Vasopressin differentially modulates noradrenaline release in the rat supraoptic nucleus.

Vasopressin is released not only from axon terminals in the neurohypophysis but also from soma/dendrite regions in the supraoptic nucleus. In order to investigate presynaptic roles of dendritically released vasopressin, we examined effects of local application of vasopressin upon noradrenaline release within the supraoptic nucleus by a microdialysis method. Noradrenaline release within the supraoptic nucleus was facilitated by local perfusion with high K+ or an NMDA receptor antagonist. Vasopressin augmented noradrenaline increase after high K+ but reduced it after an NMDA receptor antagonist, AP-5. The results suggest that dendritically released vasopressin modulates noradrenaline release within the supraoptic nucleus in a bimodal fashion.