Immediate and long-term alterations in maximal electroshock seizure responsiveness in rats neonatally exposed to...

Neonatal rats were injected (sc) with 0, 0.25, 0.5, 1.0, 2.5, or 5.0 mg/kg triethyltin bromide (TET) in a 2% ethanol vehicle on Days 0, 5, 10, 15, and 20 postnatally. TET-exposed neonates exhibited a dose-dependent delay in the ontogenetic appearance of both the clonic and tonic maximal electroshock seizure (MES) responses which were apparent up to Day 45, as evaluated by the MES grade distributions and the durations of the individual phases of the MES. In marked contrast, adult rats (exposed to TET only as neonates) exhibited long-term increases in MES severity, as evaluated by the durations of the individual phases of the MES. At 75 days of age, a time when the 1.0 mg/kg developmentally TET-treated group exhibited an increased seizure severity, a single challenge dose of 1.0 mg/kg TET (ip) produced a proportional decrease in MES severity in both developmentally treated and control rats. No changes in preweaning or postweaning body weight were observed in the animals in the 0.25, 0.5, 1.0, or 2.5 mg/kg groups. A 30% decrease in weaning weight and an approximate 15% decrease in postweaning weight were observed in the 5.0 mg/kg group. These seizure results demonstrate that developmental exposure to TET produces immediate and long-term alterations in central nervous system functioning, which are of an opposite character. Interesting, we have previously shown that developmental lead exposure produces a similar developmental/adult dichotomy of effects with regard to the MES severity; however, the two patterns are reversed (D. A. Fox, S. R. Overmann, and D. E. Woolley (1979).