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-per forated hatch recording configuration. Glycine evoked a Cl- current in a co ncentration-dependent manner with a half-maximum effective concentration (E C50) of 3.3 x 10(-5) M. Strychnine inhibited the 3 x 10(-5) M glycine-induc ed current in a concentration-dependent manner with a half-maximal inhibito ry concentration (IC50) of 6.8 x 10(-7) M. At low concentrations (3 x 10(-8 ) M-3 x 10(-6) M), Zn2+ potentiated the current elicited by 3 x 10(-5) M gl ycine. On the other hand, at concentrations higher than 10(-5) M, Zn2+ inhi bited the glycine response. The biphasic action of Zn2+ was mimicked by Ni2 +, but La3+ and Co2+ had only potentiating effect. Zn2+ shifted the concent ration-response curve for the glycine-induced current without changing the maximum response, and the EC50 values for the glycine response in the absen ce and presence of 10(-6) M and 10(-4) M Zn2+ were 3.3 x 10(-5) M, 1.3 x 10 (-5) M and 1.3 x 10(-4) M, respectively. These results suggest that the bip hasic modulation of glycine response by Zn2+ results from changes in appare nt glycine affinity. (C) 1999 Elsevier Science B.V. All rights reserved.