Neuronal extension and glial supply: functional significance of glia.

Wang and Brown8 were the first to describe the terminal rebound and, except for the fact that it is seen after stimulation of purely muscular nerves, the present experiments confirm theirs in essence. It is agreed that afferent C fibers must be active for the effect to appear. Another condition seems to be that the C fiber reflex must fall during the course of the A fiber reflex; otherwise, the C fiber reflex is inhibited as in the last record of Figure 4. Wang and Brown8 discuss the terminal rebound effect in terms of inhibition of the C fiber reflex during the period of stimulation by activity of larger cold-receptive fibers. However, as here shown, the effect is present when stimulation is confined to muscular afferent fibers (Figure 4), which means at the least that it is not specifically related to the action of cold-receptive fibers. In the classical view, terminal rebound is a sign of concealed inhibition with excitatory effects outlasting the inhibitory to produce a response at the close of stimulation. As this seems the only explanation, it is probably correct to conclude, with Wang and Brown, that there exists an inhibitory reflex although one cannot specify the executant afferent pathway.