EEG spectral analysis for the evaluation of the central effects of delta6-tetrahydrocannabinol in rabbits.

The effects of delta6-THC on the frequency spectrum of the hippocampal EEG were examined with the assistance of an electronic integrator. Six rabbits bearing chronically implanted cortical and hippocampal electrodes were dosed intravenously with delta6-THC (2.5 percent solution in polyethylene glycol 300; doses of 10, 50, 100, 250 and 1000 mug/kg) once a week. A comparison of epochs of arousal in the pre-drug control and post-drug periods demonstrated that a dose as low as 50 mug/kg produced a consistent, statistically significant diminution in "power" of the 7,8,9 Hz frequencies of the hippocampal EEG, with 8 Hz the most sensitive. Doses above 250 mug/kg produced an overall decrease in the "power" spectrum from 7 to 22 Hz. Spectral analysis of the EEG offers a method which is sufficiently sensitive to reveal a central effect of detla6-THC in rabbits at doses equivalent to the human threshold for psychic effects.