Vasopressin administration modulates anxiety-related behavior in rats

Experiments were performed to measure the influence of centrally and peripherally applied arginine vasopressin (AVP) on anxiety-related behavior as indicated by the elevated plus maze test. Central administration was performed into the septum using a microdialysis technique. In initial experiments, the microdialysis probes were characterized for substance application in vivo by means of 125I AVP, measuring the substance-specific percent passover and the spatial distribution around the microdialysis membrane within the brain. Both microdialysis administration of 200 pg of AVP into the septum and and intraperitoneal application of 500 ng of AVP induced an increase in the percentage of time spent on the open arms of the elevated plus maze. The blockade of vasopressinergic neurotransmission or neuromodulation into the septal area by 40 ng of the AVP receptor antagonist d(CH2)5Thyr(Et)VAVP failed to induce a significant effect in this respect. The observation that neither centrally nor peripherally applied AVP influenced the locomotor activity on the elevated plus maze supports the hypothesis that AVP is involved in the modulation of anxiety-related behavior in rats.