Hippocampal serotonin depletion is related to the presence of generalized tonic–clonic seizures, but not to psychiatric disorders in patients with temporal lobe epilepsy

• The concentration of 5HT was evaluated in a large series of hippocampal tissue of homogeneous sample of patients.
• All patients included had refractory temporal lobe epilepsy caused by hippocampal sclerosis.
• Lower concentrations of 5HT were correlated with a history of GTC seizures.
• The presence of psychiatric disorders was not correlated with 5 HT levels.

SummaryObjectivePrevious 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 clinical 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 hippocampal 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.MethodsWe 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).ResultsLower [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.SignificanceOur findings demonstrated that serotonin depletion in the hippocampus play an important role in some aspects of the severity of epilepsy (i.e., the presence of GTC seizures) in a homogeneous sample of patients with refractory temporal lobe epilepsy determined by hippocampal sclerosis, but not with the presence of psychiatric disorders.