title: Differential effects of dopamine signalling on long-term memory formation and consolidation in rodent brain.
abstract: BACKGROUND
  Using auditory discrimination learning in gerbils, we have previously shown that activation of auditory-cortical D1/D5 dopamine receptors facilitates mTOR-mediated, protein synthesis-dependent mechanisms of memory consolidation and anterograde memory formation. To understand molecular mechanisms of this facilitatory effect, we tested the impact of local pharmacological activation of different D1/D5 dopamine receptor signalling modes in the auditory cortex. To this end, protein patterns in soluble and synaptic protein-enriched fractions from cortical, hippocampal and striatal brain regions of ligand- and vehicle-treated gerbils were analysed by 2D gel electrophoresis and mass spectrometry 24 h after intervention.
  
  
  RESULTS
  After auditory-cortical injection of SKF38393 - a D1/D5 dopamine receptor-selective agonist reported to activate the downstream effectors adenylyl cyclase and phospholipase C - prominent proteomic alterations compared to vehicle-treated controls appeared in the auditory cortex, striatum, and hippocampus, whereas only minor changes were detectable in the frontal cortex. In contrast, auditory-cortical injection of SKF83959 - a D1/D5 agonist reported to preferentially stimulate phospholipase C - induced pronounced changes in the frontal cortex. At the molecular level, we detected altered regulation of cytoskeletal and scaffolding proteins, changes in proteins with functions in energy metabolism, local protein synthesis, and synaptic signalling. Interestingly, abundance and/or subcellular localisation of the predominantly presynaptic protein α-synuclein displayed dopaminergic regulation. To assess the role of α-synuclein for dopaminergic mechanisms of memory modulation, we tested the impact of post-conditioning systemic pharmacological activation of different D1/D5 dopamine receptor signalling modes on auditory discrimination learning in α-synuclein-mutant mice. In C57BL/6JOlaHsd mice, bearing a spontaneous deletion of the α-synuclein-encoding gene, but not in the related substrains C57BL/6JCrl and C57BL/6JRccHsd, adenylyl cyclase-mediated signalling affected acquisition rates over future learning episodes, whereas phospholipase C-mediated signalling affected final memory performance.
  
  
  CONCLUSIONS
  Dopamine signalling modes via D1/D5 receptors in the auditory cortex differentially impact protein profiles related to rearrangement of cytomatrices, energy metabolism, and synaptic neurotransmission in cortical, hippocampal, and basal brain structures. Altered dopamine neurotransmission in α-synuclein-deficient mice revealed that distinct D1/D5 receptor signalling modes may control different aspects of memory consolidation.
authors: Special Lab Molecular Biological Techniques, Leibniz Institute for Neurobiology, Magdeburg, 39118 Germany ; Present address: Research Group Neurovascular Diseases, German Center for Neurodegenerative Diseases (DZNE), Ludwig-Erhard-Allee 2, Bonn, 53175 Germany.
authors: Nicole
authors: N
authors: Reichenbach
authors: Special Lab Molecular Biological Techniques, Leibniz Institute for Neurobiology, Magdeburg, 39118 Germany ; Present address: Division of Cellular Neurobiology, Zoological Institute, TU Braunschweig, Braunschweig, 38106 Germany.
authors: Ulrike
authors: U
authors: Herrmann
authors: Institute of Experimental Internal Medicine, Medical School, Otto von Guericke University, Magdeburg, 39120 Germany.
authors: Thilo
authors: T
authors: Kähne
authors: Special Lab Molecular Biological Techniques, Leibniz Institute for Neurobiology, Magdeburg, 39118 Germany.
authors: Horst
authors: H
authors: Schicknick
authors: Department Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, Magdeburg, 39118 Germany.
authors: Rainer
authors: R
authors: Pielot
authors: Institute of Experimental Internal Medicine, Medical School, Otto von Guericke University, Magdeburg, 39120 Germany.
authors: Michael
authors: M
authors: Naumann
authors: Research Group Neuralomics, Leibniz Institute for Neurobiology, Magdeburg, 39118 Germany ; Institute for Pharmacology and Toxicology, Medical Faculty, Otto-von-Guericke-University Magdeburg, Magdeburg, 39120 Germany ; Center for Behavioral Brain Sciences, Magdeburg, 39106 Germany.
authors: Daniela C
authors: DC
authors: Dieterich
authors: Department Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, Magdeburg, 39118 Germany ; Center for Behavioral Brain Sciences, Magdeburg, 39106 Germany ; Molecular Neurobiology, Medical Faculty, Otto-von-Guericke-University Magdeburg, Magdeburg, 39120 Germany.
authors: Eckart D
authors: ED
authors: Gundelfinger
authors: Special Lab Molecular Biological Techniques, Leibniz Institute for Neurobiology, Magdeburg, 39118 Germany ; Center for Behavioral Brain Sciences, Magdeburg, 39106 Germany.
authors: Karl-Heinz
authors: KH
authors: Smalla
authors: Special Lab Molecular Biological Techniques, Leibniz Institute for Neurobiology, Magdeburg, 39118 Germany ; Center for Behavioral Brain Sciences, Magdeburg, 39106 Germany.
authors: Wolfgang
authors: W
authors: Tischmeyer
keywords: 2D gel; Auditory discrimination learning; Brain; Cortex; Dopamine agonist; Hippocampus; Memory consolidation; Proteome; Striatum; α-synuclein