Acid-sensitive ion channels (ASICs) are a family of ligand-gated channels that permit Na* influx in response to H. The tarantula toxin, psalmotoxin 1 (PcTXI), inhibits some ASICs. A researcher exposes four different ASIC family members in vivo to PCTXI at a concentration of 10 nM and takes electrophysiological recordings. Changing the pH from 7.4 to the pH indicated on each recording opens the channel. The black bar above each recording shows when PCTXI was present, after which time the researcher rapidly washed the taxin from the system.