Multielemental stimulus control: Effects of saccharin concentration on a discriminated morphine-saccharin taste aversion

The effects of saccharin concentration on the stimulus control by a compound stimulus consisting of morphine, saccharin (0.01, 0.03, or 0.10%, wt/vol), and a ball bearing drinking nozzle in a discriminated taste aversion (DTA) procedure were examined in rats (Rattus norvegicus). In paired rats injections of lithium followed presentation of this compound stimulus, whereas in unpaired rats saline injections followed this stimulus. DTA acquisition was more rapid at higher saccharin concentrations. In testing with each individual stimulus element, stimulus control was clearly exerted by all 3 stimulus elements. When another stimulus element was presented jointly with saccharin, behavioral control was similar to that of saccharin alone. Behavioral control by saccharin increased with saccharin concentration. However, behavioral control by the 2 other stimulus elements was relatively unaffected when the saliency of the saccharin element was increased.