Morphine self-administration and EEG power spectra in the rat

Abstract

Power spectral analyses were used to study changes in cortical EEG during morphine self-administration in freely-moving dependent rats prepared with chronic cortical and muscle electrodes and with permanent indwelling IV cannulae. As time progressed from a morphine self-injection toward another injection, a significant spectral shift of the EEG to lower frequencies occurred during successive REM sleep episodes. Each morphine self-injection reinstated the predominance of higher frequencies in the EEG spectra. These EEG changes which preceded lever pressing may reflect changes in morphine plasma levels and in the state of the CNS that precede drug-seeking behavior.