The effect of PGF2 alpha on in vivo cerebral arteriolar diameter in cats and rats.

We compared the effect of topical application of PGF2 alpha on cerebral arterioles in cats and rats equipped with an acutely implanted cranial window. Arterial diameter was measured using a microscope and image splitting device. PGF2 alpha in a concentration ranging from 10(-7) to 10(-5) M had no effect on large (greater than or equal to 100 microns) or small (less than 100 microns) cat pial arterioles, but induced a dose dependent constriction of rat pial arterioles with a maximum constriction to 76% of control diameter. Dilation of cat large cerebral arterioles by topically applied PGE2 was not affected by simultaneous application of PGF2 alpha and PGE2 induced dilation of small arterioles was decreased 3% by PGF2 alpha. While we and others have previously shown that both cat and rat brain can synthesize PGF2 alpha, it appears that PGF2 alpha is not likely to normally be a major modulator of cerebral arteriolar resistance in all species.