PET study of 5-HT1A and GABA receptors in temporal lobe epilepsy.

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It has been demonstrated that serotonin inhibits epileptiform discharge by activation of 5-HT1A receptors in CA1 pyramidal neurons. Further, inhibitory role of 5-HT1A receptor for the development of amygdaloid kindling in rats has been known. In spite of possible involvements of serotoriergic activities, there have been few studies to investigate central serotonergic system in epilepsy, since suitable ligands have been limited. Using a new radioligand, [11C]WAY 100635 for 5-HT1A receptors, we investigated 5-HT1A receptors in patients with temporal lobe epilepsy and healthy controls. Parametric images of binding potential(BP) were made using the reference tissue model, and were analyzed using SPM99. We found marked decrease of 5-HT1A receptor binding in the temporal lobe ipsilateral to EEG foci. But decreased binding was also observed in the contra lateral temporal lobe. Decreased area of 5-HT1A binding was more restricted compared with that of GABA/benzodiazepine receptor which was measured using [11C]frumazenil. Deceresed 5-HT1A binding in the cortex may reflect decreased inhibitory role of 5-HT1A receptor in patients with temporal lobe epilepsy. The present findings suggest that neuroreceptor imaging techniques with [11C]WAY 100635 may give rise to new perspectives for understanding the pathophysiology of epilepsy.