Vasodilator effects on canine basilar artery induced by intracisternal interleukin-1β

The effect of interleukin-1β (IL-1β) on a cerebral artery was investigated in anesthetized dogs. Intracisternal administration of IL-1β (0.03 and 0.3 μg) dilated the canine basilar artery in a dose-dependent manner, without affecting systemic blood pressure or heart rate. The increase in diameter induced by 0.3 μg of IL-1β was 28.4% ± 13.4% of control at 2 hours and was inhibited by 30 μg of the IL-1β receptor antagonist, zinc protoporphyrin (4.5% ± 13.5%, P < 0.05). Interleukin-1β did not affect the concentration of nitric oxide metabolites in CSF. However, there was an increase in the concentration of eicosanoids in CSF, and the elevation of 6- keto-PGF1(α) paralleled the vasodilation. Pretreatment with 30 μg of the selective inducible cyclooxygenase (COX-2) inhibitor NS-398 also inhibited the IL-1β-induced vasodilation significantly (5.9% ± 9.4% at 2 hours, P < 0.01). Western blot analysis revealed the expression of s 68-kD COX-2-like protein in basilar artery extracts. These findings suggest that the IL-1β- induced vasodilator effect is linked to the prostaglandin cascade, predominantly to prostaglandin I₂, by induction of COX-2, but not to the stimulation of nitric oxide metabolism.