Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Karen G Anderson


Impulsive choice is often examined using a delay-discounting procedure where choice is between two reinforcers of different magnitudes presented at varying delays. Individual discounting rates can be influenced by many factors including strain differences and drug effects. Lewis (LEW) and Fischer 344 (F344) rats have behavioral and neurochemical differences relevant to delay discounting and were used to examine effects of acute and repeated diazepam administration on impulsive choice. Consistent with previous literature, larger-reinforcer choice decreased as a function of increasing delays for all rats, and steeper discounting functions occurred for LEW relative to F344 rats. Acute and repeated diazepam administration resulted in differential effects between rat strains and sometimes between subjects within the same rat strain. Overall, larger-reinforcer choice was unchanged across multiple phases of the experiment for LEW rats, with some exceptions during the acute phase. For F344 rats, larger-reinforcer choice increased following acute administration of smaller doses of diazepam and decreased following acute administration of the largest dose tested. Decreases in larger-reinforcer choice occurred for F344 rats during repeated conditions and persisted throughout a non-drug baseline phase. Results from the present study have raised more questions about, and potential directions for future investigation of, multiple environmental, genetic, and neurochemical variables involved in delay discounting and effects of benzodiazepines on delay discounting.