Not directly activated by nematocin (PubMed:23112336, PubMed:23112335). May modulate activity of the nematocin receptor ntr-1, leading to reduced intracellular cAMP production (PubMed:23112335). Plays a role in male mating behavior (PubMed:23112335). Detected in the ADL sensory neurons, the RMED and RMEV motor neurons, and the PQR tail neuron (PubMed:23112336). In males, detected in SPC tail neurons involved in spicule penetration and sperm transfer, and male-specific oblique muscles involved in vulval contact (PubMed:23112335). Viable and fertile. Males have reduced reproductive success, due to a range of aberrant mating behaviors. Double knockouts with ntr-1 partially rescue the reproductive phenotypes. Belongs to the G-protein coupled receptor 1 family. Vasopressin/oxytocin receptor subfamily.