Reversal of neuronal hyperexcitability by the CBS inhibitor AOAA. A, Administration of AOAA (i.p., 5 mg/kg once daily for consecutive 7 d) markedly hyperpolarized RP (AOAA, n = 18, NS, n = 19, *p < 0.05 compared with NS, 2-sample t test). B, AOAA treatment did not significantly alter R_in compared with CON (AOAA, n = 18, NS, n = 19, p > 0.05 compared with NS, Mann–Whitney test). C, Administration of AOAA remarkably increased rheobase (AOAA, n = 18, NS, n = 19, *p < 0.05 compared with NS, Mann–Whitney test). D, AOAA treatment significantly increased AP threshold (AOAA, n = 18; NS, n = 19, *p < 0.05 compared with NS, 2-sample t test). E, F, AOAA treatment also greatly reduced numbers of AP evoked by 2× and 3× rheobase current stimulation (AOAA, n = 18, NS, n = 19, *p < 0.05, Mann–Whitney test). G, Examples of APs by 300 pA and 500 pA current injection from AOAA and NS-treated rats. H, Bar graph showed a significant decrease in numbers of APs evoked by 300 and 500 pA ramp stimulation in AOAA-treated diabetic rats (AOAA, n = 15, NS, n = 18, **p < 0.01 compared with NS, Mann–Whitney test).