Behavioral effects of Rho GTPase modulation in a model of Alzheimer's disease

Small GTPases of the Rho family, including Rho, Rac and CDC42 subfamilies, play key role in neural connectivity and cognition. The pharmacological modulation of these regulatory proteins is associated with enhancement of learning and memory. We sought to determine whether the modulation of cerebral Rho GTPases may correct behavioral disturbances in a mouse model of Alzheimer's disease (AD). TgCRND8 mice show early-onset Abeta amyloid deposits associated with deficits in several cognitive tasks. We report that four-month old TgCRND8 mice display (a) increased locomotor activity in an open field, (b) mild deficits in the learning of a fixed platform position in a water maze task. More markedly, after displacement of the escape platform, TgCRND8 mice exhibit impairment in the learning of the novel position (reversal learning), as they perseverate searching in the familiar position. The administration of the Rho GTPase activator Cytotoxic Necrotizing Factor 1 (CNF1, 1.0 fmol kg(-1) intracerebroventricularly) reduces locomotor hyperactivity and corrects the deficits in reversal learning, thus re-establishing normal behavioral plasticity. We conclude that the pharmacological modulation of Rho GTPase signaling might be beneficial for the treatment of AD. Reversal learning in TgCRND8 mice may represent a convenient pre-clinical assay for the efficacy of therapeutic interventions in AD.