Neurotoxic action of inorganic mercury injected in the intraventricular space of mouse cerebrum

Abstract

To examine the neurotoxic action of inorganic mercury, HgCl₂ was injected in the intraventricular space of a mouse brain as a mimic for an Hg(0) vapor-exposed model, and the Hg distribution in the brain and behavioral changes were compared with those of Hg(0)-exposed mice. Although no difference was found in the Hg accumulation and its localization in the brains of two model mice at 3 weeks after Hg treatment, the turnover rate of the brain Hg in the Hg(0)-exposed mice was higher than in the Hg(II)-injected mouse. Despite a similar Hg level in the cerebrum at 3 weeks, behavioral alterations, hyper-activity in an open field test and shortening of latency in a passive avoidance test, were significant only in Hg(II)-injected mice. Considered together with the differences in the turnover rate and the effectiveness of neurotoxic action of the brain Hg, the microenvironment of Hg, such as biomolecules with which Hg interacts, might not be the same in both model mice. Inorganic Hg-induced neurotoxic action could be observed with a minimum dose of Hg(II) without any effects on the other organs, such as the kidney and lung. The present study demonstrated that intraventricular injection of HgCl₂ might be a convenient method to study the neurotoxic action of inorganic Hg, and, at least partly, to represent an animal model of Hg(0) vapor exposure.