In another set of experiments, a morphine concentration-response curve was obtained in TG neurons isolated from the parent C57/BL6 line (i.e. not modified genetically). The data showed that the curves for 118AA and parent mice neurons were similar (data not shown). The IC50 (nM), maximum current inhibition (%, ± s.e.m.) and Hill coefficient (± s.e.m.) values were 99 [22 to 434], 50 ± 5.0 [37 to 62], and 1.23 ± 0.26 [-0.81 to 3.28], respectively (n = 4 to 19 neurons; 95% confidence intervals are in brackets). Statistical comparison of 118AA and parent wild-type neuron curve fits did not reach significance (P = 0.69). Thus, the TG neurons isolated from homozygous AA mice and the parent colony did not show detectable differences in the morphine-mediated Ca2+ current inhibition.
