A quantitative analysis of the glial cell reaction in primary sensory termination areas following sciatic nerve injury and treatment with nerve growth factor in the adult rat

The time course of the astroglial cell reaction in the nucleus gracilis and the spinal cord dorsal horn was examined following sciatic nerve transection in the adult rat with qualitative and quantitative analysis of glial fibrillary acidic protein immunoreactivity and in situ hybridization for its mRNA. In addition, the potential effect of exogenous nerve growth factor (NGF) was examined on the astroglial and microglial cells in the spinal cord dorsal horn at certain time points following sciatic nerve transection. An increase in glial fibrillary acidic protein immunoreactivity as well as mRNA labelling was observed from 1 day after lesioning, with a peak at about 1 week and 2 days after lesioning, respectively, followed by a decline. However, NGF application during 1, 2 and 4 weeks following nerve transection did not result in any significantly reduced astroglial or microglial activity. Our results show that the astroglial cell response in the nucleus gracilis and the spinal cord dorsal horn is rapid in comparison with previously described central degenerative changes following peripheral nerve lesions (transganglionic degeneration), that the astroglial cell reaction develops concomitantly with the microglial cell reaction previously described and that the "signal" from the axotomized neurons which induces these reactions can not be prevented by exogenous NGF applied to the peripheral nerve.