Preloads of water, but not isotonic saline, reduce drinking in domestic fowls.
Fowls were deprived of water for 2 or 6 hr, and then given graded intravenous (IV) injections of water or isotonic saline. With both levels of deprivation, water preloads caused dose-dependent reductions in water intake which matched closely the volumes of preload given, whereas isotonic saline preloads had no effect on drinking, and feeding was unaffected in both cases. These results imply that drinking elicited by short periods of water deprivation is a response to increased plasma osmolality rather than to a loss of extracellular fluid volume. In further experiments, water intakes were reduced by at least as much as the volume administered when undeprived fowls were given 6 hr continuous IV infusions or IV injections of water, and food intakes were also suppressed. Plasma analyses taken at the end of continuous infusions of water indicated a fall in osmolality during this time. It was concluded that whereas increases in plasma osmolality increase drinking in fowls, a fall in osmolality below normal inhibits both drinking and feeding. It is suggested that spontaneous drinking may be regulated mainly by changes in plasma osmolality, rather than in extracellular volume.
Yeomans
M R
MR
Department of Psychology, University of Edinburgh, Scotland.
Savory
C J
CJ
D000818:Animals; D002645:Chickens; D004326:Drinking / Q000187:drug effects; D005247:Feeding Behavior / Q000187:drug effects; D012965:Sodium Chloride / Q000494:pharmacology; D014868:Water Deprivation; D014882:Water-Electrolyte Balance / Q000187:drug effects
D012965:Sodium Chloride