NMDA receptor in conditioned flavor-taste preference learning: blockade by MK-801 and enhancement by D-cycloserine.

Full Abstract

Conditioned flavor-taste preference (CFTP) is a robust form of learning in which animals acquire a preference for a flavor (e.g. Kool-Aid) previously mixed with a highly preferred tastant (e.g. fructose) over a flavor previously mixed with a less-preferred tastant (e.g. saccharin). Here, the role of the N-methyl-D-aspartate (NMDA) glutamate-glycine receptor (NR) was probed using systemic MK-801, a non-competitive antagonist, and D-cycloserine (DCS), a glycine agonist. Rats were injected with MK-801 (100 microg/kg) or vehicle 30 min prior to a daily 2-h conditioning session with 1-bottle access to a Kool-Aid flavor (grape or cherry) mixed with either 8% fructose (CS+/F) or 0.2% saccharin (CS-/S). CFTP expression was measured in 2-bottle preference tests between the Kool-Aid flavors mixed with 0.2% saccharin (CS+/S vs. CS-/S). While vehicle-treated rats acquired a preference for CS+/S over CS-/S, MK-801 prior to conditioning completely blocked CFTP learning. The effect of MK-801 was specific to CFTP acquisition, because follow-up experiments demonstrated that MK-801 did not induce a conditioned taste aversion, cause state-dependent learning, or affect CFTP expression. In a second approach, rats were injected with DCS (15 mg/kg) 60 min prior to daily conditioning. In contrast to MK-801, administration of DCS prior to conditioning enhanced CFTP learning (but not reversal conditioning). These results demonstrate that NR neurotransmission is critical for CFTP learning. Furthermore, enhancement of CFTP learning by DCS suggests that endogenous levels of glycine or D-serine may be a limiting factor in CFTP learning.

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Author information

Author/s: Golden, Glen J (GJ); Houpt, Thomas A (TA);

Affiliation: Department of Biological Science, Program in Neuroscience, The Florida State University, Tallahassee, FL 32306-4340, USA.

Grants: DC03198 (Agency:NIDCD NIH HHS) ; R01 DC003198-08 (Agency:NIDCD NIH HHS) ; T32 DC00044 (Agency:NIDCD NIH HHS)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't

Journal: Pharmacology, biochemistry, and behavior (Pharmacol Biochem Behav), published in United States. (Language: eng)

Reference: 2007-Mar; vol 86 (issue 3) : pp 587-96

Dates: Created 2007/03/30; Completed 2007/05/22; Revised 2008/11/20;

PMID: 17350084, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Animals
Conditioning (Psychology) - drug effects; physiology
Cycloserine - pharmacology
Dizocilpine Maleate - pharmacology
Glycine - agonists

Male
Rats
Rats, Sprague-Dawley
Receptors, N-Methyl-D-Aspartate - agonists; antagonists & inhibitors; physiology
Taste

Associated Chemicals: Receptors, N-Methyl-D-Aspartate (0) ; Glycine (56-40-6) ; Cycloserine (68-41-7) ; Dizocilpine Maleate (77086-22-7)

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