Enhanced excitability of gastric projection DRG neurons. A, Top: Example of a Dil-labeled DRG neuron (arrow). Asterisk indicates the place where a neuron is not labeled by DiI. Bottom: Phase image of the same DRG neuron labeled by DiI is shown on the left (arrow) and the neuron not labeled by DiI is shown on the right (*). Scale bar, 50 μm. Patch-clamp recordings were performed on DiI-labeled colon neurons. A total of 20 DiI-labeled neurons form CON rats and 17 DiI-labeled neurons from STZ-treated rats were recorded under current-clamp conditions. B, STZ injection significantly depolarized RPs of gastric projection DRG neurons (**p < 0.01 compared with CON, Mann–Whitney test). C, STZ injection did not significantly alter R_in compared with CON (STZ, n = 17, CON, n = 20, p > 0.05 compared with CON, Mann–Whitney test). D, STZ injection markedly reduced rheobase (**p < 0.01 compared with CON, 2-sample t test). E, STZ injection remarkably hyperpolarized AP threshold (**p < 0.01 compared with CON, Mann–Whitney test). F, G, STZ injection also greatly increased numbers of APs evoked by 2× and 3× rheobase current stimulation (*p < 0.05, **p < 0.01 compared with CON, Mann–Whitney test). H, Examples of APs by 300 and 500 pA ramp current injection from CON (top) and diabetic (bottom) rats. I, Bar graph showed a significant increase in numbers of APs evoked by 300 pA and 500 pA ramp current stimulation in STZ-injected rats (**p < 0.01 compared with CON, 2-sample t test).