Cyclooxygenase 1–Derived Prostaglandin E2 and EP1 Receptors Are Required for the Cerebrovascular Dysfunction Induced by Angiotensin II
Prostaglandin E2 (PGE2) EP1 receptors (EP1Rs) may contribute to hypertension and related end-organ damage. Because of the key role of angiotensin II (Ang II) in hypertension, we investigated the role of EP1R in the cerebrovascular alterations induced by Ang II. Mice were equipped with a cranial window, and cerebral blood flow was monitored by laser-Doppler flowmetry. The attenuation in cerebral blood flow responses to whisker stimulation (−46±4%) and the endothelium-dependent vasodilator acetylcholine (−40±4%) induced by acute administration of Ang II (250 ng/kg per minute; IV for 30 to 40 minutes) were not observed after cyclooxygenase 1 or EP1R inhibition or in cyclooxygenase 1 or EP1-null mice. In contrast, cyclooxygenase 2 inhibition or genetic inactivation did not prevent the attenuation. Ang II–induced oxidative stress was not observed after cyclooxygenase 1 or EP1R inhibition or in EP1R-null mice. Prostaglandin E2 reinstated the Ang II–induced cerebrovascular dysfunction and oxidative stress after cyclooxygenase 1 inhibition. Brain prostaglandin E2 levels were not increased by Ang II but were attenuated by cyclooxygenase 1 and not cyclooxygenase 2 inhibition. The cerebrovascular dysfunction induced by 14-day administration of “slow-pressor” doses of Ang II (600 ng/kg per minute) was attenuated by neocortical application of SC51089. Cyclooxygenase 1 immunoreactivity was observed in microglia and EP1R in endothelial cells. We conclude that the cerebrovascular dysfunction induced by Ang II requires activation of EP1R by constitutive production of prostaglandin E2 derived from cyclooxygenase 1. The findings provide the first evidence that EP1Rs are involved in the deleterious cerebrovascular effects of Ang II and suggest new therapeutic approaches to counteract them.
Hypertension is an independent risk factor for major neurological diseases, including stroke, vascular cognitive impairment, and Alzheimer dementia.1 Cerebral blood vessels are the main target of the deleterious effects of hypertension on the brain.2 In addition to inducing structural changes in cerebral vessels, hypertension alters cerebrovascular regulatory mechanisms that are critical for the structural and functional integrity of the brain. For example, hypertension suppresses the increase in cerebral blood flow (CBF) induced by neural activity, a vital response that matches local energy demands with the delivery of nutrients through blood flow and disrupts the endothelial regulation of cerebral blood vessels.3–6 These alterations compromise cerebrovascular reserves and render the brain more vulnerable to ischemia, setting the stage for devastating diseases, such as stroke and dementia.2 In models of hypertension induced by angiotensin II (Ang II), an octapeptide thought to play a central role in essential hypertension,7 the cerebrovascular alterations are mediated by reactive oxygen species (ROS) produced by the enzyme NADPH oxidase.3 However, the factors modulating the ROS production induced by Ang II in cerebral blood vessels and contributing to the vascular dysfunction are poorly understood.
Prostanoids are powerful lipid mediators that are synthesized from arachidonic acid by cyclooxygenase (COX) 1 and 2 and exert a wide variety of biological effects by acting on multiple G-coupled membrane receptors.8 In the cardiovascular system, prostanoids have long been implicated both in the normal regulation of vascular tone9 and in the pathobiology of cardiovascular diseases, including hypertension.8 Recent evidence suggests that prostaglandin E2 (PGE2), a prostanoid that acts on 4 receptors (EP1 through EP4), participates in the mechanisms of hypertension and related complications.10–12 In particular, EP1 receptors have been implicated in the vasoconstriction and blood pressure elevation induced by Ang II.11,13 Furthermore, EP1 receptor antagonists lower blood pressure in spontaneously hypertensive rats and in db/db diabetic mice.11,13 However, it is not known whether PGE2 and EP1 receptors also play a role in the deleterious effects of Ang II on cerebral blood vessels, a key determinant of the end-organ damage to the brain.2
In this study, we investigated the role of EP1 receptors in the cerebrovascular dysfunction induced by Ang II. Using a mouse model of acute Ang II hypertension, we examined whether PGE2 and EP1 receptors contribute to the cerebrovascular alterations induced by Ang II and whether these effects involve Ang II–dependent ROS production. In addition, we sought to define the enzymatic sources of PGE2 and the brain cells involved in PGE2 synthesis.
