Effects of acute delta 9-THC administration on EEG and EEG power spectra in the rat.

This study was designed to determine the acute effects of delta 9-THC on the cortical EEG with the spectral analysis technique. Adult female Sprague-Dawley rats were implanted with chronic cortical and temporalis muscle electrodes. Intraperitoneally administered delta 9-THC (5 and 10 mg/kg) produced a reduction in peak-to-peak voltage of the desynchronized cortical EEG during wakefulness. Associated spectral power was reduced to about 50% of control during the first hour after injection of delta 9-THC and gradually returned toward the control value over an 8-hr period. Occurrences of delta 9-THC-induced high-voltage EEG bursts, overriding the reduced EEG tracing, were associated with an EEG spectral peak at 6 Hz. The first few slow-wave sleep (SWS) episodes appearing after delta 9-THC administration were associated with more slow-frequency waveforms and more slow-frequency spectral power than with control slow-wave sleep episodes. During control rapid eye movement (REM) sleep episodes, an EEG theta wave pattern, with an associated spectral peak at about 8 Hz, was characteristic. Conversely, the first few REM sleep episodes emerging after delta 9-THC administration contained overriding high-voltage bursts, the related power spectra of which had two peaks at about 7 and 11 Hz.