ELECTROPHYSIOLOGICAL AND NEUROPSYCHOLOGICAL EFFECTS OF A CENTRAL ALPHA(2)-ANTAGONIST ATIPAMEZOLE IN HEALTHY-VOLUNTEERS

We studied the electrophysiological and neuropsychological effects of acute modulation of central noradrenergic (NA) transmission using a sp ecific alpha2-antagonist atipamezole (ATI) in sic healthy volunteers. ATI had effects on resting EEG, auditory event-related potentials and neuropsychological tests. Quantitative EEG revealed increased total po wer in frontal, parietal and temporo-occipital areas without significa nt changes in the mean or peak frequencies. Event-related potentials s howed no effects on the active attention-related processing negativity or the passive mismatch negativity, but frontally recorded mean ampli tude of target-P300 was decreased. Neuropsychological tests after ATI revealed improvement in Digit Span, more errors in Word Recognition ta sk, and no effects on Moss spatial recognition task. In healthy subjec ts with intact NA systems and without any attention deficit, ATI produ ced evident NA overactivity. ATI decreased the spontaneous thalamocort ical oscillation of EEG and improved focused attention (Digit Span). I t impaired, however, more divided attention (decreased mean P300 ampli tude, increased errors in Word Recognition).