The Effect of High Fat-Induced Obesity on Cardiovascular and Physical Activity and Opioid Responsiveness in Conscious Rats

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 β-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...