Brain Extracellular pH Changes During Alterations in Substrate Supply

Abstract

The alterations in brain extracellular ionic composition during spreading depression (SD), anoxia, ischemia, and profound hypoglycemia have been clarified to a large extent through the use of double-barrelled liquid ion exchanger (LIX) microelectrodes. Recently, a neutral carrier H+- LIX has become available, permitting examination of the extracellular pH (pHe) changes associated with these events [1, 9]. Construction of pH microelectrodes with this exchanger provide the specific advantages of double-barreled LIX microelectrodes, i. e., small tip diameters (2–4 pm as used in these studies), an immediately adjacent reference electrode, and rapid transient response (90% response in ≤ 2 s). We examined the pHe changes during SD and also the pHe changes during events which are initiated by altered substrate supplies, i. e., cerebral ischemia, terminal anoxia, and profound hypoglycemia (the hypoglycemia experiments are work in progress by W. A. C. Mutch in association with A. R. Gardner-Medwin).