Please see the online Data Supplement at http://hyper.ahajournals.org for a more detailed description of the methods.
General Surgical Procedures
All of the procedures were approved by the institutional animal care and use committee of Weill Cornell Medical College. Studies were conducted in 3-month–old male mice (weight: 27 to 30 g). EP1−/−, COX-1−/−, COX-2−/−, and NADPH oxidase−/− (NOX 2−/−) mice were obtained from in-house colonies.14–17 Mice were congenic with the C57Bl/6 strain, and C57Bl/6 mice (The Jackson Laboratory, Bar Harbor, ME) were used as wild-type controls. Mice were anesthetized with isoflurane intubated and artificially ventilated (SAR-830, CWE Inc).4,5 Mean arterial pressure (MAP), rectal temperature, and blood gases were monitored and controlled.4,5 After surgery, anesthesia was maintained with urethane (750 mg/kg IP) and chloralose (50 mg/kg IP).4,5 In some studies, mice were anesthetized with isoflurane and implanted with osmotic minipumps delivering saline or Ang II (600 ng/kg per minute).3,4 CBF was tested 14 days after pump implantation.
Monitoring of CBF
CBF was monitored with a laser-Doppler probe (Periflux System 5010, Perimed AB) in a cranial window overlying the somatosensory cortex.5 CBF was expressed as percentage increases relative to the resting level.
The COX-1 inhibitor SC-560, the COX-2 inhibitor NS398, PGE2, prostaglandin F2α (PGF2α; all from Cayman Chemical), or the EP1 antagonist SC-51089 (Biomol) were dissolved in dimethylsulfoxide and superfused on the somatosensory cortex.16
MAP and blood gases are presented in Table S1 (see the online Data Supplement at http://hyper.ahajournals.org). The cranial window was first superfused with Ringer solution (vehicle), and CBF responses were recorded.3–6,18,19 The whisker-barrel cortex was activated for 60 seconds by stroking the contralateral vibrissae,4 and the evoked changes in CBF were recorded. The endothelium-dependent vasodilator acetylcholine (ACh; 10 μmol/L; Sigma) or the smooth muscle relaxant adenosine (400 μmol/L; Sigma) was superfused on the exposed neocortex for 5 minutes. After testing baseline CBF responses, saline or Ang II was infused intravenously at a rate of 0.25±0.02 μg/kg per minute.4 CBF responses were tested again after 30 to 40 minutes of Ang II or saline infusion in wild-type, EP1, COX-1, COX-2, or NOX2-null mice. In experiments using pharmacological inhibitors, CBF responses were first tested with vehicle superfusion and then after 30 minutes of superfusion with SC51089 (10 μmol/L), SC560 (25 μmol/L), or NS398 (100 μmol/L). Then, the infusion of Ang II was started and CBF responses were tested again 30 to 40 minutes later. In some experiments, the effect of 30 minutes of neocortical application of PGE2 (1 μmol/L) or PGF2α (1 μmol/L) on the CBF responses was evaluated after Ang II or saline infusion in mice treated with SC560 or in EP1 and NOX2-null mice.14,16,17 In experiments with Ang II administration for 14 days, CBF responses were tested before and after neocortical application of SC51089.
