Enables extracellularly ATP-gated cation channel activity. Acts upstream of or within several processes, including excitatory postsynaptic potential; nitric oxide biosynthetic process; and vasodilation. Located in apical part of cell. Is expressed in several structures, including cardiovascular system; gut; immune system; nervous system; and viscerocranium. Orthologous to human P2RX4 (purinergic receptor P2X 4). [provided by Alliance of Genome Resources, Apr 2022]