Autoregulation in the ocular and cerebral arteries during the cold pressor test and handgrip exercise

Area of Science:

• Ophthalmology
• Neurology
• Cardiovascular Physiology

Background:

• Ocular and cerebral vessels, both branching from the internal carotid artery, are crucial for blood supply.
• Understanding their autoregulation mechanisms is vital for managing conditions affecting vision and brain function.

Purpose of the Study:

• To investigate if autoregulation effects are similar in ocular (retinal, choroidal) and cerebral vessels.
• To compare the responses of ocular and cerebral blood flow during physiological stress (handgrip exercise and cold pressor test).

Main Methods:

• Measured ocular blood flow velocities (superior/inferior temporal retinal arterioles, retinal/choroidal vasculature) using laser speckle flowmetry.
• Measured middle cerebral artery mean blood flow velocity (MCAVmean) via transcranial Doppler ultrasound.
• Calculated conductance index (CI) and analyzed changes during resting, static handgrip exercise (HG), and cold pressor test (CPT) in 11 subjects.

Main Results:

• Cold pressor test (CPT) increased retinal and choroidal vasculature (RCV) blood flow velocity by 19% (P < 0.05), while middle cerebral artery (MCA) CI decreased.
• Handgrip exercise (HG) increased RCV, inferior temporal retinal arteriole (ITRA), and MCAVmean velocities (8-11%, P < 0.05), but not superior temporal retinal arteriole (STRA) flow.
• Autoregulation in RCV appeared impaired during CPT and HG, unlike MCAVmean which was maintained.

Conclusions:

• Cerebral blood flow autoregulation was maintained during CPT, but autoregulation in the retinal and choroidal vasculature was compromised.
• Static handgrip exercise similarly affected ocular and cerebral blood flow velocities, but not vascular conductance.
• Findings suggest differential autoregulatory responses between ocular and cerebral circulations under physiological stress.