Kainate-induced K+ efflux and plasma membrane depolarization in cultured cerebellar granule cells

It is becoming increasingly evident that activation of ionotropic glutamate receptors leads to significant changes in cytosolic [K+] ([K+](c)), a majo r determinant of the plasma membrane (PM) potential, E-m. Since E-m affects fluxes of key cations, such as Ca2+, it is important to precisely quantify [K+](c) and E-m in neurons exposed to glutamate receptor agonists. Here we studied the relationships between [K+](c) and E-m in primary cultures of c erebellar granule cells, and found that kainate elicits a rapid drop in [K](c) below 10 mM. Using patch electrodes containing 10 or 150 mM K+, we det ermined that kainate depolarizes the PM to -2 or -28 mV, respectively. Ther efore, the actual PM depolarization elicited by kainate is much larger than that routinely measured with K+-rich electrodes. NeuroReport 12:59-62 (C) 2001 Lippincott Williams & Wilkins.