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Ascending spinal pathways for the somatosympathetic A and C reflexes
The American Journal of Physiology
|September 11, 1979
Summary
Stimulating different nerve fibers in cats reveals distinct spinal pathways controlling sympathetic activity. A-fiber stimulation causes a net decrease, while C-fiber stimulation leads to a net increase in sympathetic nerve activity.
Area of Science:
- Neuroscience
- Physiology
Background:
- Sympathetic nerve activity is crucial for regulating cardiovascular function.
- Understanding the neural pathways that modulate sympathetic outflow is essential for treating autonomic disorders.
Purpose of the Study:
- To elucidate the specific spinal pathways involved in mediating somatosympathetic reflexes elicited by A and C afferent fiber stimulation.
- To determine the net effect of A and C fiber activation on overall sympathetic nerve activity.
Main Methods:
- Recording sympathetic unit nerve activity from the cervical sympathetic trunk in anesthetized cats.
- Applying electrical stimulation to the common peroneal nerve to selectively activate afferent A or C fibers.
- Utilizing targeted spinal cord lesions in the dorsolateral sulcus (DLS) and dorsolateral funiculus (DLF) to identify ascending pathways.
Main Results:
- Lesions in the DLS eliminated the sympathetic C reflex.
- Lesions in the DLF abolished the somatosympathetic A reflex and influenced the duration of the silent period.
- A-fiber activation resulted in a net decrease in sympathetic activity, while C-fiber activation led to a net increase.
Conclusions:
- Ascending pathways in the DLF and DLS differentially mediate somatosympathetic reflexes.
- A-fiber activation involves DLF and DLS pathways, causing a net decrease in sympathetic activity.
- C-fiber activation primarily involves the DLS pathway, resulting in a net increase in sympathetic activity.