The cardiovascular effects of insulin-like growth factor-1 in the nucleus tractus solitarii of rats

• Main Authors: Shin-shue Lin, 林鑫秀
• Other Authors: none
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/58697789420334874150

碩士 === 國立中山大學 === 生物醫學科學研究所 === 93 === Insulin-like growth factor 1 (IGF-1) was considered as a factor potentially involved in arterial hypertension because of its effects on vascular tone. Several studies have suggested that IGF-1 might play an important role in the cardiovascular system for regulation of blood pressure. Previously, microinjection of insulin into the NTS of rats preceded prominent depressor and bradycardic and activates the PI3K downstream Akt. The aims of this study was to compare the cardiovascular responses induced by IGF-1 and to investigate the mechanisms of IGF-1induced signaling pathway in the nucleus tractus solitarius (NTS) between spontaneously hypertensive rat (SHR) and normotensive Wistar-Kyoto rat (WKY) at 8/16 weeks old. The results indicate that microinjection of IGF-1 into the NTS of WKY and SHR produced dramatically depressor and bradycardic effects. The cardiovascular effects evoked by IGF-1 are less in SHR than WKY rats. The defect in IGF-1 vascular action is also present in young spontaneously hypertensive rats (age 8 weeks). Pretreatment with the phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 significantly attenuated the responses evoked by microinjection of IGF-1 in both SHR and WKY at 8/16 weeks old. Moreover, mitogen-activated protein kinase kinase (p44/p42MAPK) inhibitor PD98059 administration attenuated the cardiovascular effects of IGF-1 in WKY at 8/16 weeks old but had no effect in SHR at age matched. In conclusion, both IGF-1/PI3K and p44/p42MAPK signal transduction pathways are involved in controlling central cardiovascular effects in WKY, whereas PI3K but not p44/p42MAPK signaling pathway is involved in SHR. This different condition suggests that such insensitive pathway may play a causative role in the development of hypertension.