Figure 2. The photomicrographs of the lumbar cord illustrating the differential distribution of immunoreactive Fos neurons in the dorsal horn with (A) injection of formalin alone, (B) control group (no formalin and no lidocaine), (C) lidocaine given before formalin, and (D) lidocaine given after formalin injection. The most prominent changes in Fos expression were observed in laminae I and II of the dorsal horn. The image is magnified x250 its original size, and images are oriented with the superficial layer of the spinal dorsal horn to the left of each photomicrograph.