Influence of clonazepam on electrocorticographic changes induced by metrazol in rats during ontogenesis

The action of clonazepam (CZP) pretreatment on metrazol-induced ECoG phenomena was studied in Wistar albino rats. ECoG was recorded in acute experiments in male rats 7, 12, 18, 25 and 90 days old (N = 162). CZP (0.1 or 0.02 mg/kg) was injected i.p. 10 min prior to the start of repetitive administration of metrazol (PTZ, 20 mg/kg i.p. every 5 min). Latencies of the first signs of PTZ action, of the rhythmic metrazol activity, of the first ictal activity and of the generalized seizure were measured. CZP exhibited a dose-related effect against ECoG signs elicited by PTZ. A statistically significant increase in latencies was observed with the dose of 0.1 mg/kg in 18 day old and older animals. The 0.1 mg/kg dose of CZP also completely blocked generalized ictal activity in 7 day old rats. In adult animals, CZP pretreatment led to the appearance of partial seizures, a phenomenon never seen in controls. The development of CZP effects corresponds to the maturation of benzodiazepine binding sites.