Decline in spontaneous activity of group Aalphabeta sensory afferents after sciatic nerve axotomy in rat

Changes are observed in the strength of central synaptic transmission and the firing behavior of primary afferents damaged by peripheral nerve injury. To clarify the relationship between synaptic strength and amount of spontaneous activity, firing behavior was studied in adult, male Sprague-Dawley rats in which sciatic nerve afferents were axotomized. Intra-axonal recordings were taken from Aalphabeta afferents within 7 h (acute, n = 309), at 3 days (n = 228), or at 10 days (n = 230) after sciatic nerve cut. The proportion of spontaneously discharging afferents fell from 22% in the acute group to < or = 13% in chronic groups. Thus, neither the progressive decline in the strength of central synaptic transmission from cut primary afferents nor the altered sensation observed after nerve cut can be explained by chronic changes in spontaneous activity of cut Aalpha/Abeta afferents.