Effects of Continuous Low-Dose Exposure to Organic and Inorganic Mercury During Development on Epileptogenicity in Rats

• Published in: Neurotoxicology (Park Forest South) 2002-07, Vol.23 (2), p.197-206
• Main Authors: Szász, András, Barna, Barbara, Gajda, Zita, Galbács, Gábor, Kirsch-Volders, Micheline, Szente, Magdolna
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Biological and medical sciences; Cerebral Cortex - drug effects; Cerebral Cortex - growth & development; Cerebral Cortex - metabolism; Chemical and industrial products toxicology. Toxic occupational diseases; Epilepsy - chemically induced; Epilepsy - metabolism; Epileptogenicity; Female; Male; Medical sciences; Mercurials; Mercuric Chloride - administration & dosage; Mercuric Chloride - adverse effects; Mercuric Chloride - pharmacokinetics; Mercury Compounds - administration & dosage; Mercury Compounds - adverse effects; Mercury Compounds - pharmacokinetics; Mercury Poisoning, Nervous System - metabolism; Metals and various inorganic compounds; Neurotoxicity; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Rats, Wistar; Toxicology
• ISSN: 0161-813X; 1872-9711
• DOI: 10.1016/S0161-813X(02)00022-0

The effects of chronic, low-dose fetal and lactational organic (MeHgCl) and inorganic (HgCl 2) 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, HgCl 2 facilitated the duration of seizure discharges in younger animals. HgCl 2 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.