Proton-gated cation channel; it is activated by a drop of the extracellular pH and then becomes rapidly desensitized (By similarity). Has high selectivity for sodium ions and can also transport lithium ions with high efficiency (By similarity). Can also transport potassium ions, but with lower efficiency (By similarity). It is nearly impermeable to the larger rubidium and cesium ions (By similarity). Promotes synaptic vesicle fusion to positively regulate the release of dopamine at dopaminergic neuron synapses (PubMed:31494966). Homotrimer. Belongs to the amiloride-sensitive sodium channel (TC 1.A.6) family.