| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4345504 | Neuroscience Letters | 2011 | 5 Pages |
In animals, somatic stimulation of the limbs can evoke sympathetic reflexes of supraspinal origin. In addition, spinal reflexes can be elicited by stimulation of somatic tissues of the trunk. However, limited evidence is available concerning the specific modulation of sympathetic reflexes by afferents from the thoracic spine. This has also been largely overlooked in healthy humans. The aim of the present study was to determine whether tonic noxious heat (NH) applied to the skin over T3–T5 could segmentally increase supraspinal sympathetic reflexes (skin conductance responses – SCRs) induced by phasic electrical stimulation of the sural nerve. In addition, the effect of spinal manipulation (SM) on SCR amplitude and SCR amplification by NH was investigated. During the control session, palmar and plantar SCR amplitude was stable, showing no significant modulation. During NH and SM, however, palmar SCR amplitude was respectively increased and decreased in comparison to baseline, leading to a robust difference in SCR amplitude between the 2 conditions (p < 0.001). Moreover, these changes were also significantly and marginally different compared to the control session (p = 0.041 and p = 0.053, respectively). Interestingly, when applied immediately before NH, SM had a preventive effect on palmar SCR amplification induced by NH. In sharp contrast, changes in plantar SCRs were not significantly different between sessions (p = 0.42). Altogether, these results indicate that somatic stimulation of the thoracic spine may modulate somato-sympathetic reflexes segmentally in conscious, healthy volunteers.
Research highlights▶ Segmental modulation of sympathetic reflexes in humans has not been investigated. ▶ Here we evoked palmar and plantar skin conductance responses (SCRs). ▶ SCRs were conditioned by thoracic (T3–T5) noxious heat and spinal manipulation. ▶ Palmar but not plantar SCRs were significantly modulated by thoracic stimulation. ▶ This indicates that sympathetic reflexes may be modulated segmentally in humans.
