Psychostimulant induced behavioral sensitization: The contribution of drug stimuli to context and Pavlovian conditioned stimuli

Abstract

The drug induced enhancement of behavioral stimulation effects with repeated drug treatments is frequently context specific implicating associative processes. Attempts to label these effects as Pavlovian conditioned drug responses have generally been dismissed as it has frequently been demonstrated that the test environment cues alone are insufficient to elicit the sensitized drug response. In this paper evidence will be presented showing that the sensitized drug response can in fact be elicited by test environment cues in a non-drug test. The key reason test environment cues alone are an inadequate conditioned stimulus to elicit the sensitized drug response with commonly used behavioral sensitization protocols is because drug stimulus cues of the drug used to induce behavioral sensitization are conflated with the test environment cues so that the conditioned stimulus has been transformed into a compound conditioned stimulus comprised of the test environment cues co-mingled with the drug stimulus cues In this paper we will present evidence that shows that modifications in the drug testing protocol such as placement of the subject into the test environment immediately after drug administration so that the test environment cues precede the onset of the drug response creates the opportunity for a Pavlovian test environment/drug response association. Also, the use of posttest drug administration can enable the test environment stimulus trace to be selectively paired with the drug response and acquire conditioned stimulus properties and become sufficient to elicit the sensitized behavioral drug response. From a Pavlovian conditioning perspective, repeated pairing of the drug with the test environment enables the conditioned drug response test response to add to the unconditioned drug response to generate a behavioral sensitization effect. Critically, the context needs to be recognized as a conditioned stimulus composite comprised of the test environment cues coupled with the drug generated stimulus cues.