Endothelium-dependent responses after experimental brain injury

Area of Science:

• Neuroscience
• Vascular Biology
• Traumatic Brain Injury

Background:

• Fluid percussion brain injury (FPBI) significantly impacts cerebrovascular function.
• Vasoactive agents like acetylcholine and serotonin have endothelium-dependent effects on cerebral blood vessels.
• Oxidative stress is implicated in the pathophysiology of brain injury.

Purpose of the Study:

• To investigate the effects of FPBI on the cerebrovascular responses to topical acetylcholine and serotonin.
• To determine the role of oxygen radicals, specifically hydroxyl radical, in mediating these altered responses.
• To assess the potential of antioxidant therapy in restoring normal vascular function post-brain injury.

Main Methods:

• Anesthetized cats with cranial windows were subjected to FPBI.
• Topical application of acetylcholine and serotonin was performed before and after injury.
• Administration of antioxidants (superoxide dismutase plus catalase, deferoxamine) was used to scavenge reactive oxygen species.

Main Results:

• Following FPBI, acetylcholine induced arteriolar constriction and abolished vasodilation in larger vessels.
• Serotonin responses shifted from vasoconstriction to vasodilation in small arterioles and were abolished in large arterioles post-injury.
• Antioxidant treatment restored normal vasodilator responses to acetylcholine and vasoconstrictor responses to serotonin.

Conclusions:

• FPBI eliminates endothelium-dependent vasodilation induced by acetylcholine via a mechanism involving oxygen radical generation, particularly hydroxyl radical.
• Oxygen radicals likely inactivate a vasoconstrictor factor, explaining the altered serotonin response after brain injury.
• Antioxidant interventions show promise in mitigating cerebrovascular dysfunction following traumatic brain injury.