Vasomotor Reactivity of the Spasm Model by the Polystyrene Latex Bead

ABSTRACT

OBJECTIVE: It has been reported that the presence of a pharmacologically inactive foreign substance, polystyrene latex bead, in subarachnoid space activates a non-specific immunological response and elicits arterial narrowing. In vivo study was undertaken to characterize vascular reactivity of bead-induced constriction. METHODS: The spasm models similar to that by subarachnoid blood injection were created by injection of bead(5 volume% or 10 volume %) into rabbit cisterna magna. The basilar artery was visualized using transclival exposure, and its diameter was monitored using videomicroscopy on day two after cisternal injection. Consequently, many kinds of vasodilators such as papaverine, endothelin receptor antagonist, nicardipine, H7, dibutyryl-c-AMP, 8-bromo-c-GMP, nitroglycerine, forskolin, calcitonin gene-related peptide, and cromakalim were topically applied to determine what vasodilators attenuate arterial constriction induced by bead in 31 rabbits. RESULTS: Injection of bead elicited an arterial constriction, reducing arterial diameter to 78.5% of resting tone in 5 volume% and 67.7% in 10 volume%. ATP-sensitive potassium channel activator, cromakalim, inhibited 5 volume% or 10 volume% bead induced constriction. This effect achieved statistical significance (p<0.05) at a concentration of 10nM. However, other vasodilators did not make a significant vasodilatation of bead induced constriction. CONCLUSION: These results suggest that inactivation of ATP-sensitive potassium channel by inflammation is possibly responsible for the polysytrene latex bead-induced vasospasm, and support the concept that targeting vascular potassium channels can be of benefit in preventing the development of vasospasm.