The effect of various metal ions on neuronal membrane fluidity was exa
mined using oxypropyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy, which h
as been used for the examination of membrane fluidity in hydrophobic a
reas by electron spin resonance spectrometry. Potassium, cobalt, calci
um, magnesium, nickel, copper, ferric, and aluminium ions decreased th
e membrane fluidity while ferrous ions increased it at each high conce
ntration. Sodium and zinc ions had no effect. Ethylenediaminetetraacet
ic acid decreased membrane fluidity at high concentrations. Nicardipin
e lowered membrane fluidity and flunarizine elevated it at each high c
oncentration. There was no change in membrane fluidity by other calciu
m antagonists, nimodipine and nifedipine.