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Differential cardiorespiratory and sympathetic reflex responses to microinjection of neuromedin U in rat rostral ventrolateral medulla.
MedLine Citation:
PMID:  22262923     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The rostral ventrolateral medulla (RVLM) regulates sympathetic vasomotor outflow and reflexes. Intracerebroventricular neuromedin U (NMU) increases sympathetic nerve activity (SNA), mean arterial pressure (MAP) and heart rate (HR), but the central nuclei that mediate these effects are unknown. In urethane-anaesthetized, vagotomized and artificially ventilated male Sprague-Dawley rats (n = 36) the effects of bilateral microinjection of NMU (50 nl, each side) into RVLM on cardiorespiratory variables, somatosympathetic, arterial baro- and chemo- reflexes were investigated. Microinjection of NMU into RVLM elicited a hypertension, tachycardia, and an increase in splanchnic SNA (SSNA) and lumbar SNA (LSNA) at lower doses (25 and 50 pmol). At higher dose (100 pmol), NMU caused a biphasic response, a brief hypertension and sympathoexcitation followed by a prolonged hypotension and sympathoinhibition. The peak excitatory and inhibitory response was found at 100 pmol NMU with an increase in MAP, HR, SSNA and LSNA of 36 mmHg, 20 bpm, 34% and 89%, respectively, and a decrease of 33 mmHg, 25 bpm, 42% and 52%, respectively, from baseline. NMU, in the RVLM, also increased phrenic nerve amplitude, expiratory period, and reduced inspiratory period. NMU (100 pmol) attenuated the somatosympathetic reflex, and the sympathoexcitatory and respiratory responses to hypoxia and hypercapnia. Following NMU injection in RVLM, the maximum gain of the SSNA baroreflex function curve was increased, but that of the LSNA was reduced. The present study provides functional evidence for a complex differential modulatory activity of NMU on the cardiovascular and reflex responses that are integrated in the RVLM.
Authors:
Ahmed A Rahman; Israt Z Shahid; Paul M Pilowsky
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-1-18
Journal Detail:
Title:  The Journal of pharmacology and experimental therapeutics     Volume:  -     ISSN:  1521-0103     ISO Abbreviation:  -     Publication Date:  2012 Jan 
Date Detail:
Created Date:  2012-1-20     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0376362     Medline TA:  J Pharmacol Exp Ther     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Macquarie University.
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