TY - JOUR
T1 - Osmolality
T2 - A physiological long-term regulator of lumbar sympathetic nerve activity and arterial pressure
AU - Scrogin, Karie E.
AU - Grygielko, Eugene T.
AU - Brooks, Virginia L.
PY - 1999/6
Y1 - 1999/6
N2 - Acute infusion of hypertonic fluid increases mean arterial pressure (MAP) in part by elevating nonrenal sympathetic activity. However, it is not known whether chronic, physiological increases in osmolality also increase sympathetic activity. To test this hypothesis, MAP, heart rate (HR), and lumbar sympathetic nerve activity (LSNA) were measured in conscious, 48-h water-deprived rats (WD) during a progressive reduction in osmolality produced by a 2-h systemic infusion (0.12 ml/min) of 5% dextrose in water (5DW). Water deprivation significantly increased osmolality (308 ± 2 vs. 290 ± 2 mosmol/kgH2O, P < 0.001), HR (453 ± 7 vs. 421 ± 10 beats/min, P < 0.05), and LSNA (63.5 ± 1.8 vs. 51.9 ± 3.8% baroreflex maximum, P < 0.01). Two hours of 5DW infusion reduced osmolality (-15 ± 5 mosmol/kgH2O), LSNA (-23 ± 3% baseline), and MAP (-10 ± 1 mmHg). To evaluate the role of vasopressin in these changes, rats were pretreated with a V1-vasopressin receptor antagonist. The antagonist lowered MAP (-5 ± 1 mmHg) and elevated HR (32 ± 7 beats/min) and LSNA (11 ± 3% baseline) in WD (P < 0.05), but not in water-replete, rats. 5DW infusion had a similar cumulative effect on all variables in V1-blocked WD rats, but had no effect in water-replete rats. Infusion of the same volume of normal saline in WD rats did not change osmolality, LSNA or MAP. Together these data indicate that, in dehydrated rats, vasopressin supports MAP and suppresses LSNA and HR and that physiological changes in osmolality directly influence sympathetic activity and blood pressure independently of changes in vasopressin and blood volume.
AB - Acute infusion of hypertonic fluid increases mean arterial pressure (MAP) in part by elevating nonrenal sympathetic activity. However, it is not known whether chronic, physiological increases in osmolality also increase sympathetic activity. To test this hypothesis, MAP, heart rate (HR), and lumbar sympathetic nerve activity (LSNA) were measured in conscious, 48-h water-deprived rats (WD) during a progressive reduction in osmolality produced by a 2-h systemic infusion (0.12 ml/min) of 5% dextrose in water (5DW). Water deprivation significantly increased osmolality (308 ± 2 vs. 290 ± 2 mosmol/kgH2O, P < 0.001), HR (453 ± 7 vs. 421 ± 10 beats/min, P < 0.05), and LSNA (63.5 ± 1.8 vs. 51.9 ± 3.8% baroreflex maximum, P < 0.01). Two hours of 5DW infusion reduced osmolality (-15 ± 5 mosmol/kgH2O), LSNA (-23 ± 3% baseline), and MAP (-10 ± 1 mmHg). To evaluate the role of vasopressin in these changes, rats were pretreated with a V1-vasopressin receptor antagonist. The antagonist lowered MAP (-5 ± 1 mmHg) and elevated HR (32 ± 7 beats/min) and LSNA (11 ± 3% baseline) in WD (P < 0.05), but not in water-replete, rats. 5DW infusion had a similar cumulative effect on all variables in V1-blocked WD rats, but had no effect in water-replete rats. Infusion of the same volume of normal saline in WD rats did not change osmolality, LSNA or MAP. Together these data indicate that, in dehydrated rats, vasopressin supports MAP and suppresses LSNA and HR and that physiological changes in osmolality directly influence sympathetic activity and blood pressure independently of changes in vasopressin and blood volume.
KW - Conscious rats
KW - Heart rate
KW - Sodium chloride
KW - V-vasopressin antagonist
KW - Vasopressin
UR - http://www.scopus.com/inward/record.url?scp=0033039146&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033039146&partnerID=8YFLogxK
U2 - 10.1152/ajpregu.1999.276.6.r1579
DO - 10.1152/ajpregu.1999.276.6.r1579
M3 - Article
C2 - 10362734
AN - SCOPUS:0033039146
SN - 0363-6119
VL - 276
SP - R1579-R1586
JO - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
JF - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
IS - 6 45-6
ER -