Somatostatin 2 receptor activation in the rostral ventrolateral medulla does not mediate the decompensatory phase of haemorrhage

Phillip Bokiniec, Peter G. R. Burke, Anita J. Turner, Simon McMullan, Ann K. Goodchild

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    1 Citation (Scopus)

    Abstract

    Decompensation, a critical phase in the response to hemorrhage, is characterized by profound sympathoinhibition and the overriding of baroreflex mediated compensation. As sympathoexcitatory neurons of the rostral ventrolateral medulla (RVLM) maintain vasomotor tone and are essential for sympathetic baroreceptor reflex function, the RVLM is the likely mediator. However, how decompensation occurs is a mystery. Our previous work demonstrated that the inhibitory neuropeptide somatostatin (SST), evokes potent sympathoinhibition. Here we test the hypothesis that, in response to hypovolemia, SST in the RVLM evokes sympathoinhibition, driving decompensation and suppressing baroreflex compensation. We evaluated neuronal activation at sites that contain SSTmRNA and project to the RVLM and, in SST2A expressing neurons in the RVLM. We determined the effects on cardiovascular and sympathetic responses to haemorrhage, of bilateral
    blockade of SST2 receptors in both the RVLM and A1 regions. Haemorrhage in conscious rats evoked c-Fos immunoreactivity in the amygdala, periaqueductal gray, and parabrachial nuclei, regions previously associated with hemorrhage, shown to contain SSTand project to the RVLM. Although c-Fos labeling was found throughout the ventrolateral medulla, only a small subset of RVLM SST2A receptor expressing neurons were activated, consistent with the idea that these neurons are inhibited during hemorrhage. However, SST2 receptor antagonists bilaterally injected in the RVLM or the A1 region did not affect the decompensation response to hemorrhage. Thus somatostatin in the RVLM does not mediate decompensation. The physiological role associated with somatostatin-induced sympathoinhibition in the RVLM together with the central
    mechanisms responsible for decompensation remain elusive.
    Original languageEnglish
    Pages (from-to)331-338
    Number of pages8
    JournalShock
    Volume50
    Issue number3
    Early online date4 Oct 2017
    DOIs
    Publication statusPublished - 1 Sep 2018

    Keywords

    • Somatostatin receptors
    • blood loss
    • decompensation
    • sympathetic nerve activity
    • ventral medulla
    • Blood loss
    • Decompensation
    • Ventral medulla
    • Sympathetic nerve activity

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