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Psychopharmacology (Berl). 2002 Jul;162(3):225-31. Epub 2002 May 14.

Evidence for dopamine D(1) receptor involvement in the stimulus selection task: overshadowing in the rat.

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1
Department of Psychology, University of Leicester, University Road, Leicester LE1 7RH, UK.

Abstract

RATIONALE:

A number of lines of evidence suggest that dopamine might play a role in stimulus selection, the process whereby specific cues are selected to guide action.

OBJECTIVES:

In order further to define the potential role for dopamine in stimulus selection, the present series of studies examined whether dopaminergic drugs modulate overshadowing, a paradigm that involves stimulus selection in rats. Overshadowing is where preferential learning occurs to one (usually the more salient) element of a stimulus compound.

METHODS:

Overshadowing was measured in rats using a thirst motivated conditioned emotional response paradigm (CER). Two simultaneously presented stimuli (light and tone) were paired with an aversive unconditioned stimulus (mild footshock); overshadowing is observed when learning to the less salient stimulus is weaker than learning to the same stimulus when it is conditioned alone.

RESULTS:

d-Amphetamine sulphate (1 mg/kg, IP) was found selectively to disrupt overshadowing, without affecting the CER in control animals. The dopamine (DA) D(2) receptor antagonists, haloperidol (0.2 mg/kg, IP) or raclopride (0.5 mg/kg, IP), failed to reverse amphetamine-induced disruption of overshadowing. In contrast, the selective DA D(1) antagonist SCH 23390 (0.05 mg/kg, IP) reversed amphetamine-induced disruption of overshadowing. The partial DA D(1) agonist SKF 38393 (5 mg/kg, IP) was found to abolish overshadowing when given alone.

CONCLUSION:

These data indicate a modulatory role for the DA D(1) receptor in the expression of stimulus selection and suggest that the DA D(1) receptor might play a role in salience allocation aspects of learning.

PMID:
12122479
DOI:
10.1007/s00213-002-1107-1
[Indexed for MEDLINE]
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