After-potential of Spinal Axons I N Vivo* by Donald O. Rudin~ and George Eisenman

This investigation is concerned with certain properties of the action potential in tracts of the central nervous system. During the course of other studies (16, 3) it became important to know the after-potential sequence of rapidly conducting tract fibers in the intact spinal cord. This paper presents a method for obtaining this information and evidence for the existence in dorsal column axons of an after-potential sequence which is significantly different from that of peripheral nerve A fibers. In succeeding papers (17) the role of the dorsal column after-potential in producing intramedullary and dorsal root current flows is examined. Study of these currents affords an experimental test of predictions which follow directly from the conclusions of the present paper on the form of the dorsal column after-potential. Finally in another paper (3) are presented for comparison the results of a direct examination of the afterpotential sequence of spinal funiculi in vitro. In addition, the findings of a general survey of the properties of spinal funiculi are presented there.