Coronal brain sections were cut through the somatosensory cortex using a cryostat and incubated with primary antibodies against COX-1, neuronal nuclei, CD31, ionized calcium-binding adaptor molecule 1, glial fibrillary acidic protein, or EP1 receptors. After incubation with a secondary antibody, sections were mounted on slides and examined using a Leica confocal microscope.
ROS production was assessed by hydroethidine (HE) microfluorography.5,6,15 HE was topically superfused on the somatosensory cortex for 60 minutes. Ringer solution containing HE or HE plus SC51089, SC560, or NS398, was superfused and, 30 minutes later, the intravenous infusion of Ang II or vehicle was started. Mice were killed 30 to 40 minutes later, coronal brain sections were cut through cortex underlying the cranial window, and ROS was determined as described previously.5,6,15 In some experiments, the effect of neocortical application of PGE2 or PGF2α on ROS production after COX-1 or EP1 receptor inhibition was also studied after Ang II or saline infusion.
Mice were surgically prepared as described above and killed after 30 to 40 minutes of intravenous Ang II infusion. Samples were immediately collected from the somatosensory cortex, and the renal medulla samples were weighed and homogenized, and prostanoid concentration was determined using an enzyme immunoassay kit.14
Data are expressed as mean±SEM. Two group comparisons were evaluated using the Student t test. Multiple comparisons were evaluated by the ANOVA and the Tukey test. Differences were considered statistically significant for P<0.05.
EP1 Receptors Are Required for the Cerebrovascular Effects of Ang II
In agreement with previous studies,3–6,18,19 administration of Ang II to wild-type mice (n=5 per group) elevated MAP (see Table S1) and attenuated the increase in CBF evoked by whisker stimulation (−46±4%) or by ACh superfusion (−40±4%; P<0.05, ANOVA and Tukey test) but not adenosine (Figure 1; P<0.05; see Figure S1). In wild-type mice, neocortical superfusion with the EP1 receptor antagonist SC51089 did not alter Ang II hypertension or resting CBF (see Tables S1 and S2), but it prevented the attenuation of the CBF responses to whisker stimulation and ACh (Figure 1; n=5 per group). Similarly, in EP1-null mice, Ang II elevated MAP (see Table S1) but failed to attenuate the increased in CBF induced by whisker stimulation or ACh (Figure 1; n=5 per group). In contrast, topical application of Aß1-40 (5 μmol/L for 40 minutes), a peptide that induces cerebrovascular dysfunction through NOX2-derived ROS,15,20 attenuated the CBF responses in EP1 nulls (whisker stimulation: −43±5%; ACh: −44±7; P<0.05; n=5 per group), indicating that NOX2 is functional in EP1 null mice. Administration of slow-pressor doses of Ang II for 14 days elevated MAP and attenuated the increase in CBF induced by whisker stimulation or ACh (Figure 2A,B; see Table S1 at http://hyper.ahajournals.org). The cerebrovascular dysfunction was attenuated by neocortical application of SC51089 (Figure 2; n=5 per group; P<0.05 from vehicle).
COX-1 But Not COX-2 Inhibition Attenuates the Cerebrovascular Effects of Ang II
The observation that EP1 receptors are required for the cerebrovascular effects of Ang II points to the involvement of PGE2, a reaction product of the COX pathway.8 Therefore, we sought to determine whether the source of PGE2 was COX-1 or COX-2. Topical superfusion with the COX-2 inhibitor NS398 did not alter resting CBF (see Table S2) and attenuated the increase in CBF induced by whisker stimulation but not ACh (Figure 3), as described previously.17 However, NS398 did not affect the attenuation of CBF responses to whisker stimulation or ACh induced by acute Ang II administration (P<0.05 from control; n=5 per group; Figure 3). Similarly, Ang II attenuated the CBF response to whisker stimulation (vehicle: 15±1%; Ang II: 10±1%) and ACh (vehicle: 22±1%; Ang II: 13±1%) in COX-2 null mice (P<0.05 from wild type; n=5 per group). Superfusion with the COX-1 inhibitor SC560 lowered resting CBF but not the increase in CBF evoked by whisker stimulation or ACh (Figure 3; n=5 per group).16
However, SC560 prevented the attenuation of these responses induced by Ang II without altering the CBF response to adenosine (Figure 3; see Figure S1 and Table S1; n=5 per group). Similarly, Ang II failed to attenuate the increase in CBF induced by whisker stimulation (vehicle: 25±1%; Ang II: 24±1%) and ACh (vehicle: 23±1%; Ang II: 23±1%) in COX-1 null mice (P>0.05; n=5 per group).
