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Departments of Anesthesia and Pharmacology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
This study was designed to characterize the role of the
newly described endogenous opioid nociceptin/orphanin FQ (NOC/oFQ) in
reduced cerebral blood flow (CBF) observed after
ischemia-reperfusion (I/R) and combined hypoxia and
ischemia-reperfusion (H-I/R), as a function of time after onset
of reperfusion in newborn pigs equipped with a closed cranial window.
Global cerebral ischemia (20 min) was induced via elevation of
intracranial pressure, whereas hypoxia (10 min) decreased
PO2 to 35 ± 3 mmHg with unchanged PCO2. I/R elevated cerebrospinal
fluid (CSF) NOC/oFQ from 67 ± 4 to 266 ± 29 pg/ml within 1 h,
whereas values returned to control level within 4 h of reperfusion.
H-I/R elevated CSF NOC/oFQ to 483 ± 67 pg/ml within 1 h, and such
values returned slowly to control level within 12 h of reperfusion.
Topical NOC/oFQ (10
8 M,
10
6 M)-induced vasodilation was
attenuated by I/R and reversed to vasoconstriction by H-I/R at 1 h of
reperfusion (control, 9 ± 1 and 16 ± 1%; I/R, 3 ± 1 and 6 ± 1%; H-I/R,
6 ± 1 and
11 ± 1%). Such altered
dilation returned to control values within 4 h in I/R animals and
within 12 h in H-I/R animals. Blood flow in the cerebrum was reduced
from 58 ± 4 to 33 ± 2 ml · min
1 · 100 g
1 within 1 h and returned to
control value within 4 h in I/R animals. In animals pretreated with
[F/G]NOC/oFQ(1-13)-NH2 (1 mg/kg iv), an
NOC/oFQ antagonist, however, CBF only fell to 43 ± 3 ml · min
1 · 100 g
1 at 1 h of reperfusion. Similar
observations were made in H-I/R animals. These data suggest that an
elevated CSF NOC/oFQ concentration and altered vascular responsiveness
to this opioid contribute to reductions in CBF observed after either
I/R or H-I/R.
newborn; cerebral circulation; opioids
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