Wave onset in central gray matter - its intrinsic optical signal and phase transitions in extracellular polymers

Anais da Academia Brasileira de Ciências

Vera M. Fernandes-de-lima²  JoÃo E. Kogler²  Jocelyn Bennaton¹  Wolfgang Hanke¹ 

[1] ,Universidade de São Paulo Escola Politécnica Laboratory of Integrated SystemsSão Paulo SP ,Brazil

关键词: intrinsic optic signals;    volume phase transitions;    polymers;    spreading depression;    central gray matter;    extracellular matrix;    sinais ópticos intrínsecos;    transição de fase volumétrica;    polímeros;    depressão alastrante;    substância cinzenta central;    matriz extracelular;   

DOI  :  10.1590/S0001-37652001000300006

来源: SciELO

【 摘 要 】

The brain is an excitable media in which excitation waves propagate at several scales of time and space. ''One-dimensional'' action potentials (millisecond scale) along the axon membrane, and spreading depression waves (seconds to minutes) at the three dimensions of the gray matter neuropil (complex of interacting membranes) are examples of excitation waves. In the retina, excitation waves have a prominent intrinsic optical signal (IOS). This optical signal is created by light scatter and has different components at the red and blue end of the spectrum. We could observe the wave onset in the retina, and measure the optical changes at the critical transition from quiescence to propagating wave. The results demonstrated the presence of fluctuations preceding propagation and suggested a phase transition. We have interpreted these results based on an extrapolation from Tasaki's experiments with action potentials and volume phase transitions of polymers. Thus, the scatter of red light appeared to be a volume phase transition in the extracellular matrix that was caused by the interactions between the cellular membrane cell coat and the extracellular sugar and protein complexes. If this hypothesis were correct, then forcing extracellular current flow should create a similar signal in another tissue, provided that this tissue was also transparent to light and with a similarly narrow extracellular space. This control tissue exists and it is the crystalline lens. We performed the experiments and confirmed the optical changes. Phase transitions in the extracellular polymers could be an important part of the long-range correlations found during wave propagation in central nervous tissue.

【 授权许可】

CC BY   
 All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License