[The effect of epiphysectomy on the power of hexenal to alter the EEG spectral characteristics over a transitional 24-hour period].

In pinealectomized rats, in the morning (06.00-09-00) the ability of hexobarbital sodium, 60 mg/kg i. p., to increase cortical and hippocampal EEG spectral characteristics was significantly enhanced. On the contrary, in the evening (18.00-21.00) it was decreased. These changes may be associated with pineal gland involvement in circadian rhythm.