Fig. 6.

Pretreatment with Saz-A eliminates the HS-phase of ACh-induced LSP function, and changes the EC₅₀ of LS-phase responses. X. laevis oocytes injected with unmodified HSP (squares) and LSP (circles) mRNA were exposed to acute ACh challenges (1 second, concentrations specified on the x axis; log M scale), before (filled symbols) and after (open symbols) pretreatment with Saz-A (3.16 nM, 5 minutes). All concentration-response data are normalized to the maximum response measured for each concentration series, in each oocyte (mean ± S.E.M., n = 8–12). For HSP α4β2-nAChRs, no change in ACh EC₅₀ value was seen after preincubation with Saz-A. For LSP α4β2-nAChRs, the HS-phase of the CRC (below approximately 10^−5.5 M) was abolished by preincubation with Saz-A, whereas the potency of the LS-phase response was reduced. Log EC₅₀ values for HS- and LS-phase responses, fractions of HS- versus LS-phase function, and statistical analyses are reported in Table 1.