Due to the significant pharmacological shift of the morphine concentration responses in 118GG relative to 118AA neurons, we next measured the antinociceptive response to morphine in both humanized mouse lines. Morphine (3 mg/kg) was administered subcutaneously and the change in response latency was measured and converted to %MPE (Figure 5A) as described above (see Materials and Methods, page 9, second paragraph). In addition, the %MPE area under the curve was calculated to determine the extent and duration of morphine antinociception for both genotypes. The data depicted in Figure 5B show that 118AA mice had a significantly (P < 0.05) greater %MPE area under the curve when compared to 118GG. These results suggest that the 118GG carrying mice exhibited an impaired analgesic response with morphine.
