Inward rectifier potassium channels are characterized by a greater tendency to allow potassium to flow into the cell rather than out of it (PubMed:36149965, PubMed:7590287, PubMed:9490857). Their voltage dependence is regulated by the concentration of extracellular potassium; as external potassium is raised, the voltage range of the channel opening shifts to more positive voltages (PubMed:7590287, PubMed:7696590). The inward rectification is mainly due to the blockage of outward current by internal magnesium (PubMed:9490857). Can be blocked by extracellular barium or cesium (PubMed:7590287, PubMed:7696590). Probably participates in establishing action potential waveform and excitability of neuronal and muscle tissues (PubMed:7590287, PubMed:7696590, PubMed:7840300). {ECO:0000269|PubMed:11371347, ECO:0000269|PubMed:15761194, ECO:0000269|PubMed:15922306, ECO:0000269|PubMed:16571646, ECO:0000269|PubMed:17324964, ECO:0000269|PubMed:36149965, ECO:0000269|PubMed:7590287, ECO:0000269|PubMed:7696590, ECO:0000269|PubMed:7840300, ECO:0000269|PubMed:8821791, ECO:0000269|PubMed:9490857, ECO:0000269|PubMed:9533862}. This is the function of ENSG00000123700 (KCNJ2, potassium inwardly rectifying channel subfamily J member 2).