Different Postnatal Development of Convulsions and Lethality Induced by Strychnine in Rats

Abstract

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.

Centrally administered corticotropin-releasing hormone and peripheral injections of strychnine hydrochloride potentiate the acoustic startle response in preweanling rats.

“…It should be noted that the dose of strychnine used in the present study (0.25 mg/kg) is much lower than the 1–2-mg/kg dose used to potentiate startle in adult rats in previous studies and, indeed, is relatively ineffective at enhancing startle in adult rats (Kehne et al, 1981). We found that doses higher than 0.25 mg/kg were lethal in 16-day-old rats, as was also found by Kubova and Mares (1995), who reported that the convulsive and lethal effects of strychnine peak in rats 18–25 days of age.…”

A Brief Guide to Studying Fear in Developing Rodents: Important Considerations and Common Pitfalls

“…That is, whereas a dose of 1‐2 mg/kg of strychnine is required to induce potentiation of startle in adults, a dose of only 0.25 mg/kg was required in infants (i.e., one quarter of the adult dosage). In fact, strychnine doses above 0.25 mg/kg have been reported to have convulsive or lethal effects during infancy (Kubova & Mares, ). In contrast, the intracerebroventricular dose of CRH required to induce potentiated startle was four times higher in infants than in adults (1.0 µg for adults, 4.0 µg for infants).…”