Prostacyclin, indomethacin and the cerebral circulation

Abstract

The effect of intracarotid prostacyclin (PGI 2) on cerebral blood flow (CBF) was measured by the 133xenon intracarotid injection technique in 8 baboons. Intracarotid prostacyclin increased CBF by 22% at 10 −7 g/kg/min and by 71% at 5 × 10 −6 g/kg/min, accompanied by systemic hypotension and tachycardia. The effects of PGI 2 (10 −7 g/kg/min) were not potentiated by transient opening of the blood-brain barrier with the intracarotid hypertonic urea technique. At hypercapnia, the vasoconstrictor effect of indomethacin on the cerebral circulation was reversed by PGI 2. These results support our suggestion that a prostaglandin, in particular PGI 2, is required for hypercapnia to produce full cerebral vasodilatation. In separate experiments, following craniectomy in 5 cats, PGI 2, but not its stable metabolite 6-keto-PGF 1α, dilated pial arterioles when locally injected into the mock CSF overlying the arteriole.