ADENOSINE-A1-RECEPTORS MEDIATE THE PRESYNAPTIC INHIBITION OF CALCITONIN GENE-RELATED PEPTIDE RELEASE BY ADENOSINE IN THE RAT SPINAL-CORD

Electrical field stimulation evoked a reproducible outflow of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) from the dorsal half of the rat spinal cord, an effect which was abolished by prior application of capsaicin, tetrodotoxin or removal of extracellular Ca2+. Adenosine (EC50 3.2 muM) and the selective adenosine A1 receptor agonist N6-cyclohexyladenosine (EC50 8.2 nM) inhibited evoked CGRP-LI outflow, while the selective adenosine A2 receptor agonist CGS-21680 was ineffective up to 10 muM. The action of adenosine was prevented by the adenosine A1 receptor selective antagonist 8-cyclopentyl-1, 3-dipropylxanthine (30 muM), which did not affect CGRP-LI release on its own.