Cerebrovascular responses to cold pressor test during static exercise in humans

Area of Science:

• Physiology
• Cardiovascular Science
• Neuroscience

Background:

• Sympathetic stimulation, such as the cold pressor test (CPT), can impact cerebral blood flow.
• The interplay between exercise and sympathetic nervous system activity on cerebrovascular regulation is not fully understood.

Purpose of the Study:

• To investigate how exercise modulates middle cerebral artery blood velocity (MCA V(mean)) and cerebrovascular conductance (CVCi) responses to sympathetic stimulation (CPT).

Main Methods:

• Eight healthy subjects underwent CPT, static handgrip exercise (HG) at 30% maximal voluntary contraction, and a combined condition (HG + CPT) in a counterbalanced order.
• Non-invasive measurements included blood pressure (BP), cardiac output (CO), end-tidal partial pressure of carbon dioxide (PETCO(2)), and MCA V(mean).
• Cerebrovascular conductance index (CVCi) was calculated.

Main Results:

• Blood pressure increased significantly during CPT, HG, and HG + CPT, with the greatest augmentation during HG + CPT.
• MCA V(mean) increased similarly during HG and HG + CPT but remained unchanged during CPT alone.
• CVCi decreased during HG and was significantly reduced by CPT. The CPT-induced reduction in CVCi was attenuated when combined with HG.

Conclusions:

• The cold pressor test reduces cerebral vascular conductance.
• Concurrent handgrip exercise attenuates this reduction in cerebrovascular conductance.
• This attenuation is crucial for maintaining middle cerebral artery blood velocity during combined sympathetic stimulation and exercise.