Department of Physiology and Biophysics and Program in Neuroscience, Miller School of Medicine, University of Miami, Miami, Florida 33136, USA.
J Neurosci. 2011 Apr 13;31(15):5782-91. doi: 10.1523/JNEUROSCI.5559-10.2011.
Taste buds consist of at least three principal cell types that have different functions in processing gustatory signals: glial-like (type I) cells, receptor (type II) cells, and presynaptic (type III) cells. Using a combination of Ca2+ imaging, single-cell reverse transcriptase-PCR and immunostaining, we show that GABA is an inhibitory transmitter in mouse taste buds, acting on GABA(A) and GABA(B) receptors to suppress transmitter (ATP) secretion from receptor cells during taste stimulation. Specifically, receptor cells express GABA(A) receptor subunits β2, δ, and π, as well as GABA(B) receptors. In contrast, presynaptic cells express the GABA(A) β3 subunit and only occasionally GABA(B) receptors. In keeping with the distinct expression pattern of GABA receptors in presynaptic cells, we detected no GABAergic suppression of transmitter release from presynaptic cells. We suggest that GABA may serve function(s) in taste buds in addition to synaptic inhibition. Finally, we also defined the source of GABA in taste buds: GABA is synthesized by GAD65 in type I taste cells as well as by GAD67 in presynaptic (type III) taste cells and is stored in both those two cell types. We conclude that GABA is an inhibitory transmitter released during taste stimulation and possibly also during growth and differentiation of taste buds.
味蕾至少包含三种主要的细胞类型，它们在处理味觉信号方面具有不同的功能：胶质样（I 型）细胞、受体（II 型）细胞和突触前（III 型）细胞。我们使用 Ca2+成像、单细胞逆转录 PCR 和免疫染色的组合方法，表明 GABA 是小鼠味蕾中的一种抑制性递质，通过 GABA(A)和 GABA(B)受体起作用，在味觉刺激期间抑制受体细胞中递质（ATP）的分泌。具体而言，受体细胞表达 GABA(A)受体亚基β2、δ和π，以及 GABA(B)受体。相比之下，突触前细胞表达 GABA(A)β3 亚基，偶尔表达 GABA(B)受体。与 GABA 受体在突触前细胞中的独特表达模式一致，我们没有检测到 GABA 对突触前细胞中递质释放的抑制作用。我们认为，GABA 可能在味觉中除了突触抑制之外还具有其他功能。最后，我们还确定了 GABA 在味蕾中的来源：GABA 由 I 型味觉细胞中的 GAD65 以及突触前（III 型）味觉细胞中的 GAD67 合成，并储存在这两种细胞类型中。我们得出结论，GABA 是一种在味觉刺激期间释放的抑制性递质，也可能在味觉的生长和分化期间释放。
