title: Role of nociceptin/orphanin FQ in age-dependent cerebral hemodynamic effects of brain injury.
abstract: This study was designed to compare the role of the newly described endogenous opioid nociceptin/orphanin FQ (NOC/oFQ) in the reductions of cerebral blood flow (CBF) and pial artery diameter observed following fluid percussion brain injury (FPI) in chloralose anesthetized newborn and juvenile pigs as a function of time postinsult. FPI elevated CSF NOC/oFQ concentration from 70 +/- 3 to 444 +/- 51 within 1 h and to 1,931 +/- 112 pg/mL (n = 7) within 8 h, whereas concentrations returned to control value within 168 h in the newborn. In contrast, FPI elevated CSF NOC/oFQ from 77 +/- 4 to 202 +/- 16 pg/mL (n = 7) within 1 h, while values returned to control value within 8 h in the juvenile. Topical NOC/oFQ (10(-8), 10(-6) M) induced vasodilation was reversed to vasoconstriction by FPI in the newborn while such responses were only attenuated in the juvenile at 1 h post insult (control, 9 +/- 1 and 16 +/- 1%; FPI newborn, -8 +/- 1 and -14 +/- 1%; FPI juvenile, 2 +/- 1 and 5 +/- 1%, n = 7). Such altered dilation returned to control value within 168 h in newborns and 8 h in juveniles. Blood flow in the cerebrum was reduced from 57 +/- 4 to 23 +/- 3 mL x min(-1) x 100 g(-1) (n = 7) within 1 h and returned to control value with 168 h post FPI in newborns. In animals pretreated with [F/G] NOC/oFQ (1-13) NH2 (1 mg/kg, i.v.), a NOC/oFQ antagonist, however, CBF only fell to 39 +/- 4 mL x min(-1) x 100 g(-1) (n = 7) at 1 h post insult in newborns. In contrast, CBF was only reduced from 57 +/- 6 to 32 +/- 2 in untreated and to 39 +/- 3 mL/min(-1) x 100 g(-1) (n = 7) in treated juveniles within 1 h post FPI. Similar observations for reductions in pial artery diameter were made in untreated and treated newborns and juveniles. These data suggest that an elevated CSF NOC/oFQ concentration and altered vascular responsiveness to this opioid contribute to reductions in CBF and pial artery diameter observed following FPI. Because such NOC/oFQ changes were greater in newborns versus juveniles, these data further suggest that NOC/oFQ contributes to age-related cerebral hemodynamic differences in the effects of FPI.
authors.affiliation: Department of Anesthesia, University of Pennsylvania, Philadelphia 19104, USA. armsteaw@mail.med.upenn.edu
authors.forename: W M
authors.initials: WM
authors.lastname: Armstead
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001784:Blood Gas Analysis; D001794:Blood Pressure; D001930:Brain Injuries / Q000134:cerebrospinal fluid* / Q000503:physiopathology*; D001933:Brain Stem / Q000098:blood supply; D002421:Caudate Nucleus / Q000098:blood supply; D002531:Cerebellum / Q000098:blood supply; D002540:Cerebral Cortex / Q000098:blood supply; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D008297:Male; D018847:Opioid Peptides / Q000134:cerebrospinal fluid*; D010487:Periaqueductal Gray / Q000098:blood supply; D010841:Pia Mater / Q000098:blood supply; D013552:Swine; D014661:Vasoconstriction / Q000502:physiology; D000097629:Nociceptin
chemical_list: D018847:Opioid Peptides; D000097629:Nociceptin