On the electrotonic coupling mechanism of crayfish segmented axons: temperature dependence of junctional conductance.

It is generally accepted that the mechanism for electrotonic coupling involves the presence of hydrophilic channels connecting the cytoplasm of neighboring cells. These channels are presumed to be water filled holes. To test this hypothesis, we measured the temperature dependence of coupling parameters and calculated the specific resistance of junctional synapses of crayfish segmented axons. Results demonstrate that: (i) low temperature increases the junctional resistance in a manner that depends on the time course of cooling; (ii) the specific junctional resistance is, at most, 1-20 omega cm2. These results are consistent with a hypothesis of cell communication based on hydrophilic channels and suggest the presence of a temperature-dependent component of these channels.