Demonstration of retrogradely transported endogenous nerve growth factor in axons of sympathetic neurons

The presence of retrogradely transported endogenous nerve growth factor (NGF) in sympathetic nerves of the guinea pig was demonstrated directly by fluorescent and peroxidase immunohistochemistry in the ligated superior postganglionic nerve of the superior cervical ganglion. Fixed, frozen sections of previously ligated nerve were incubated with either rabbit antiserum against guinea pig NGF (gpNGF), rabbit antibodies against gpNGF purified on a mouse NGF (mNGF) affinity column, the portion of rabbit antiserum against gpNGF that did not bind to the mNGF affinity column, or nonimmune rabbit serum. Positive staining on the peripheral side of the ligation was obtained only with unfractionated antiserum against gpNGF and with purified antibodies against gpNGF. The staining properties of the various antiserum preparations correlated with their ability to block gpNGF- and mNGF-induced neurite outgrowth in the embryonic chick dorsal root ganglion bioassay and in the PC12 bioassay. Homogenates of superior postganglionic nerve supported growth of embryonic chick dorsal root ganglia and differentiation of PC12 cells. This support was blocked by the specific antisera against NGF used in the immunohistochemistry experiments. These experiments demonstrate that endogenous NGF, presumably released by peripheral target tissues, is retrogradely transported in vivo.