Hypertonic saline solution (HTS) treatment of uncontrolled hemorrhagic shock (UCHS) in anesthetized animals leads to increased bleeding, fall in mean arterial pressure (MAP), and increased mortality. To rule out the effect of anesthetic drugs on this response, HTS infusion in UCHS was studied in awake rats. 24 h prior to the experiment, the animals were cannulated under neurolidal-ketalar anesthesia and two major branches of the ileo-colic artery were encircled with a silk suture. On the next day the awake animals were randomly divided into two groups: in group 1 (n = 16) controlled hemorrhagic shock (CHS) was induced by arterial bleeding of 20 mL/kg; in group 2 (n = 16) UCHS was induced by transcutaneous tear of two branches of the ileo-colic artery. The animals in each group were then divided into two subgroups: group A was untreated and group B was treated with 5 mL/kg 7.5% NaCl (HTS) after 10 min. Arterial bleeding in group 1A was followed by a fall in MAP to 63 +/- 2 mmHg (p < .001), and the hematocrit decreased to 37 +/- 3% (p < .01) in 10 min. Injury to two branches of the ileo-coli artery was followed by intra-abdominal bleeding, fall in MAP to 87 +/- 6 mmHg (p < .01), and a decrease in hematocrit to 32 +/- 2% (p < .01) in 10 min. Infusion of HTS in group 1B was followed by an increase in MAP to 84 +/- 4 mmHg (p < .01) and a fall in hematocrit to 22 +/- 2% (p < .01) after 60 min, while in the untreated group 1A, the MAP was 65 +/- 4 mmHg (p < .05).(ABSTRACT TRUNCATED AT 250 WORDS)