Magnesium is a cerebrovasodilator in newborn piglets.
Kim, Chang-Ryul, William Oh, Barbara S. Stonestreet.
Brown University School of Medicine, Department of Pediatrics,
Women and Infants' Hospital, Providence, Rhode Island 02905
APStracts 3:0327H, 1996.
We tested the hypothesis that, in newborn piglets, magnesium results
in a dose dependent prostanoid mediated cerebrovasodilation. Pial
arterioles 50-200 [mu]m in diameter were serially measured and
cortical subarachnoid cerebrospinal fluid collected for
radioimmunoassay of 6-keto-prostaglandin F1[alpha] (6-keto
-PGF1[alpha], hydrolysis product of PGI2) and thromboxane B2 (TXB2,
metabolite of TxA2) before and after cerebrospinal fluid containing
1.2, 2.4, 4.8, and 9.6 mM MgCl2 was suffused over the parietal cortex
under a closed cranial window in twelve 2 to 4 day-old piglets.
Magnesium suffusion resulted (P<0.05) in a dose-dependent pial
arteriolar vasodilation. The increase in vessel diameter was greater
(P<0.001) to 2.4, 4.8 and 9.6 mM than to 1.2 mM concentration of
magnesium. The increase in vessel diameter to 9.6 mM was also greater
(P<0.001) than to the 2.4 mM concentration of magnesium.
Magnesium suffusion did not result in changes in cortical
cerebrospinal fluid prostanoid concentrations. The effect of
intravenous indomethacin (5 mg x Kg-1) on cyclooxygenase inhibition
in the pial arterioles was confirmed by a 24 +/- 3% decrease in
vessel diameter at the baseline (1.2 mM) magnesium concentration. In
contrast, cyclooxygenase inhibition with intravenous indomethacin did
not attenuate the magnesium induced cerebrovasodilation. We conclude
that, in newborn piglets, magnesium suffusion over the parietal
cortex results in a dose-dependent cerebrovasodilation, which is most
likely not mediated by prostanoids.
Received 6 March 1996; accepted in final form 12 July 1996.
APS Manuscript Number H220-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 21 August 1996