It is now widely recognized that there is a sexual dimorphism in the development of arginine vasopressin (AVP) immunoreactivity in certain parts of the brain, and that changes in brain A immunoreactivity change with manipulation of androgen status. The aim of this experiment was determine specifically any AVP receptor changes in response to manipulation of androgen levels using selective V1 antagonist radioligand. Following castration, plasma testosterone levels fell and A immunoreactivity was reduced in the lateral septum and bed nucleus of the stria terminalis. W testosterone supplementation in castrated animals, the immunoreactivity in these regions was restored to a higher degree than in sham-operated animals. Central and peripheral V1 AVP receptor binding determined using the selective AVP V1 antagonist radioligand [125I](d(CH2)(5),sarcosine7)Avp was changed in any of the brain regions studied or in liver or kidney membranes from the three groups. T study demonstrates that there is no change in brain AVP receptor binding despite changes in regional AVP immunoreactivity in the brain, and excludes any confounding interaction with changes oxytocin receptors.