Figure 3.

Concentration-response relationships for ACh-, nicotine-, muscarine- and oxotremorine-induced peak current component. All responses were normalized to the peak current induced by 3×10⁻⁷ M ACh. Each point shows the average of 4 – 8 experiments, and vertical bars indicate mean±s.e.mean. The continuous theoretical curves for the response to nicotine, muscarine and oxotremorine-M were drawn according to the following equation: I=I_maxCⁿ/(Cⁿ+Kⁿ) where I is the observed agonist-induced current, I_max is the maximum current, C is the agonist concentration, n is the Hill coefficient, and K is the agonist concentration that evoked the half-maximal response. The curve for ACh response was drawn as sum of the two concentration-response curves according to the following equation: I=I_max1 Cⁿ¹/(^Cn1+K₁ⁿ¹)+I_max2Cⁿ²/(Cⁿ²+K₂ⁿ²) where Imax1 and Imax2 are the plateau amplitudes at lower and higher concentrations, and K₁ and K₂ are the agonist concentration (4.94×10⁻⁷ and 2.03×10⁻⁵ M, respectively) that evoked the half-maximal response of each current component, respectively.