Protein kinase C activation generates superoxide and contributes to impairment of cerebrovasodilation induced by G protein activation after brain injury

Previous studies have observed that activation of protein kinase C (PKC) contributes to generation of superoxide anion (O(-)(2)) after fluid percussion brain injury (FPI). This study was designed to characterize the effects of FPI on the vascular activity of two activators of a pertussis toxin sensitive G protein, mastoparan and mastoparan-7, and the role of PKC dependent O(-)(2) generation in such effects in newborn pigs equipped with a closed cranial window. Mastoparan (10(-8), 10(-6) M) elicited pial artery dilation that was blunted by FPI and partially restored by the PKC inhibitor chelerythrine (10(-7) M) or the O(-)(2) free radical scavengers polyethylene glycol superoxide dismutase and catalase (SODCAT) (9+/-1 and 16+/-1, sham control; 3+/-1 and 5+/-1, FPI; and 7+/-1 and 11+/-1%, FPI SODCAT pretreated). Similar results were observed for mastoparan-7 but the inactive analogue mastoparan-17 had no effect on pial artery diameter. Exposure of the cerebral cortex to a xanthine oxidase O(-)(2) generating system blunted mastoparan induced pial artery dilation similar to FPI (10+/-1 and 17+/-1 vs. 2+/-1 and 3+/-1%). Pertussis toxin (1 microg/ml) exposure blocked mastoparan and mastoparan-7 vasodilation. These data show that pertussis toxin sensitive G protein activation elicits cerebrovasodilation that is blunted following FPI in a PKC dependent manner. These data also show that O(-)(2) generation similarly blunts G protein mediated cerebrovasodilation. These data suggest that PKC dependent O(-)(2) generation contributes to impaired G protein mediated cerebrovasodilation after FPI.     

190例颅脑外伤后智力研究

目的:探讨车祸导致颅脑外伤后智力受损情况及其影响因素. 方法:对190例颅脑外伤患者资料进行回顾性分析. 结果:智力受损者177例(93.2%).中重度智力受损组颅内血肿、颅骨骨折、脑干损伤以及≥3个脑叶同时受损的发生率均明显高于轻度智力受损组(P＜0.05或P＜0.01). 结论:颅脑外伤所致智力障碍发生率较高,智力受损与颅脑外伤严重程度和受伤部位有明显的相关性.     

Differential role of PTK,ERK and p38 MAPK in superoxide impairment of NMDA cerebrovasodilation

Previous studies in piglets have shown that the generation of oxygen free radicals (O(-)(2)) following traumatic brain injury and hypoxia/ischemia contribute to the reversal of N-methyl-D-aspartate (NMDA)-induced pial artery dilation to vasoconstriction. This study determined the contribution of protein tyrosine kinase (PTK) and mitogen-activated protein (MAPK) activation to impairment of NMDA cerebrovasodilation by O(-)(2) in piglets equipped with a closed window. Exposure of the cerebral cortex to a xanthine oxidase O(-)(2) generating system (OX) reversed NMDA (10(-8), 10(-6) M) dilation to vasoconstriction but such impairment was partially prevented by the PTK inhibitor, genistein, the MAPK (ERK isoform) inhibitor, U0126, and the MAPK (p38 isoform) inhibitor, SB203580 (9+/-1 and 15+/-1 vs. -1+/-1 and -1+/-1 vs. 5+/-1 and 9+/-1% for sham control, OX and OX in the presence of genistein, respectively). However, the p38 MAPK inhibitor, SB203580, prevented NMDA dilator impairment significantly less than the ERK MAPK inhibitor, U0126. Similar results were obtained for glutamate. These data show that PTK and MAPK activation by the presence of O(-)(2) contributes to the impairment of NMDA dilation. Furthermore, these data indicate a differential role for ERK and p38 MAPK activation in impairment of NMDA dilation by O(-)(2) in the brain.     

