Long-term synaptic changes in rat cerebellar slices reflected in extracellular K+ activity.

In rat cerebellar slices, a [K+]o increase evoked locally by molecular layer stimulation was recorded by a K(+)-sensitive microelectrode. This K+ response was reduced clearly during application of low-Ca2+ medium, kynurenate or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Sustained depression of the K+ response by about 20% was observed after simultaneously but not after alternately combined stimulation of the molecular layer and the white matter/granule cell layer. It is concluded from these results that long-term depression of parallel fiber-Purkinje cell transmission can be detected as depression of the K+ response.