Figure 1.

Types of response in Aα/β-fiber dorsal root ganglion neurons to paired pulse stimulation to dorsal roots. (A) Recordings from a glabrous rapidly adapting neuron (left panel) and muscle spindle neuron (right panel) stimulated with paired pulses of variable interstimulus intervals. These responses represent the two types of response to paired pulse stimulation in Aα/β-fiber neurons. The fractionating response is characterized by variable amplitude and fractionation of the second AP as it begins to fail at shorter intervals, whereas the all-or-none response is characterized by an all-or-none response of the second AP. (B) Differential derivatives of the respective recordings in Figure 1A.

Notes: The sweeps before and after failure of the second AP are shown separately. Left panels represent differentiated recordings and corresponding measurements typical of the fractionating type of response, and also show the NM-spike and the S-spike components and their dynamics during paired stimuli. The right panels represent those for the all-or-none type of response, in which no fractionation of the second spike was observed and only the S-spike component was seen. Parameters 1–4 are measurements of the rise time and the maximum rising rate of the second spike and the residual AP; S1–S3 represent the number of the stimulus pair as they are brought together.

Abbreviations: AP, action potential; NM, nonmyelinated; S, somatic.