AMINO-ACID RECEPTORS FROM INSECT MUSCLE - ELECTROPHYSIOLOGICAL CHARACTERIZATION IN XENOPUS OOCYTES FOLLOWING EXPRESSION BY INJECTION OF MESSENGER-RNA

Poly(A)+ messenger ribonucleic acid (mRNA) was extracted from leg muscles of the locust Schistocerca gregaria and injected into oocytes of Xenopus laevis. After 5-10 days incubation, receptors for l-glutamate, l-quisqualate, dl-ibotenate and γ-aminobutyric acid (GABA) were expressed. Agonist-induced currents were dose-dependent, and, in the concentration range 1 μM to 1 mM, generally had peak values of 50 nA. The responses to all agonists, apart from GABA, exhibited desensitization which could not be reversed even by prolonged washing with Ringer. Application of 100 μM GABA to oocytes voltage clamped at -60 mV produced a smooth inward current with a reversal potential of -22 ± 1 mV, which is consistent with the involvement of chloride ions. At 100 μM, picrotoxin reversibly abolished this current, while 100 μM bicuculline had no effect. l-Glutamate elicited a smooth current with a reversal potential of -52 ± 3 mV. l-Quisqualate elicited an inward current at -60 mV with a reversal potential of -9 ± 2 mV; this current occasionally had an oscillatory component. The response to ibotenate comprised a smooth inward current with a reversal potential of -21 ± 3 mV which was probably mediated by chloride ions. © 1990.