title: Heterogenous GABA(B) receptor-mediated pathways are involved in the local GABAergic system of the rat trigeminal ganglion: possible involvement of KCTD proteins.
abstract: It is well known that Gamma-aminobutyric acid (GABA) plays an important role in signal transduction in the central nervous system. However, the function of GABA in the peripheral nervous system, including sensory ganglions, is still unclear. In this study we have characterized the expression, cellular distribution, and function of GABA(B) receptor subunits, and the recently discovered GABA(B) auxiliary subunits, K(+) channel tetramerization domain-containing (KCTD) proteins, in rat trigeminal ganglion (TG) neuronal cells, which are devoid of synapses. We found heterogeneous expression of both GABA(B1) and GABA(B2) subunits, and a near-plasma membrane localization of KCTD12. In addition, we found that GABA(B2) subunits correlated with KCTD16. Whole-cell current-clamp recordings showed that responses to the GABA(B) receptor agonist, baclofen, were variable and both increases and decreases in excitability were observed. This correlated with observed differences in voltage-dependent K(+) current responses to baclofen in voltage-clamped TG neuronal cells. The functional diversity of the GABA(B)ergic regulation on the excitability of the TG neuronal cell bodies could be due to the heterogenous expression of KCTD proteins, and subsequent regulation of plasma membrane K(+) channels. Taken together with our previous demonstration of a local GABA(A) receptor-mediated system in rat TG, we provide an updated GABAergic model in the rat TG that incorporates both GABA(A)- and GABA(B)-receptor systems.
authors.affiliation: Department of Anatomy, Osaka Medical College, Takatsuki, Osaka 569-8686, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Hayasaki
authors.forename: Y
authors.initials: Y
authors.lastname: Sohma
authors.forename: K
authors.initials: K
authors.lastname: Kanbara
authors.forename: Y
authors.initials: Y
authors.lastname: Otsuki
mesh_terms: D000818:Animals; D015153:Blotting, Western; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000378:metabolism; D018080:Receptors, GABA-B / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D012668:Trigeminal Ganglion / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D011963:Receptors, GABA-A; D018080:Receptors, GABA-B; D005680:gamma-Aminobutyric Acid