Chronic Dietary Administration of Valproic Acid Protects Neurons of the Rat Nucleus Basalis Magnocellularis from Ibotenic Acid Neurotoxicity

Abstract

Valproic acid (VPA) has been used for many years as a drug of choice for epilepsy and mood disorders. Recently, evidence has been proposed for a wide spectrum of actions of this drug, including antitumoral and neuroprotective properties. Valproic acid-mediated neuroprotection in vivo has been so far demonstrated in a limited number of experimental models. In this study, we have tested the neuroprotective potential of chronic (4 + 1 weeks) dietary administration of VPA on degeneration of cholinergic and GABAergic neurons of the rat nucleus basalis magnocellularis (NBM), injected with the excitotoxin, ibotenic acid (IBO), an animal models that is relevant for Alzheimer's disease-like neurodegeneration. We show that VPA treatment significantly protects both cholinergic and GABAergic neurons present in the injected area from the excitotoxic insult. A significant level of neuroprotection, in particular, is exerted towards the cholinergic neurons of the NBM projecting to the cortex, as demonstrated by the substantially higher levels of cholinergic markers maintained in the target cortical area of VPA-treated rats after IBO injection in the NBM. We further show that chronic VPA administration results in increased acetylation of histone H3 in brain, consistent with the histone deacetylase inhibitory action of VPA and putatively linked to a neuroprotective action of the drug mediated at the epigenetic level.