Periventricular cerebral impedance after intraventricular injection of calcium

Injection of small volumes of calcium solution into the lateral ventricle of the cat wa followed by large electrical-impedance changes in gray matter bounding the ventricle, including the caudate nucleus and hippocampus. These changes lasted more than 24 hours and were accompanied by epileptiform electroencephalographic activity. Biweekly injections led to status epilepticus. Injections of similar amounts of magnesium ions were without comparable effects. Possible interactions between calcium ions and intercellular macromolecular material are discussed as a basis for certain impedance shifts in cerebral tissue.