Journal of neuroscience research
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The actions of nerve growth factor (NGF) are mediated by two receptor proteins, trk and p75. Recent evidence indicates that NGF upregulates the expression of both trk and p75 in responsive neurons including rat dorsal root ganglion (DRG) neurons. Axotomy by disconnecting the neuron from its source of target-derived NGF is predicted to lead to the downregulation of trk and p75 expression. ⋯ Similar changes are observed following nerve transection although mRNA levels are slower in returning to normal and do not exceed control levels at later timepoints. Thus, trk and p75 expression decline early following target disconnection and later recover irrespective of target reinnervation. These observations indicate that target derived NGF is required for the maintenance of NGF receptor expression in adult rat DRG neurons and that non-target derived factors can appropriate this function following peripheral nerve injury.