Acid-sensing ion channels(ASICs),the main H+receptors in the central nervous system,sense extracellular pH fluctuations and mediate cation influx.ASIC1a,the major subunit responsible for acid-activated current,is widely expressed in brain neurons,where it plays pivotal roles in diverse functions including synaptic transmission and plasticity.However,the underlying molecular mech-anisms for these functions remain mysterious.Using extracellular epitope tagging and a novel antibody recog-nizing the hASIC1a ectodomain,we examined the mem-brane targeting and dynamic trafficking of hASIC1a in cultured cortical neurons.Surface hASIC1a was distributed throughout somata and dendrites,clustered in spine heads,and co-localized with postsynaptic markers.By extracel-lular pHluorin tagging and fluorescence recovery after photobleaching,we detected movement of hASIC1a in synaptic spine heads.Single-particle tracking along with use of the anti-hASIC1a ectodomain antibody revealed long-distance migration and local movement of surface hASIC1a puncta on dendrites.Importantly,enhancing synaptic activity with brain-derived neurotrophic factor accelerated the trafficking and lateral mobility of hASIC1a.With this newly-developed toolbox,our data demonstrate the synaptic location and high dynamics of functionally-relevant hASIC1a on the surface of excitatory synapses,supporting its involvement in synaptic functions.