A local GABAergic system within rat trigeminal ganglion cells

H. Hayasaki, Y. Sohma, K. Kanbara, K. Maemura, T. Kubota, M. Watanabe

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73 Citations (Scopus)


We investigated the GABAergic system within the Sprague-Dawley rat (2-3-weeks old) trigeminal ganglion (TG). Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed expression of glutamate decarboxylase (GAD) 65 and GAD67 mRNAs and mRNAs encoding GABAA receptor subunits α1-6, β1-3, γ1-3, and δ. In situ hybridization revealed that GAD65 and GAD67 mRNAs were expressed in neuronal cell bodies but not satellite cells. Immunohistochemical analysis showed that only GAD65 was expressed in all neuronal cell bodies, and approximately 70% of all neurons exhibited GABA immunoreactivity. Satellite cells were strongly immunopositive for GABA. GABAA receptor α1, α5, β2/3 and γ1/2/3 subunit immunoreactivities were observed in the majority of neurons, but no immunoreactivity for α2 was observed. Two types of cells were identified in TG based on cell size and morphology, type A and B. The percentage of cells expressing α3, α4, α6, and δ subunits appeared to be dependent on cell size, as δ and α6 expression were only observed in small (B-type) neurons. In whole-cell patch clamp experiments, GABA application induced inward Cl- currents in all neurons examined. The EC50 for GABA varied from 5.3 to 240 μm, and the Hill Coefficient (nH) varied between 0.98 and 2.6 at -60 mV. We found that GABA was released from TG cells by increasing extracellular K+ concentration to 100 mm. We speculate that GABA acts as a nonsynaptically released diffusible neurotransmitter, which may modulate somatic inhibition of neurons within the TG.

Original languageEnglish
Pages (from-to)745-757
Number of pages13
JournalEuropean Journal of Neuroscience
Issue number3
Publication statusPublished - 2006 Feb
Externally publishedYes


  • GABA
  • GABA receptor
  • Immunohistochemistry
  • Satellite cell
  • Sprague-Dawley rats
  • Trigeminal ganglion

ASJC Scopus subject areas

  • General Neuroscience


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