PERIPHERAL REGENERATION AND CENTRAL SPROUTING OF SENSORY NEURON AXONSIN APLYSIA-CALIFORNICA FOLLOWING NERVE INJURY

Morphological methods were used to examine injury-induced growth of pe ripheral and central axons of nociceptive mechanosensory neurones in t he ventrocaudal (VC) dusters of the pleural ganglia of Aplysia califor nica. Pedal nerve crush transected all axons in the nerve while leavin g the overlying sheath largely intact. Immunohistochemical staining wa s performed with an antibody to a sensory-neurone-specific peptide, se nsorin-A. Following bilateral crush of pedal nerve p9, which innervate s the tail, sensorin-A immunofluorescence was lost distal to the crush site within 2 days. Fine immunopositive fibres began to invade the cr ush region within 5 days. These fibres arborized in the crush region a nd gradually extended down the crushed nerve. Immunopositive fibres we re found near the tail within 3 weeks. Similar results were obtained a fter injecting individual sensory neurone somata in the tail/p9 region of the VC cluster with biocytin. Biocytin injections and horseradish peroxidase injections 3 weeks after ipsilateral pedal nerve crush reve aled new fibres projecting rostrally from the tail/p9 region of the VC cluster and entering the pleural-cerebral and pleural-abdominal conne ctives. Such projections were never observed in control, uncrushed pre parations. These results demonstrate that nerve injury triggers extens ive growth of both peripheral and central processes of the VC sensory neurones.