Salt appetite and the renin-angiotensin system: effect of oxytocin deficiency.
To explore the role of oxytocin in the regulation of salt appetite and blood pressure, we conducted studies in oxytocin gene-knockout mice and determined (1) blood pressure and heart rate during day and night periods, (2) salt appetite after iso-osmotic volume depletion, and (3) salt appetite and blood pressure after central injection of angiotensin II. Long-term arterial catheters were inserted, and blood pressure and heart rate were recorded for 24 hours. There was a modest decrease in blood pressure and heart rate in knockout mice. Salt appetite was measured with a 2- bottle choice (water and 2% NaCl), with measurement of licking activity. Mice were injected subcutaneously with 30% polyethylene glycol (0.5 mL), and voluntary intakes were measured for 24 hours. Knockout mice consumed 3 times the amount of NaCl than did controls, 276+/-77 vs 90+/-38 licks/24 h (P<0.05). Water consumption was similar between groups. Angiotensin II (5, 50, and 200 ng/3 microL) injected intracerebroventricularly produced dose-related increases in intake, with no differences between the groups. The 50-ng dose of angiotensin II elicited salt and water intakes of 151+/-43 vs 160+/-33 licks and 250+/-53 vs and 200+/-51 licks, respectively (control vs knockout). The pressor response to angiotensin II was not different between the groups. Results suggest that oxytocin plays a role in the regulation of blood pressure and salt appetite, specifically as mediated by volume receptors, and that the renin-angiotensin system is not involved in these changes.
Rigatto
Katya
K
Department of Physiology and Pharmacology, Federal University of Pelotas, Pelotas, Brazil.
Puryear
Robert
R
Bernatova
Iveta
I
Morris
Mariana
M
D000284:Administration, Oral; D000804:Angiotensin II / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001066:Appetite / Q000187:drug effects; D001794:Blood Pressure; D002552:Cerebral Ventricles; D004326:Drinking / Q000187:drug effects; D006339:Heart Rate; D020896:Hypovolemia / Q000139:chemically induced; D007267:Injections; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010121:Oxytocin / Q000235:genetics / Q000502:physiology*; D011092:Polyethylene Glycols / Q000633:toxicity; D012084:Renin-Angiotensin System; D012965:Sodium Chloride / Q000008:administration & dosage*
D000804:Angiotensin II; D011092:Polyethylene Glycols; D012965:Sodium Chloride; D010121:Oxytocin