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Effects of Transcranial Direct Current Stimulation on Hemodynamic Responses to Pain

Painful (noxious) stimuli cause increases in heart rate blood pressure, and peripheral vascular resistance. This response is due to a both direct nociceptive reflex responses and conscious pain perception. Transcranial direct current stimulation (tDCS) is effective in modulating pain perception threshold in healthy volunteers and thus might be used to dissociate afferent (skin pain receptors) and efferent (cortical pain perception) components in the response to pain. We examined systemic (heart rate and blood pressure) and regional (calf blood flow/resistance) responses to cold pressor tests at 14, 7, and 0 °C before and after tDCS (active and sham) in 15 volunteers. All hemodynamic responses were graded with temperature (14<7<0 °C, P<0.05). tDCS reduced the perceived pain score, but only at 14 °C (P<0.05). This coincided with a slight reduction in peak heart rate response of ~1–2 beats. However, aside from this, tDCS had no effect on hemodynamic responses. Hence, tDCS may alter the pain perception threshold but this has minimal impact on nociceptive activation of cardiovascular centers.