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Neuronal application of capsaicin modulates somatic pressor reflexes
1Dept. of Physiology, University of South Alabama College of Medicine, Mobile, AL 36688, USA.
Summary
Capsaicin application to peripheral nerves differentially affects cardiovascular reflexes. It attenuates muscle contraction reflexes but enhances nociceptor-evoked cardiovascular responses, suggesting altered dorsal horn processing.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Pain Research
Background:
- Skeletal muscle contraction and noxious stimuli trigger cardiovascular reflexes.
- Dorsal horn spinothalamic cells are implicated in these reflexes.
- Capsaicin (Cap) is known to affect nociceptors.
Purpose of the Study:
- To investigate if capsaicin sensitizes dorsal horn cells involved in cardiovascular reflexes.
- To determine the effect of capsaicin on cardiovascular responses to static muscle contraction and nociception.
Main Methods:
- Cats underwent anesthesia and surgical exposure.
- Static muscle contraction was induced via tibial nerve stimulation.
- Nociceptors were stimulated using saphenous or tibial nerve stimulation.
- Capsaicin (3%) was applied to the common peroneal nerve.
- Reflex cardiovascular responses (mean arterial pressure) were measured before and after capsaicin application.
Main Results:
- Capsaicin application attenuated the increase in mean arterial pressure during static muscle contraction.
- Conversely, capsaicin enhanced the mean arterial pressure response to saphenous nerve (cutaneous nociceptor) stimulation.
- Capsaicin also increased the mean arterial pressure response to muscle nociceptor activation.
Conclusions:
- Capsaicin application to the common peroneal nerve differentially affects cardiovascular reflexes evoked by muscle contraction and nociception.
- These findings suggest a capsaicin-induced alteration in dorsal horn processing underlies the divergent effects on these reflexes.