Abstract
Repeated pairings of a neutral context and the effects of haloperidol give rise to conditioned catalepsy when the context is subsequently presented in a drug-free test. In order to confirm whether this response is based on Pavlovian processes, we conducted two experiments involving two manipulations that affect conditioning intensity in classical conditioning procedures: time of joint exposure to the conditioned and the unconditioned stimulus, and the length of the inter-stimulus interval (ISI). The results revealed that both an increase in the length of context-drug pairings during conditioning and a reduced ISI between drug administration and context exposure increased conditioned catalepsy. These results are discussed in terms of the temporal peculiarities of those procedures that involve drugs as the unconditioned stimulus along with the role of Pavlovian conditioning in context-dependent catalepsy.
Highlights
The oldest antecedents of the study of classical conditioning using drugs as Unconditioned Stimuli (US) can be traced back to experiments by I.P
As can be seen in the figure, haloperidol-induced catalepsy appeared for those animals in the Pair condition, and it increased across trials reflecting a sensitization process
In the case where drugs are used as the US, the inter-stimulus interval (ISI) presents peculiarities that make this type of paradigm different from traditional Pavlovian procedures, since in the first case, the US is administered first, and the Conditioned Stimulus (CS)-context is exposed, whereas in the traditional procedure the CS is presented before the US
Summary
The oldest antecedents of the study of classical conditioning using drugs as Unconditioned Stimuli (US) can be traced back to experiments by I.P. Pavlov (1849–1936), who reported that repeated administration of morphine in the presence of the same context resulted in Conditioned Responses (CR) similar to those produced by the drug itself (Pavlov, 1927) Based on these pioneering studies, numerous investigations have been conducted demonstrating the conditioning of various responses produced by a wide range of drugs, and revealing that sometimes the CR was similar to that induced by the drug (e.g., Battisti et al, 2000; Mena and De la Casa, 2013), while in other cases the CR was opposite to the unconditioned effect of the drug (e.g., Siegel, 1975; Solomon, 1980). In the second case, the CR is opposite to the response induced by the drug at the central level, and there is ample evidence showing that conditioning of such opponent response is governed by Pavlovian processes (e.g., Tiffany and Baker, 1981; Paletta and Wagner, 1986)
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