Comparison of backward and delayed groups in Pavlovian drug-drug conditioning procedures : implications for control of nonassociative factors

Davey, Valerie Anne (1990) Comparison of backward and delayed groups in Pavlovian drug-drug conditioning procedures : implications for control of nonassociative factors. Masters thesis, Memorial University of Newfoundland.

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Abstract

Rats receiving paired injections of sodium pentobarbital followed 30 minutes later by d-amphetamine sulfate have been reported to show an effect of pairings over trials in the form of an increase in heart rate in response to pentobarbital relative to rats receiving the two drugs 24 hours apart (delayed control; e.g., Revusky, Davey, & Zagorski, 1989). This Pavlovian conditional response (CR) has been obtained only if rats are placed in a heart rate recording apparatus during acquisition. However, home cage conditioning was assessed relative to rats that received the two drugs in reverse order (backward control), which without direct evidence assumes that delayed and backward groups are equivalent. The unconditional response to pentobarbital (UR) in drug-naive rats is similar to the pentobarbital CR: A nonassociative drug interaction could maintain the pentobarbital UR, which otherwise diminishes over trials in delayed controls. In two experiments reported here, equivalent increases in heart rate in forward and backward groups were found relative to a delayed control whether training or testing was carried out in the recording apparatus or in the home cage. This finding suggests that a drug interaction present in forward and backward groups and absent in the delayed control has yet to be eliminated in accounting for the heart rate effect. Comparison of backward and delayed controls in a drug-drug conditioning procedure using a taste aversion test revealed that both forward and delayed pairings can produce attenuated aversions relative to a backward group whether the US is amphetamine (Experiment 2) or lithium chloride (Experiment 3). This finding was discussed in terms of the role of number and intensity of US preexposures in attenuating subsequent taste aversion conditioning.

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