title: Ghrelin increases memory consolidation through hippocampal mechanisms dependent on glutamate release and NR2B-subunits of the NMDA receptor.
abstract: BACKGROUND
  Ghrelin (Ghr) is a peptide that participates in the modulation of several biological processes. Ghr administration into the hippocampus improves learning and memory in different memory tests. However, the possible mechanisms underlying this effect on memory have not yet been clarified.
  
  
  OBJECTIVE
  The purpose of the present work is to add new insights about the mechanisms by which Ghr modulates long-term memory consolidation in the hippocampus. We examined Ghr effects upon processes related to increased synaptic efficacy as presynaptic glutamate release and changes in the expression of the NR2B-subunits containing n-methyl-d-aspartate receptors (NMDAR), which are critical for LTP induction. We also attempted to determine the temporal window in which Ghr administration induces memory facilitation and if the described effects depend on GHS-R1a stimulation.
  
  
  RESULTS
  The present research demonstrated that Ghr increased glutamate release from hippocampal synaptosomes; intra-hippocampal Ghr administration increased NR2B-subunits expression in CA1 and DG subareas and also reversed the deleterious effects of the NR2B-subunit-specific antagonist, Ro 25-6981, upon memory consolidation and LTP generation in the hippocampus. These effects are likely to be the consequence of GHS-R1a activation.
  
  
  CONCLUSIONS
  According to the results above mentioned and previous findings, we can hypothesize some of the mechanisms by which Ghr modulates memory consolidation. At presynaptic level, Ghr stimulates glutamate release, probably by enhancing [Ca(2+)]i. At postsynaptic level, the glutamate released activates NMDAR while Ghr also mediates effects directly activating its specific receptors and increases NR2B-subunit expression.
authors.affiliation: Dpto. de Farmacología, Facultad de Ciencias Químicas, Instituto de Farmacología Experimental de Córdoba, IFEC-CONICET, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende s/n, Ciudad Universitaria, 5000, Córdoba, Argentina, mghersi@fcq.unc.edu.ar.
authors.forename: Marisa S
authors.initials: MS
authors.lastname: Ghersi
authors.forename: L A
authors.initials: LA
authors.lastname: Gabach
authors.forename: F
authors.initials: F
authors.lastname: Buteler
authors.forename: A A
authors.initials: AA
authors.lastname: Vilcaes
authors.forename: H B
authors.initials: HB
authors.lastname: Schiöth
authors.forename: M F
authors.initials: MF
authors.lastname: Perez
authors.forename: S R
authors.initials: SR
authors.lastname: de Barioglio
mesh_terms: D000818:Animals; D054439:Ghrelin / Q000494:pharmacology*; D018698:Glutamic Acid / Q000378:metabolism*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D057567:Memory, Long-Term / Q000187:drug effects / Q000502:physiology*; D021122:Protein Subunits / Q000819:agonists / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000096:biosynthesis*
chemical_list: D054439:Ghrelin; C121001:NR2B NMDA receptor; D021122:Protein Subunits; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid