Fluid temperature and volume dependence of the dissociated plasma epinephrine and norepinephrine response to drinking

The ingestion of cold fluids results in a rise in plasma norepinephrine (NE) and a fall in plasma epinephrine (E). To assess the relative roles of fluid volume and temperature in mediating this dissociated sympathetic response to drinking, NE and E levels were measured on 3 separate occasions in 10 men before and after ingestion of either 750 ml distilled water at 4 C, 750 ml at 25 C, or 150 ml at 4 C. An increase in plasma NE occurred after drinking 750 ml water at both 4 C and 25 C. Levels rose during ingestion of fluid and fell again when drinking was completed, consistent with a sympathetic response to deglutition. There was no change after 150 ml at 4 C. In contrast, plasma E fell after the men drank 750 ml water at 4 C, but it did not change after they drank 750 ml water at 25 C or 150 ml at 4 C. The fall was maximal 10 min after drinking was completed and levels remained depressed for a further 30 min. These findings suggest that the fall in E is temperature dependent and is a response to the presence of cold fluid in the stomach rather than to deglutition. We conclude that the dissociation of the plasma NE and E response after drinking cold fluids is therefore a result of independent and contrasting influences of, respectively, the volume and temperature of the fluid ingested.