The osmoregulation of the arginine vasopressin (AVP) neuron system is so precise that only 1–2% increases in serum Na levels significantly stimulate its release as well as the transcription of AVP gene in the SON and PVN 1).

1)
Arima H, Kondo K, Kakiya S, Nagasaki H, Yokoi H, Yambe Y, et al. Rapid and sensitive vasopressin heteronuclear RNA responses to changes in plasma osmolality. J Neuroendocrinol, 1999; 11: 337–341.