A study of neuronal response to mechanical tension

Abstract

In this study, mechanical response features of neuronal cells subjected to tension are characterized using a home­built force apparatus. We find that axons, when subjected to increasing stress in a stepwise fashion, show nonlinear viscoelastic behaviour. We propose an explanation for this behaviour based on energy release following stress dependent dissociation of cytoskeletal crosslinkers, which would result in viscous dissipation. We do not observe this behaviour for fixed cells, when comparison is done on same cell before and after fixation. This observation is in favour of our hypothesis, since the crosslinker binding in fixed cells will be covalent. We are further testing the hypothesis by developing a model based on it, the predictions of which will be tested experimentally. Other response features studied include the axonal tension and net elastic constant, their variation with strain. Both are found to decrease with strain. Thus, we observe live axons to show strain weakening response when subjected to increasing stretch. The work establishes the use of a novel optical fibre based force apparatus for quantitative measurements on axons, which can be used in future to address diverse problems in axonal mechanics.