Inhibition of N-type voltage-activated calcium channels in rat dorsal root ganglion neurons by P2Y receptors is a possible mechanism of ADP-induced analgesia.
Patch-clamp recordings from small-diameter rat dorsal root ganglion (DRG) neurons maintained in culture demonstrated preferential inhibition by ATP of high-voltage-activated, but not low-voltage-activated, Ca2+ currents (I(Ca)). The rank order of agonist potency was UTP > ADP > ATP. ATP depressed the omega-conotoxin GVIA-sensitive N-type current only. Pyridoxal-5-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) and 2'-deoxy-N6-methyladenosine 3',5'-bisphosphate tetraammonium, two P2Y1 receptor antagonists, almost abolished the ATP-induced inhibition. Both patch-clamp recordings and immunocytochemistry coupled with confocal laser microscopy indicated a colocalization of functional P2X3 and P2Y1 receptors on the same DRG neurons. Because the effect of ATP was inhibited by intracellular guanosine 5'-O-(2-thiodiphosphate) or by applying a strongly depolarizing prepulse, P2Y1 receptors appear to block I(Ca) by a pathway involving the betagamma subunit of a G(q/11) protein. Less efficient buffering of the intracellular Ca2+ concentration ([Ca2+]i) by reducing the intrapipette EGTA failed to interfere with the ATP effect. Fura-2 microfluorimetry suggested that ATP raised [Ca2+]i by a Galpha-mediated release from intracellular pools and simultaneously depressed the high external potassium concentration-induced increase of [Ca2+]i by inhibiting I(Ca) via Gbetagamma. Adenosine 5'-O-(2-thiodiphosphate) inhibited dorsal root-evoked polysynaptic population EPSPs in the hemisected rat spinal cord and prolonged the nociceptive threshold on intrathecal application in the tail-flick assay. These effects were not antagonized by PPADS. Hence, P2Y receptor activation by ADP, which is generated by enzymatic degradation of ATP, may decrease the release of glutamate from DRG terminals in the spinal cord and thereby partly counterbalance the algogenic effect of ATP.
Gerevich
Zoltan
Z
Rudolf-Boehm-Institute of Pharmacology and Toxicology, University of Leipzig, D-04107 Leipzig, Germany.
Borvendeg
Sebestyen J
SJ
Schröder
Wolfgang
W
Franke
Heike
H
Wirkner
Kerstin
K
Nörenberg
Wolfgang
W
Fürst
Susanna
S
Gillen
Clemens
C
Illes
Peter
P
D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000494:pharmacology / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000698:Analgesia; D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000378:metabolism*; D002478:Cells, Cultured; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D007278:Injections, Spinal; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010146:Pain / Q000378:metabolism / Q000517:prevention & control*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000378:metabolism*; D058477:Receptors, Purinergic P2X3; D058472:Receptors, Purinergic P2Y1; D013873:Thionucleotides / Q000494:pharmacology
D000700:Analgesics; D020864:Calcium Channels, N-Type; C546410:P2rx3 protein, rat; C546384:P2ry1 protein, rat; D018048:Receptors, Purinergic P2; D058477:Receptors, Purinergic P2X3; D058472:Receptors, Purinergic P2Y1; D013873:Thionucleotides; D006153:Guanosine Diphosphate; C030812:adenosine 5'-O-(2-thiodiphosphate); D000244:Adenosine Diphosphate; C023427:guanosine 5'-O-(2-thiodiphosphate); D000255:Adenosine Triphosphate; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D011188:Potassium; D002118:Calcium