What happens to mean arterial pressure when the nerves from all arterial baroreceptors (baroreceptors) are cut in an experimental animal?

Effect of Complete Baroreceptor Denervation on Mean Arterial Pressure

When all arterial baroreceptor nerves are cut in an experimental animal, mean arterial pressure does not show sustained elevation but exhibits dramatically increased variability around a similar average level compared to baseline.

Acute vs. Chronic Effects

The response to complete baroreceptor denervation follows a distinct temporal pattern:

Immediate Response (Seconds to Minutes)

• Acute baroreceptor denervation causes an immediate increase in mean arterial pressure due to loss of tonic inhibitory input on sympathetic nerve activity 1, 2.
• This demonstrates that baroreceptors are vitally important for short-term (seconds to minutes) blood pressure control 1.

Chronic Response (Days to Weeks)

• The long-term effect shows no sustained hypertension, with mean arterial pressure returning to near-baseline levels despite the absence of baroreceptor input 1, 2.
• However, blood pressure variability increases dramatically, with marked fluctuations throughout the day that were not present before denervation 1.
• This highly variable pattern persists chronically, representing the loss of moment-to-moment buffering capacity 2.

Mechanistic Understanding

The lack of sustained hypertension after complete denervation occurs because:

• Other long-term regulatory mechanisms compensate for the loss of baroreceptor input, including renal pressure-natriuresis and hormonal systems 2.
• The baroreceptor system appears designed primarily for short-term buffering rather than long-term pressure setting 1.
• Complete denervation may represent a different physiological state than chronic baroreceptor unloading, where some recent evidence suggests sustained pressure elevation can occur 1.

Clinical Caveat

Important distinction: While complete surgical denervation doesn't cause sustained hypertension, this finding has been debated for over 75 years and recent models of chronic baroreceptor unloading (rather than complete denervation) suggest the role in long-term pressure control may need reconsideration 1, 2.