Title: the Psychostimulant Modafinil Facilitates Water Maze Performance and Augments Synaptic Potentiation in Dentate Gyrus the Psychostimulant Modafinil Facilitates Water Maze Performance and Augments Synaptic Potentiation in Dentate Gyrus

psychostimulant modafinil facilitates water maze performance and augments synaptic potentiation in This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 1 These authors contributed equally to the study Running title: Modafinil enhances hippocampal learning and synaptic plasticity. Abstract Modafinil is a psychostimulant drug used widely for the treatment of narcolepsy, which also has additional positive effects on cognition. Here, we investigate the effects of modafinil on behavioral performance and synaptic plasticity in rats. Improved acquisition of water maze task was observed for animals that underwent chronic treatment with modafinil. We found that the distance travelled and escape latency were reduced after the first day in chronically-treated rats, compared to controls. Importantly, the swim velocity was similar for both groups, excluding pharmacological effects on motor skills. We also found that modafinil increases synaptic plasticity in the dentate gyrus of urethane-anaesthetized rats; modafinil induced a robust augmentation of the population spike, evident after application of 2 bursts of 200Hz, high-frequency stimulation. Furthermore, the modafinil-dependent enhancement of postsynaptic potentials correlated selectively with theta rhythm augmentation. We propose that modafinil may facilitate spatial orientation via increased theta-related hippocampal plasticity.