title: Chronic valproic acid administration impairs contextual memory and dysregulates hippocampal GSK-3β in rats.
abstract: Valproic acid (VPA), a long-standing anti-epileptic and anti-manic drug, exerts multiple actions in the nervous system through various molecular mechanisms. Neuroprotective properties have been attributed to VPA in different models of neurodegeneration, but contrasting results on its improvement of learning and memory have been reported in non-pathologic conditions. In the present study, we have tested on a hippocampal-dependent learning test, the contextual fear conditioning, the effect of chronic VPA administration through alimentary supplementation that allows relatively steady concentrations to be reached by a drug otherwise very rapidly eliminated in rodents. Contextual fear memory was significantly impaired in rats chronically treated with VPA for 4 weeks. To understand the cellular and molecular correlates of this amnesic effect with particular regard to hippocampus, we addressed three putatively memory-related targets of VPA action in this brain area, obtaining the following main results: i) chronic VPA promoted an increase of post-translational modifications of histone H3 (acetylation and phosphorylation) known to favor gene transcription; ii) adult neurogenesis in the dentate gyrus, which has been controversially reported to be affected by VPA, was unchanged; and iii) GSK-3β, a kinase playing a key role in hippocampal plasticity, as well as in learning and memory, was dysregulated by VPA treatment. These results point at GSK-3β dysregulation in the hippocampus as an important parameter in the amnesic effect of VPA. The VPA amnesic effect in the animal model here reported is also supported by some observations in patients and, therefore, it should be taken into account and monitored in VPA-based therapies.
authors.affiliation: Department of Pharmacy and BioTechnology, University of Bologna, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Sintoni
authors.forename: Ewelina
authors.initials: E
authors.lastname: Kurtys
authors.forename: Marilyn
authors.initials: M
authors.lastname: Scandaglia
authors.forename: Antonio
authors.initials: A
authors.lastname: Contestabile
authors.forename: Barbara
authors.initials: B
authors.lastname: Monti
mesh_terms: D000818:Animals; D015153:Blotting, Western; D005239:Fear; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006624:Hippocampus / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008568:Memory / Q000187:drug effects*; D055495:Neurogenesis / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D014635:Valproic Acid / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D014635:Valproic Acid; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3