Fig 3. Inhibition of ACh-evoked current at α7-nAChR expressed in X. laevis oocytes by rSLURP-1.

(A). Electrophysiological recordings of α7 nAChR inhibition by 13 μM rSLURP-1. Currents were obtained in response to 20 seconds 100 μM ACh pulses (horizontal bars). Inhibition of current amplitude was observed after 5 min pre-incubation with 13 μM rSLURP-1. Vertical bar represents current scale (500 nA). (B). Dose-response curve of 1 mM acetylcholine-evoked current by rSLURP-1. Each point is mean ± S.E. of independent measurements on three oocytes. The Hill equation (Eq 1) was fitted to normalized data (% of control) for each of the three experiments independently. After averaging the following values for IC₅₀, nH and A1 were obtained 1.1 ± 0.5 μM, 1.4 ± 0.3 and 31 ± 3% (mean ± S.E., n = 3). (C). Dependence of 5 μM rSLURP-1 effect at α7-nAChR on ACh concentration. Data of rSLURP-1 induced inhibition is shown by filled squares, 5 μM ws-Lynx1 effect on 1 mM ACh is shown by circle. Asterisks indicate significant (p<0.05, t-test) difference from receptor inhibition by rSLURP-1 at 1 μM ACh (6 on plot). (D). Dose-response curves of acetylcholine-evoked current amplitudes in the absence (dotted line, empty circles) and presence (solid line, filled circles) of 1 μM rSLURP-1. The calculated parameters EC₅₀ and nH were 232 ± 25 μM and 1.9 ± 0.3 in absence of rSLURP-1, and 214 ± 60 μM and 2.2 ± 0.3 in presence of rSLURP-1 (mean ± S.E., n = 3).