Decline in spontaneous activity of group A alpha beta sensory afferents after sciatic nerve axotomy in rat

Changes are observed in the strength of central synaptic transmission and t he firing behavior of primary afferents damaged by peripheral nerve injury. To clarify the relationship between synaptic strength and amount of sponta neous activity, firing behavior was studied in adult, male Sprague-Dawley r ats in which sciatic nerve afferents were axotomized. Intra-axonal recordin gs were taken from A alpha beta afferents with in 7 h (acute, n = 309), at 3 days (n = 228), or at 10 days (n = 230) after sciatic nerve cut. The prop ortion of spontaneously discharging afferents fell from 22% in the acute gr oup to less than or equal to 13% in chronic groups. Thus, neither the progr essive decline in the strength of central synaptic transmission from cut pr imary afferents nor the altered sensation observed after nerve cut can be e xplained by chronic changes in spontaneous activity of cut A alpha/A beta a fferents. (C) 1999 Elsevier Science ireland Ltd. All rights reserved.