Effects of continuous low-dose exposure to organic and inorganic mercury during development on epileptogenicity in rats.
The effects of chronic, low-dose fetal and lactational organic (MeHgCl) and inorganic (HgCl2) mercury intoxication on epileptogenicity were investigated and compared in rats. The main observations after both mercury treatments were a facilitated seizure expression and propagation evoked by 4-aminopyridine (4-AP). The seizure susceptibility of the offspring seemed to be in a parallel relation to the mercury concentration in the cortical tissue, which was significantly higher in treated animals as compared to the controls. While MeHgCl enhanced the number of ictal periods, HgCl2 facilitated the duration of seizure discharges in younger animals. HgCl2 intoxication seemed to be more permanent than MeHgCl. Changes in the summated ictal activity--which is an indication of epileptogenicity--were observed in the opposite directions in the two treated groups with increasing age. The amplitudes of seizure discharges were smaller in both mercury-treated groups than in the controls, which could be a consequence of a depressed proliferation of neurons or enhanced cell death in the neocortex. In summary, we observed that adult rats exposed to organic or inorganic mercury chemicals during their embryonic life, are more prone to epilepsy than control rats given only 4-AP.
Szász
András
A
Department of Comparative Physiology, University of Szeged, Hungary. szente@bio.u-szeged.hu
Barna
Barbara
B
Gajda
Zita
Z
Galbács
Gábor
G
Kirsch-Volders
Micheline
M
Szente
Magdolna
M
D000818:Animals; D000831:Animals, Newborn; D002540:Cerebral Cortex / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D004827:Epilepsy / Q000139:chemically induced* / Q000378:metabolism; D005260:Female; D008297:Male; D008627:Mercuric Chloride / Q000008:administration & dosage* / Q000009:adverse effects* / Q000493:pharmacokinetics; D017669:Mercury Compounds / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics; D020262:Mercury Poisoning, Nervous System / Q000378:metabolism; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats; D017208:Rats, Wistar
D017669:Mercury Compounds; D008627:Mercuric Chloride