Figure 3.

Spontaneous extracellular H⁺ oscillations and their abolishment by nifedipine, cobalt, nominally 0mM extracellular Ca²⁺, and kainate. (A) Representative trace from one cell showing spontaneous extracellular H⁺ oscillations; addition of 10 μM nifedipine abolished the oscillations and resulted in a standing acidic H⁺ signal. (B) Representative trace showing oscillations from a second cell that were abolished reversed upon addition of 4 mM Co²⁺; a standing extracellular acidification was observed following cobalt application. (C) H⁺ oscillations observed in a third cell were eliminated by applying a solution containing nominally 0 mM external Ca²⁺. A continuous extracellular acidification was observed following the addition of the nominally 0 mM external calcium solution. (D) H⁺ oscillations in the final cell were quieted in an extracellular alkalinized state following the addition of 20 μM kainate.