Effects of melatonin and epiphysectomy on electrical activity of the rat brain at different times of the day]

The pineal hormone melatonin in a dose-effect manner (0.1, 1 and 10 mg/kg) reorganized EEG spectral characteristics of rat sensorimotor cortex and hippocampus, decreasing medium (6-12 Hz) and high frequency (12-22 Hz) waves only in the evening. On the contrary, pinealectomy increased high-frequency waves only during morning hours. It is suggested that the observed changes may accompany anxiolytic and hypnotic effects of melatonin.