Identification and Function of Glycine Receptors in Cultured Cerebellar Granule Cells

Poly(A) + mRNA was isolated from cultured mouse cerebellar granule cells and injected into Xenopus oocytes. This led to the expression of receptors that evoked large membrane currents in response to glycine. Current‐responses were also obtained after application of β‐alanine and taurine, but these were very low relative to that of glycine (maximal β‐alanine and taurine responses were 8 and 3% of that of glycine, respectively). The role of glycine receptors on K + ‐evoked transmitter release in cultured cerebellar granule cells was also assayed. Release of preloaded d ‐[ 3 H]aspartate evoked by 40 m M K + was dose dependently inhibited by glycine, and the concentration producing half‐maximal inhibition was 50 μ M. Taurine, β‐alanine, and the specific GABA A receptor agonist isoguvacine also inhibited K + ‐evoked release, and the maximal inhibition was similar for all agonists (˜40%). The EC 50 value was 200 μ M for taurine, 70 μ M for β‐alanine, and 4 μ M for isoguvacine. Bicuculline (150 μ M ) antagonized the inhibitory effect of isoguvacine (150 μ M ) but not that of glycine (1 m M ). In contrast, strychnine (20 μ M ) antagonized the inhibitory effect of glycine (1 m M ) but not that of isoguvacine (150 μ M ). The pharmacology of the responses to β‐alanine and taurine showed that these agonists activate both glycine and GABA A receptors. The results indicate that cultured cerebellar granule cells translate the gene for the glycine receptor and that activation of glycine receptors produces neuronal inhibition.