Effect of glutamate antagonists on nitric oxide production in rat brain following intrahippocampal injection

Abstract

Stimulation of glutamate receptors induces neuronal nitric oxide (NO) release, which in turn modulates glutamate transmission. The involvement of ionotropic glutamate NMDA and AMPA/kainate receptors in induction of NO production in the rat brain was examined after injection of kainate, a non-NMDA receptor agonist; kainate plus 6-cyano- 7-nitroquinoxaline-2,3-dione (CNQX), a selective AMPA/kainate receptor antagonist; or kainate plus 2-amino-5-phosphonopentanoic acid (APV), a selective NMDA receptor antagonist. Competitive glutamate receptor antagonists were injected with kainate unilaterally into the CA3 region of the rat hippocampus. The accumulation of nitrite, the stable metabolite of NO, was measured by the Griess reaction at different times (5 min, 15 min, 2 h, 48 h, and 7 days) in hippocampus, forebrain cortex, striatum, and cerebellum homogenates. The used glutamate antagonists APV and CNQX both provided sufficient neuroprotection in the sense of reducing nitrite concentrations, but with different mechanisms and time dynamics. Our findings suggest that NMDA and AMPA/kainate receptors are differentially involved in nitric oxide production.Stimulacija glutamatskih receptora dovodi do stvaranja azot oksida (NO) u neuronima mozga što dovodi do modulacije glutamatske neurotransmisije. Ispitivana je uloga glutamatskih NMDA i AMPA/kainatnih receptora u stvaranju NO u mozgu pacova posle intracerebralne aplikacija kainata, agonista AMPA/kainatnih receptora, kainata sa 6-ciano-7- nitrokinoksalin-2,3-dionom (CNQX), selektivnim antagonistom AMPA/kainatnih receptora ili kainata sa 2-amino-5-fosfonopentanoiskom kiselinom (APV) selektivnim antagonistom NMDA receptora. Antagonisti glutamata su aplicirani unilateralno u selektivno osetljiv CA3 region hipokampusa. Stvaranje NO je praćeno preko akumulacije nitrita, stabilnih metabolita NO, Griess-ovom metodom. Merenja su vršena u hipokampusu, korteksu, stiatumu i cerebelumu mozga pacova 5 min, 15 min, 2 h, 48 h i 7 dana nakon aplikacije. U svim praćenim moždanim strukturama neuroprotektivno je delovala primena CNQX i APV u smislu smanjenja produkcije NO, ali sa očiglednom razlikom u mehanizmu dejstva i vremenskoj dinamici. Rezultati našeg istraživanja dokazuju da su glutamatski NMDA i AMPA/kainatni receptori različito uključeni u proces produkcije NO.nul