Effects of adenosine on neurally mediated norepinephrine release from the cat spleen

The effects of adenosine on the release of 3H-norepinephrine (3H-NE) from the isolated, perfused cat spleen consequent to nerve stimulation were evaluated. Electrical stimulation of the splenic nerve (5 Hz/100 impulses total) caused a release of 3H-NE and a rise in perfusion pressure. Adenosine added to the perfusion fluid (final concentrations 1 X 10(-6), 1 X 10(-5), and 1 X 10(-4) M) significantly reduced the pressure response elicited by nerve stimulation. In addition, adenosine (1 X 10(-4) M) slightly increased the release of total 3H consequent to nerve stimulation. Theophylline (1 X 10(-4) M) produced both a slight increase in the release of total 3H and a diminished pressure response. The effects of adenosine were effectively antagonized by this concentration of theophylline. Neither substance had any effect on the spontaneous release of total 3H. Adenosine (1 X 10(-4) M) also antagonized the pressure response elicited by perfusion of NE.