Abstracts

Rationale: In patients with mesial temporal lobe epilepsy (MTLE), Positron Emission Tomography (PET) reveals reduced D2/D3-receptor binding at the pole and lateral aspects of the epileptogenic temporal lobe. While these findings support that the dopaminergic system is modified in the epileptic brain, information concerning binding to D1 receptors and dopamine transporter (DT) is lacking. The main purpose of the present study was to evaluate the binding to D1, D2 receptors and DT in the temporal neocortex of patients with pharmacoresistant temporal lobe epilepsy. Methods: We used in vitro autoradiography which provides a measure of binding in specific brain areas. Temporal cortices were surgically obtained from epileptic patients with MTLE (n=11) or temporal lobe epilepsy associated with tumors (n=14). Correlations between binding values, clinical data and memory scores were carried out. Autopsy material acquired from subjects without epilepsy (n=6) was used as control. Results: When compared with control tissue, the neocortex from patients with MTLE demonstrated enhanced D1 receptor binding in all cortical layers (I-II, 123%; III-IV, 123%; V-VI, 133%), and no significant changes in binding to D2 receptors and DT. No differences were detected between data obtained from controls and patients with temporal lobe epilepsy secondary to tumors. Significant correlations were found between receptor binding from all epileptic patients and epilepsy duration (D2, r=0.5797) and duration of the pharmacological treatment (D1, r=0.5119; D2, r=0.5963). Different memory scores correlated negatively with D1 receptor binding. Conclusions: The present study supports an impaired dopaminergic transmission in the neocortex surrounding the epileptic focus of patients with pharmacoresistant temporal lobe epilepsy. This situation may be involved in the mechanisms of propagation of seizure activity to other brain areas as well as in the neuropsychological deficits observed in epileptic patients.