Effects of Nano-MnO(2) on Dopaminergic Neurons and the Spatial Learning Capability of Rats

This study aimed to observe the effect of intracerebrally injected nano-MnO(2) on neurobehavior and the functions of dopaminergic neurons and astrocytes. Nano-MnO(2), 6-OHDA, and saline (control) were injected in the substantia nigra and the ventral tegmental area of Sprague-Dawley rat brains. The neurobehavior of rats was evaluated by Morris water maze test. Tyrosine hydroxylase (TH), inducible nitric oxide synthase (iNOS) and glial fibrillary acidic protein (GFAP) expressions in rat brain were detected by immunohistochemistry. Results showed that the escape latencies of nano-MnO(2) treated rat increased significantly compared with control. The number of TH-positive cells decreased, GFAP- and iNOS-positive cells increased significantly in the lesion side of the rat brains compared with the contralateral area in nano-MnO(2) group. The same tendencies were observed in nano-MnO(2)-injected rat brains compared with control. However, in the the positive control, 6-OHDA group, escape latencies increased, TH-positive cell number decreased significantly compared with nano-MnO(2) group. The alteration of spatial learning abilities of rats induced by nano-MnO(2) may be associated with dopaminergic neuronal dysfunction and astrocyte activation.