Depletion of GDNF from primary afferents in adult rat dorsal horn following peripheral axotomy

Glial cell line-derived neurotrophic factor (GDNF) is produced in a subset of adult rat spinal ganglion neurons and anterogradely transported to the superficial dorsal horn. In this study the effect of sciatic nerve axotomy on the expression of GDNF protein in the dorsal horn was investigated, using immunocytochemistry. Image analysis showed a 44% decrease relative to the non-transected side after 5 days survival, progressing to more than 80% decrease after 10 days and remaining so for at least 100 days. This rapid and strong decrease suggests active down-regulation of GDNF protein after peripheral axotomy. The observed down-regulation of GDNF is compared with changes observed for other substances in primary afferents after peripheral axotomy and is discussed in light of its presumed trophic or transmitter role in nociception.