Different postnatal development of convulsions and lethality induced by strychnine in rats.

The convulsant action of strychnine was studied in 310 male albino rats, aged 3 to 25 days. Doses of 0.25-4 mg/kg were administered intraperitoneally and the animals were observed for 30 min. Generalized tonic-clonic seizures involving also tonic hindlimb extension occurred in all age groups. The convulsant effects of strychnine increased from day 3 to day 18, and decreased again from day 25, as indicated by the incidence and latencies of seizures. Lethal effects did not occur before day 12. Hyperactivity was seen as the first sign of strychnine action in rats during the first week of life, automatisms predominating in 18-day-old animals. Electroencephalographic study in 30 rat pups with implanted electrodes demonstrated an extremely poor electro-clinical correlation.