NaHS enhanced neuronal excitability. (A) NMD significantly decreased the rheobase comparing with CON. n=28 cells for CON, n=41 cells for NMD. **P<0.01. Similarly, NaHS application significantly decreased the rheobase comparing with PRE. n=13 cells, **P<0.01. (B) NMD failed to change AP threshold compared with control. n=41 and 27 cells for NMD and CON, respectively. However, NaHS application markedly hyperpolarized AP thresholds. n=13,*P<0.05. (C) Representative traces of APs were induced by 300 ms depolarizing current pulses at 2 times and 3 times rheobase in DiI labeled neurons from control and NMD rats (far two left traces) and DiI labeled neurons from healthy control rats before and after NaHS application (far two right traces) under current-clamp conditions. (D) Bar graph showing that NMD treatment significantly increased average number of APs elicited by a 2 or 3 times rheobase current injection of DiI neurons compared with controls (left). n=25 and 21 cells for CON in 2 times and 3 times rheobase stimuli, respectively, n=40 and 36 cells for NMD in 2 times and 3 times rheobase stimuli, respectively. *P<0.05. Similarly, application of NaHS remarkably increased the number of APs evoked by 2 and 3 times current stimulation (right). n=13 cells for each group in 2 times rheobase stimuli, n=9 cells for each group in 3 times rheobase stimuli. *P<0.05, **P<0.01.