The Korean Journal of Physiology and Pharmacology

The Korean Society of Pharmacology (대한약리학회)
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Mechanism of Glutamate-induced $[Ca^{2+}]i$ Increase in Substantia Gelatinosa Neurons of Juvenile Rats

  • Jung, Sung-Jun (Department of Physiology, College of Medicine, Kangwon National University) ;
  • Choi, Jeong-Sook (Department of Physiology, College of Medicine, Kangwon National University) ;
  • Kwak, Ji-Yeon (Department of Physiology, Seoul National University College of Medicine) ;
  • Kim, Jun (Department of Physiology, Seoul National University College of Medicine) ;
  • Kim, Jong-Whan (Department of Physiology, College of Medicine, Kangwon National University) ;
  • Kim, Sang-Jeong (Department of Physiology, College of Medicine, Kangwon National University)
  • Published : 2003.04.21
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Abstract

The glutamate receptors (GluRs) are key receptors for modulatory synaptic events in the central nervous system. It has been reported that glutamate increases the intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) and induces cytotoxicity. In the present study, we investigated whether the glutamate-induced $[Ca^{2+}]_i$ increase was associated with the activation of ionotropic (iGluR) and metabotropic GluRs (mGluR) in substantia gelatinosa neurons, using spinal cord slice of juvenile rats (10${\sim}21 day). $[Ca^{2+}]_i$ was measured using conventional imaging techniques, which was combined with whole-cell patch clamp recording by incorporating fura-2 in the patch pipette. At physiological concentration of extracellular $Ca^{2+}$, the inward current and $[Ca^{2+}]_i$ increase were induced by membrane depolarization and application of glutamate. Dose-response relationship with glutamate was observed in both $Ca^{2+}$ signal and inward current. The glutamate-induced $[Ca^{2+}]_i$ increase at holding potential of -70 mV was blocked by CNQX, an AMPA receptor blocker, but not by AP-5, a NMDA receptor blocker. The glutamate-induced $[Ca^{2+}]_i$ increase in $Ca^{2+}$ free condition was not affected by iGluR blockers. A selective mGluR (group I) agonist, RS-3,5-dihydroxyphenylglycine (DHPG), induced $[Ca^{2+}]_i$ increase at holding potential of -70 mV in SG neurons. These findings suggest that the glutamate-induced $[Ca^{2+}]_i$ increase is associated with AMPA-sensitive iGluR and group I mGluR in SG neurons of rats.

Keywords

References

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