Constitutive expression of the low-affinity neurotrophin receptor and changes during axotomy-induced death of sensory neurones in the neonatal rat dorsal root ganglion.

Sensory neurones in the dorsal root ganglion (DRG) of the neonatal rat express the 75-kDa low-affinity neurotrophin receptor (p75NTR) and these neurones degenerate rapidly after axotomy. p75NTR belongs to the tumour necrosis factor superfamily, several members of which have a role in cell death and it is constitutively expressed within a subpopulation of DRG neurones. p75NTR has been implicated in mediating the degeneration of these neurones after axotomy. In this study, we characterize the expression of p75NTR in sensory neurones of the newborn rat DRG using immunohistochemistry. Furthermore, we investigate the change in constitutive expression pattern of p75NTR in these neurones following axotomy. In the C7 and C8 DRG of the newborn rat, p75NTR is expressed in approximately 70% of DRG neurones. Those expressing p75NTR can be classified into subpopulations with moderate or intense p75NTR expression, each present in approximately equal proportions. Whilst p75NTR expression is observed in neurones throughout the entire neuronal diameter range, a correlation exists between neuronal diameter and p75NTR expression intensity. We also found that the most vulnerable population following axotomy were those sensory neurones which constitutively express the highest levels of p75NTR, i.e. the large-diameter neurones.