Effects of a chronic exposure to cadmium on the glial architecture in the lizard brain: an immunocytochemical study.

The astroglial cells are positioned to be the first cells of the brain parenchyma to encounter metals crossing the blood-brain barrier(1). For this they have also a neuroprotective action for the encephalon from cytotoxic action of heavy metals like cadmium. Numerous studies provide evidence that cadmium induces neuronal toxicity and damage to the brain. In this work we have studied the effects of this metal on the glial architecture in the brain of the lizard Podarcis sicula treated for four months with CdCl2 at dose of 1mg/kg-BW in the drinking water. The study was performed by the immunodetection of GFAP by ABC technique on serial sections of brains at 10, 30, 60, 90 and 120 days of treatment. After 10 days the encephalon of treated lizards showed a decrement of GFAP-immunoreactivity only in grey matter of the cerebellum. After 30 days a reduction of expression and distribution of GFAP-immunopositive structures was observed in the telencephalon, mesencephalon and medulla. After 60 days only few GFAP-immunopositive structures were revealed and the absence of the radial glia was observed. Indeed at 90 days the radial glia was observed again in the telencephalon and at 120 days there was a return of occurrence of GFAP structures similar to that of control lizards. This study confirms the cytotoxic effect of cadmium on the lizard glial cells like we have just observed in lizard exposed to an acute treatment(2). However a chronic exposure to cadmium involved a maximum reduction of the glial cells at 60 days.