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Departments of Anesthesia and Pharmacology, University of Pennsylvania, and The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104
In piglets, pial arteries constrict,
ATP-sensitive K+
(KATP) channel function is
impaired, and cerebrospinal fluid endothelin-1 (ET-1) increases to
10
10 M after brain injury
[fluid percussion injury (FPI)]. Nitric oxide (NO) elicits
dilation via guanosine 3',5'-cyclic monophosphate (cGMP)
and KATP channel activation. This
study was designed to characterize the relationship between ET-1 and
impaired function of KATP channels
after FPI. Injury was produced via the lateral FPI technique in piglets
equipped with a closed cranial window. Cromakalim, a
KATP agonist, produced dilation
that was attenuated by FPI and partially restored by BQ-123, an ET-1
antagonist (11 ± 1 and 23 ± 2 vs. 2 ± 1 and 4 ± 1 vs. 8 ± 1 and 17 ± 2% for responses to
10
8 and
10
6 M cromakalim before
FPI, after FPI, and after FPI with BQ-123, respectively). Because ET-1
constriction may antagonize dilation, separate experiments were
conducted under conditions of equivalent baseline diameter in the
absence and presence of ET-1
(10
10 M). Cromakalim
dilation was attenuated by ET-1 and partially restored by the protein
kinase C (PKC) inhibitor staurosporine (12 ± 1 and 28 ± 1 vs. 2 ± 1 and 21 ± 3 vs. 9 ± 1 and 29 ± 2% for
10
8 and
10
6 M cromakalim,
cromakalim with ET-1, and cromakalim with ET-1+staurosporine, respectively). Similar interactions were observed with
calcitonin gene-related peptide, 8-bromoguanosine
3',5'-cyclic monophosphate, and the NO releasers sodium
nitroprusside and
S-nitroso-N-acetylpenicillamine. These data show that ET-1 blunts
KATP channel-, NO-, and
cGMP-mediated dilation. These data suggest that ET-1 contributes to
altered cerebral hemodynamics after FPI through impairment of
KATP channel function via PKC
activation.
newborn; cerebral circulation; nitric oxide; cyclic nucleotides
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