P2X2 characteristics of the ATP receptor coupled to [Ca2+]i increases in cultured Purkinje neurons from neonatal rat cerebellum.
P2X receptors present in cerebellar Purkinje cells have been studied by recording ATP-elicited [Ca2+]i signals from immuno-identified (calbindin+) cells in culture using fura-2 microfluorescence. The [Ca2+]i increases evoked by ATP were mimicked by 2MeSATP but not by alpha, beta-meATP and other purinoceptor agonists. The selective P2X1 antagonist diinosine pentaphosphate failed to inhibit ATP-elicited [Ca2+]i transients, but suramin and PPADS rapidly and reversibly blocked the [Ca2+]i responses to ATP and 2MeSATP. The IC50 values for suramin and PPADS inhibition were 48.7 +/- 4.4 and 5.9 +/- 0.3 microM, respectively. Both antagonists blocked completely the signal elicited by ATP, revealing that there was not a separate antagonist-insensitive P2X receptor population in Purkinje cells. The effect of ATP was potentiated by Zn2+ and H+ ions. A one unit acidification from pH 7.4 to 6.4 enhanced by 172% the [Ca2+]i transient elicited by an intermediate concentration of ATP. Conversely, alkalinization of the medium to pH 8.4 reduced the ATP response by 88%. This combination of pharmacological and modulatory properties indicates that endogenous P2X receptors present in Purkinje neurons are formed by P2X2 subunits, rather than the more abundantly expressed P2X4 purinoceptor subunits.
García-Lecea
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M
Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad Complutense de Madrid, Spain.
Delicado
E G
EG
Miras-Portugal
M T
MT
Castro
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E
D000255:Adenosine Triphosphate / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D000970:Antineoplastic Agents / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured / Q000187:drug effects; D002531:Cerebellum / Q000166:cytology* / Q000187:drug effects; D015226:Dinucleoside Phosphates / Q000494:pharmacology; D009479:Neuropeptides / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D058919:Purinergic P2 Receptor Antagonists; D011689:Purkinje Cells / Q000187:drug effects / Q000502:physiology*; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000502:physiology*; D058476:Receptors, Purinergic P2X2; D013498:Suramin / Q000494:pharmacology
D000970:Antineoplastic Agents; D015226:Dinucleoside Phosphates; D009479:Neuropeptides; C546403:P2rx2 protein, rat; D010975:Platelet Aggregation Inhibitors; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; C109479:diinosine pentaphosphate; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D013498:Suramin; D000255:Adenosine Triphosphate