Adenosine triphosphate accelerates recovery from hypoxic/hypoglycemic perturbation of guinea pig hippocampal neurotransmission via a P(2) receptor.
The present study was designed to assess the effects of adenosine triphosphate (ATP) on hippocampal neurotransmissions under the normal and hypoxic/hypoglycemic conditions. ATP reversely depressed population spikes (PSs), which were monitored in the dentate gyrus of guinea pig hippocampal slices, in a dose-dependent manner at concentrations ranged from 0.1 micro M to 1 mM. A similar depression was obtained with the P(2) receptor agonist, alpha,beta-methylene ATP (alpha,beta-MeATP), and the effect was inhibited by the P(2) receptor antagonists, suramin and PPADS. The inhibitory action of ATP or alpha,beta-MeATP was inhibited by the gamma-aminobutyric acid(A) (GABA(A)) receptor antagonist, bicuculline, but it was not affected by theophylline, a broad inhibitor of adenosine (P(1)) receptors, tetraethylammonium, a broad inhibitor of K(+) channels, or ecto-protein kinase inhibitors. ATP or alpha,beta-MeATP enhanced GABA release from guinea pig hippocampal slices, that was inhibited by deleting extracellular Ca(2+) or in the presence of tetrodotoxin, while ATP had no effect on GABA release from cultured rat hippocampal astrocytes or postsynaptic GABA-gated channel currents in cultured rat hippocampal neurons. Twenty-minutes deprivation of glucose and oxygen from extracellular solution abolished PSs, the amplitude recovering to about 30% of basal levels 50 min after returning to normal conditions. ATP or alpha,beta-MeATP accelerated the recovery after hypoxic/hypoglycemic insult (approximately 80% of basal levels). Adenosine diphosphate and adenosine monophosphate accelerated the recovery, but to a much lesser extent, and adenosine had no effect. The results of the present study thus suggest that ATP inhibits neuronal activity by enhancing neuronal GABA release via a P(2) receptor, perhaps a P2X receptor, thereby protecting against hypoxic/hypoglycemic perturbation of hippocampal neurotransmission.
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D007003:Hypoglycemia / Q000503:physiopathology*; D002534:Hypoxia, Brain / Q000503:physiopathology*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D011963:Receptors, GABA-A / Q000502:physiology; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D011963:Receptors, GABA-A; D018048:Receptors, Purinergic P2; D005680:gamma-Aminobutyric Acid; D000255:Adenosine Triphosphate