Experimental vasoconstriction of cerebral arteries by prostaglandins

Abstract

✓ Effects of intracarotid infusion of prostaglandins (PG) E1 and F2a on the circulation to the dog brain were examined by fluorescein angiography, by measuring diameter changes in the epicerebral vessels, and by measuring microregional cerebral blood flow with 133xenon and lithium-drift silicon detectors. PGE1 at doses of 0.5 µg/min constricted the epicerebral arteries 700 µ or less in diameter, arrested fluorescein dye injected into the carotid system, and reduced rCBF by 42% with increase of collateral flow to the brain by the vertebrobasilar system. This effect was not obtained by PGE1 to which 0.08% ethanol had been added. PGF2a at doses of 25 µg/min constricted epicerebral arterial vessels less than 200 µ in diameter, reduced rCBF by 35%, and decreased fluorescein dye in the cortical microcirculation with lengthening of the cerebral circulation time. Selective clipping of external and internal carotid arteries indicated that PGE1 acts by constricting these vessels as well as the epicerebral arteries. Since prostaglandins are released from platelets as well as from stimulation of the cerebral cortex they should be considered as factors involved in the regulation of cerebral blood flow and in the mechanism of cerebral vasospasm. These properties of PGE1 and PGF2a also imply the need for caution when these substances are used for clinical investigation.