PERSISTANCE OF ETHANOL SELF-ADMINISTRATION AS A FUNCTION OF INTERREINFORCER INTERVAL AND CONCENTRATION

Dipper cups filled with an ethanol solution were presented to Long-Eva ns hooded rats according to multiple extinction x s fixed-ratio 1 (mul t EXT x s FR1) schedules of reinforcement. The scheduled duration of t he EXT component was varied to manipulate minimum interreinforcer inte rval. Increasing the minimum interreinforcer interval by increasing EX T component was used to challenge responding maintained by ethanol for purposes of evaluating the persistance of ethanol-maintained respondi ng. EXT durations of 0 s (baseline conditions of continuous reinforcem ent) to 480 s were examined across ethanol concentrations if 0 (water, vehicle), 2, 4, 8, 16, and 32% (w/v). Increasing the EXT component du ration resulted in reductions in the number of dipper presentations ob tained at each concentration. Reductions in dipper presentations were less, relative to 0-s baseline conditions, the higher the concentratio n of the ethanol solution available. It was concluded that increasing the ethanol concentration that is self-administered increases the stre ngth of responding that is subsequently maintained in that drug-mainta ined behaviour becomes more resistant to modulation by a procedure (sc heduling minimum interreinforcer intervals) which generally reduces nu mbers of drug deliveries.