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.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0809104-140113 |
| Date | 09 August 2004 |
| Creators | Weng, Wen-Tsan |
| Contributors | Ming-Hong Tai, Long-Sen Chang, Jwu-Lai Yeh, Ching-Jiunn Tseng |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0809104-140113 |
| Rights | withheld, Copyright information available at source archive |
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