Measurement of glycine receptor function by radioactive chloride uptake

The glycine receptor is an important inhibitory receptor for both spinal and supraspinal functions, and mutations in receptor subunits are responsible for neurological disorders in several species, including humans. However, functional measurements of glycine receptors have generally been restricted to electrophysiological analysis of immature, cultured neurons. We developed a 36Cl- flux assay to measure glycine receptor function using membrane vesicles from spinal cord and brainstem of adult mice. The uptake of 36Cl- stimulated by glycine was characterized by a glycine EC50 of 22 microM for the major component and an EC50 of 0.5 microM for a minor component. Strychnine inhibited the glycine-stimulated uptake with an IC50 of 0.4 microM. The uptake was not affected by picrotoxin, bicuculline, or pentobarbital. Glycine-stimulated uptake reached a maximum by 10 s. This technique should prove useful for genetic and pharmacological analysis of the function of glycine receptors.