Tellurium-induced cognitive deficits in rats are related to neuropathological changes in the central nervous system.

The effects of sodium tellurite 0.1 and 0.4 mg/kg were assessed in the Morris water maze. Two days after treatment rats were tested for acquisition (posttreatment days 3-6) and on seventh day on a spatial retention task. Tellurium treatment was found to cause significant impairment in retention of the spatial learning task. Locomotor disturbances were not the cause of the observed effects. Ultrastructural observations showed neuropathological changes in hippocampus subfields and prefrontal cortex with swelling of synapses, astrocytes and astrocytic processes around the vessels in the cerebral cortex neuropil. Severity of the observed changes in glial-neuronal unit was in correlation with the extent of learning impairment. A direct injury of Schwann cells with the secondary myoclasis was noted in the sciatic nerve. Our results indicate that acute treatment with sodium tellurite results in impairment of learning and spatial memory.