Satiety and inhibition of vasopressin secretion after drinking in dehydrated dogs

The roles of oropharyngeal and gastric factors in satiation and arginine vasopressin (AVP) secretion were examined in water-deprived dogs. Dogs were prepared with chronic gastric fistulas and received six treatments after 24 h of water deprivation: rehydration with H2O or extracellular fluid (ECF) with the fistula closed; rehydration with H2O or ECF with the fistula open; gastric administration of H2O or ECF via the fistula. Drinking occurred immediately after presentation and was always completed by 6 min. At the end of the 60-min period of observation, water was offered in order to assess the degree of satiety. No differences were observed between the volumes of H2O or ECF consumed. However, only absorption of the water drunk produced complete satiety assessed 60 min later. Drinking H2O caused a fall in plasma AVP 6 min before a detectable decline in osmolality and reached water-replete levels by 15 min after drinking. Drinking H2O or ECF plus removal via the fistula and drinking ECF also brought about a rapid decline in plasma AVP without any change in plasma osmolality. Gastric administration of H2O caused a fall in plasma AVP that coincided with the fall in osmolality, and gastric administration of ECF had no effect on plasma AVP. We conclude that oropharyngeal factors account for temporary satiety and the rapid inhibition of vasopressin secretion.