Adenosine 5′ triphosphate evoked mobilization of intracellular calcium in central nervous system white matter of adult mouse optic nerve

Although it has been established that immature glial cells express functional purinergic receptors, the responsiveness of mature glial cells in vivo had not been elucidated. This question was addressed using fura-2 ratiometric measurements of [Ca2+](i) in the adult mouse optic nerve, a central nervous system (CNS) white matter tract, taking advantage of the facts that (i), the optic nerve contains glial cells but not neurons and (ii), that fura-2 loads primarily astrocytes in isolated intact optic nerves. We show that adenosine 5' triphosphate (ATP) evoked an increase in [Ca2+](i) in a concentration-dependent manner with a half-maximal effect at 3 mu m ATP, and with a rank order of agonist potency of ATP > ADP > alpha,beta-methyline-ATP > UDP > adenosine. The results indicate mainly P-2Y and P-2X components, consistent with the in vitro astroglial purinergic receptor profile. The in vivo response of mature glia to ATP may be important in their response to CNS damage. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.