title: P2 purinoceptor-mediated depolarization of rat supraoptic neurosecretory cells in vitro.
abstract: 1. Intracellular recordings were obtained from supraoptic magnocellular neurosecretory cells (MNCs) in superfused explants of rat hypothalamus. Application of ATP and UTP, but not adenosine, produced TTX-insensitive depolarizations accompanied by increases of input conductance. 2. The P2X agonists alpha,beta-methylene ATP, beta,gamma-methylene ATP and 2-methylthio ATP mimicked the effects of ATP in > 77% of the cells tested. Depolarizing responses to ATP were reversibly inhibited by PPADS (pyridoxal-phosphate-6-azophenyl-2',4'- disulphonic acid; IC50 approximately 0.5 microM), a selective P2X antagonist. 3. The reversal potential of responses to ATP (-37 mV) was not strongly affected by intracellular Cl- injection or by removal of Cl- from the external solution. The reversal potential of responses to the most potent P2X agonist, alpha,beta-methylene ATP, was -29 mV. These values suggest the involvement of non-selective cationic channels, a finding which is consistent with the ionotropic cationic channel structure of cloned P2X purinoceptors. 4. The reversal potential of UTP-mediated responses (-33 mV) was also consistent with the involvement of non-selective cationic channels. Since cloned P2U receptors display homology with G-protein-coupled receptors, cationic channels modulated by UTP are probably different from those mediating P2X responses.
authors.affiliation: Centre for Research in Neuroscience, McGill University, Montreal, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Hiruma
authors.forename: C W
authors.initials: CW
authors.lastname: Bourque
mesh_terms: D000227:Adenine Nucleotides / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D004594:Electrophysiology; D066298:In Vitro Techniques; D008024:Ligands; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009490:Neurosecretory Systems / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D013495:Supraoptic Nucleus / Q000166:cytology / Q000502:physiology*; D014544:Uridine Triphosphate / Q000494:pharmacology
chemical_list: D000227:Adenine Nucleotides; D008024:Ligands; D010975:Platelet Aggregation Inhibitors; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D014544:Uridine Triphosphate