Epoxyeicosatrienoic acid-dependent cerebral vasodilation evoked by metabotropic glutamate receptor activation in vivo

Xiaoguang Liu, Chunyuan Li, Debebe Gebremedhin, Sung Hee Hwang, Bruce D. Hammock, John R. Falck, Richard J. Roman, David R. Harder, Raymond C. Koehler

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

Group I metabotropic glutamate receptors (mGluR) on astrocytes have been shown to participate in cerebral vasodilation to neuronal activation in brain slices. Pharmacological stimulation of mGluR in brain slices can produce arteriolar constriction or dilation depending on the initial degree of vascular tone. Here, we examined whether pharmacological stimulation of mGluR in vivo increases cerebral blood flow. A 1-mM solution of the group I mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG) superfused at 5 μl/min over the cortical surface of anesthetized rats produced a 30 ± 2% (±SE) increase in blood flow measured by laser-Doppler flowmetry after 15-20 min. The response was completely blocked by superfusion of group I mGluR antagonists and attenuated by superfusion of an epoxyeicosatrienoic acid (EET) antagonist (5 ± 4%), an EET synthesis inhibitor (11 ± 3%), and a cyclooxygenase-2 inhibitor (15 ± 3%). The peak blood flow response was not significantly affected by administration of inhibitors of cyclooxygenase-1, neuronal nitric oxide synthase, heme oxygenase, adenosine A2B receptors, or an inhibitor of the synthesis of 20- hydroxyeicosatetraenoic acid (20-HETE). The blood flow response gradually waned following 30-60 min of DHPG superfusion. This loss of the flow response was attenuated by a 20-HETE synthesis inhibitor and was prevented by superfusion of an inhibitor of epoxide hydrolase, which hydrolyzes EETs. These results indicate that pharmacological stimulation of mGluR in vivo increases cerebral blood flow and that the response depends on the release of EETs and a metabolite of cyclooxygenase-2. Epoxide hydrolase activity and 20- HETE synthesis limit the duration of the response to prolonged mGluR activation.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume301
Issue number2
DOIs
StatePublished - Aug 2011

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Metabotropic Glutamate Receptors
Vasodilation
Acids
Cerebrovascular Circulation
Epoxide Hydrolases
Pharmacology
Adenosine A2B Receptors
Excitatory Amino Acid Agonists
Heme Oxygenase (Decyclizing)
Silicone Elastomers
Excitatory Amino Acid Antagonists
Cyclooxygenase 1
Nitric Oxide Synthase Type I
Laser-Doppler Flowmetry
Cyclooxygenase 2 Inhibitors
Brain
Cyclooxygenase 2
Constriction
Astrocytes
Blood Vessels

Keywords

  • Astrocyte
  • Cerebral blood flow
  • Epoxide hydrolase
  • Epoxygenase
  • Neurovascular coupling

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)
  • Cardiology and Cardiovascular Medicine

Cite this

Epoxyeicosatrienoic acid-dependent cerebral vasodilation evoked by metabotropic glutamate receptor activation in vivo. / Liu, Xiaoguang; Li, Chunyuan; Gebremedhin, Debebe; Hwang, Sung Hee; Hammock, Bruce D.; Falck, John R.; Roman, Richard J.; Harder, David R.; Koehler, Raymond C.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 301, No. 2, 08.2011.

Research output: Contribution to journalArticle

Liu, Xiaoguang ; Li, Chunyuan ; Gebremedhin, Debebe ; Hwang, Sung Hee ; Hammock, Bruce D. ; Falck, John R. ; Roman, Richard J. ; Harder, David R. ; Koehler, Raymond C. / Epoxyeicosatrienoic acid-dependent cerebral vasodilation evoked by metabotropic glutamate receptor activation in vivo. In: American Journal of Physiology - Heart and Circulatory Physiology. 2011 ; Vol. 301, No. 2.
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abstract = "Group I metabotropic glutamate receptors (mGluR) on astrocytes have been shown to participate in cerebral vasodilation to neuronal activation in brain slices. Pharmacological stimulation of mGluR in brain slices can produce arteriolar constriction or dilation depending on the initial degree of vascular tone. Here, we examined whether pharmacological stimulation of mGluR in vivo increases cerebral blood flow. A 1-mM solution of the group I mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG) superfused at 5 μl/min over the cortical surface of anesthetized rats produced a 30 ± 2{\%} (±SE) increase in blood flow measured by laser-Doppler flowmetry after 15-20 min. The response was completely blocked by superfusion of group I mGluR antagonists and attenuated by superfusion of an epoxyeicosatrienoic acid (EET) antagonist (5 ± 4{\%}), an EET synthesis inhibitor (11 ± 3{\%}), and a cyclooxygenase-2 inhibitor (15 ± 3{\%}). The peak blood flow response was not significantly affected by administration of inhibitors of cyclooxygenase-1, neuronal nitric oxide synthase, heme oxygenase, adenosine A2B receptors, or an inhibitor of the synthesis of 20- hydroxyeicosatetraenoic acid (20-HETE). The blood flow response gradually waned following 30-60 min of DHPG superfusion. This loss of the flow response was attenuated by a 20-HETE synthesis inhibitor and was prevented by superfusion of an inhibitor of epoxide hydrolase, which hydrolyzes EETs. These results indicate that pharmacological stimulation of mGluR in vivo increases cerebral blood flow and that the response depends on the release of EETs and a metabolite of cyclooxygenase-2. Epoxide hydrolase activity and 20- HETE synthesis limit the duration of the response to prolonged mGluR activation.",
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AU - Falck, John R.

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