FIG. 3.

CBS is localized to astrocytes and 3MST to neurons in the brain. There is a reciprocal interaction between neurons and astrocytes. Neuronal excitation induces Ca²⁺ influx in astrocytes, which in turn regulate synaptic activity. H₂S produced by CBS in astrocytes may be involved in the induction of Ca²⁺ waves, which propagate to surrounding astrocytes and contribute to the signaling between astrocytes. H₂S generated by CBS in astrocytes and by 3MST in neurons may be involved in enhancing the activity of NMDA receptors and the synaptic activity.