Effects of NMDA antagonists ketamine, methoxetamine and phencyclidine on the odor span test of working memory in rats
Michael Mathews, R. N. Mead, M. Galizio
Experimental and Clinical Psychopharmacology February 1, 2018 DOI: 10.1037/pha0000158 (opens in new tab) via Semantic Scholar
Summary
AI-generated from the abstractNMDA receptor antagonists impair working memory in rodents, but the effects differ across drugs. In the odor span task, which tests memory for multiple stimuli, phencyclidine (PCP) and methoxetamine (MXE) reduced accuracy only when memory load was high, without affecting simple discrimination. Ketamine (KET) produced less selective impairments. These findings support the glutamate hypothesis, which links NMDA receptor hypofunction to cognitive symptoms of schizophrenia, but suggest that not all NMDA antagonists affect memory identically.
Study at a glance
| Characteristics | Controlled experiment Peer reviewed |
|---|---|
| Population | Rodents (rats) |
| Interventions | Phencyclidine Ketamine Methoxetamine |
| Keywords | Medicine Psychology |
| Key finding | PCP and MXE impaired odor span accuracy at high memory loads without affecting simple discrimination, while ketamine's effects were less selective. |
Abstract
The glutamate hypothesis proposes that N-Methyl-D-aspartate (NMDA) receptor hypofunction underlies cognitive and perhaps other schizophrenic symptoms. The present study used the odor span task to assess the effects of NMDA antagonists on remembering multiple stimuli in rodents. This task uses an incrementing nonmatching-to-sample procedure in which responses to a new olfactory stimulus are reinforced on each trial, whereas responses to previously presented stimuli are not. NMDA antagonists have been associated with memory impairments in a variety of animal models; however, there are inconsistencies across different NMDA antagonists and tasks used. The current study compared the acute effects of phencyclidine (PCP), ketamine (KET), and the novel NMDA antagonist methoxetamine (MXE) on responding in the odor span task and a simple discrimination control task. PCP and MXE impaired odor span accuracy at doses that did not impair simple discrimination in most rats; however, the effects of KET were less selective. Within-session analyses indicated that the effects of PCP and MXE depended on the number of stimuli to remember, that is, impairment only occurred when the memory load was relatively high. These effects of PCP and MXE were consistent with the hypothesis that NMDA antagonists may interfere with working memory, but the basis for less selective results with KET are unclear.