The difference in temporal distribution of c-Fos immunoreactive neurons between the medullary dorsal horn and the trigeminal subnucleus oralis in therat following experimental tooth movement

The difference in temporal distribution of c-fos-immunoreactivity (Fos-IR) was assessed in the medullary dorsal horn (MDH) and in the dorsomedial part of the trigeminal subnucleus oralis (Vodm) following experimental tooth mo vement of the rat maxillary molars. The number of MDH c-Fos-immunoreactive neurons increased bilaterally at 2 h and decreased markedly by 12 h, and th en increased again with a small peak at 48 h. In contrast, Vodm c-Fos expre ssion was not up-regulated until 12 h, but increased in number after 24 h, which increase lasted until 72 h. These findings indicate that experimental tooth movement induced nociceptive c-Fos response in a biphasic manner. Fu rthermore, the later response appeared after 24 h, and lasted for a few day s, mainly manifested in the Vodm during experimental tooth movement. (C) 20 00 Elsevier Science Ireland Ltd. All rights reserved.