Increased osmolality of conscious water-deprived rats supports arterial pressure and sympathetic activity via a brain action.
To test the hypothesis that high osmolality acts in the brain to chronically support mean arterial pressure (MAP) and lumbar sympathetic nerve activity (LSNA), the osmolality of blood perfusing the brain was reduced in conscious water-deprived and water-replete rats by infusion of hypotonic fluid via bilateral nonoccluding intracarotid catheters. In water-deprived rats, the intracarotid hypotonic infusion, estimated to lower osmolality by approximately 2%, decreased MAP by 9+/-1 mmHg and LSNA to 86+/-7% of control; heart increased by 25+/-8 beats per minute (bpm) (all P<0.05). MAP, LSNA, and heart rate did not change when the hypotonic fluid was infused intravenously. The intracarotid hypotonic fluid infusion was also ineffective in water-replete rats. Prior treatment with a V1 vasopressin antagonist did not alter the subsequent hypotensive and tachycardic effects of intracarotid hypotonic fluid infusion in water-deprived rats. In summary, acute decreases in osmolality of the carotid blood of water-deprived, but not water-replete, rats decreases MAP and LSNA and increases heart rate. These data support the hypothesis that the elevated osmolality induced by water deprivation acts via a region perfused by the carotid arteries, presumably the brain, to tonically increase MAP and LSNA and suppress heart rate.
Brooks
Virginia L
VL
Dept. of Physiology and Pharmacology, L-334, Oregon Health & Science Univ., 3181 SW Sam Jackson Park Rd., Portland, OR 97239, USA. brooksv@ohsu.edu
Qi
Yue
Y
O'Donaughy
Theresa L
TL
D000818:Animals; D001790:Blood Physiological Phenomena; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D007038:Hypotonic Solutions / Q000494:pharmacology; D008297:Male; D009994:Osmolar Concentration; D051381:Rats; D017207:Rats, Sprague-Dawley; D013564:Sympathetic Nervous System / Q000502:physiology*; D013997:Time Factors; D014868:Water Deprivation / Q000502:physiology*; D014882:Water-Electrolyte Balance
D007038:Hypotonic Solutions