Cold pressor-induced sympathetic activation blunts the femoral but not carotid artery vascular responsiveness.

Abstract

Vascular responsiveness due to passive leg movement (PLM) on the brain remains unknown. This study aimed to evaluate the effects of cold-induced sympathetic activation (CPT) on femoral and ipsilateral and contralateral carotid arteries' vascular responsiveness evoked by PLM. Thirteen participants (seven males and six females; age: 27.0 ± 2.3 years) undertook a randomized session in which PLM was performed on the right leg at rest and during CPT. Right femoral (fBF) and right (ipsilateral) and left (contralateral) carotid (cBF) blood flows were measured by ultrasounds, and heart hemodynamics were assessed via photoplethysmography and impedance cardiograph. Systolic arterial pressure (SAP) time series were used to infer sympathetic modulation to the vessels. Femoral (fVC) and carotid (cVC) vascular conductance (BF/MAP) were calculated. CPT evoked changes in PLM on cBF, fBF, and fVC (interaction and time effect). cBF peak and cBF and cVC area under the curve were higher in the contralateral carotid in the two interventions. Low-frequency power of SAP was higher in PLM-CPT than in PLM; all p < 0.05. These results suggest that the CPT-induced increases in sympathetic modulation attenuate the vascular responsiveness in the femoral, but not the carotid, arteries. Also, the contralateral carotid increased blood flow during PLM, regardless of the CPT.