Changes in EEG spectral power in the prefrontal cortex of conscious rats elicited by drugs interacting with dopaminergic and noradrenergic transmission

1 The electroencephalographic (EEG) effects of drugs interacting with dopam inergic and noradrenergic systems were studied in conscious rats. Power spe ctra (0-30 Hz) were recorded from electrodes implanted bilaterally in the p refrontal cortex. Drug effects on EEG power were calculated as the spectral power following drug administration divided by the spectral power after ve hicle administration. 2 Dopaminergic agonists at low doses, (apomorphine 0.01 mg kg(-1) s.c., qui npirole 0.01 mg kg(-1) i.p.) and dopaminergic antagonists (haloperidol 1 mg kg(-1) i.p., raclopride 2.5 mg kg(-1) s.c.), which decrease dopaminergic t ransmission, induced an increase of EEG power. Conversely, dopaminergic ago nists at higher doses (apomorphine 0.5 mg kg(-1) s.c., quinpirole 0.5 mg kg (-1) i.p.) which increase activation of postsynaptic D-2 and D-3 receptors, induced a decrease of EEG power. 3 The alpha(1)-adrenoceptor antagonists (phenoxybenzamine 0.64 mg kg(-1) s. c., prazosin 0.32 mg kg(-1) s.c.) and the alpha(2)-adrenoceptor agonists (U K 14303 0.05 mg kg(-1) s.c., clonidine 0.025 mg kg(-1) i.p.), which decreas e noradrenergic transmission, induced an increase of EEG power. Conversely, the alpha(1)-adrenoceptor agonist, cirazoline (0.05 mg kg(-1) s.c.), the a drenergic agent modafinil (250, 350 mg kg(-1) i.p.) and alpha(2)-adrenocept or antagonists (RX 821002 0.01 mg kg(-1) s.c., yohimbine 0.5 mg kg(-1) i.p. ), which increase noradrenergic transmission, induced a decrease of EEG pow er. The effects of prazosin (0.64 mg kg(-1) s.c.) were dose-dependently ant agonized by coadministration with modafinil and cirazoline, but not by apom orphine. 4 In conclusion, pharmacological modulation of dopaminergic and noradrenerg ic transmission may result in consistent EEG changes: decreased dopaminergi c or noradrenergic activity induces an increase of EEG spectral power; whil e increased dopaminergic or noradrenergic activity decreases EEG spectral p ower.