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Identification of two taurine receptor subtypes on the primary afferent terminal of frog spinal cord
Author(s) -
Kudo Yoshihisa,
Akiyoshi Eri,
Akagi Hiroyuki
Publication year - 1988
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1988.tb11621.x
Subject(s) - taurine , depolarization , strychnine , hyperpolarization (physics) , extracellular , bicuculline , tetrodotoxin , glycine receptor , spinal cord , chemistry , medicine , inhibitory postsynaptic potential , endocrinology , sucrose gap , receptor , gabaa receptor , glycine , biochemistry , biology , neuroscience , amino acid , organic chemistry , nuclear magnetic resonance spectroscopy
1 Effects of taurine on primary afferent terminals in the frog spinal cord were examined by a sucrose‐gap method applied to a dorsal root (9th or 10th segment). 2 In a normal Ringer solution, taurine (1 mM, applied for 5 s at a rate of 0.04 ml s −1 , 0.2 μmol) caused a hyperpolarization, but a higher concentration (10 mM, applied at the same rate, 2.0 μmol) caused a biphasic response consisting of a hyperpolarization followed by a slow onset depolarization. A similar biphasic response could also be observed in tetrodotoxin‐treated preparations. 3 When the concentration of extracellular Mg 2+ was increased up to 9.0 mM, the depolarizing response to taurine was augmented. The rate of the augmentation was dependent upon the extracellular Mg 2+ concentration. 4 The depolarizing effect was selectively antagonized by bicuculline in concentrations (10–30 μ m ) that had no significant antagonizing action on γ‐aminobutyric acid (GABA)‐induced depolarization. On the other hand the hyperpolarizing effect of taurine was selectively reduced by strychnine (0.1 μ m ) which had no antagonizing effect on responses to glycine. 5 These results suggest that in the frog spinal cord there are at least two subtypes of taurine receptor whose pharmacological profiles resemble GABA and glycine receptors in the mammalian central nervous system, and whose sensitivity may be modulated by extracellular Mg 2+ .