Physiological mechanisms for thirst in the nonhuman primate.
The relationship between body fluid deficits and drinking has been investigated in a nonhuman primate. Intravenous sodium chloride infusions (0.93-3.25 M) given to rhesus monkeys caused drinking correlated with increases in plasma osmolality and sodium concentrations. Sucrose infusions (0.3 M in 0.15 M NaCl) also caused drinking while equiosmolal urea infusions did not. It was found that the drinking threshold corresponded to a 2.3% increase in plasma osmolality. Water deprivation for 24 h caused significant cellular dehydration, as indicated by a 5.8% elevation in plasma osmolality that exceeded the threshold for thirst, and a significant hypovolemia as indicated by elevated plasma protein and hematocrit values. Intravenous water preloads decreased plasma osmolality and produced a dose-related decrease in subsequent drinking. Infusions that restored plasma osmolality to predeprivation values, reduced intake by 85%. Intravenous isotonic saline preloads which abolished the hypovolemia did not have a consistent effect and reduced mean water intakes by only 3.2%. Thus in the rhesus monkey, cellular dehydration is an effective stimulus for thirst, and it is the primary determinant of drinking after water deprivation, used as an example of a natural thirst stimulus. In contrast to findings in nonprimates, the extracellular deficit contributes very little to drinking after water deprivation.
D000818:Animals; D001696:Biomechanical Phenomena; D001826:Body Fluids / Q000502:physiology; D001834:Body Water / Q000502:physiology; D004056:Differential Threshold; D004326:Drinking / Q000187:drug effects; D007552:Isotonic Solutions; D008253:Macaca mulatta; D008297:Male; D012462:Saline Solution, Hypertonic / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D013894:Thirst / Q000502:physiology*; D014868:Water Deprivation / Q000502:physiology
D007552:Isotonic Solutions; D012462:Saline Solution, Hypertonic; D012965:Sodium Chloride