An engineering study of the peristaltic drive of axonal flow.

By determination of the rheological flow curve of minute quantities of axoplasm drawn into a microcapillary tube connected to a high vacuum, extruded axoplasm was shown to behave as a pseudoplastic fluid with a viscosity of 10(6)-times that of water and without significant signs of time-dependent thixotropic or viscoelastic properties. A theoretical analysis of peristaltic pumping of such pseudoplastic fluids by sinusoidal surface waves was combined with experimental studies of a mechanical model designed to simulate peristaltic drive. The correlation of the respective data permitted quantitative predictions for the peristaltic mechanism of axonal flow, with speed being a function of peristaltic wave geometry and fluid properties, yielding a theoretical mean value of 0.45 mm/day, i.e., of the same order as that observed in the living nerve fiber.