Effect of nitric oxide on viscosity of nerve cell membranes

The influence of nitric oxide on the microviscosity of nerve cell membranes was investigated by resonance Raman (RR) spectroscopy. Changes in membrane viscosity were estimated from the resonance Raman-spectra of carotenoids localized in the axon plasmatic membrane and membranes of subcellular vesicles (cytosomes). For the nerve fibre, the extracellular addition of nitric oxide donor, sodium nitroprusside (0.5 mM), caused an increase in the 1526 cm(-1) band relative half-width and the modification of 1160 cm-1 band structure. Moreover, sodium nitroprusside led to an increase in the I1526/I1160 ratio by 13% in 25 min and a decrease in this ratio by 10% in 50 min. In the case of cytosomes, sodium nitroprusside (0.5 mM) resulted in the reduction of the I1526/I1160 ratio by 8% in 25 and 50 min. It was shown that the neuron rhythmic activity correlated with the I1526/I1160 ratio and cytosome membrane microviscosity. We suppose that nitric oxide causes a conformational transition of carotenoids in the axon plasmatic membrane and the membranes of cytosomes. This process can be due to nitric oxide-induced changes of the membrane microviscosity or potential.