Antiepileptic Drugs Do Not Affect 5-HT1A Receptor Binding Measured by Positron Emission Topography

Objective

To study the effect of antiepileptic drugs on 5-HT_1A receptor binding in patients with temporal lobe epilepsy.

Background

5-HT_1A receptor binding is reduced in patients with temporal lobe epilepsy. Animal models show serotonergic effects of antipepileptic drugs including carbamazepine and lamotrigine.

Methods

We studied 31 patients and 10 normal controls. Patients with structural lesions, progressive neurological disorders, or taking other medications were excluded. None had a seizure for at least two days before PET. [¹⁸F]FCWAY PET was performed on a GE Advance scanner with continuous EEG monitoring. Functional images of the distribution volume (V) were generated. Anatomic regions of interest were applied to coregistered PET images, after correction for partial volume effect.

Results

Patients had significantly higher [¹⁸F]FCWAY free fraction (f₁) than controls. 5HT1A receptor binding was reduced in temporal lobe epileptic foci after partial volume correction. There were no AED effects on interictal [¹⁸F]FCWAY binding after correction for plasma free fraction. [¹⁸F]FCWAY V/f₁ reduction in epileptic foci was not affected by AEDs.

Conclusions

Antiepileptic drugs do not appear to have significant effects on 5HT1A receptor binding. Plasma free fractions should be measured when PET receptor studies are performed in patients with epilepsy.