CONCURRENT PENTOBARBITAL-MAINTAINED AND SACCHARIN-MAINTAINED RESPONDING - EFFECTS OF SACCHARIN CONCENTRATION AND SCHEDULE CONDITIONS

Responses of rhesus monkeys were reinforced by delivery of either a pe ntobarbital (4.0 mg/ml) solution or a vehicle (water) or saccharin sol ution under a concurrent signaled differential reinforcement of low ra tes 30-s schedule. After 30 s of no responding, the first response on the pentobarbital or saccharin spout resulted in the delivery of the a ppropriate solution and reset the timing on both spouts (i.e. a mutual ly exclusive choice). In the first experiment, the concentration of sa ccharin was gradually increased across sessions. As saccharin concentr ation increased, pentobarbital deliveries decreased and saccharin as w ell as total session deliveries increased. In a second experiment, pen tobarbital and 0.24 (mg/ml) saccharin were made available under concur rent signaled differential reinforcement of low rates 30-s schedules w hich operated independently. Under these conditions responding on one spout had no consequences with respect to the other spout. The reducti on of pentobarbital deliveries was substantially attenuated when the c hoice was not mutually exclusive.