PGE2 But Not PGF2α Counteracts the Effect of COX-1 Inhibition by acting on EP1 Receptors
The findings presented above implicate COX-1–derived PGE2 in the cerebrovascular alterations induced by Ang II. To test this hypothesis, we examined whether exogenous PGE2 could re-establish the cerebrovascular effects of Ang II after COX-1 inhibition. On the basis of a dose-response study, we chose a concentration of PGE2 (1 μmol/L) that does not alter resting CBF or the increase in CBF induced by whisker stimulation, ACh, or adenosine (Figure 1; n=5 per group; see Table S2 and Figure S2). Superfusion with this concentration of PGE2 re-established the attenuation of the CBF response to whisker stimulation or ACh in mice treated with SC560, whereas PGF2α was not effective (Figure 3; n=5 per group). In contrast, PGE2 failed to re-establish the cerebrovascular effects of Ang II in wild-type mice treated with the EP1 antagonist SC51089 or in EP1-null mice (Figure 1; n=5 per group), attesting to the fact that the effect of PGE2 requires EP1 receptors. NOX2-null mice are protected from the cerebrovascular dysfunction induced by Ang II.3 However, PGE2 did not re-establish the vascular dysfunction induced by Ang II in NOX2-null mice (Figure 4; n=5 per group), indicating that PGE2 is upstream of NOX2 in the signaling pathway mediating the cerebrovascular effects of Ang II.
EP1 Receptors and COX-1–Derived PGE2 Contribute to Ang II–Induced ROS Production
In wild-type mice, Ang II increased ROS production in neocortical cerebral blood vessels, as reported previously5 (Figure 5A; n=5 per group). The increase in ROS evoked by Ang II was markedly attenuated by SC51089 superfusion (Figure 5A). Furthermore, the ROS increase was attenuated by the COX-1 inhibitor SC560 but not by the COX-2 inhibitor NS398 (Figure 5B; n=5 per group). In vehicle-treated mice, PGE2 superfusion did not affect baseline ROS production, but, in mice treated with SC560, PGE2 re-established the increase in ROS induced by Ang II, whereas PGF2α had no effect (Figure 5; n=5 per group).
Cellular Localization of COX-1 and EP1 Receptors
In the somatosensory cortex, COX-1 immunoreactivity was localized to small cells with fine ramified processes that were also immunopositive for the microglial marker ionized calcium-binding adaptor molecule 1 (Figure 6). COX-1 immunoreactivity was not observed in cerebral blood vessels, identified by the endothelial cell marker CD31 (Figure 6), neurons (neuronal nuclei), or astrocytes (glial fibrillary acidic protein, see Figure S3). In contrast, EP1 receptor immunoreactivity was observed in CD31+ vascular profiles and neurons (Figure 6 and see Figure S3) but did not colocalize with microglial and astrocytic markers (see Figure S3). Therefore, COX-1 is present in microglia, whereas EP1 receptors are present in neurons and endothelial cells.
