Journal
CLINICAL AND EXPERIMENTAL HYPERTENSION
Volume 28, Issue 2, Pages 133-145Publisher
TAYLOR & FRANCIS INC
DOI: 10.1080/10641960500468326
Keywords
beta-FNA; blood pressure; DAMGO; heart rate; mu opioids
Funding
- NIGMS NIH HHS [GM-058905] Funding Source: Medline
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Both obesity and increased endorphin production are associated with an increase in blood pressure. We have previously demonstrated that the acute and chronic central nervous system (CNS) administration of beta-endorphin can increase or decrease blood pressure, respectively. Also high fat (HF) diet-induced obesity is associated with increased hypothalamic mu opioid receptors and increased blood pressure in response to ss-endorphins. In this study we investigated the effect of high fat diet-induced obesity on blood pressure, heart rate, and physical activity as well as determined the effect of mu opioids in unanesthetized rats. Male Wistar rats were implanted with a radiotelemetry transmitter to record cardiovascular dynamics and activity. They were fed either a HF diet (HF; 59% fat by caloric content, soy bean oil) or regular chow (control; 12% fat by caloric content). HF rats had higher body weights and their total caloric intake was greater than controls. The systolic blood pressures (SBP) were greater in the HF-obese rats. After 12-13 weeks the rats were infused chronically with a mu opioid agonist (D)-Ala(2) , N-Me-Phe(4) , Gly(5)-ol]-ENKEPHALIN (DAMGO) or a mu opioid antagonist ss-funaltrexamine (ss-FNA) via intracerebroventricular cannula. DAMGO increased the SBP and heart rate in controls, but not in HF obese rats. DAMGO did not affect physical activity; ss-FNA decreased SBP and increased HR in controls. We concluded that HF rats consumed more calories, gained more weight, and had higher SBP. However, the responsiveness to the mu-receptor agonist was not higher in the HF rats.
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