NOC/oFQ activates ERK and JNK but not p38 MAPK to impair prostaglandin cerebrovasodilation after brain injury

Fluid percussion brain injury (FPI) elevates the CSF concentration of the opioid nociceptin/orphanin FQ (NOC/oFQ), which contributes to impairment of pial artery dilation to the prostaglandins (PG) PGE2 and PGI2. This study investigated the role of the ERK, p38, and JNK isoforms of mitogen-activated protein kinase (MAPK) in impaired PG cerebrovasodilation after FPI, and the relationship of brain injury induced release of NOC/oFQ to MAPK in such vascular impairment in newborn pigs equipped with a closed cranial window. FPI blunted PGE2 pial artery dilation, but U 0126 and SP 600125 (10(-6) M) (ERK and JNK MAPK inhibitors, respectively) partially prevented such impairment (7 +/- 1, 12 +/- 1, and 17 +/- 1 vs. 2 +/- 1, 3 +/- 1, and 5 +/- 1 vs. 4 +/- 1, 7 +/- 1, and 12 +/- 1% for 1, 10, and 100 ng/ml PGE2 in control, FPI, and FPI + U 0126 pretreated animals, respectively). In contrast, administration of SB 203580 (10(-5) M) (p38 MAPK inhibitor) did not prevent FPI impairment of PGE2 dilation. Co-administration of NOC/oFQ at the dose of 10(-10) M, the cerebrospinal fluid concentration observed after FPI, with PGE2 under non-brain injury conditions blunted PG dilation, but U 0126 or SP 600125 partially prevented such impairment (7 +/- 1, 11 +/- 1, and 16 +/- 2 vs. 0 +/- 1, 1 +/- 1, and 2 +/- 1, vs. 5 +/- 1, 9 +/- 1, and 13 +/- 2 for responses to PGE2 in control, NOC/oFQ, and NOC/oFQ + U 0126 treated animals, respectively). Administration of SB 203580 did not prevent impairment of PG pial artery dilation by NOC/oFQ. These data show that activation of ERK and JNK but not p38 MAPK contributes to impairment of PG cerebrovasodilation after FPI. These data suggest that NOC/oFQ induced ERK and JNK but not p38 MAPK activation contributes to impaired cerebrovasodilation to PG after FPI.     

Superoxide generation links nociceptin/orphanin FQ (NOC/oFQ) release to impaired N-methyl-D-aspartate cerebrovasodilation after brain injury

BACKGROUND AND PURPOSE: Although activation of the N-methyl-D-aspartate (NMDA) receptor is thought to contribute to altered cerebrovascular regulation after traumatic brain injury, the effects of such injury on the vascular response to NMDA itself has been less well appreciated. The newly described opioid nociceptin/orphanin FQ (NOC/oFQ) elicits pial artery dilation, at least in part, in a prostaglandin-dependent manner and is released into cerebrospinal fluid after fluid percussion brain injury (FPI). Generation of superoxide anion (O(2)(-)) occurs after FPI, and a byproduct of cyclooxygenase metabolism is the generation of O(2)(-). This study was designed to determine whether NOC/oFQ generates O(2)(-), which in turn could link NOC/oFQ release to impaired NMDA-induced pial artery dilation after FPI. METHODS: Injury of moderate severity (1.9 to 2.1 atm) was produced by the lateral FPI technique in anesthetized newborn pigs equipped with a closed cranial window. Superoxide dismutase-inhibitable nitroblue tetrazolium (NBT) reduction was determined as an index of O(2)(-) generation. RESULTS: Under non-brain injury conditions, topical NOC/oFQ (10(-)(10) mol/L, the concentration present in cerebrospinal fluid after FPI) increased superoxide dismutase-inhibitable NBT reduction from 1+/-1 to 20+/-3 pmol/mm(2) but had no effect itself on pial artery diameter. Indomethacin (5 mg/kg IV) blunted such NBT reduction (1+/-1 to 6+/-2 pmol/mm(2)), whereas the NOC/oFQ receptor antagonist [F/G] NOC/oFQ (1-13) NH(2) (10(-)(6) mol/L) blocked NBT reduction. [F/G] NOC/oFQ (1-13) NH(2) and indomethacin also blunted the NBT reduction observed after FPI (1+/-1 to 15+/-1 versus 1+/-1 to 4+/-1 versus 1+/-1 to 4+/-1 pmol/mm(2) for sham, NOC/oFQ antagonist, and indomethacin-treated animals, respectively). NMDA (10(-)(8) and 10(-)(6) mol/L)-induced pial artery dilation was reversed to vasoconstriction after FPI, and [F/G] NOC/oFQ (1-13) NH(2) attenuated such vasoconstriction (sham 9+/-1% and 16+/-1% versus FPI -7+/-1% and -12+/-1% versus FPI-[F/G] NOC/oFQ (1-13) NH(2)-pretreated animals -2+/-1% and -3+/-1%). Indomethacin and the free radical scavengers polyethylene glycol superoxide dismutase and catalase also partially restored NMDA-induced vasodilation. CONCLUSIONS: These data show that NOC/oFQ, in concentrations present in cerebrospinal fluid after FPI, increased O(2)(-) production in a cyclooxygenase-dependent manner and contributes to such production after FPI. These data show that NOC/oFQ contributes to impaired NMDA-induced pial artery dilation after FPI. Therefore, these data suggest that cyclooxygenase-dependent O(2)(-) generation links NOC/oFQ release to impaired NMDA-induced cerebrovasodilation after brain injury.     

