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Methylphenidate and nicotine focus responding to an informative discrete CS over successive sessions of appetitive conditioning
School of Psychology, University of Nottingham, Nottingham,
UK.
* To whom correspondence should be addressed.
Methylphenidate (MP) and nicotine would be expected to improve associative learning, though previous evidence suggests that they should reduce the selectivity with which associations are formed. Here we tested their effects on learning the association between a conditioned stimulus(CS) and food (unconditioned stimulus, UCS) in male Wistar rats. The UCS was delivered immediately (0 s) following CS offset or after a 10 s trace. In addition to the measures of discrete CS conditioning, contextual and trace responding was measured in the inter–trial– and the inter–stimulus interval, respectively. In all cases, conditioning was measured as nosepoking for food. Both MP and nicotine improved the acquisition of discrete cue conditioning. Acquisition was accelerated (compared to saline) under 5 but not 1mg/kg MP and 0.6, but not 0.4mg/kg nicotine. In each case, this effect was observed in 0 s but not 10 s conditioned groups. For comparison, some earlier published data obtained following the same procedure with D–amphetamine were re–analysed in the same way. Amphetamine similarly improved conditioning in the 0 s group, in this case at 0.5, but not 1.5mg/kg. Thus three different dopamine agonists increased the ability to focus responding to CS presentations oversuccessive sessions of appetitive acquisition. Key Words: methylphenidate, nicotine, trace interval, appetitive conditioning, rat
First published on January 21, 2008, doi:10.1177/0269881107083842 |
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