Modulation of glycine-induced currents by zinc and other metal cations in neurons acutely dissociated from the dorsal motor nucleus of the vagus of the rat.
Effects of Zn2+ and other polyvalent cations on glycine-induced currents in the freshly dissociated rat dorsal motor nucleus of the vagus neurons were investigated under voltage-clamp conditions by the use of the nystatin-perforated patch recording configuration. Glycine evoked a Cl- current in a concentration-dependent manner with a half-maximum effective concentration (EC50) of 3.3x10-5 M. Strychnine inhibited the 3x10-5 M glycine-induced current in a concentration-dependent manner with a half-maximal inhibitory concentration (IC50) of 6.8x10-7 M. At low concentrations (3x10-8 M-3x10-6 M), Zn2+ potentiated the current elicited by 3x10-5 M glycine. On the other hand, at concentrations higher than 10-5 M, Zn2+ inhibited the glycine response. The biphasic action of Zn2+ was mimicked by Ni2+, but La3+ and Co2+ had only potentiating effect. Zn2+ shifted the concentration-response curve for the glycine-induced current without changing the maximum response, and the EC50 values for the glycine response in the absence and presence of 10-6 M and 10-4 M Zn2+ were 3.3x10-5 M, 1.3x10-5 M and 1.3x10-4 M, respectively. These results suggest that the biphasic modulation of glycine response by Zn2+ results from changes in apparent glycine affinity.
Doi
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A
Department of Physiology, Faculty of Medicine, Kyushu University, Fukuoka 812-8582, Japan.
Kishimoto
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K
Ishibashi
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H
D000818:Animals; D002412:Cations / Q000494:pharmacology*; D018118:Chloride Channels / Q000187:drug effects; D005998:Glycine / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D009046:Motor Neurons / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D014630:Vagus Nerve / Q000187:drug effects*; D015032:Zinc / Q000494:pharmacology*
D002412:Cations; D018118:Chloride Channels; D015032:Zinc; D005998:Glycine