Adrenomedullin reduces gender-dependent loss of hypotensive cerebrovasodilation after newborn brain injury through activation of ATP-dependent K channels.

Cerebrovascular dysregulation during hypotension occurs after fluid percussion brain injury (FPI) in the newborn pig owing to impaired K channel function. This study was designed to (1) determine the role of gender and K channel activation in adrenomedullin (ADM) cerebrovasodilation, (2) characterize the role of gender in the loss of hypotensive cerebrovasodilation after FPI, and (3) determine the role of gender in the ability of exogenous ADM to modulate hypotensive dysregulation after FPI. Lateral FPI (2 atm) was induced in newborn male and female newborn pigs (1 to 5 days old) equipped with a closed cranial window, n=6 for each protocol. Adrenomedullin-induced pial artery dilation was significantly greater in female than male piglets and blocked by the K(ATP) channel antagonist glibenclamide, but not by the K(ca) channel antagonist iberiotoxin. Cerebrospinal fluid ADM was increased from 3.8+/-0.7 to 14.6+/-3.0 fmol/mL after FPI in female but was unchanged in male piglets. Hypotensive pial artery dilation was blunted to a significantly greater degree in male versus female piglets after FPI. Topical pretreatment with a subthreshold vascular concentration of ADM (10(-10) mol/L) before FPI reduced the loss of hypotensive pial artery dilation in both genders, but protection was significantly greater in male versus female piglets. These data show that hypotensive pial artery dilation is impaired after FPI in a gender-dependent manner. By unmasking a gender-dependent endogenous protectant, these data suggest novel gender-dependent approaches for clinical intervention in the treatment of perinatal traumatic brain injury.     

Role of altered cyclooxygenase metabolism in impaired cerebrovasodilation to nociceptin/orphanin FQ following brain injury

This study was designed to determine the role of altered cyclooxygenase metabolism in impaired pial artery dilation to the newly described opioid, nociceptin orphanin FQ (NOC/oFQ), following fluid percussion brain injury (FPI) in newborn pigs equipped with a closed cranial window. Recent studies show that NOC/oFQ contributes to oxygen free radical generation observed post FPI in a cyclooxygenase dependent manner. FPI was produced by using a pendulum to strike a piston on a saline filled cylinder that was fluid coupled to the brain via a hollow screw inserted through the cranium. NOC/oFQ (10(-8), 10(-6) M) modestly increased cerebrospinal fluid (CSF) 6-keto-PGF(1alpha), and thromboxane B(2) (TXB(2)), the stable breakdown products of PGI(2) and TXA(2), in sham animals (1148 +/- 83 to 1681 +/- 114 and 308 +/- 16 to 424 +/- 21 pg/ml for control and 10(-6) M NOC/oFQ 6-keto-PGF(1alpha), and TXB(2), respectively). In 1-h post FPI animals, basal levels of 6-keto-PGF(1alpha), and TXB(2) were elevated. NOC/oFQ stimulated release of 6-keto-PGF(1alpha), was blocked while such release of TXB(2) was enhanced (720 +/- 63 to 1446 +/- 117 pg/ml for control and 10(-6) M NOC/oFQ CSF TXB(2)). NOC/oFQ (10(-8), 10(-6) M) induced pial artery dilation that was reversed to vasoconstriction by FPI while the cyclooxygenase inhibitor indomethacin (5 mg/kg, intravenous) partially restored such vascular responses (8 +/- 1 and 15 +/- 1 vs. -7 +/- 1 and -12 +/- 1 vs. 7 +/- 1 and 12 +/- 1% for 10(-8), 10(-6) M NOC/oFQ in sham, FPI and FPI-Indo pretreated animals). Similar observations were made in FPI animals pretreated with the thromboxane receptor antagonist SQ 29,548 or the free radical scavenger polyethylene glycol superoxide dismutase and catalase. These data indicate that altered NOC/oFQ induced cyclooxygenase metabolism contributes to impairment of dilation to this opioid following FPI.     

