Binding and functions of extracellular ATP in cultured cerebellar granule neurons.
Selected purinoceptor modulators were previously shown to prevent glutamate-evoked cytotoxicity in cerebellar granule neurons. In the same cellular system, we now identify and characterize the presence of P2 receptors. The binding of [3H]ATP to membranes of cerebellar granule neurons grows monotonically as a function of neuronal differentiation, is saturable and reaches steady state within 6 min. Scatchard plot of the equilibrium saturation data is curvilinear with a Kd value of 28 nM and a Bmax value of 87 pmol/ mg of protein for the high affinity binding sites and a Kd value of 1.5 microM and Bmax value of 1.2 nmol/mg of protein, for the more numerous low affinity binding sites. We also show that extracellular ATP increases the release, but not the uptake, of [3H]D-aspartate and that it furthermore potentiates the release of [3H]D-aspartate evoked by glutamate and KCI. ATP itself is released by cerebellar granule cultures and such release grows monotonically as a function of neuronal differentiation. These data are consistent with the role that ATP is believed to play as a cotransmitter for the central nervous system.
Merlo
D
D
Institute of Neurobiology, C.N.R. Viale Marx, Rome, Italy. cinzia@biocell.irmkant.rm.cnr.it
Volonté
C
C
D000227:Adenine Nucleotides / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D007700:Kinetics; D009474:Neurons / Q000166:cytology / Q000187:drug effects; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism
D000227:Adenine Nucleotides; D018048:Receptors, Purinergic P2; D001224:Aspartic Acid; D000255:Adenosine Triphosphate