Topical arachidonic acid restores pial arteriolar dilation to hypercapnia of postischemic newborn pig brain.

In the newborn pig, cerebral vasodilator responses to hypercapnia are lost after cerebral ischemia. We examined the effect of topical application of arachidonic acid (30 micrograms/ml, 20 min) to the postischemic piglet brain on subsequent pial arteriolar dilated in response to hypercapnia (10% CO2 ventilation) and topical isoproterenol (10(-6), 10(-7) M). After 20 min cerebral ischemia, pial arterioles did not dilate to hypercapnia but responded to isoproterenol in a fashion similar to before ischemia. Treatment with arachidonic acid after ischemia restored pial arteriolar dilation to hypercapnia. Hypercapnia caused an increase in cortical periarachnoid concentration of 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) before but not after ischemia. After postischemic treatment with arachidonic acid, the increase in cortical periarachnoid fluid 6-keto-PGF1 alpha during hypercapnia was restored. Therefore, topical application of arachidonic acid to cerebral vessels restores cerebral prostanoid synthesis and pial arteriolar dilation in response to hypercapnia that has been abolished by ischemia.