Resection of sciatic nerve re-triggers central sprouting of A-fibre primary afferents in the rat

We have investigated whether nerve injury or target deprivation is responsi ble for the injury induced central sprouting of A-fibres. Cholera toxin B s ubunit conjugated horseradish peroxidase was used to trace the termination of A-fibre primary afferents. Transection of the sciatic nerve induces cent ral sprouting of sciatic myelinated A-fibre primary afferents into the spin al dorsal horn lamina II, which normally is the termination site of unmyeli nated C-fibre primary afferents. The sprouting A-fibre terminals withdrew f rom lamina II after six to eight months. A second cut to the previously sec tioned and ligated sciatic nerve re-triggered the central sprouting of A-fi bre primary afferents into the spinal dorsal horn lamina II, suggesting tha t nerve injury per se rather than the deprivation of target tissues is the cause of central sprouting of A-fibre primary afferents. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.