• Nitric oxide;
  • Synaptic vesicles;
  • Glutamate;
  • Neurotransmitter uptake;
  • V-ATPase;
  • H+-ATPase

Abstract: Nitric oxide (NO; including NO, NO+, and NO) was found to inhibit glutamate uptake by isolated synaptic vesicles of rat brain. This was observed when two unrelated NO donors, S-nitrosogluthathione and S-nitroso-N-acetylpenicillamine, were used. The primary target of NO is the H+-ATPase found in the synaptic vesicles, which leads to dissipation of the electrochemical proton gradient and inhibition of glutamate uptake. Oxyhemoglobin (12 µM) and, to a much lesser extent, methemoglobin protected the vacuolar H+-ATPase from inhibition. Inhibition of H+ pumping by NO was reversed by addition of 0.5 mM dithiothreitol. The results indicate that the vacuolar H+-ATPase from synaptic vesicles is inhibited by NO by a mechanism that involves S-nitrosylation of critical sulfhydryl groups in the enzyme. The interaction of NO with synaptic vesicles might be of importance for the understanding of the multiple effects of NO in neurotransmission.