title: Effects of low dose methylmercury administration during the postnatal brain growth spurt in rats.
abstract: Male Sprague-Dawley rats from eight litters were orally administered 0.75 mg/kg/day methylmercury (MeHg) chloride from postnatal day (PD) 14 to PD 23. One male pup per litter from eight different litters per treatment group was used. Each pup was used only for a single behavioral test and tested once. The MeHg dose level resulted in Hg brain concentrations of 0.82+/-0.05 microg/g tissue (n=4). Locomotor behavior was studied in the Opto-Varimex apparatus by testing rats (n=8) weekly from PD 24 to PD 45. Performance of rats (n=8) on learning paradigm was analysed on PD 90. MeHg treatment induced a significant reduction in the number of rearings without altering the distance travelled, the resting time and the time spent in the central part of the arena. Results of conditioned avoidance task showed that, unlike control rats, MeHg-treated animals did not show improvement over blocks and never reached a level of performance that would indicate significant learning had taken place. The present results show that low level exposure to MeHg during late brain growth spurt induces subtle and persistent motor and learning deficits, further underlining the serious potential hazard for the exposed children.
authors.affiliation: Department of Pharmacology and Human Physiology, Medical School, University of Bari, Policlinico, Piazza G. Cesare 11, 70124 Bari, Italy.
authors.forename: Addolorata
authors.initials: A
authors.lastname: Coluccia
authors.forename: Pietro
authors.initials: P
authors.lastname: Borracci
authors.forename: Arcangela
authors.initials: A
authors.lastname: Giustino
authors.forename: Mineshi
authors.initials: M
authors.lastname: Sakamoto
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Carratù
mesh_terms: D000284:Administration, Oral; D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001362:Avoidance Learning / Q000187:drug effects; D001522:Behavior, Animal / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D001921:Brain / Q000187:drug effects* / Q000254:growth & development / Q000473:pathology; D005260:Female; D008297:Male; D008767:Methylmercury Compounds / Q000378:metabolism / Q000633:toxicity*; D009043:Motor Activity / Q000187:drug effects; D009929:Organ Size / Q000187:drug effects; D011247:Pregnancy; D011597:Psychomotor Performance / Q000187:drug effects; D051381:Rats; D011930:Reaction Time / Q000187:drug effects
chemical_list: D008767:Methylmercury Compounds