Effect of Ang II, NS398, and SC560 on PGE2 in the Somatosensory Cortex
To determine whether Ang II increases PGE2 production in the brain, we studied the effect of acute Ang II infusion on PGE2 concentration in the somatosensory cortex and the renal cortex. Ang II infusion increased PGE2 in the kidney (saline: 0.53±0.09 ng/mg of tissue; Ang II: 1.43±0.03 ng/mg of tissue; P<0.05; n=5 per group) but not in the brain (saline: 3.49±0.34 ng/mg of tissue; Ang II: 3.54±0.4 ng/mg of tissue; P>0.05; n=5 per group). In separate mice, superfusion with SC560, but not NS398, markedly attenuated PGE2 concentration (vehicle: 4.32±0.76 ng/mg of tissue; SC560: 0.23±0.04 ng/mg of tissue, P<0.05; NS398: 4.52±0.29 ng/mg of tissue; P>0.05; n=5 per group), attesting to the dominant role of COX-1 in constitutive PGE2 production in the neocortex.
We have demonstrated that the cerebrovascular dysfunction induced by acute or chronic Ang II is prevented by the EP1 receptor antagonist SC51089. The COX-1 inhibitor SC560 prevented the cerebrovascular effects of acute Ang II, whereas the COX-2 inhibitor NS398 did not, implicating COX-1 as the enzymatic source of PGE2. Measurements of PGE2 documented that COX-1 is the major source of this prostaglandin in the somatosensory cortex. Neocortical superfusion with PGE2 reinstated the cerebrovascular effects of Ang II in mice treated with SC560. However, PGE2 was not effective in mice treated with SC51089 or in EP1-null mice, ruling out the participation of other prostanoid receptors in the effect of PGE2. Ang II–induced ROS production was attenuated after inhibition of COX-1 or EP1 receptors, and PGE2 counteracted the attenuation observed with COX1 inhibition. Using immunocytochemistry to determine the cellular source(s) and targets of PGE2, we observed COX-1 in microglia and EP1 receptors in endothelial cells and neurons. These novel findings provide the first evidence that the deleterious cerebrovascular effects of Ang II require COX-1–derived PGE2 and EP1 receptors.
The observation that PGE2 reinstates the cerebrovascular dysfunction induced by Ang II after COX-1 inhibition cannot be attributed to a deleterious cerebrovascular effect of PGE2, because PGE2 did not alter resting CBF or its response to whisker stimulation, ACh, or adenosine. SC51089 and NS398 did not alter resting CBF, but SC560, as anticipated,16 produced a small CBF reduction that does not affect the interpretation of the data. Although the concentration of PGE2 applied to the cerebral cortex (1 μmol/L) is larger than the endogenous concentration, we anticipate that the effective concentration reaching the volume of tissue in which CBF was recorded (≈1 mm3) is lower, because the bioavailability of PGE2 is reduced in biological fluids.8 In addition, the observation that PGE2 does not counteract the cerebrovascular dysfunction in mice treated with SC51089 or in EP1-null mice, and that PGF2α does not mimic the effects of PGE2, rules out nonspecific effects.
We have shown here that in the cerebral cortex, unlike the renal cortex, circulating Ang II does not increase PGE2 production. This observation is consistent with the well-established finding that COX-1, the source of the PGE2 precursor prostaglandin H2 in our model, is present in microglial cells,21 which reside inside the blood-brain barrier and are not accessible to circulating Ang II. It is, therefore, likely that constitutive PGE2 production by COX-1, rather than Ang II–stimulated PGE2 production, is required for the expression of the cerebrovascular dysregulation induced by Ang II. Our finding that SC560, but not NS398, reduces baseline PGE2 production in the neocortex supports this hypothesis. Collectively, our data raise the possibility that microglial COX-1–dependent PGE2 production plays a role in cerebrovascular dysregulation induced by Ang II. However, we cannot rule out that endothelial COX-1 is expressed below immunocytochemistry detection levels or that COX-1–derived prostaglandin H2 from microglia is converted to PGE2 by PGE2 synthase present in the vessel wall.22