Secondary thalamic atrophy related to brain infarction may contribute to post-stroke cognitive impairment

Background and purposeThe thalamus is a key brain hub that is globally connected to many cortical regions. Previous work highlights thalamic contributions to multiple cognitive functions, but few studies have measured thalamic volume changes or cognitive correlates. This study investigates associations between thalamic volumes and post-stroke cognitive function.MethodsParticipants with non-thalamic brain infarcts (3-42 months) underwent MRI and cognitive testing. Focal infarcts and thalami were traced manually. In cases with bilateral infarcts, the side of the primary infarct volume defined the hemisphere involved. Brain parcellation and volumetrics were extracted using a standardized and previously validated neuroimaging pipeline. Age and gender-matched healthy controls provided normal comparative thalamic volumes. Thalamic atrophy was considered when the volume exceeded 2 standard deviations greater than the controls.ResultsThalamic volumes ipsilateral to the infarct in stroke patients (n=55) were smaller than left (4.4 ± 1.4 vs. 5.4 ± 0.5 cc, p < 0.001) and right (4.4 ± 1.4 vs. 5.5 ± 0.6 cc, p < 0.001) thalamic volumes in the controls. After controlling for head-size and global brain atrophy, infarct volume independently correlated with ipsilateral thalamic volume (β= -0.069, p=0.024). Left thalamic atrophy correlated significantly with poorer cognitive performance (β = 4.177, p = 0.008), after controlling for demographics and infarct volumes.ConclusionsOur results suggest that the remote effect of infarction on ipsilateral thalamic volume is associated with global post-stroke cognitive impairment     

Protein tyrosine kinase and mitogen-activated protein kinase activation contribute to K(ATP) and K(ca) channel impairment after brain injury

Previous studies have observed that pial artery dilation to activators of the ATP sensitive K (K(ATP)) and calcium sensitive K (K(ca)) channel was blunted following fluid percussion brain injury (FPI) in the piglet. In recent studies in the rat, protein tyrosine kinase (PTK) activation was observed to contribute to K(ATP) channel impairment after FPI, but such a role in K(ca) channel impairment was unclear. This study investigated the role of PTK and mitogen activated protein kinase (MAPK) activation in blunted pial dilation to K(ATP) and K(ca) channel agonists following FPI in piglets equipped with a closed cranial window. Cromakalim and NS1619 (10(-8), 10(-6) M) induced pial artery dilation was blunted after FPI, but partially restored by the PTK inhibitors genistein (10(-6) M) and tyrphostin A23 (10(-5) M) (10+/-1 and 19+/-1%, sham control; 2+/-1 and 4+/-1%, FPI; and 7+/-1 and 11+/-1% FPI-genistein pretreated for NS1619 10(-8), 10(-6) M, respectively). Cromakalim- and NS1619-induced pial dilation was also partially restored after FPI by pretreatment with the MAPK inhibitors U0126 (10(-6) M) and PD98059 (10(-5) M) (12+/-1 and 21+/-1%, sham control; 2+/-1 and 4+/-1%, FPI; and 6+/-1 and 10+/-2%, FPI-U0126 pretreated for NS1619 10(-8), 10(-6) M, respectively). These data suggest that PTK and MAPK activation contribute to K(ATP) and K(ca) channel impairment following FPI.     

