fm1-43 and linsidomine

A new fluorescence method using the dye FM1-43 was used to examine exocytotic release from hippocampal synaptosomes. Nitric oxide caused a marked transient stimulation of vesicle release. Several structurally unrelated nitric oxide donors, sodium nitroprusside, S-nitroso-N-acetylpenicillamine, 3-morpholino-sydnonimine, and acidified sodium nitrite, were effective. Release stimulated by nitric oxide and KCl were comparable in time course, using both the fluorescence assay and [3H]L-glutamate to monitor neurotransmitter release. Activation of guanylyl cyclase was not responsible for nitric oxide-stimulated release. Unlike release stimulated by KCl or A23187, nitric oxide-stimulated release was found to be independent of a rise in intrasynaptosomal Ca2+. Indo-1/AM measurements indicated that nitric oxide actually decreased intracellular Ca2+, and the Ca2+ channel blocker Cd2+ did not affect nitric oxide-stimulated vesicle release. Nitric oxide does, however, appear to act on the Ca(2+)-sensitive pool of vesicles. Nitric oxide may be the first physiological mediator that induces vesicle exocytosis without raising Ca2+ and may provide an interesting new tool for the study of molecules involved in vesicle exocytosis.

Topics: Animals; Calcium; Fluorescent Dyes; Glutamates; Glutamic Acid; Hippocampus; Indoles; Kinetics; Male; Molsidomine; Nitric Oxide; Nitroprusside; Penicillamine; Potassium Chloride; Pyridinium Compounds; Quaternary Ammonium Compounds; Rats; Rats, Sprague-Dawley; S-Nitroso-N-Acetylpenicillamine; Sodium Nitrite; Spectrometry, Fluorescence; Synaptic Vesicles; Vasodilator Agents