title: Morphologic changes after prolonged electrical stimulation of the cat's cortex at defined charge densities.
abstract: Experiments were conducted correlating neuronal activity, changes in ionic concentrations in the cerebral extracellular compartment, and neural damage during 4-h continuous electrical stimulations of the cat's sensorimotor cortex. Here we describe histological evaluations with the light and electron microscope of cortical tissue subjected to charge-balanced, biphasic, constant-current pulses delivered through subdurally implanted electrodes. Three combinations of charge density and pulse repetition rate were used. The results indicated a positive correlation of neural damage with both charge density and total charge. With electrical stimulation of low charge density [20 microC/cm2 . ph, 50 pulses per second (pps)] a transient increase in [K+]0 was observed with no histologically demonstrable neural damage. The most intense electrical stimulation studied (100 microC/cm2 . ph, 50 pps) resulted in a tonic increase and episodic fluctuations of [K+]0 and a marked decrease in [Ca2+]0 accompanied by moderate neural damage in the form of shrunken neurons, widespread extracellular edema, and swollen axons and dendrites.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002415:Cats; D004558:Electric Stimulation; D005260:Female; D008297:Male; D009474:Neurons / Q000648:ultrastructure; D011188:Potassium / Q000378:metabolism; D013003:Somatosensory Cortex / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D011188:Potassium; D002118:Calcium