FIGURE 4.

Functional expression of concatenated α₄β₂δ receptors in Xenopus oocytes. For comparison, the top line shows the classical subunit arrangements of αβγ and αβ receptors. Nine pentamers with different subunit arrangements were built, as indicated under “Results.” Pentamers were either composed of concatenated subunits, or these were combined loose subunits (R1-R9). Also, two pentameric constructs (P1 and P5) were built. The figure shows subunit composition and current amplitudes (in nanoamperes) elicited by 1 mm GABA in the presence of 1 μm THDOC (mean ± S.E.) and, in some cases, EC₅₀ for GABA/THDOC (mean ± S.D.). n, number of oocytes; −, not analyzed. a, this subunit configuration might also assemble into R3. b, this subunit configuration might also assemble into R2. c, this subunit configuration might also assemble into R5. The receptor configurations shown in red contain one concatenated subunit resulting in current expression by itself.