FUNCTIONAL EXPRESSION OF 2-AMINO-4-PHOSPHONOBUTYRATE (APB) RECEPTORS IN XENOPUS-LAEVIS OOCYTES BY INJECTION OF POLY(A)(+) RNA FROM QUAIL BRAIN

The glutamate analogue 2-amino-4-phosphonobutyrate (APB) is known to a ctivate a subtype of metabotropic glutamate receptor in the central ne rvous system, including the retina. In the present study, APB receptor s were studied using the Xenopus oocyte expression system. No endogeno us APB sensitivity was detected in control oocytes. In contrast, micro injection of mRNA, extracted from quail brain, into Xenopus oocytes re sulted in the functional expression of APB receptors after 3-5 days in cubation. Application of 50 mu M-1 mM APB to injected oocytes voltage clamped at a holding potential of -60 mV produced a sustained outward current which was associated with a significant decrease in membrane c onductance; the reversal potential was around -11 mV. The response to APB was dose-dependent and non-desensitizing. This is the first demons tration of the expression of a conductance-decreasing receptor mechani sm in Xenopus oocytes.