TRYPTAMINERGIC MECHANISMS IN PUNISHED AND NONPUNISHED BEHAVIOR

Abstract

The dose-effect relationships of two tryptaminic antagonists, methysergide and bromolysergic acid, and the agonist, α-methyltryptamine, on key-pecking behavior of the pigeon were determined. A multiple fixed-interval five-minute fixed-ratio 30-response food presentation schedule and a concurrent fixed-interval five-minute food, fixed-ratio 30-electric-shock punishment schedule were used. Lower doses of the two tryptaminic antagonists increased low response rates occurring at the beginning of the fixed-interval component of the multiple schedule and the overall response rates of the punished fixed interval. They also increased the high overall rates of responding during the fixed ratio. Higher doses of methysergide and bromolysergic acid decreased high rates of responding occurring at the end of the fixed-interval and the fixed-ratio components of the multiple schedule. α-Methyltryptamine produced only decreases in responding with both schedules studied. These results suggest the existence of a tryptaminergic mechanism involved in behavioral inhibition.