Osmosensitive mechanisms contribute to the water drinking-induced pressor response in humans.
BACKGROUND
Water drinking elicits a sympathetically mediated pressor response in multiple-system atrophy patients through an unknown mechanism. We reasoned that gastrointestinal distention, hyposomotic stimulation, or both contribute to the water-induced pressor response.


METHODS
We compared the response to normal saline and water on blood pressure in 10 patients with probable multiple-system atrophy. Patients featured moderate to severe autonomic dysfunction. EKG and finger arterial blood pressure were recorded continuously, and 500 mL normal saline and distilled water were each given in a single-blinded fashion. Fluids were applied through a previously inserted nasogastric tube within a 5-minute period.


RESULTS
Blood pressure began to increase within 10 minutes after water administration and reached a maximum after 20 minutes. Blood pressure did not change after saline administration. The blood pressure change after 20 minutes was 8 +/- 9/2 +/- 5 mmHg with water and -1 +/- 11/-1 +/- 7 mmHg with normal saline administration (p = 0.02 between interventions). Heart rate did not change with either intervention.


CONCLUSIONS
Ingestion of water elicits a greater pressor response than the ingestion of normal saline. Thus, gastric distention is probably not the crucial mechanisms for the water-induced pressor response. Instead, the response may be mediated through osmosensitive afferent structures in the gastrointestinal tract, portal vein, and liver.
Lipp
A
A
Department of Neurology, Medical University Charité, Berlin, Germany.
Tank
J
J
Franke
G
G
Arnold
G
G
Luft
F C
FC
Jordan
J
J
D001342:Autonomic Nervous System Diseases / Q000503:physiopathology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D004326:Drinking; D041981:Gastrointestinal Tract / Q000294:innervation / Q000502:physiology; D006801:Humans; D008099:Liver / Q000294:innervation / Q000502:physiology; D008959:Models, Neurological; D019578:Multiple System Atrophy / Q000503:physiopathology*; D011169:Portal Vein / Q000294:innervation / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D017833:Visceral Afferents / Q000187:drug effects / Q000502:physiology; D014867:Water / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
D014867:Water; D012965:Sodium Chloride