[Use of the fluorescent probe 1-anilinonaphthalene-8-sulfonate to study the transmembrane potential of synaptosomes].

The properties of the transmembrane potential (TMP) of synaptosomes (Sin) from the rat brain cortex were studied by means of the fluorescent probe I-anilinonaphthalene-8-sulfonate (ANS). The fluorescent emission that increased at 464 nm (lambda ex = 365 nm) after addition of valinomycin to synaptosomes was considered as the reflection of Sin hyperpolarization. The reduction of K+-gradient across Sin membrane (decrease in TMP) induced by Sin preincubation with ouabain (1 mM) or by K+ increase from 5 to 20 mM noticeably decreased the effect of valinomycin. Valinomycin exerted no effect on Sin subjected to osmotic shock. It is suggested that valinomycin-induced changes in ANS fluorescence may be made use of for testing the ability of Sin obtained to retain K+-gradient (TMP presence), that is for testing the Sin nativity.