Interactions between vasoconstrictors in isolated human cerebral arteries

Area of Science:

• Neuroscience
• Vascular Biology
• Pharmacology

Background:

• Cerebral vasospasm, a dangerous narrowing of brain arteries, can occur after bleeding (subarachnoid hemorrhage).
• The role of combined actions of naturally occurring substances that constrict blood vessels (vasoconstrictors) in causing vasospasm is not fully understood.

Purpose of the Study:

• To investigate if different endogenous vasoconstrictors work together (synergistically) to cause contractions in isolated human cerebral arteries.
• To explore the potential role of these synergistic effects in the development of cerebral vasospasm.

Main Methods:

• Human pial arteries were isolated and mounted on a wire myograph.
• Concentration-response curves for 5-hydroxytryptamine (5-HT) were measured alone and in the presence of threshold concentrations of thromboxane A2 analog (U46619) and endothelin-1 (ET-1).
• The effects of vasoconstrictors were assessed before, during, and after washout, and correlated with endothelium-dependent relaxation.

Main Results:

• U46619 and ET-1 significantly enhanced the contractile response to 5-HT.
• These potentiated responses persisted even after the removal (washout) of U46619 and ET-1.
• The potentiation of 5-HT's effect was independent of endothelial function.

Conclusions:

• Synergistic interactions occur between vasoconstrictors like 5-HT, U46619, and ET-1 in human cerebral arteries.
• These potent and persistent synergistic effects, independent of the endothelium, likely contribute to the pathogenesis of cerebral vasospasm following subarachnoid hemorrhage.