Progressive Increase in Renal Sympathetic Nerve Activity Induced by Cold Exposure

Area of Science:

• Cardiovascular Physiology
• Environmental Medicine
• Neuroscience

Background:

• Cold environments can trigger hypertension by activating sympathetic nerve activity (SNA) and impairing the baroreceptor reflex.
• Direct measurement of SNA and baroreflex control during cold-induced hypertension is not well understood.

Purpose of the Study:

• To directly measure sympathetic nerve activity (SNA) during cold-induced hypertension.
• To investigate changes in baroreflex control of SNA in response to cold exposure.

Main Methods:

• Rats were exposed to cold (10°C) for 4 days, with simultaneous measurement of renal and lumbar sympathetic nerve activity (SNA).
• Baroreflex curves for SNA and heart rate were generated by manipulating arterial pressure with vasoactive drugs.

Main Results:

• Renal SNA (RSNA) increased progressively during cold exposure and remained elevated afterward, indicating cumulative effects.
• Cold exposure elevated the maximum capacity for renal sympathetic drive, with a rightward and upward shift in the RSNA baroreflex curve.
• Lumbar SNA, heart rate, and arterial pressure increased during cold but returned to baseline after exposure ended.

Conclusions:

• Cold exposure induces time-dependent, cumulative effects on renal SNA, increasing its maximum drive capacity.
• A self-activating pathway for RSNA, initiated by cold exposure, contributes to cold-induced hypertension.
• While lumbar SNA and heart rate effects were reversible, sustained changes in RSNA suggest a persistent mechanism for cold-induced hypertension.