Responses to GABA, glycine and β-alanine induced in Xenopus oocytes by messenger RNA from chick and rat brain

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Abstract
Poly (A) + messenger RNA (mRNA) was extracted from rat and chick brains, and injected into oocytes of Xenopus laevis . This led to the expression of receptors that evoked membrane currents in response to γ -aminobutyric acid (GABA), glycine and β-alanine. These currents all inverted at about the chloride equilibrium potential in the oocyte, and showed a marked rectification at negative potentials. Oocytes injected with mRNA from chick optic lobe gave large responses to GABA and β-alanine, but small responses to glycine. In contrast, one fraction of mRNA from rat cerebral cortex (obtained by sucrose density gradient centrifugation) caused oocytes to develop sensitivity to GABA, glycine and β-alanine, whereas a different fraction induced sensitivity to glycine and β-alanine, but very little to GABA. The pharmacological properties of the three amino acid responses also differed. Barbiturate and benzodiazepines potentiated the responses to GABA and β-alanine, but not to glycine. Strychnine reduced the responses to glycine and β-alanine, but not to GABA, whereas bicuculline reduced the responses to GABA and β-alanine, but not to glycine. We conclude that different species of mRNA code for receptors to GABA and glycine, and possibly also for separate β-alanine receptors.