Transient increase in plasma catecholamines following hypertonic/hyperosmotic fluid administration in conscious rats

Plasma norepinephrine and epinephrine levels were monitored to determine possible alterations of the sympathetic nervous system caused by hypertonic fluid administration. Iv infusion (3.5 ml/kg, 1 min) of 7.5% NaCl/6% Hespan transiently increased both plasma norepinephrine and epinephrine levels to 197 +/- 28% and 220 +/- 30% of control, respectively, at 1 min. These increases were no longer significant 5 or 15 min following infusion. A brief hypotension was also observed immediately following hypertonic fluid administration. Thus, prolonged sympathetic activation does not occur following hypertonic fluid infusion in normovolemic conscious rats.