Figure 6
From: Peripheral nerve injury sensitizes neonatal dorsal horn neurons to tumor necrosis factor-α
Intrinsic excitability of immature dorsal horn neurons is increased by TNFα under neuropathic conditions. (A) Example of current-clamp recording from an immature SDH neuron exhibiting a tonic pattern of AP discharge in response to direct current injections of increasing amplitude. (B) Incubation with TNFα significantly decreased the current intensity required to evoke AP firing (rheobase) in SDH cells following SNI (right; *p < 0.05 compared to SNI+Vehicle; two-way ANOVA) but not in sham-operated littermates (left). SNI alone did not significantly change rheobase levels. (C) Similarly, while the SNI itself failed to modulate AP threshold in SDH neurons, TNFα lowered AP threshold in the SNI group (right; *p < 0.05 compared to SNI+Vehicle; two-way ANOVA) but not following sham operations (left). (D) Plot of neuronal firing frequency as a function of the amount of injected current, demonstrating that there were no significant differences between groups in the mean number of APs discharged during the 1 second current injection. (E) TNFα increased the fraction of SDH neurons exhibiting the hyperpolarization-activated inward current (Ih) after nerve injury (p = 0.029; Chi-square test).