Metallothionein I and II mitigate age-dependent secondary brain injury

Both the immediate insult and delayed apoptosis contribute to functional deficits after brain injury. Secondary, delayed apoptotic death is more rapid in immature than in adult CNS neurons, suggesting the presence of age-dependent protective factors. To understand the molecular pathobiology of secondary injury in the context of brain development, we identified changes in expression of oxidative stress response genes during postnatal development and target deprivation-induced neurodegeneration. The antioxidants metallothionein I and II (MT I/II) were increased markedly in the thalamus of adult C57BL/6 mice compared to mice <15 days old. Target deprivation generates reactive oxygen species that mediate neuronal apoptosis in the central nervous system; thus the more rapid apoptosis observed in the immature brain might be due to lower levels of MT I/II. We tested this hypothesis by documenting neuronal loss after target-deprivation injury. MT I/II-deficient adult mice experienced greater thalamic neuron loss at 96 hr after cortical injury compared to that in controls (80 +/- 2% vs. 57 +/- 4%, P < 0.01), but not greater overall neuronal loss (84 +/- 4% vs. 79 +/- 3%, MT I/II-deficient vs. controls). Ten-day-old MT I/II-deficient mice, however, experienced both faster onset of secondary neuronal death (30 vs. 48 hr) and greater overall neuronal loss (88 +/- 2% vs. 69 +/- 4%, P = 0.02). MT I/II are thus inhibitors of age-dependent secondary brain injury, and the low levels of MT I/II in immature brains explains, in part, the enhanced susceptibility of the young brain to neuronal loss after injury. These findings have implications for the development of age-specific therapeutic strategies to enhance recovery after brain injury.     

Early neuronal expression of tumor necrosis factor-alpha after experimental brain injury contributes to neurological impairment

Tumor necrosis factor-alpha (TNF alpha) is a pleiotropic cytokine involved in inflammatory cascades associated with CNS injury. To examine the role of TNF alpha in the acute pathophysiology of traumatic brain injury (TBI), we studied its expression, localization and modulation in a clinically relevant rat model of non-penetrating head trauma. TNF alpha levels increased significantly in the injured cortex at 1 and 4, but not at 12, 24 or 72 h after severe lateral fluid-percussion trauma (2.6-2.7 atm). TNF alpha was not elevated after mild injury. At 1 and 4 h after severe TBI, marked increases of TNF alpha were localized immunocytochemically to neurons of the injured cerebral cortex. A small population of astrocytes, ventricular cells and microvessels, also showed positive TNF alpha staining, but this expression was not injury-dependent. Macrophages that were present in a hemorrhagic zone along the external capsule, corpus callosum and alveus hippocampus at 4 h after TBI did not express TNF alpha. Intracerebroventricular administration of a selective TNF alpha antagonist--soluble TNF alpha receptor fusion protein (sTNFR:Fc) (37.5 microg)--at 15 min before and 1 h after TBI, improved performance in a series of standardized motor tasks after injury. In contrast, intravenous administration of sTNFR:Fc (0.2, 1 or 5 mg/kg) at 15 min after trauma did not improve motor outcome. Collectively, this evidence suggests that enhanced early neuronal expression of TNF alpha after TBI contributes to subsequent neurological dysfunction.     

Nociceptin/orphanin FQ contributes to hypoxic/ischemic impairment of hypercapnic cerebrovasodilation

Previous studies in piglets show that hypercapnic pial artery dilation was blunted following cerebral ischemia. Unrelated studies show that the newly described opioid nociceptin orphanin FQ (NOC/oFQ) is released into cerebrospinal fluid and contributes to altered cerebral hemodynamics following hypoxia/ischemia. This study was designed to determine the contribution of NOC/oFQ to hypoxic/ischemic impairment of hypercapnic pial dilation in piglets equipped with a closed cranial window. Global cerebral ischemia was produced via elevated intracranial pressure. Hypoxia decreased P(O2) to 34 +/- 3 mmHg. Topical NOC/oFQ (10(-10) M), the CSF concentration following hypoxia/ischemia, had no effect on pial artery diameter by itself but attenuated hypercapnia P(CO2) of (73 +/- 2 mmHg)-induced pial artery dilation (28 +/- 2 vs. 19 +/- 2%). Hypercapnia pial artery dilation was blunted by hypoxia/ischemia but such dilation was partially protected by pretreatment with the putative NOC/oFQ receptor antagonist, [F/G] NOC/oFQ (1-13) NH(2) (10(-6) M), (25 +/- 1, sham control; 4 +/- 1, hypoxia/ischemia; and 12 +/- 3%, hypoxia/ischemia + [F/G] NOC/oFQ (1-13) NH(2), respectively). These data suggest that NOC/oFQ release contributes to impaired hypercapnia-induced cerebrovasodilation following hypoxia/ischemia.     

