Chronic cerebellar stimulation in the monkey. Electron microscopic and biochemical observations.

The effects of chronic electrical stimulation to the surface of cerebellum in the Macaca mulatta monkey were studied with morphologic and biochemical techniques. There was considerable damage and loss of Purkinje cells in all specimens examined, including an area without electrodes, but the greatest changes appeared in tissue beneath the cathode and anode. Despite the damage, normal appearing synapses persisted in the molecular layer of all specimens. Fibrous glial processes were more numerous beneath the cathode. There were abnormalities in gamma-amino butyric acid (GABA) and polyamine concentrations in virtually all specimens, consistent with the morphologic evidence of widespread tissue damage.