We found that the increase in ROS induced by Ang II requires COX-1–derived PGE2 and EP1 receptors. We have demonstrated previously that the increase in ROS induced by circulating Ang II is restricted to cerebrovascular cells, mainly endothelial cells, and is mediated by a NOX2-containing NADPH oxidase.3,5 NOX2-derived superoxide reacts with NO derived from endothelial NO synthase to form peroxynitrite, which, in turn, is responsible for the attenuation of endothelium-dependent responses and functional hyperemia.6 The findings of the present study suggest that constitutive PGE2-induced activation of EP1 receptors is needed for Ang II to trigger ROS production from NOX-2. The observation that PGE2 by itself does not increase ROS indicates that PGE2 does not affect NADPH oxidase activity directly but that baseline levels of this prostanoid are needed to enable the NADPH oxidase activation induced by Ang II. This scenario is reminiscent of the effect of PGE2 on Ca2+ in neurons, in which PGE2 does not increase intracellular Ca2+ but is required for the Ca2+ rise induced by N-methyl-d-aspartate.14 The finding that PGE2 does not increase ROS if EP1 receptors are inhibited provides evidence that only EP1 receptors, and not other prostanoids receptors, are involved in this process. Considering that EP1 receptors can increase intracellular Ca2+ through the Na+/Ca2+ exchanger,14 their activation may be needed to facilitate the intracellular Ca2+ increase required to activate NADPH oxidase. This possibility is supported by evidence that the Na+/Ca2+ exchanger contributes to the increase in cytosolic Ca2+ induced by Ang II in renal arterioles.23
EP1-null mice have been reported previously to have small reductions in resting blood pressure,10 a finding confirmed here, although the MAP change did not reach statistical significance. An EP1-null mouse developed more recently exhibited reduced resting MAP and an attenuation of the increase in blood pressure induced by Ang II.11 In our study, we did not observe a reduction in the acute hypertensive effects of Ang II, despite the attenuation of the cerebrovascular effects. The reasons for this discrepancy are not clear, although confounding effects of anesthesia could play a role. Furthermore, the mice used by Guan et al11 were generated using a different gene-targeting strategy and cannot be directly compared with the EP1-null mice used in the present study. Irrespective of the role of EP1 receptors in the elevation in blood pressure, our findings clearly establish their involvement in the cerebrovascular effects of Ang II.
Essential hypertension attenuates the increase in CBF induced by neural activity,24 but, to our knowledge, the role of COX inhibitors in such attenuation has not been examined. However, there is evidence that the COX pathway participates in the systemic endothelial dysfunction observed in hypertensive patients.25 We found that EP1 receptors are essential in the cerebrovascular dysfunction induced by acute or chronic Ang II administration. With chronic Ang II administration, the rescue of the cerebrovascular dysfunction is not complete, suggesting that a component of the dysfunction is mediated by mechanisms independent of EP1 receptors.
We have demonstrated that the vascular dysregulation induced by Ang II requires COX-1–derived PGE2 acting on EP1 receptors. PGE2 and EP1 receptors do not increase ROS directly, but they are necessary for the NADPH oxidase–dependent ROS production induced by Ang II. Ang II does not increase PGE2 in the cerebral cortex, indicating that COX-1–dependent constitutive PGE2 production is involved in the effect. On the basis of the localization of COX-1 in microglia and of EP1 receptors in cerebral arterioles, we speculate that PGE2 could originate from microglia and acts on vascular EP1 receptors to enable Ang II–induced vascular oxidative stress. These observations provide evidence for a previously unrecognized permissive role of EP1 receptors in the cerebrovascular dysfunction induced by Ang II and raise the possibility that microglial cells are capable of modulating cerebrovascular responses through COX-1–derived PGE2.
Sources of Funding
This work was supported by National Institutes of Health grants HL18974, HL96571, and NS35806.
- Received October 12, 2009.
- Revision received November 4, 2009.
- Accepted January 28, 2010.
Iadecola C, Park L, Capone C. Threats to the mind: aging, amyloid, and hypertension. Stroke. 2009; 40: S40–S44.
Kazama K, Anrather J, Zhou P, Girouard H, Frys K, Milner TA, Iadecola C. Angiotensin II impairs neurovascular coupling in neocortex through NADPH-oxidase-derived radicals. Circ Res. 2004; 95: 1019–1026.
