Drug-taking behavior is typically associated with a wide array of sensory stimuli. For example, methadone can become associated to the taste cues occurring with the ingestion process, as well as with distinct visual and auditory stimuli provided by the clinic setting. Similarly, crack cocaine may become associated to the odor cues occurring with the inhalation process, as well as with distinct visual and tactile stimuli provided by the drug paraphernalia. These multiple stimuli that signal the onset of the drug experience are important in the maintenance of drug-taking behavior, as well as in the phenomenon of drug craving. While it is widely recognized that drug-associated cues may serve as effective conditioned stimuli (CS) in eliciting a conditioned response (CR), there is surprisingly little known about the role of different types of CS elements (gustatory, olfactory, visual, tactile) in the conditioning process. The long-term objective of the present project is to ascertain the relative control that different CS types have in the conditioning process. Such information may have important clinical implications for treating cue-elicited craving and relapse among drug abusers. The present application will examine the ability of a taste or odor cue to serve as a CS when paired with morphine in a locomotor test in rats. Preliminary evidence indicates that a taste CS paired with morphine elicits hypoactive CR, whereas an odor CS paired with morphine elicits a hyperactive CR.
The specific aims of this project are to: (1) determine what attributes of the CS are important in establishing these locomotor CRs; (2) rigorously test the associative nature of these two different CRs; (3) examine the potential role of different opioid receptors (mu, sigma and kappa) in mediating these CRs; and (4) determine what happens to the CR when a taste and odor cue are paired together with morphine during conditioning.
