Expression of functional AChRs from *C. elegans* in *X. laevis* oocytes. (*A*) A single oocyte coinjected with the 8 cRNAs *unc-29*, *unc-38*, *unc-63*, *lev-1*, *lev-8*, *ric-3*, *unc-50*, and *unc-74* displays large inward currents elicited by ACh (100 μM) or levamisole (Lev, 100 μM) but not by nicotine (Nic, 100 μM). (*B*) Coexpression of 5 receptor subunits (black squares) and 3 ancillary factors (gray squares) is mandatory for robust expression of the L-AChR. Currents were measured at the peak. Average peak current for coinjection of all 8 cRNAs was 4.1 ± 3.7 μA (*n* = 49). (*C*) A single oocyte coinjected with the *acr-16* and *ric-3* cRNAs displays large transient inward currents elicited by ACh (500 μM) or nicotine (500 μM), but not by levamisole (500 μM). (*D*) Functional expression of the homopentameric ACR-16 nicotine-sensitive AChR requires the ancillary factor RIC-3 but not UNC-50 or UNC-74. Currents were measured at the peak. Average peak current for coinjection of *acr-16* and *ric-3* cRNAs was 6 ± 4.2 μA (*n* = 33). All recordings were made with 1 mM external CaCl_{2}. Numbers above bars represent the number of oocytes recorded for each condition.

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