Effects of synaptic Activity on the metabolism and release of purines in the rat superior cervical ganglion

The release of radioactive metabolites from isolated rat superior cervical ganglia was measured under various conditions following preloading with 3H-adenosine. The 3H label was recovered primarily in the adenosine metabolites, ATP, ADP, AMP, IMP, and inosine, rather than in adenosine itself. Increased release was evoked by preganglionic stimulation or by exposure to a high-K+ medium, whereas in a low-Ca2+-high-Mg2+ medium, both spontaneous release and evoked release of most metabolites were inhibited. Exposure of the ganglion to an atmosphere of N2 also increased the release of most labeled metabolites, but this release was not substantially affected by a low-Ca2+ medium. The fluorescent derivatives of the endogenous adenine-containing compounds present in the ganglion were prepared from homogenates and separated by high-performance liquid chromatography (HPLC). By the end of the testing period (6 hr), levels of ATP in the isolated ganglia had dropped to 10-20% of the initial values, while levels of ADP, AMP, and adenosine increased. There was little difference in these values between nonstimulated ganglia and those exposed to N2 or to a high-K+ medium.