Studies show that H2S protects PC12 cells (neurocytes derived from pheochromocytoma of adrenal medulla of rat) [16] and hippocampal slices [17] against oxidative damage and toxicity by regulating BDNF-TrkB pathway, suggesting a close association of H2S and BDNF-TrkB pathway in CNS. The gene discussed is NTRK2; the disease is hereditary pheochromocytoma-paraganglioma.