Glycine receptors belong to the family of fast ligand gated receptors. Glycine is a major inhibitory neurotransmitter that acts on postsynaptic glycine receptors located mainly in the spinal cord and brainstem.
Here, we used hGlyRα1-expressing L(tk)-cell which are activated by glycine. A positive modulator was tested at different concentrations and the recordings reveal a potentiated current activated by submaximal concentrations of Glycine.
Furthermore, strychnine was used as an example of an inhibitor. The receptors were first activated by 100 μM glycine and after washout inhibited by 1 μM strychnine plus 100 μM glycine. Repeating this set of experiments on the same cell show nicely the reproducibility of the data.

Ligand dependent activation of hGlyRα1. The Glyicine receptor hGlyRα1 expressend in LTK cells was characterized by the
application of increasing concentrations of glycine ranging from 10 μM to 1 mM (left). Between two concentrations of glycine the cell was washed two times with glycine free solution.  The right picture shows the Hill plot of normalized and averaged peak currents (n=8) for the determination of the EC₅₀-value for glycine activation of hGlyRα1-channels expressed in L(tk)-cells. Error bars are the standard error around the mean for each concentration. Cells were kindly provided by Astrazeneca, Södertälje, Sweden.

Positive modulation of the ligand dependent activation of hGlyRα1. Original traces of one application of 20 μM glycine followed by 6 applications of 20 μM glycine together with increasing concentrations of a positive modulator. 1 mM glycine was used as a second positive control. Cells and positive modulator were kindly provided by Astrazeneca, Södertälje, Sweden.

Inhibition of hGlyRα1-currents by Strychnine. In the above figure the traces are shown which have been recorded when 100 μM glycine was used to activate the Glycine receptor hGlyRα1. Glycine was removed and in the second application 100 μM glycine + 1 μM strychnine was applied. To see whether the responses were stable, the addition of glycine followed by the addition of glycine + strychine were repeated two times on the same cell.