title: Spontaneous synaptic activity is primarily GABAergic in vestibular nucleus neurons of the chick embryo.
abstract: The principal cells of the chick tangential nucleus are vestibular nucleus neurons participating in the vestibular reflexes. In 16-day embryos, the application of glutamate receptor antagonists abolished the postsynaptic responses generated on vestibular-nerve stimulation, but spontaneous synaptic activity was largely unaffected. Here, spontaneous synaptic activity was characterized in principal cells from brain slices at E16 using whole cell voltage-clamp recordings. With KCl electrodes, the frequency of spontaneous inward currents was 3.1 Hz at -60 mV, and the reversal potential was +4 mV. Cs-gluconate pipette solution allowed the discrimination of glycine/GABA(A) versus glutamate receptor-mediated events according to their different reversal potentials. The ratio for spontaneous excitatory to inhibitory events was about 1:4. Seventy-four percent of the outward events were GABA(A), whereas 26% were glycine receptor-mediated events. Both pre- and postsynaptic GABA(B) receptor effects were shown, with presynaptic GABA(B) receptors inhibiting 40% of spontaneous excitatory postsynaptic currents (sEPSCs) and 53% of spontaneous inhibitory postsynaptic currents (sIPSCs). With TTX, the frequency decreased approximately 50% for EPSCs and 23% for IPSCs. These data indicate that the spontaneous synaptic activity recorded in the principal cells at E16 is primarily inhibitory, action potential-independent, and based on the activation of GABA(A) receptors that can be modulated by presynaptic GABA(B) receptors.
authors.affiliation: Department of Anatomy and Cell Biology and Neuroscience Program, George Washington University Medical Center, Washington DC 20037, USA.
authors.forename: Mei
authors.initials: M
authors.lastname: Shao
authors.forename: June C
authors.initials: JC
authors.lastname: Hirsch
authors.forename: Christian
authors.initials: C
authors.lastname: Giaume
authors.forename: Kenna D
authors.initials: KD
authors.lastname: Peusner
mesh_terms: D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D002642:Chick Embryo; D004594:Electrophysiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials; D018755:GABA Agonists / Q000494:pharmacology; D005998:Glycine / Q000502:physiology; D009433:Neural Inhibition; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D018079:Receptors, GABA / Q000502:physiology*; D011963:Receptors, GABA-A / Q000502:physiology; D018080:Receptors, GABA-B / Q000502:physiology; D009435:Synaptic Transmission; D014726:Vestibular Nuclei / Q000166:cytology / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018755:GABA Agonists; D018079:Receptors, GABA; D011963:Receptors, GABA-A; D018080:Receptors, GABA-B; D005680:gamma-Aminobutyric Acid; D001418:Baclofen; D005998:Glycine