Effect of increased plasma osmolality on cold-induced thirst attenuation.

The effects of elevating plasma osmolality (P (osm)) on thirst ratings was studied in eight dehydrated males during exposure to 4 degrees C. On two occasions, subjects were dehydrated (DH; 3-4% body mass) via 90 min exercise-heat exposure and overnight fluid restriction (day 1). On a third occasion, subjects were exposed to heat but were given fluid (EU). On day 2, subjects consumed NaCl (NaCl; 0.1 g NaCl kg(-1) body mass in 500 ml H(2)O; DH only) or Placebo (P; 500 ml H(2)O; DH and EU). Subjects stood for 30 min at 24 degrees C and for 45 min at 4 degrees C (75 min post-dose). P (osm) was elevated (P < 0.05) 30 and 75 min after NaCl administration in DH + NaCl versus DH + P and EU + P treatments. Thirst ratings remained elevated (P < 0.05) in the DH + NaCl treatment 30 min after dosing and 45 min at 4 degrees C versus DH + P and EU + P. Attenuation of thirst when dehydrated in the cold can be over-ridden by increasing P (osm).