USE OF APLYSIA NEURONS FOR THE STUDY OF CELLULAR ALTERATIONS AND THE RESEALING OF TRANSECTED AXONS IN-VITRO

The present report describes the experimental advantages offered by th e combined use of Aplysia neurons and contemporary techniques to analy ze the cellular events associated with nerve injury in the form of axo tomy. The experiments were performed by transecting, under visual cont rol, the main axon of identified Aplysia neurons in primary culture wh ile monitoring several related parameters, We found that in cultured A plysia neurons axotomy leads to the elevation of the [Ca2+](i) in both the proximal and distal axonal segments from a resting level of 100 n M up to the millimolar range for a duration of 3-5 min. This increase in [Ca2+](i) led to identical alterations in the cytoarchitecture of t he proximal and distal segments. The formation of a membrane seal over the transected ends by their constriction and the subsequent fusion o f the membrane is a [Ca2+](i)-dependent process and is triggered by th e elevation of [Ca2+](i) to the mu M level. Seal formation was followe d by down-regulation of the [Ca2+](i) to control levels. Following the formation of the membrane seal an increase in membrane retrieval was observed. We hypothesize that the retrieved membrane serves as an imme diately available membrane reservoir for growth cone extension.