The role of total flavone of Camellia on cerebrovascular vasopasm after subarachnoid hemorrhage in rats.

Background: This study was undertaken to explore the role of total flavones of Camellia (TFC) on the cerebrovascular dysfunction in rats after experimental subarachnoid hemorrhage (SAH). Materials and Methods: The contraction and dilation of cerebral basilar artery (BA), nitric oxide (NO) level, and nitric oxide synthase (NOS) activity in rat serum and the expression of endothelial NOS (eNOS) in cerebral vessels were measured. Furthermore, the effect of potassium channel blockers, endothelium removal, L-NG-nitroarginine methyl ester (L-NAME), or prostacyclin I₂ (PG I₂) production inhibitor on the response of isolated BA derived from normal rats was also evaluated to explore the underlying mechanism of vasodilation induced by total flavones. Results: The contraction of rat BA to U46619 markedly increased and the vasodilation to acetylcholine remarkably reduced after SAH. Interestingly, these vascular dysfunctions were profoundly ameliorated by pretreatment of TFC. Moreover, total flavones could induce a concentration-dependent relaxation in isolated BA from normal rats, which was obviously eliminated by co-application of potassium channel blockers, ChTx and Apamin, application of L-NAME, or endothelial removal. In addition, total flavones pretreatment obviously improved the expression of eNOS in BA, serum NO level, and NOS activity at 48 h after SAH. Conclusion: These findings revealed that TFC has protective effect on cerebrovascular dysfunction after SAH and demonstrated that the protection could be due to its upregulation of eNOS expression and activation of potassium channel. [ABSTRACT FROM AUTHOR]