EVIDENCE FOR PHYSIOLOGICALLY ACTIVE AXONAL ADENOSINE RECEPTORS IN THERAT CORPUS-CALLOSUM

Several neurotransmitter receptors have been identified on axons, and emerging evidence suggests that central axonal conduction may be modul ated by neurotransmitters. We have recently demonstrated the presence of extra-synaptic adenosine Al receptors along rat hippocampal axons. We now present immunocytochemical evidence for Al receptors on rat cor pus callosum axons and show that these receptors actively modulate axo n physiology. Using rat brain coronal slices, we stimulated the corpus callosum and recorded the evoked extracellular compound action potent ial. The lipid-soluble, Al-specific adenosine receptor agonist cyclope ntyladenosine, dose-dependently decreased the compound action potentia l amplitude, an effect reversed by the specific Al antagonist 8-cyclop entyl-1,3-dipropylxanthine. These data provide the first direct eviden ce that axonal Al adenosine receptors modulate axon physiology in the adult mammalian brain. Influencing axonal transmission is a potentiall y powerful mechanism of altering information processing in the nervous system. (C) 1998 Elsevier Science B.V.