Cytosolic calcium during glucose deprivation in hippocampal pyramidal cells of rats.

Glucose deprivation (GD) results in a hyperpolarization by turning on a potassium conductance (gK,GD) in hippocampal CA3 pyramidal cells. We used combined intracellular and microfluorometric recording techniques to evaluate whether gK,GD is activated by a rise in the concentration of intracellular calcium ([Ca2+]i). We found that the activation of gK,GD is only followed, but not preceded by a rise in [Ca2+]i. Furthermore, gK,GD is not blocked by the sulfonylurea glibenclamide, a blocker of ATP-regulated potassium conductance. We conclude that activation of gK,GD does not simply reflect breakdown of the calcium of ATP homeostasis, but on the contrary might represent an active restoring mechanism which delays the pathological consequences of sustained glucose deficiency.