Cardiovascular responses to tonic pain in REM sleep-deprived rats. Role of melatonin and beta endorphin

Chronic pain is associated with increased incidence of hypertension. Sleep deprivation, common in patients with chronic pain, is associated with increased blood pressure and heart rate. This study was designed to determine whether sleep deprivation induces increased cardiovascular responses to pain. In addition; we examined the role of melatonin and endorphins in mediating these responses. The study was conducted in Sprague-Dawely rats divided into a control group [n=8] and Rapid Eye Moment sleep deprived [REMSD] group [n=8]. REM sleep deprivation was done for three days using the inverted flowerpot technique. Systolic BP and HR were recorded at baseline as well as 5, 10 and 30 minutes after intra-plantar formalin injection. In addition, serum melatonin and endorphin levels were determined. Under basal conditions, BP and HR and following acute pain [1[st] phase of formalin injection] were comparable with non-sleep deprived [non-SD] state. In contrast, the REMSD rats showed significantly greater increases in HR and BP during the 2[nd] phase of formalin pain as compared to non-SD state. These changes were associated with significant reductions in serum melatonin and endorphin levels in REMSD rats. These data indicate that exaggerated blood pressure and HR responsiveness to pain in sleep deprivation could be mediated through reductions in melatonin and endorphin

Interactions between leptin, neuropeptide-Y and insulin with chronic diurnal fasting during Ramadan

Background: Fasting during the month of Ramadan for Muslims is a unique metabolic model that includes abstinence from food and fluid intake during the period from dawn to sunset as well as a reduction in meal frequency and alterations in the sleep-wakefulness cycle. Leptin, neuropeptide-Y and insulin are thought to play an important role in long-term regulation of caloric intake and energy expenditure. However, the long-term changes and interactions between these factors during this pattern of fasting are not known

Subjects and Methods: The study was conducted on 46 healthy female volunteers [age, 22 +/- 2 years; BMI, 25.3 +/- 0.7 kg/m2]. Anthropometrical measurements, estimation of body fat and fasting serum levels of neuropeptide Y, leptin, insulin and glucose were estimated at baseline [day 1], days 14 and 28 of the month of Ramadan and 2 weeks after Ramadan

Results: Baseline serum levels of leptin correlated positively with body fat [r=0.87, P=0.0002]. Serum leptin levels exhibited a significant increase by approximately 41% and neuropeptide-Y levels were decreased by 30.4% throughout the month of Ramadan. In addition, a significant correlation [r=0.63, P=0.0001] was found between changes in serum leptin and serum insulin. However, changes in serum neuropeptide-Y levels did not correlate with those of leptin or insulin

Conclusion: Long-term fasting with interrupted nocturnal eating is associated with significant elevations in serum leptin and insulin and reduction in serum neuropeptide-Y. The changes in serum leptin are likely mediated through insulin. However, changes in neuropeptide-Y appears to be mediated independently of leptin or insulin during this type of fasting