In vivo ANTI-NGF induces sprouting of sensory axons in dorsal roots

Authors

  • C. E. Hulsebosch,

    1. Departments of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston, Texas 77550-2772
    2. Marine Biomedical Institute, University of Texas Medical Branch, Galveston, Texas 77550-2772
    Search for more papers by this author
  • J. R. Perez-Polo,

    1. Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, Texas 77550-2772
    Search for more papers by this author
  • R. E. Coggeshall

    1. Departments of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston, Texas 77550-2772
    2. Departments of Biophysics and Physiology, University of Texas Medical Branch, Galveston, Texas 77550-2772
    3. Marine Biomedical Institute, University of Texas Medical Branch, Galveston, Texas 77550-2772
    Search for more papers by this author

Abstract

Newborn rats were given subcutaneous injections of antibodies to mouse β -NGF (ANTI-NGF) daily for 1 month. The number of neurons in T4-T6 dorsal root ganglia (DRG) and the numbers of myelinated and unmyelinated axons in the dorsal roots of the same segments were counted in the ANTI-NGF animals and in normal littermates. The ANTI-NGF rats had 38% fewer neurons in thoracic ganglia but 17% more myelinated and 40% more unmyelinated fibers than their untreated littermates. Dorsal root ganglion cells also have a larger average size in the ANTI-NGF animals, which we interpret as a disproportionate loss of small cells. These data are interpreted as showing that some dorsal root ganglion cells, principally small ones, die when endogenous NGF is inactivated, and that the remaining cells emit more processes than normal. Thus, removal of NGF has what appears to be a paradoxical effect, a reduction in dorsal root ganglion cell numbers but an increase in dorsal root axon numbers. The relation of myelin thickness to fiber diameter is also altered, with small fibers being more thinly myelinated in the ANTI-NGF group. Thus, Schwann cell-neuronal interactions are also affected by inactivation of NGF.

Ancillary