Enhanced baroreflex sensitivity in free-moving calponin knockout mice

Area of Science:

• Cardiovascular Physiology
• Smooth Muscle Biology
• Autonomic Nervous System Regulation

Background:

• Calponin is an actin-binding protein in vascular smooth muscle, influencing contractile responses.
• The precise role of calponin in regulating mean arterial pressure (MAP) remains unclear.

Purpose of the Study:

• To investigate the role of calponin in mean arterial pressure (MAP) regulation.
• To assess the impact of calponin deficiency on heart rate (HR) and MAP dynamics.
• To elucidate the mechanisms underlying altered autonomic control in calponin knockout mice.

Main Methods:

• Measurement of MAP and HR in free-moving calponin knockout (KO) and wild-type (WT) mice over three days.
• Analysis of spontaneous changes in HR and MAP, including baroreflex sensitivity (BRS).
• Assessment of MAP responses to pharmacological challenges (phenylephrine and sodium nitroprusside) and effects of carotid sinus denervation.

Main Results:

• KO mice exhibited significantly lower mean HR during rest but similar MAP compared to WT mice.
• KO mice displayed increased HR variability and twofold higher spontaneous BRS, with MAP maintained within a narrow range.
• Pharmacological BRS and MAP responses to phenylephrine were blunted in KO mice, while responses to sodium nitroprusside were unaffected.
• Carotid sinus denervation abolished differences in HR variability and spontaneous BRS between KO and WT mice.

Conclusions:

• Increased spontaneous arterial baroreflex sensitivity in calponin knockout mice drives higher HR variability.
• This heightened BRS appears to be a compensatory adaptation to blunted peripheral vascular responses to sympathetic stimulation.
• Calponin plays a significant role in modulating autonomic cardiovascular control, particularly through its influence on baroreflex pathways.