Electrical stimulation of primary olfactory nerve induces two types of variations in the extracellular potassium activity within the glomerulus of the rat olfactory bulb in vivo.

Primary olfactory nerve stimulation induces a two-step increase in extracellular potassium, as recorded by K+-sensitive microelectrodes inserted into single glomeruli of the rat olfactory bulb. The second rise in K+ (K-peak) occurs in a graded, activity-dependent manner at the basal pole of the glomerular neuropile. This phenomenon appears to be directly related to the rate of extracellular K+ accumulation and is accompanied by a substantial depression of the mitral cell firing rate.