SIGNALING EFFECT OF ELEVATED POTASSIUM CONCENTRATIONS AND MONOAMINES ON GRAIN ENERGY-METABOLISM AT THE CELLULAR-LEVEL

The effects of elevated K+ concentrations and monoamine transmitters o n different cell types in the CNS and on different subcellular structu res in these cells are reviewed. Pronounced differences exist in the m etabolic processes that are stimulated by excess K+ and by adrenergic agonists, e.g., noradrenaline. An elevation in the extracellular K+ co ncentration appears to enhance neuronal-astrocytic interaction by stim ulating metabolic processes involved in (1) the promotion of supply of precursors for transmitter glutamate, and (2) reestablishment of rest ing ion distribution following neuronal excitation. The monoamine tran smitters stimulate energy production and Na+,K+-ATPase activity in ast rocytes in a complex manner and, in so doing, facilitate their role in ion regulation. However, in contrast to excess K+, they do not enhanc e the production of astrocytic precursors for neuronal glutamate produ ction. Emphasis is placed on possible profound differences in metaboli c effects on excitatory and inhibitory neurotransmission and on the im portance of stimulation of glycolytic metabolism in astrocytes versus oxidative metabolism in neurons.