SUBSTANCE-P RELEASES AND AUGMENTS THE MORPHINE-EVOKED RELEASE OF ADENOSINE FROM SPINAL-CORD

The effects of substance P on the morphine-evoked release of adenosine were examined. Substance P alone produced a multiphasic effect on rel ease of adenosine, with release occurring at low nanomolar concentrati ons and at a micromolar concentration, but not at intermediate concent rations. An inactive dose of substance P augmented the morphine-evoked release of adenosine at a nanomolar concentration of morphine. Releas e of adenosine by substance P alone (1 nM) or substance P/morphine (10 0 nM/10 nM) was Ca2+-dependent and originated from capsaicin-sensitive nerve terminals. (C) 1997 Elsevier Science B.V.