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Intrathecal melanin concentrating hormone reduces sympathetic tone and blocks cardiovascular reflexes.
MedLine Citation:
PMID:  22814666     Owner:  NLM     Status:  Publisher    
Melanin concentrating hormone (MCH) is a neuropeptide that acts to increase feeding behaviour and decrease energy expenditure. The role of MCH in central cardiorespiratory regulation is still poorly understood. Experiments were conducted on urethane-anaesthetised, vagotomised and artificially ventilated male Sprague-Dawley rats (n= 22) to ascertain if MCH modulates sympathetic vasomotor tone as well as baro-, chemo- and somato-sympathetic reflexes at the level of the spinal cord. Intrathecal injection of 10µl MCH produced a dose-dependent hypotension, bradycardia, and sympatho-inhibition. Peak response was observed following administration of 1mM MCH, causing a decrease in mean arterial pressure of 39 ± 2 mmHg (P < 0.001), splanchnic sympathetic nerve activity of 78 ± 11 % (P < 0.001) and heart rate of 87 ± 11 beats/min (P < 0.01). The two peaks of the somatosympathetic reflex were decreased by intrathecal MCH, 7 ± 3 % (P < 0.01), and 31 ± 6 % (P < 0.01) respectively, and the spinal component of the reflex was accentuated 96 ± 23 % (P < 0.05), with respect to the baseline for MCH, compared to the two peaks and spinal component of the somatosympathetic reflex elicited following saline injection with respect to the baseline for saline. MCH decreased the sympathetic gain to 120s of hyperoxic hypercapnea (10% CO(2) in 90% O(2)) and to 10-12s poikilocapneic anoxia (100% N(2)) from 0.74 ± 0.14%/s to 0.23 ± 0.04 %/s (P < 0.05) and 16.47 ± 3.2 % to 4.35 ± 1.56 % (P < 0.05) respectively. There was a 34% decrease in gain and a 62% decrease in range of the sympathetic baroreflex with intrathecal MCH. This data demonstrates that spinal MCH blunts the central regulation of sympathetic tone and adaptive sympathetic reflexes.
Eyitemi Joseph Egwuenu; Angelina Y Fong; Paul M Pilowsky
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-18
Journal Detail:
Title:  American journal of physiology. Regulatory, integrative and comparative physiology     Volume:  -     ISSN:  1522-1490     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-20     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901230     Medline TA:  Am J Physiol Regul Integr Comp Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1Macquarie University.
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