BACTERIAL-ENDOTOXINS IMPAIR ELECTROPHYSIOLOGICAL PROPERTIES OF CULTURED ASTROCYTES BUT NOT OF CULTURED NEURONS

The endotoxins of bacteria are lipopolysaccharides which are released in the central nervous system during bacterial meningitis. Endotoxin t iters in cerebrospinal fluid correspond to the appearance of severe ne urological symptoms like seizures and coma. The pathogenic mechanism, however, by which endotoxins disturb neuronal function, is unclear. Th e functional deficit may originate either from direct alteration of ne uronal excitability or from indirect effects mediated by glial cells. Therefore, we investigated the effects of lipopolysaccharides on elect rophysiological properties of cortical neurons and astrocytes in separ ate cell cultures. Membrane potential, resistance and membrane current s of neurons were unaffected. By contrast, astrocytes depolarized mark edly in a dose dependent manner (concentration range 1.0-10.0 mu g/ml) . The depolarization was Na+ dependent and amiloride sensitive (250 mu M), both indicating an activation of an electrogenic sodium dependent transport system like the Na+/Ca2+ exchanger as a source of the depol arization. These results suggest that endotoxin induced neurological d eficits are not caused by direct effects on neurons. but may result fr om an impaired glial cell function.