The effects of an alpha-2 adrenergic agonist, guanfacine, on rCBF in human cortex in normal controls and subjects with focal epilepsy

Alpha-2 noradrenergic agonists may have wide applicability in the treatment of pre-frontal cortex deficits in primates and behavioral dysfunction in man. We have undertaken this study to determine the effect on an alpha-2 agonist, guanfacine, on regional cerebral blood flow (rCBF) in humans. Three subject groups were evaluated: normal controls, subjects with frontal lobe epilepsy (FLE), and subjects with temporal lobe epilepsy (TLE). All underwent a number of PET scans using O-15-water, with half before and half after a single dose of guanfacine in controls and subjects with TLE. Smaller areas of decrease in rCBF were seen in the posterior temporal-occipital cortex. In the FLE group a decrease in rCBF was seen in the dorsal prefrontal cortex on the epileptogenic side with only small increases seen in the mid- to anterior temporal perisylvian areas. The ability of alpha-2 agonists to enhance performance of tasks reliant on prefrontal cortex, without improving tasks believed to rely on intact temporal-hippocampal function, may be explained by these results. Epileptogenic zones appear to create both direct and indirect changes in patterns of drug response. Further studies on the cognitive properties of these agents in humans should be encouraged. (C) 2000 American College of Neuropsychopharmacology. Published by Elsevier Science Inc. All rights reserved.