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Distinct contributions of hippocampal NMDA and AMPA receptors to encoding and retrieval of one-trial place memory.

ABSTRACT: Allocentric place memory may serve to specify the context of events stored in human episodic memory. Recently, our laboratory demonstrated that, analogous to event-place associations in episodic memory, rats could associate, within one trial, a specific food flavor with an allocentrically defined place in an open arena. Encoding, but not retrieval, of such flavor-place associations required hippocampal NMDA receptors; retrieval depended on hippocampal AMPA receptors. This might have partly reflected the contributions of these receptors to encoding and retrieval of one-trial place, rather than flavor-place, memory. Therefore, the present study developed a food-reinforced arena paradigm to study encoding and retrieval of one-trial allocentric place memory in rats; memory relied on visuospatial information and declined with increasing retention delay, still being significant after 6 h, the longest delay tested (experiments 1 and 2). Hippocampal infusion of the NMDA receptor antagonist d-AP-5 blocked encoding without affecting retrieval; hippocampal infusion of the AMPA receptor antagonist CNQX impaired retrieval (experiment 3). Finally, we confirmed that the d-AP-5 infusions selectively blocked induction of long-term potentiation, a form of synaptic plasticity, whereas CNQX impaired fast excitatory transmission, at perforant-path dentate gyrus synapses in the dorsal hippocampus in vivo (experiment 4). Our results support that encoding, but not retrieval, of one-trial allocentric place memory requires the NMDA receptor-dependent induction of hippocampal synaptic plasticity, whereas retrieval depends on AMPA receptor-mediated fast excitatory hippocampal transmission. The contributions of hippocampal NMDA and AMPA receptors to one-trial allocentric place memory may be central to episodic memory and related episodic-like forms of memory in rats.

SUBMITTER: Bast T

PROVIDER: S-EPMC6724786 | biostudies-literature | 2005 Jun

REPOSITORIES: biostudies-literature

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Distinct contributions of hippocampal NMDA and AMPA receptors to encoding and retrieval of one-trial place memory.

Bast Tobias T da Silva Bruno M BM Morris Richard G M RG

The Journal of neuroscience : the official journal of the Society for Neuroscience 20050601 25

Allocentric place memory may serve to specify the context of events stored in human episodic memory. Recently, our laboratory demonstrated that, analogous to event-place associations in episodic memory, rats could associate, within one trial, a specific food flavor with an allocentrically defined place in an open arena. Encoding, but not retrieval, of such flavor-place associations required hippocampal NMDA receptors; retrieval depended on hippocampal AMPA receptors. This might have partly refle ...[more]

PMID: 15976073

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Project description:Stressful life events induce abnormalities in emotional and cognitive behaviour. The endogenous opioid system plays an essential role in stress adaptation and coping strategies. In particular, the µ-opioid receptor (?R), one of the major opioid receptors, strongly influences memory processing in that alterations in ?R signalling are associated with various neuropsychiatric disorders. However, it remains unclear whether ?R signalling contributes to memory impairments induced by acute stress. Here, we utilized pharmacological methods and cell-type-selective/non-cell-type-selective ?R depletion approaches combined with behavioural tests, biochemical analyses, and in vitro electrophysiological recordings to investigate the role of hippocampal ?R signalling in memory-retrieval impairment induced by acute elevated platform (EP) stress in mice. Biochemical and molecular analyses revealed that hippocampal ?Rs were significantly activated during acute stress. Blockage of hippocampal ?Rs, non-selective deletion of ?Rs or selective deletion of ?Rs on GABAergic neurons (?RGABA) reversed EP-stress-induced impairment of memory retrieval, with no effect on the elevation of serum corticosterone after stress. Electrophysiological results demonstrated that stress depressed hippocampal GABAergic synaptic transmission to CA1 pyramidal neurons, thereby leading to excitation/inhibition (E/I) imbalance in a ?RGABA-dependent manner. Pharmaceutically enhancing hippocampal GABAA receptor-mediated inhibitory currents in stressed mice restored their memory retrieval, whereas inhibiting those currents in the unstressed mice mimicked the stress-induced impairment of memory retrieval. Our findings reveal a novel pathway in which endogenous opioids recruited by acute stress predominantly activate ?RGABA to depress GABAergic inhibitory effects on CA1 pyramidal neurons, which subsequently alters the E/I balance in the hippocampus and results in impairment of memory retrieval.

Dataset Information

Distinct contributions of hippocampal NMDA and AMPA receptors to encoding and retrieval of one-trial place memory.

Publications

Distinct contributions of hippocampal NMDA and AMPA receptors to encoding and retrieval of one-trial place memory.

Similar Datasets

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