DRUGS OF ABUSE, REWARD COMPARISON, AND THE THALAMUS

Project: Research project

Project Details

Description

DESCRIPTION: (Adapted from the Investigator's Abstract) Rats will decrease
intake of a saccharin conditioned stimulus (CS) following pairing with an
illness-inducing agent such as LiCl, a preferred high concentration of sucrose,
or a drug of abuse such as morphine or cocaine. The suppressive effects of the
illness-inducing agent are clear evidence for aversive conditioning and are
referred to as conditioned taste aversions. The suppressive effects of the
rewarding sucrose solution reflect appetitive conditioning and are referred to
as anticipatory contrast effects because the saccharin CS is thought to be
devalued as it comes to predict the future availability of the preferred
sucrose reward. Finally, despite the well-known rewarding properties of drugs
of abuse, the suppressive effects of these drugs have been viewed as
conditioned taste aversions for over 25 years. We have, however, recently posed
an alternative interpretation that eliminates this apparent paradox.
Specifically, we have suggested that rats suppress intake of a saccharin CS
following saccharin-morphine pairings, for example, because the saccharin CS is
devalued as it comes to predict the future availability of the highly rewarding
drug of abuse. Thus, we postulate that the same rewarding properties that
increase self-administration of the drug also serve to devalue the gustatory
cue that predicts its availability. The results from the Preliminary Studies
support this novel hypothesis by showing that the suppressive effects of drugs
of abuse and sucrose, but not LiCl, are influenced by deprivation state of the
animal, the caloric value of the gustatory CS, the strain of the rat, and
lesions of the gustatory thalamus. The objective of this proposal is to use a
lesion-behavioral analysis to (I) evaluate the relative contribution of the
gustatory thalamus and its terminal projection region, the gustatory cortex,
(II) identify the parametric constraints on the impairment, and (III), given
that rats will suppress saccharin intake when paired with iv cocaine
(Preliminary Study #5), examine the nature of the lesion-induced deficit using
the self-administration task.
StatusFinished
Effective start/end date9/1/005/31/01

Funding

  • National Institute on Drug Abuse: $269,325.00

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