Dopaminergic modulation of the persistence of one-trial hippocampus-dependent memory

The persistence of new memory traces in the hippocampus, encoded following appropriate activation of glutamatergic receptors and the induction of synaptic plasticity, can be influenced by heterosynaptic activation of neuromodulatory brain systems. We therefore investigated the effects of a hippocamp...

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Published in:Learning & memory (Cold Spring Harbor, N.Y.) Vol. 13; no. 6; p. 760
Main Authors: O'Carroll, Colin M, Martin, Stephen J, Sandin, Johan, Frenguelli, Bruno, Morris, Richard G M
Format: Journal Article
Language:English
Published: United States 01.11.2006
Subjects:
Analysis of Variance
Animals
Dopamine - metabolism
Dopamine Agents - pharmacology
Escape Reaction - drug effects
Escape Reaction - physiology
Hippocampus - drug effects
Hippocampus - metabolism
Male
Maze Learning - drug effects
Maze Learning - physiology
Memory - physiology
Rats
Rats, Inbred Strains
Receptors, Dopamine D1 - drug effects
Receptors, Dopamine D1 - metabolism
Receptors, Dopamine D5 - drug effects
Receptors, Dopamine D5 - metabolism
Spatial Behavior - drug effects
Spatial Behavior - physiology
Statistics, Nonparametric
ISSN:1072-0502
Online Access:Get more information
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Summary:The persistence of new memory traces in the hippocampus, encoded following appropriate activation of glutamatergic receptors and the induction of synaptic plasticity, can be influenced by heterosynaptic activation of neuromodulatory brain systems. We therefore investigated the effects of a hippocampus-specific blockade of dopamine D1/D5 receptors on the persistence of spatial memory encoded in one trial using a delayed matching-to-place (DMP) task in a watermaze in which rats learn a new escape location each day. A within-subjects design was used such that both short (20 min) and long (6 h) retention intervals, and both drug (SCH23390, a D1/D5 receptor antagonist) and vehicle (aCSF) infusions were tested on different days in the same animals. Bilateral intrahippocampal infusion of SCH23390 (5 microg in 1 microL per side) prior to trial 1 (encoding) caused a differential impairment as a function of memory delay-with no effect during trial 2 (memory retrieval) after a 20-min interval, but a block of memory at 6 h. Further experiments revealed that infusion of SCH23390 immediately after trial 1 had no effect on retention 6 h later, and the poor memory seen at long retention intervals when the drug was present at encoding was not due to a state-dependent failure of retrieval. These results suggest that activation of D1/D5 receptors during memory encoding is necessary for the formation of a persistent memory trace in the hippocampus. The complementary effects of D1/D5 receptor blockade on the persistence of LTP and the duration of memory are consistent with the idea that changes in synaptic strength underlie memory.
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ISSN:1072-0502
DOI:10.1101/lm.321006