Epilepsy Research (2015) 111, 18—25 j ourna l h om epa ge: www.elsevier.com/locate/epilepsyres Hippocampal serotonin depletion is related to the presence of generalized tonic—clonic seizures, but not to psychiatric disorders in patients with temporal lobe epilepsy Natascha C. da Fonseca a,* , Helena P.G. Joaquim b , Leda L. Talib b , Silvia de Vincentiis a,c , Wagner F. Gattaz b , Kette D. Valente a,c,d a Laboratory of Clinical Neurophysiology, Institute of Psychiatry, University of São Paulo School of Medicine Hospital das Clínicas, São Paulo, SP, Brazil b Laboratory of Neuroscience, Institute of Psychiatry, University of São Paulo School of Medicine Hospital das Clínicas, São Paulo, SP, Brazil c Laboratory of Neuroimaging, Institute of Psychiatry, University of São Paulo School of Medicine Hospital das Clínicas, São Paulo, SP, Brazil d Center for the Support of Research in Applied Neuroscience, University of São Paulo, São Paulo, SP, Brazil Received 6 August 2014; received in revised form 18 December 2014; accepted 30 December 2014 Available online 17 January 2015 Summary Objective: Previous studies suggest that concentration of serotonin ([5-HT]) plays a pathogenic role in various types of epilepsy inhibiting seizures. However, most have not considered the clin- ical variables of epilepsy, and all of these studies included small and heterogeneous samples with refractory epilepsy, regardless of etiology. In this work, we measured [5-HT]s in hippocam- pal tissues from a large series of patients with refractory temporal lobe epilepsy caused by hippocampal sclerosis who underwent epilepsy surgery and evaluated the relationship between [5HT] and epilepsy-related clinical variables and psychiatric disorders. Methods: We included 44 patients with refractory unilateral TLE-HS who underwent surgical treatment for epilepsy. Hippocampal samples were collected, and serotonin concentrations were measured with high-pressure liquid chromatography (HPLC). Results: Lower [5-HT]s were correlated with a history of GTC seizures (Student’s t-test: p 0.041). There were no differences in [5-HT]s according to the other clinical variables and the presence of psychiatric disorders. ∗ Corresponding author. Tel.: +55 4291285656. E-mail address: nataschafonseca@gmail.com (N.C. da Fonseca). http://dx.doi.org/10.1016/j.eplepsyres.2014.12.013 0920-1211/© 2015 Elsevier B.V. All rights reserved.