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The Cardiovascular Effects of alpha-Melanocyte-Stimulating Hormone in the Nucleus Tractus Solitarii of Spontaneously Hypertensive Rats

by Weng, Wen-Tsan

Abstract (Summary)
alpha-melanocyte stimulating hormone (alpha-MSH) is an important regulator of food intake, metabolic rate, and inflammation. Recently, alpha-MSH was shown to influence sympathetic activity and blood pressure regulation. In the present study, we investigated the cardiovascular effects of alpha-MSH in the nucleus tractus solitarii (NTS) of spontaneously hypertensive rats (SHR). Because nitric oxide (NO) is well-known to involve in central cardiovascular regulation, we elucidated the role of NO in the cardiovascular responses induced by alpha-MSH. In urethane-anesthetized SHR, unilateral microinjection of alpha-MSH (0.3-300 pmol) into the NTS produced dose-responsive depressor and bradycardic effects. The cardiovascular effects of alpha-MSH were abrogated by the antagonist of melanocortin receptor (MC3/4-R), SHU9119. Pretreatment with precursor of nitric oxide, L-arginine, enhanced the duration of alpha-MSH-mediated hypotensive effects, whereas prior application of L-NAME, a universal inhibitor of nitric oxide synthase (NOS), significantly attenuated the effects of alpha-MSH. Prior injection with inhibitor of inducible NOS, aminoguanidine, but not inhibitor of neuronal NOS, 7-nitroindazole, attenuated the hypotensive effect of alpha-MSH. In summary, these results indicated alpha-MSH induced depressor and bradycardic effects in the NTS of SHR. Besides, the hypotensive mechanism of alpha-MSH was mediated via MC4-R and involved with iNOS activation in the NTS of SHR.
Bibliographical Information:

Advisor:Ming-Hong Tai; Long-Sen Chang; Jwu-Lai Yeh; Ching-Jiunn Tseng

School:National Sun Yat-Sen University

School Location:China - Taiwan

Source Type:Master's Thesis

Keywords:spontaneously hypertensive rats shr nucleus tractus solitarii nts depressor and bradycardic effects nitric oxide no melanocortin receptor cardiovascular effect alpha melanocyte stimulating hormone

ISBN:

Date of Publication:08/09/2004

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