Toxicity to heavy metals and relationship to seizure thresholds

The present study was designed to provide information on the effects of lead, mercury, and nickel on lethality, body weight, and brain excitability in the adult rat. Both short- (2 days) and long-term (6 wk) drug administrations were carried out in adult male albino rats (Sprague-Dawley, Zivic-Miller). Based on the mg/kg/day of drug given over a 2-day period, the LD50 values were as follows: Pb(Ac)2, 215; Pb(NO3)2, 65.9; MMC, 11.9; HgCl2, 4.5; Ni(Ac)2, 35-40; NiSO4, 35-40. High doses of each of the metals administered acutely caused a drop in body weight but had an inconsistent effect on flurothyl-induced seizure thresholds. Pb(Ac)2, 200 mg/kg/day for 2 days, produced a statistically significant anticonvulsant effect, while 50 mg/kg Pb(NO3)2 resulted in a fall in threshold. Both NiSO4 and Ni(Ac)2, 30 mg/kg, increased seizure threshold. Neither the organic nor inorganic mercury altered thresholds. Long-term administration of Pb(Ac)2, MMC, or HgCl2 resulted in marked effects on body weight but no significant change in brain excitability.