Fig. 4. ( A ) Western blots labeled with anti-MOR1 of membrane (subscript M) and cytosolic (subscript C) fractions of dorsal horn neuron cultures untreated (C) and treated with 1 μm morphine (M1), 100 μm morphine (M100), or 1 μm DAMGO (D) for 7 days. The detected MOR1 protein was approximately 50 kd in size. The 57-kd marker is shown. ( B ) Surface expressions of MOR1 in dorsal horn neurons treated for 7 days with 1 μm DAMGO, 100 μm morphine, and 1 μm morphine were not significantly reduced. (One-way analysis of variance).