Binds to isotocin. Can also be activated by vasotocin, mesotocin, oxytocin and Arg-vasopressin, although these have lower potencies than isotocin. Produces an induction of membrane chloride currents indicating that it is coupled to the inositol phosphate/calcium pathway. Expressed in brain, intestine, bladder, skeletal muscle, lateral line, gills and kidney. Belongs to the G-protein coupled receptor 1 family. Vasopressin/oxytocin receptor subfamily.