Role of AMPA/kainate receptors in transmission of the sympathetic baroreflex in rat CVLM

Takashi Miyawaki, Satoshi Suzuki, Jane Minson, Leonard Arnolda, John Chalmers, Ida Llewellyn-Smith, Paul Pilowsky*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    37 Citations (Scopus)

    Abstract

    We examined the role of α-amino-3-hydroxy-5-methyl-4- isoxazolepropionic acid (AMPA)/kainate receptors within the caudal ventrolateral medulla (CVLM) in mediating the sympathetic baroreceptor reflex in anesthetized and paralyzed rats. Bilateral microinjection into CVLM of either DL-2-amino-5-phosphonovaleric acid [APV; a selective N-methyl-D- aspartic acid (NMDA) receptor antagonist, 20 mM, 100 nl] or 6-cyano-7- nitroquinoxaline-2,3-dione (CNQX; a selective AMPA/kainate receptor antagonist, 2 mM, 100 nl) alone failed to eliminate the aortic nerve stimulation-evoked hypotension and inhibition of splanchnic sympathetic nerve activity (SNA) or the cardiac-related rhythmicity of SNA. All components of the sympathetic-baroreceptor reflex were abolished when kynurenate (100 mM, 30 nl) or mixtures of APV and CNQX (10 and 1 mM, respectively, 100 or 30 nl) were injected into CVLM. Injection of APV or CNQX into CVLM reduced aortic nerve-evoked inhibitory responses of bulbospinal sympathoexcitatory neurons in rostral ventrolateral medulla (RVLM). The extent of this reduction was variable. Usually, significant inhibition was preserved. In seven RVLM neurons, intravenous injection of MK-801 (NMDA receptor antagonist, 2 mg/kg) failed to eliminate aortic nerve-evoked inhibitory responses. However, inhibitory responses were abolished when CNQX was injected into CVLM after intravenous MK-801. We conclude that both NMDA and AMPA/kainate receptors in CVLM transmit baroreceptor information.

    Original languageEnglish
    Pages (from-to)R800-812
    Number of pages13
    JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
    Volume272
    Issue number3 Pt. 2
    Publication statusPublished - Mar 1997

    Keywords

    • baroreceptor
    • blood pressure
    • excitatory amino acids
    • MK-801
    • sympathetic nerve activity

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