Electrocorticographic activity elicited by metrazol during ontogenesis in rats

Electrocorticographic changes induced by intraperitoneal injections of metrazol were studied in 72 male rats aged from 4 to 29 days. The initial paroxysmal signs varied according to age; 4- to 7-day-old rats: discharges of waves in the alpha and theta range; 11- to 20-day-old rats: spikes in the frontal area; rats aged 24 days and more: theta waves discharges (of about 5Hz) in the occipital area, i.e. a typical mature reaction. In 4- and 5-day-old rats, generalized seizures were manifested as slow waves only. A shift towards fast frequencies was observed during further development; a substantial part of this shift took place before the 14th day. After this age, bilateral synchrony of long-lasting seizure discharges was also present.