Influence of a low dose of silver nanoparticles on cerebral myelin and behavior of adult rats

Nanoscale particles have large surface to volume ratio that significantly enhances their chemical and biological reactivity. Although general toxicity of nano silver (nanoAg) has been intensively studied in both in vitro and in vivo models, its neurotoxic effects are poorly known, especially those of low-dose exposure. In the present study we assess whether oral administration of nanoAg influences behavior of exposed rats and induces changes in cerebral myelin. We examine the effect of prolonged exposure of adult rats to small (10 nm) citrate-stabilized nanoAg particles at a low dose of 0.2 mg/kg b.w. (as opposed to the ionic silver) in a comprehensive behavioral analysis. Myelin ultrastructure and the expression of myelin-specific proteins are also investigated. The present study reveals slight differences with respect to behavioral effects of Ag+- but not nanoAg-treated rats. A weak depressive effect and hyperalgesia were observed after Ag+ exposure whereas administration of nanoAg was found to specifically increase body weight and body temperature of animals. Both nanoAg and Ag+ induce morphological disturbances in myelin sheaths and alter the expression of myelin-specific proteins CNP, MAG and MOG. These results suggest that the CNS may be a target of low-level toxicity of nanoAg.