title: Dopaminergic modulation of the persistence of one-trial hippocampus-dependent memory.
abstract: 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.
authors.affiliation: Laboratory for Cognitive Neuroscience, Centre for Cognitive and Neural Systems, The University of Edinburgh, Edinburgh EH8 9JZ, United Kingdom.
authors.forename: Colin M
authors.initials: CM
authors.lastname: O'Carroll
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Martin
authors.forename: Johan
authors.initials: J
authors.lastname: Sandin
authors.forename: Bruno
authors.initials: B
authors.lastname: Frenguelli
authors.forename: Richard G M
authors.initials: RG
authors.lastname: Morris
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D015259:Dopamine Agents / Q000494:pharmacology; D004924:Escape Reaction / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology*; D008568:Memory / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D017447:Receptors, Dopamine D1 / Q000187:drug effects / Q000378:metabolism; D050641:Receptors, Dopamine D5 / Q000187:drug effects / Q000378:metabolism; D013037:Spatial Behavior / Q000187:drug effects / Q000502:physiology; D018709:Statistics, Nonparametric
chemical_list: D015259:Dopamine Agents; D017447:Receptors, Dopamine D1; D050641:Receptors, Dopamine D5; D004298:Dopamine