Sexual dimorphism in the vasopressin system: lack of an altered behavioral phenotype in female V1a receptor knockout mice.

Previous findings with an AVP V1a receptor knockout mouse (V1aRKO) demonstrate a significant role for this receptor in anxiety-like behavior in males. Here we report the lack of anxiety-like effects of the null mutation in female mice. V1aRKO females performed normally on all tests for anxiety-like behavior. This sex difference may be due to the sexual dimorphism in the extra-hypothalamic vasopressin system, with males having significantly more vasopressin fibers in this system.