Independent ethanol- and sucrose-maintained responding on a multiple schedule of reinforcement

Assessment of drug effects an two different reinforcers at the same time re quires that each reinforcer be sampled at approximately the same time. One procedure that effectively produces this result is the use of a multiple sc hedule of reinforcement in which two different reinforcers are presented in alternating P-min components. In our study, sucrose and ethanol solutions were made available after appropriate lever-press responding, Subjects were trained to self-administer 10% ethanol using a sucrose-substitution proced ure and to discriminate light cues associated with the different reinforcer s until stable reinforcer-directed responding was achieved on both the etha nol- and the sucrose-associated lever during the changing 2-min components of the schedule. Subsequently, the reinforcer solution presented on one lev er was field constant while the concentration of the alternate reinforcer w as manipulated, i,e,, ethanol concentrations of 0 to 15% end sucrose concen trations of 0 to 10% were assessed, This multiple schedule procedure result ed in sustained and independent ethanol- and sucrose-reinforced behavior. M anipulation of the characteristics of one reinforcer had no effect on behav ior maintained by the alternate reinforcer, Increases In sucrose concentrat ion resulted in Increases in sucrose-directed responding with no change in ethanol responding, and increases in ethanol concentration resulted in incr eases In ethanol intake with no change in sucrose responding. Our methods c an be used to examine differential drug effects on ethanol- and sucrose-rei nforced behavior in the same animal over a single time course without the c onfounds or interference from the concurrently available reinforcer.