The Journal of Neuroscience, August 15, 2000, 20(16):6294-6301
Nitric Oxide-Stimulated Increase in Extracellular Adenosine
Accumulation in Rat Forebrain Neurons in Culture Is Associated with ATP
Hydrolysis and Inhibition of Adenosine Kinase Activity
Paul A.
Rosenberg,
Ya
Li,
Minou
Le, and
Yumin
Zhang
Department of Neurology and Program in Neuroscience, Children's
Hospital and Harvard Medical School, Boston, Massachusetts 02115
Adenosine is a putative endogenous sleep-inducing substance, and
nitric oxide has been implicated in arousal and sleep mechanisms. We
found that various nitric oxide donors, including diethylamine NONOate
(DEA/NO), stimulated large increases in extracellular adenosine in
nearly pure cultures of forebrain neurons. The effect of DEA/NO could
be blocked by 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-oxide and
could not be mimicked by degraded solutions of DEA/NO or by DEA itself;
therefore, it was caused by nitric oxide release on hydrolysis
of the parent compound. The accumulation of adenosine was not blocked
by probenecid or GMP, suggesting that neither extracellular cAMP nor
extracellular AMP was the source, and that adenosine was therefore the
most likely species transported across the plasma membrane. To pursue
this further, we tested the effect of DEA/NO on cellular ATP and found
a significant fall in ATP associated with exposure to nitric oxide. In
addition, exposure to DEA/NO nearly completely inhibited adenosine
kinase activity. It has been found previously that adenosine kinase is
inhibited by its substrate, adenosine. We found that exposure to nitric oxide increased intracellular adenosine to 125 ± 18% of control values (p < 0.01), consistent with the
possibility that in our system the inhibition of adenosine kinase is
related to an increase in intracellular adenosine, and that the effect
of nitric oxide on extracellular adenosine is significantly potentiated
by substrate inhibition of adenosine kinase. Furthermore, nitric
oxide-stimulated adenosine accumulation may be important in the
regulation of behavioral state.
Key words:
nitric oxide; adenosine; sleep; adenosine kinase; ATP; laterodorsal tegmental nucleus; pedunculopontine tegmental nucleus
Copyright © 2000 Society for Neuroscience 0270-6474/00/20166294-08$05.00/0