Figure 3.

RgIA4 selectively blocks mouse α9α10 nAChRs. nAChRs were expressed in Xenopus laevis oocytes. (A) The concentration response curves for α9α10 and α7 are shown. The IC₅₀ for α9α10 was 1.2 (0.95–1.6) nM with a Hill slope of 1.6 (0.91–2.2). The IC₅₀ for α7 was 4.5 (3.1–6.4) μM with a Hill slope of 2.0 (0.84–3.2). The values in parenthesis denote the 95% confidence intervals; n = 3–7 for each condition. (B) Recovery from toxin block of α9α10 is relatively slow. Example trace of block by 33 nM RgIA4. Recovery after 15 min toxin washout was ~2%. Arrows indicate application of 10 μM ACh. (C) At all other indicated nAChR subtypes, RgIA4 (10 μM) blocked less than 50% of the ACh-evoked response; the percent of the ACh-response for each subtype was α1β1δϵ, 95.0 ± 3.8; α1β1δγ, 86.2 ± 3.8; α3β2, 106 ± 2.9; α3β4, 105 ± 0.7; α4β2, 102 ± 3.3; α4β4, 74.3 ± 3.0. n = 3–4 for each condition; ± is S.E.M. Example traces for α4β2, α3β4, and α3β2 are shown. Results are summarized in Table 1.