EFFECTS OF MDA, CS INTENSITY, AND UCS INTENSITY ON THE RABBITS CONDITIONED NICTITATING-MEMBRANE RESPONSE

The first experiment in a previous series of investigations in which we were concerned with assessing the dose effects of (+)-3,4-methylenedioxyamphetamine (MDA) on classical conditioning of the rabbit’s nictitating membrane response revealed an enhancement of conditioning to a light conditioned stimulus (CS) and an impairment in conditioning to a tone CS. A second study revealed that MDA’s effects on conditioning could not be attributed to the drug’s effects on nonas-sociative contributors to response occurrence. Accordingly, in several subsequent investigations we sought to localize MDA’s conditioning effects in the organism’s processing of the CS. These studies revealed that MDA attenuated tone-CS intensity and the tone CS’s unconditioned excitatory properties. The final study in the series revealed that MDA enhanced the frequency of unconditioned response (UCRs) across a range of unconditioned stimulus (UCS) intensities. These simple effects of MDA on the processing of the CS and UCS/UCR would, on the basis of empirical and theoretical considerations, accoount for the drug’s effect on conditioning. As yet, however, an assessment of the possible interactive effects of MDA’s CS and UCS/UCR effects on conditioning has not been made. Accordingly, to provide one means for assessing whether or not MDA interacted with CS and UCS intensity, in the present study we employed a between-groups MDA dosage manipulation and within-group CS and UCS intensity manipulation. Consistent with theoretical expectations was a pattern of responding that yielded a robust MDA dosage × CS intensity × UCS intensity interaction. © 1991, The psychonomic soceity, inc.. All rights reserved.