Effects of guanine nucleotides on glutamate-induced chemiluminescence in rat hippocampal slices submitted to hypoxia.
Glutamate significantly increased levels of spontaneous chemiluminescence (CL) in rat hippocampal slices incubated under hypoxic conditions. Although it has been previously shown that guanine nucleotides (GN) displace glutamate from several of its receptors, in our study only GMP, as well as the glutamate antagonist MK-801, was able to reverse the increase in CL provoked by glutamate. On the other hand, not only GTP or Gpp(NH)p failed to reverse the action of glutamate, but they increased CL production like glutamate. This effect of GTP/Gpp(NH)p was also reversed by GMP. We concluded that, under neurotoxic conditions, GMP acted as an antagonist and GTP or Gpp(NH)p acted as agonists of glutamate. These results reinforced the evidence of the existence of extracellular site(s) for GN and indicated a possible role for GN in excitotoxicity.
Regner
A
A
Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Ramirez
G
G
Belló-Klein
A
A
Souza
D
D
D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D016291:Dizocilpine Maleate / Q000494:pharmacology; D005260:Female; D018698:Glutamic Acid / Q000494:pharmacology*; D006150:Guanine Nucleotides / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D000860:Hypoxia; D066298:In Vitro Techniques; D008163:Luminescent Measurements; D051381:Rats; D017208:Rats, Wistar
D006150:Guanine Nucleotides; D006165:Guanylyl Imidodiphosphate; D018698:Glutamic Acid; D016291:Dizocilpine Maleate; D006160:Guanosine Triphosphate; D000242:Cyclic AMP