A VI Vasopressin Receptor Antagonist Has Nonspecific Neurodepressant Actions in the Spinal Cord

In the present investigation, we injected d(CH2)5Tyr(Me)AVP, a specific VI vasopressin antagonist, into the intrathecal space of the spinal cord to determine whether spinal vasopressin-containing neurons contribute to the hemodynamic effects produced by stimulation of the paraventricular nucleus (PVN). The intrathecal antagonist reduced the cardiovascular effects of PVN stimulation, but also reduced the effects produced by stimulating 2 other brain sites which do not contain vasopressin cell bodies. In addition, intrathecal administration of the vasopressin antagonist had a similar effect in Brattleboro rats which do not produce vasopressin. In conscious rats with indwelling intrathecal catheters, the vasopressin antagonist produced reversible hindlimb paralysis. These data suggest that d(CH2)5Tyr(Me)AVP has nonspecific actions within the spinal cord not related to the blockade of vasopressin receptors.