Functional magnetic resonance imaging of working memory impairment after traumatic brain injury

OBJECTIVES: To examine patterns of brain activation while performing a working memory task in persons with moderate to severe traumatic brain injury (TBI) and healthy controls. It is well established that working memory is an area of cognition that is especially vulnerable to disruption after TBI. Although much has been learned about the system of cerebral representation of working memory in healthy people, little is known about how this system is disrupted by TBI. METHODS: Functional magnetic resonance imaging (fMRI) was used to assess brain activation during a working memory task (a modified version of the paced auditory serial addition test) in nine patients with TBI and seven healthy controls. RESULTS: Patients with TBI were able to perform the task, but made significantly more errors than healthy controls. Cerebral activation in both groups was found in similar regions of the frontal, parietal, and temporal lobes, and resembled patterns of activation found in previous neuroimaging studies of working memory in healthy persons. However, compared with the healthy controls, the TBI group displayed a pattern of cerebral activation that was more regionally dispersed and more lateralised to the right hemisphere. Differences in lateralisation were particularly evident in the frontal lobes. CONCLUSIONS: Impairment of working memory in TBI seems to be associated with alterations in functional cerebral activity.     

Misplaced NMDA receptors in epileptogenesis contribute to excitotoxicity

Pharmacological blockade of NR2B-containing N-methyl-d-aspartate receptors (NMDARs) during epileptogenesis reduces neurodegeneration provoked in the rodent hippocampus by status epilepticus. The functional consequences of NMDAR activation are crucially influenced by their synaptic vs extrasynaptic localization, and both NMDAR function and localization are dependent on the presence of the NR2B subunit and its phosphorylation state. We investigated whether changes in NR2B subunit phosphorylation, and alterations in its neuronal membrane localization and cellular expression occur during epileptogenesis, and if these changes are involved in neuronal cell loss. We also explored NR2B subunit changes both in the acute phase of status epilepticus and in the chronic phase of spontaneous seizures which encompass the epileptogenesis phase. Levels of Tyr1472 phosphorylated NR2B subunit decreased in the post-synaptic membranes from rat hippocampus during epileptogenesis induced by electrical status epilepticus. This effect was concomitant with a reduced interaction between NR2B and post-synaptic density (PSD)-95 protein, and was associated with decreased CREB phosphorylation. This evidence suggests an extra-synaptic localization of NR2B subunit in epileptogenesis. Accordingly, electron microscopy showed increased NR2B both in extra-synaptic and pre-synaptic neuronal compartments, and a concomitant decrease of this subunit in PSD, thus indicating a shift in NR2B membrane localization. De novo expression of NR2B in activated astrocytes was also found in epileptogenesis indicating ectopic receptor expression in glia. The NR2B phosphorylation changes detected at completion of status epilepticus, and interictally in the chronic phase of spontaneous seizures, are predictive of receptor translocation from synaptic to extrasynaptic sites. Pharmacological blockade of NR2B-containing NMDARs by ifenprodil administration during epileptogenesis significantly reduced pyramidal cell loss in the hippocampus, showing that the observed post-translational and cellular changes of NR2B subunit contribute to excitotoxicity. Therefore, pharmacological targeting of misplaced NR2B-containing NMDARs, or prevention of these NMDAR changes, should be considered to block excitotoxicity which develops after various pro-epileptogenic brain injuries.     

Newborn pig nociceptin/orphanin FQ activates protein tyrosine kinase and mitogen activated protein kinase to impair NMDA cerebrovasodilation after ischemia

This study characterized the contributions of protein tyrosine kinase and mitogen-activated protein kinase in nociceptin/orphanin FQ induced impairment of NMDA dilation after cerebral hypoxia/ischemia in anesthetized newborn pigs equipped with a closed cranial window. Topical nociceptin/orphanin FQ, in a concentration observed after hypoxia/ischemia, impaired NMDA pial artery vasodilation. Co-administration either of the protein tyrosine kinase inhibitor genistein or the mitogen activated protein kinase inhibitor U0126 with nociceptin/orphanin FQ partially prevented the inhibition of NMDA dilation compared to that observed in their absence. After exposure to hypoxia/ischemia, pial artery dilation in response to NMDA was reversed to vasoconstriction but pretreatment with either genistein or U0126 partially protected such impairment. These data show that protein tyrosine kinase and mitogen activated protein kinase activation contribute to nociceptin/orphanin FQ induced impairment of NMDA dilation. These data suggest that protein tyrosine and mitogen activated protein kinase are involved in the mechanism by which nociceptin/orphanin FQ impairs NMDA dilation following hypoxia/ischemia.