Kazama K, Wang G, Frys K, Anrather J, Iadecola C. Angiotensin II attenuates functional hyperemia in the mouse somatosensory cortex. Am J Physiol Heart Circ Physiol. 2003; 285: H1890–H1899.
Girouard H, Park L, Anrather J, Zhou P, Iadecola C. Angiotensin II attenuates endothelium-dependent responses in the cerebral microcirculation through nox-2-derived radicals. Arterioscler Thromb Vasc Biol. 2006; 26: 826–832.
Girouard H, Park L, Anrather J, Zhou P, Iadecola C. Cerebrovascular nitrosative stress mediates neurovascular and endothelial dysfunction induced by angiotensin II. Arterioscler Thromb Vasc Biol. 2007; 27: 303–309.
Reckelhoff JF, Romero JC. Role of oxidative stress in angiotensin-induced hypertension. Am J Physiol Regul Integr Comp Physiol. 2003; 284: R893–R912.
Smyth EM, Grosser T, Wang M, Yu Y, FitzGerald GA. Prostanoids in health and disease. J Lipid Res. 2009; 50 Suppl: S423–S428.
Suganami T, Mori K, Tanaka I, Mukoyama M, Sugawara A, Makino H, Muro S, Yahata K, Ohuchida S, Maruyama T, Narumiya S, Nakao K. Role of prostaglandin E receptor EP1 subtype in the development of renal injury in genetically hypertensive rats. Hypertension. 2003; 42: 1183–1190.
Rutkai I, Feher A, Erdei N, Henrion D, Papp Z, Edes I, Koller A, Kaley G, Bagi Z. Activation of prostaglandin E2 EP1 receptor increases arteriolar tone and blood pressure in mice with type 2 diabetes. Cardiovasc Res. 2009; 83: 148–154.
Park L, Zhou P, Pitstick R, Capone C, Anrather J, Norris EH, Younkin L, Younkin S, Carlson G, McEwen BS, Iadecola C. Nox2-derived radicals contribute to neurovascular and behavioral dysfunction in mice overexpressing the amyloid precursor protein. Proc Natl Acad Sci U S A. 2008; 105: 1347–1352.
Niwa K, Haensel C, Ross ME, Iadecola C. Cyclooxygenase-1 participates in selected vasodilator responses of the cerebral circulation. Circ Res. 2001; 88: 600–608.
Niwa K, Araki E, Morham SG, Ross ME, Iadecola C. Cyclooxygenase-2 contributes to functional hyperemia in whisker-barrel cortex. J Neurosci. 2000; 20: 763–770.
Girouard H, Lessard A, Capone C, Milner TA, Iadecola C. The neurovascular dysfunction induced by angiotensin II in the mouse neocortex is sexually dimorphic. Am J Physiol Heart Circ Physiol. 2008; 294: H156–H163.
Capone C, Anrather J, Milner TA, Iadecola C. Estrous cycle-dependent neurovascular dysfunction induced by angiotensin II in the mouse neocortex. Hypertension. 2009; 54: 302–307.
Garcia-Bueno B, Serrats J, Sawchenko PE. Cerebrovascular cyclooxygenase-1 expression, regulation, and role in hypothalamic-pituitary-adrenal axis activation by inflammatory stimuli. J Neurosci. 2009; 29: 12970–12981.
Jadhav V, Jabre A, Chen MF, Lee TJ. Presynaptic prostaglandin E2 EP1-receptor facilitation of cerebral nitrergic neurogenic vasodilation. Stroke. 2009; 40: 261–269.
Fellner SK, Arendshorst WJ. Angiotensin II-stimulated Ca2+ entry mechanisms in afferent arterioles: role of transient receptor potential canonical channels and reverse Na+/Ca2+ exchange. Am J Physiol Renal Physiol. 2008; 294: F212–F219.