixed-interavl 5-min schedule of food presentation. delta-9-THC was 3-6 times more potent than SP-111 and had a faster onset of effects on behavior.