文摘
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 GABAB receptor subunits, and the recently discovered GABAB 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 GABAB1 and GABAB2 subunits, and a near-plasma membrane localization of KCTD12. In addition, we found that GABAB2 subunits correlated with KCTD16. Whole-cell current-clamp recordings showed that responses to the GABAB 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 GABABergic 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 GABAA receptor-mediated system in rat TG, we provide an updated GABAergic model in the rat TG that incorporates both GABAA- and GABAB-receptor systems.
