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Nonuniform sympathetic nerve responses after sustained elevation in arterial pressure
D E Claassen1, D A Morgan, T Hirai
1Department of Anatomy and Physiology, Kansas State University, Manhattan 66506, USA.
The American Journal of Physiology
|November 1, 1996
Summary
Sustained increases in blood pressure cause varied changes in sympathetic nerve activity across different organs after pressure normalizes. This study reveals regional differences in nerve response recovery in spontaneously hypertensive rats.
Area of Science:
- Cardiovascular Physiology
- Neuroscience
- Renal Physiology
Background:
- Sympathetic nerve activity (SNA) is crucial for regulating blood pressure.
- Hypertension is associated with altered SNA.
- Understanding regional SNA is vital for managing cardiovascular diseases.
Purpose of the Study:
- To investigate regional differences in sympathetic nerve discharges (SND) after normalizing elevated mean arterial pressure (MAP).
- To determine if baroreceptor reflex is solely responsible for post-stimulus sympathoinhibition.
Main Methods:
- Measurements of renal, adrenal, splanchnic, and lumbar SND in alpha-chloralose-anesthetized spontaneously hypertensive (SH) rats.
- Phenylephrine (PE) infusion to elevate MAP for 30 minutes.
- Recordings during and after PE infusion, including sinoaortic denervation and aortic depressor nerve (ADN) activity monitoring.
Main Results:
- SND remained reduced post-PE infusion despite MAP returning to control levels.
- Post-stimulus sympathoinhibition duration was shorter in adrenal and splanchnic SND compared to renal and lumbar SND.
- In denervated rats, SND remained at control levels during and after PE infusion.
- Prolonged renal and lumbar sympathoinhibition persisted even when ADN activity decreased below control levels.
Conclusions:
- Post-stimulus efferent SND responses in SH rats are regionally nonuniform.
- Renal and lumbar sympathoinhibition are not solely mediated by sustained increases in afferent baroreceptor nerve activity.