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Oxytocinergic regulation of cardiovascular function: studies in oxytocin-deficient mice
Lisete C Michelini1, Marialuisa C Marcelo, Janet Amico
1Department of Physiology and Biophysics, Biomedical Sciences Institute, University of Sao Paulo, Brazil.
Abstract:
Oxytocin (OT) has been implicated in the cardiovascular responses to exercise, stress, and baroreflex adjustments. Studies were conducted to determine the effect of genetic manipulation of the OT gene on blood pressure (BP), heart rate (HR), and autonomic/baroreflex function. OT knockout (OTKO -/-) and control +/+ mice were prepared with chronic arterial catheters. OTKO -/- mice exhibited a mild hypotension (102 +/- 3 vs. 110 +/- 3 mmHg). Sympathetic and vagal tone were tested using beta(1)-adrenergic and cholinergic blockade (atenolol and atropine). Magnitude of sympathetic and vagal tone to the heart and periphery was not significantly different between groups. However, there was an upward shift of sympathetic tone to higher HR values in OTKO -/- mice. This displacement combined with unchanged basal HR led to larger responses to cholinergic blockade (+77 +/- 25 vs. +5 +/- 15 beats/min, OTKO -/- vs. control +/+ group). There was also an increase in baroreflex gain (-13.1 +/- 2.5 vs. -4.1 +/- 1.2 beats x min(-1) x mmHg(-1), OTKO -/- vs. control +/+ group) over a smaller BP range. Results show that OTKO -/- mice are characterized by 1) hypotension, suggesting that OT is involved in tonic BP maintenance; 2) enhanced baroreflex gain over a small BP range, suggesting that OT extends the functional range of arterial baroreceptor reflex; and 3) shift in autonomic balance, indicating that OT reduces the sympathetic reserve.
Insights
Oxytocin gene knockout mice show lower blood pressure and altered autonomic balance. This suggests oxytocin is vital for maintaining blood pressure and regulating the baroreflex response.
Area of Science:
- Cardiovascular Physiology
- Neuroendocrinology
- Genetics
Background:
- Oxytocin (OT) influences cardiovascular responses to exercise, stress, and baroreflex adjustments.
- The role of the oxytocin gene in cardiovascular regulation remains incompletely understood.
Purpose of the Study:
- To investigate the impact of genetic oxytocin deficiency on blood pressure, heart rate, and autonomic/baroreflex function.
- To elucidate the function of the oxytocin gene in cardiovascular homeostasis.
Main Methods:
- Utilized oxytocin knockout (OTKO -/-) and control (+/+) mice with chronic arterial catheters.
- Assessed sympathetic and vagal tone via beta(1)-adrenergic and cholinergic blockade (atenolol and atropine).
- Analyzed blood pressure, heart rate, and baroreflex gain.
Main Results:
- OTKO -/- mice exhibited mild hypotension (102 +/- 3 vs. 110 +/- 3 mmHg).
- No significant difference in basal sympathetic and vagal tone magnitude, but an upward shift in sympathetic tone to higher HR values in OTKO -/- mice.
- Increased baroreflex gain over a smaller BP range in OTKO -/- mice (-13.1 +/- 2.5 vs. -4.1 +/- 1.2 beats x min(-1) x mmHg(-1)).
Conclusions:
- Oxytocin plays a role in tonic blood pressure maintenance.
- Oxytocin enhances the functional range of the arterial baroreceptor reflex.
- Oxytocin influences autonomic balance by modulating sympathetic reserve.