Limb-specific muscle sympathetic nerve activity responses to the cold pressor test

Area of Science:

• Physiology
• Autonomic Nervous System
• Cardiovascular Regulation

Background:

• Muscle sympathetic nerve activity (MSNA) responses to isometric exercise show limb-dependent variations.
• It remains unclear if the cold pressor test (CPT), a common physiological stressor, also elicits differential MSNA responses based on limb involvement.

Purpose of the Study:

• To investigate whether CPT-induced MSNA responses differ between the stimulated (affected) and non-stimulated (unaffected) limbs.
• To test the hypothesis that MSNA is greater in the stimulated lower limb compared to the contralateral lower limb and the upper limb.

Main Methods:

• Integrated peroneal MSNA was measured using microneurography in 10 healthy young adults.
• Participants underwent three separate 3-minute CPTs involving immersion of the microneurography foot, the opposite foot, or the opposite hand.
• Peak MSNA and mean arterial pressure (MAP) were recorded and analyzed.

Main Results:

• MSNA responses were significantly higher when the microneurography foot was immersed compared to the opposite foot (38 vs 28 bursts/100hb, P < 0.01).
• MSNA responses were greater during hand immersion than both foot immersions (46 vs 38 and 28 bursts/100hb, P < 0.01).
• MAP responses were also elevated during hand CPT compared to foot CPT (99 vs 96 mmHg, P < 0.01).

Conclusions:

• CPT-induced MSNA responses are limb-dependent.
• Upper limbs and immersed limbs elicit greater sympathetic nerve activity responses compared to lower and/or non-immersed limbs.
• These findings contribute to understanding the neurovascular control during cold stress.