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 3.3 x 10-5 M. Strychnine inhibited the 3 x 10- 5 M glycine-induced current in a concentration-dependent manner with a half- maximal inhibitory 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 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 3.3 x 10-5 M, 1.3 x 10-5 M and 1.3 x 10-4 M, respectively. These results suggest that the biphasic modulation of glycine response by Zn2+ results from changes in apparent glycine affinity.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Clinical Neurology
- Developmental Biology