Effects of xanomeline or carbachol pretreament on activation of PI hydrolysis by carbachol, oxotremorine, or xanomeline in CHO hM1 cells.

Cells were pretreated with 300 nM xanomeline or 10 µM carbachol for 1 h or 24 h at 37°C followed by washing and immediate use in the functional assay or for 1 h followed by washing and further incubation in the absence of free xanomeline for 23 h. Pretreated or untreated (control) cells were then incubated with increasing concentrations of carbachol, oxotremorine, or xanomeline at 37°C for 1 h and the accumulation of inositol phosphates was determined. Functional parameters were derived from computer-assisted non-linear regression analysis as described in the Methods, and are presented as mean ± S.E.M. of three to nine individual experiments conducted in triplicate.aNegative logarithm of the midpoint (potency) parameter.bMaximal response. Values are expressed as % maximal response elicited by carbachol in untreated cells (b1 24000±1800 dpm; b2 8300±900 dpm; b319000±1800 dpm).cControl, naïve cells were incubated with agonist.dNot applicable.*ANOVA followed by Dunnett’s post-test detected a significant difference (p50 or Emax between the pretreated groups compared with control.†Student’s t-test detected a significant difference (p50 or Emax between the pretreated groups compared with control.