Septal vasopressin modulates motility and passive avoidance in pinealectomized rats.

Experiments were performed to investigate the role of central arginine vasopressin (AVP) in an interrelationship with the pineal gland on motility and passive avoidance response in rats. The involvement of the pineal gland in behavioral paradigms was examined using pinealectomized (PE) and pineal-intact (sham-operated and nonoperated) animals. Central administration of 200 pg AVP or 40 ng of the AVP receptor antagonist, d(CH2)sThyr(Et)VAVP (AAVP) was performed into the mediolateral septum by means of microdialysis probes. The blockade of vasopressinergic neurotransmission or neuromodulation into the septal area by AAVP decreased the motility in both pineal-intact groups, whereas AVP was without effect. In PE rats during AVP administration an increased motility was found, but AAVP was without effect. In pineal-intact rats the avoidance latency of passive avoidance retrieval was not influenced after application of both AVP and AAVP. However, an increase in avoidance latency was found both immediately and 24 h after AVP or AAVP administration into the septum of PE rats. The results support the hypothesis that septal AVP modulate motility and passive avoidance behavior and this modulation is influenced by the pineal gland.