IMAGING OF DELTA-OPIOID AND MU-OPIOID RECEPTORS IN TEMPORAL-LOBE EPILEPSY BY POSITRON EMISSION TOMOGRAPHY

The involvement of opioid neurotransmitter systems in seizure mechanis ms is well documented. In previous positron emission tomography (PET) studies in patients with unilateral temporal lobe epilepsy, we have fo und evidence for differential regulation of the opioid-receptor subtyp es. The present study extends our previous observations to delta-opioi d receptors by using the delta-receptor-selective antagonist [C-11]met hylnaltrindole ([C-11]MeNTI). Paired measurements of delta- and mu-opi oid receptor binding and metabolic activity were performed with PET us ing [C-11]MeNTI and [C-11]carfentanil ([C-11]CFN) and [F-18]fluorodeox yglucose ([F-18]FDG), respectively. Binding of [C-11]MeNTI and [C-11]C FN increased and [F-18]FDG uptake decreased in the temporal cortex (TC ) ipsilateral to the focus. Decreases in [F-18]FDG uptake were more wi despread regionally than were increases in opioid receptors. Increases in the delta- and mu-receptor binding showed different regional patte rns. Increases in mu-receptor binding were confined to the middle aspe ct of the inferior TC, whereas binding of delta receptors increased in the mid-inferior TC and anterior aspect of the middle and superior TC . The increase in delta receptors suggests their anticonvulsant action , as previously shown for the delta-receptor subtype, whereas the diff erent regional pattern of receptor alterations suggest the distinct ro les of different opioid-receptor subtypes in seizure phenomena.