PROXIMO-DISTAL FLUID CONVECTION IN THE ENDONEURIAL SPACES OF PERIPHERAL NERVES, DEMONSTRATED BY COLORED AND RADIOACTIVE (ISOTOPE) TRACERS

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Abstract
In order to determine the direction of fluid shift in endoneurial spaces, marker substances were deposited between the nerve fibers in 420 limb nerves of rats and guinea pigs. Ca. 0.1 cu.mm. of substance was injected in soln. or in solid form. After periods ranging from less than 1 hr. to a few days, the distances to which the substance had spread up and down the nerve was detd. Injns. of India or Chinese ink (in 46 expts.) and of K4Fe(CN)6 (later precipitated to Prussian Blue) in 162 cases proved a distal shift in live nerve at a rate of from 1-3 mm. in the 1st hr. The distribution of injected radioactive isotopes (Na24Cl, Cu64Cl2), detd. with a Geiger-Muller counter (193 nerves), demonstrated a distal shift of the diffusion gradient at a rate of ca. 1 mm./hr. The shift may continue after stoppage of circulation and even in excised nerves although results with transected nerves were erratic. Expts. testing pick-up of radioactive substance by cut nerve ends, as well as the leaking of substance from such cuts, likewise suggested polar differences. The results indicate that endoneurial fluid moving proximo-distally serves as vehicle for the transport of the injected substances. The origin and fate of this fluid and the mode and motive force of its displacement down the nerve are unknown.

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