Receptor-activated modulation in rat cortical slices as measured with a K-sensitive electrode.

The effects of a variety of presynaptic receptor-activating modulating agents on potassium efflux have been investigated using a potassium (K)-sensitive extracellular electrode in rat brain cortical slices that are electrically stimulated. Purinergic, alpha 2-adrenergic, opioid and muscarinic drugs all increased K outflow. When these agents were used in combination at maximal concentrations, only morphine promoted a further increase in K efflux, suggesting that it utilized a different K channel or acted on cellular elements different from those of the other modulators.