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Interindividual differences in sympathetic and effector responses to arousal in humans
Vincenzo Donadio1, Tomas Karlsson, Mikael Elam
1Unit of Clinical Neurophysiology, Institute of Clinical Neuroscience, Sahlgren University Hospital, Göteborg S-413 45, Sweden.
The Journal of Physiology
|October 3, 2002
Summary
Repeated surprising sensory stimuli can reduce muscle sympathetic nerve activity (MSNA) in some individuals, suggesting an arousal mechanism. This inhibitory response shows habituation and is reproducible, but varies significantly between people.
Area of Science:
- Neuroscience
- Human Physiology
- Autonomic Nervous System
Background:
- Surprising sensory stimuli can transiently reduce muscle sympathetic nerve activity (MSNA) in some individuals.
- This effect is hypothesized to be mediated by arousal mechanisms.
- Previous studies indicated that a single stimulus could elicit this response.
Purpose of the Study:
- To investigate the habituation of MSNA inhibition in response to repeated sensory stimuli.
- To determine if the presence or absence of this inhibitory response is reproducible.
- To explore the role of arousal in sensory-induced MSNA modulation.
Main Methods:
- Recorded peroneal MSNA, ECG, finger blood pressure, and skin electrical resistance in 17 healthy subjects.
- Delivered five electrical stimuli to a finger, triggered by ECG R-waves.
- Used dummy stimuli as controls and repeated experiments to assess reproducibility.
Main Results:
- On a group level, stimuli attenuated initial and late MSNA bursts.
- Eight subjects showed significant inhibition of initial MSNA bursts; nine did not.
- The inhibitory effect was reproducible in 11 out of 12 subjects, with interindividual differences noted.
Conclusions:
- Repeated electrical stimuli induce rapid habituation of MSNA inhibition, supporting an arousal-induced effect.
- Significant interindividual differences in inhibitory responsiveness exist and are reproducible over time.
- Absence of MSNA inhibition was associated with a transient increase in blood pressure, unlike in inhibited subjects.