title: GABA, its receptors, and GABAergic inhibition in mouse taste buds.
abstract: 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.
authors.affiliation: Department of Physiology and Biophysics and Program in Neuroscience, Miller School of Medicine, University of Miami, Miami, Florida 33136, USA.
authors.forename: Gennady
authors.initials: G
authors.lastname: Dvoryanchikov
authors.forename: Yijen A
authors.initials: YA
authors.lastname: Huang
authors.forename: Rene
authors.initials: R
authors.lastname: Barro-Soria
authors.forename: Nirupa
authors.initials: N
authors.lastname: Chaudhari
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Roper
mesh_terms: D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D018756:GABA Antagonists / Q000494:pharmacology*; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D018377:Neurotransmitter Agents / Q000378:metabolism; D012313:RNA / Q000235:genetics; D018079:Receptors, GABA / Q000235:genetics / Q000502:physiology*; D017661:Receptors, Presynaptic / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013649:Taste / Q000187:drug effects; D013650:Taste Buds / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology*
chemical_list: D018756:GABA Antagonists; D018377:Neurotransmitter Agents; D018079:Receptors, GABA; D017661:Receptors, Presynaptic; D005680:gamma-Aminobutyric Acid; D012313:RNA; D002118:Calcium