title: Serotonin differentially modulates the electrical properties of different subsets of taste receptor cells in bullfrog.
abstract: Serotonin (5-hydroxytryptamin, 5-HT) is localized in taste bud cells of vertebrates. Effects of the external application of 5-HT on the membrane currents of frog taste receptor cells (TRCs) were investigated using patch-clamp technique in whole-cell configuration. The 5-HT (0.1-1 micro m) and 5-HT1A receptor agonist (+/-)-8-OH-2-(D1-n-propyl-amino)tetralin (8-OH-DPAT) (1-20 micro m) inhibited both voltage-gated sodium current (INa) and voltage-gated potassium current (IK) in 50% of TRCs, but potentiated IK without any significant effect on INa in another subset of 18% of TRCs. Voltage-gated currents in the residual TRCs were not affected by 5-HT or 8-OH-DPAT. External application of 10 micro m forskolin and 300 micro m 8-cpt cAMP [8-(4-chlorophenylthio)adenosine 3':5'-cyclic monophosphate] mimicked the inhibitory effect of 5-HT and 8-OH-DPAT on IK and INa while internal dialysis with 50 micro m protein kinase A inhibitor prevented the 5-HT-mediated inhibitory effects on IK and INa in TRCs. Internal dialysis of TRCs with high Ca2+-pipette solution (1 micro m) increased the IK in 58% of TRCs. The 5-HT reversibly increased the [Ca2+]i in 17% of TRCs when measured by Ca2+-imaging using a Ca2+-sensitive dye (fura-2 AM). These results suggest that 5-HT differentially modulates the voltage-gated membrane currents in different subsets of TRCs.
authors.affiliation: Integrative Sensory Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, 852-8588, Japan.
authors.forename: Kotapola G
authors.initials: KG
authors.lastname: Imendra
authors.forename: Takenori
authors.initials: T
authors.lastname: Miyamoto
authors.forename: Yukio
authors.initials: Y
authors.lastname: Okada
authors.forename: Kazuo
authors.initials: K
authors.lastname: Toda
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors / Q000502:physiology; D011892:Rana catesbeiana; D012701:Serotonin / Q000494:pharmacology* / Q000502:physiology; D013650:Taste Buds / Q000187:drug effects* / Q000502:physiology
chemical_list: D024642:Potassium Channels, Voltage-Gated; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin