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Effects of the NMDA antagonists CPP and MK-801 on delayed conditional discrimination
1Department of Psychology, University of Otago, Dunedin, New Zealand.
Psychopharmacology
|January 1, 1989
Summary
N-methyl-D-aspartate (NMDA) receptor antagonists impair working memory by reducing stimulus discriminability, not by increasing forgetting rates. These findings in rats suggest broader cognitive effects of NMDA antagonists.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Pharmacology
Background:
- N-methyl-D-aspartate (NMDA) receptor antagonists are known to impair spatial working memory and hippocampal long-term potentiation.
- Understanding the precise mechanisms of NMDA antagonist effects on cognitive functions is crucial.
Purpose of the Study:
- To investigate the dose-dependent effects of NMDA receptor antagonists on a working memory task in rats.
- To differentiate between effects on stimulus discriminability and rate of forgetting.
Main Methods:
- Utilized a delayed conditional discrimination task in rats to assess working memory.
- Administered competitive (CPP) and non-competitive (MK-801) NMDA antagonists at various doses.
- Employed signal detection analysis and an exponential memory decay model for data interpretation.
Main Results:
- Both CPP and MK-801 reduced stimulus discriminability in a dose-dependent manner.
- The reduction in discriminability was significant at higher doses (e.g., 10 mg/kg for CPP).
- No significant increase in the rate of forgetting was observed for any dose of the NMDA antagonists.
Conclusions:
- NMDA receptor antagonists disrupt delayed conditional discrimination primarily by impairing stimulus discriminability.
- These effects are consistent with known impacts on hippocampal function and spatial memory tasks.
- The findings highlight the role of NMDA receptors in the fundamental processes of working memory encoding and discrimination.