Hydrogen Sulfide Regulates the [Ca²⁺]_i Level in the Primary Medullary Neurons

In the present study, we attempted to elucidate mechanisms for the regulation of intracellular calcium levels by H₂S in primary rat medullary neurons. Our results showed that NaHS significantly increased the level of [Ca²⁺]_i in rat medullary neurons in a concentration-dependent manner. L-Cysteine and SAM significantly raised the level of [Ca²⁺]_i in the medullary neurons while HA and/or AOAA produced a reversal effect. In addition, L-cysteine and SAM significantly increased but HA and/or AOAA decreased the production of H₂S in the cultured neurons. The [Ca²⁺]_i elevation induced by H₂S was significantly diminished by EGTA-Ca²⁺-free solutions, and this elevation was also reduced by nifedipine or nimodipine and mibefradil, suggesting the role of L-type and/or T-type Ca²⁺ channels. Moreover, the effect of H₂S on [Ca²⁺]_i level in neurons was significantly attenuated by BAPTA-AM and thapsigargin, suggesting the source of Ca²⁺. Therefore, we concluded that both exogenous and endogenous H₂S elevates [Ca²⁺]_i level in primarily cultured rat medullary neurons via both increasing calcium influx and mobilizing intracellular Ca²⁺ stores from ER.