Medial vestibular nucleus in the guinea-pig: NMDA-induced oscillations.
We have recently shown in vivo that N-Methyl-D-Aspartate (NMDA) receptors are present in the guinea-pig vestibular complex and demonstrated that they are involved in the regulation of the resting discharge of vestibular neurones. A parallel in vitro study has identified in the guinea-pig medial vestibular nuclei (MVN) two main neuronal cell types, A and B MVNn, differing by their intrinsic membrane properties. One subtype of B MVNn was further characterized by the presence of a low threshold calcium spike (LTS). The present study investigated in vitro the responses of these different cell types to NMDA. Both A and B MVNn were depolarized by NMDA, which also induced a decrease in membrane resistance and an increase in the spontaneous firing rate. These effects could be blocked by D-AP5, a specific antagonist of NMDA receptors. Following a 10-30 mV hyperpolarization, a long-lasting oscillatory behavior could be induced in presence of NMDA. These oscillations were however restricted to the subtype of B MVNn without LTS. The NMDA-induced oscillations were tetrodotoxine-resistant, but could be eliminated by D-AP5 or by replacing sodium with choline. Functional implications of this oscillatory behavior are discussed.
Département de Physiologie, CMU, Genève, Switzerland.
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Serafin
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Khateb
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de Waele
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Vidal
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Mühlethaler
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology*; D000818:Animals; D001933:Brain Stem / Q000502:physiology*; D002552:Cerebral Ventricles / Q000502:physiology*; D002794:Choline / Q000494:pharmacology; D004553:Electric Conductivity / Q000187:drug effects; D005071:Evoked Potentials / Q000187:drug effects; D006168:Guinea Pigs; D066298:In Vitro Techniques; D016202:N-Methylaspartate / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D013779:Tetrodotoxin; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D012964:Sodium; D002794:Choline