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UBC Theses and Dissertations

Pipradrol enhances the effect of conditioned stimuli on behaviour Hanson, Dale Robert


This thesis examined the effects of the stimulant drug pipradrol on operant responding in the presence of stimuli paired previously with food or shock. The first series of studies replicated previous findings of enhanced acquisition of responding with conditioned reinforcement after treatment with pipradrol, using a different test paradigm. The experiment began with a pre-exposure phase to determine the operant rate of pressing two levers, one of which produced a three second tone; during a conditioning phase, the same three second tone was paired with the delivery of food pellets; in a final test phase, the rates of pressing the two levers were determined again. Conditioned reinforcement was defined as a relative increase in pressing the lever that produced the tone. Pipradrol was shown to produce a dose-dependent enhancement of this effect on lever preference. Subsequent experiments examined the possible role of non-specific stimulus change, feeding in the test environment and prior exposure to the conditioned stimulus, in producing this enhancement. The data suggested that associations involving environmental stimuli may play a role in mediating this effect; animals pre-exposed to the tone stimulus and subsequently fed in the same environment as pre-exposure and test showed evidence of "conditioned reinforcement". Disrupting the relationship between tones in the pre-exposure phase and environmental stimuli paired with food prevented this pattern of responding in drugged animals. Sensory preconditioning was suggested as a possible mechanism for these associations and data were collected that were consistent with this hypothesis. Pipradrol also was shown to enhance "conditioned suppression". In this situation, animals were tested for suppression of ongoing licking behaviour to a stimulus that had been previously classically conditioned to shock. An effect of explicit sensory preconditioning training was demonstrated in this paradigm, however, pipradrol could not be shown to enhance this effect. Implications for current theories of stimulant drug action are discussed.

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