EFFECTS OF SYSTEMIC CLONIDINE ON AUDITORY EVENT-RELATED POTENTIALS INSQUIRREL-MONKEYS

Event-related potential (ERP), electroencephalographic (EEG), and beha vioral data were collected from squirrel monkeys (Saimiri sciureus) in a 90-10 auditory oddball paradigm. Background or target tones were pr esented once every 2 s, and responses to the targets were rewarded. ER Ps were recorded from epidural electrodes following systemic administr ation of clonidine (0.1 mg/kg) or a saline placebo. EEG power spectra and behavioral performance were assessed simultaneously as indices of behavioral state. Clonidine significantly decreased the area and incre ased the latency of a P300-like potential. The amplitudes and areas of the earlier P1, N1, and P2 components and a later slow wave-like pote ntial were not reduced, nor were their latencies altered. Clonidine pr oduced increased EEG power in the alpha range (7.5-12 Hz) and decrease d power in the upper beta range (20-40 Hz) but did not affect performa nce in the oddball task. Because two major effects of clonidine are to substantially reduce activity in the noradrenergic nucleus locus coer uleus (LC) and to reduce norepinephrine (NE) release from axons, the p resent results support the hypothesis that the LC and its efferent pro jection system are important in modulating the activity of P300-like p otentials.