Figure 2.

Membrane currents from oocytes injected with a mixture of cDNAs (ratio 1:1) encoding the WT α₇ and L247T α₇ subunits. (A) AcCho dose–I_AcCho response relationship best fitted to Equation 1. The peak AcCho currents were normalized to that evoked by 5 mM AcCho (I_AcCho mean peak amplitude: −3.8 μA). Each point represents the mean ± SD (n = 6; four donors). Data fits to a function consisting of the sum of two or three Eq. 1 were not statistically different from the fit with a single Hill equation and minor number of parameters (F-distribution test; ref. 13). Data derived from six mixture-injected oocytes expressing mainly c, d, e, f, g or h type nAcChoRs (Table 1). Inset shows an example of I_AcCho blocked by α-BTX (100 nM) in one of the six oocytes examined. (B) Example of I_AcCho elicited by activation of mainly d type receptor population (see Table 1) and corresponding I–V relation. Note the inhibitory action of 5HT, the lack of response to 0.2 μM AcCho, and the slow desensitization. (C) Example of I_AcCho evoked by the activation of mainly c type receptor population. Note the lack of response to 0.2 μM AcCho, the outward I_AcCho at +20 mV (left), and the inward current elicited by 5HT. (D) Example of currents evoked by activation of a type nAcChoRs. Note a measurable I_AcCho at 0.2 μM AcCho and outward I_AcCho at +20 mV (left) with I_0.2/I₁₀₀ = 38%. (E) Superimposed currents (left) and lack of 5HT response in an oocyte that expressed a g type nAcChoR population. Note relatively small outward I_AcCho at +20 mV. (F) Another oocyte expressing type e nAcChoRs population. Note the fast desensitizing inward I_AcCho, outward I_AcCho at +20 mV (superimposed) with differences in the desensitization and the lack of response to 5HT (right). Bars, symbols and I–V curve, as Fig. 1. B, D, and E, oocytes from same donor; C and F, from two other donors. Note differences in the current desensitization at positive potentials in C–F.