Chronic continuous light exposure leads to melatonin deficiency along with complex neurohumoral activation resulting in hypertension development in rats. The aim of this study was to show, whether continuous light in duces fibrotic rebuilding of the aorta and whether the treatment with melatonin or angiotensin converting enzyme inhibitor captopril can prevent these potential alterations. In a six-week experiment, 3-month-old Wistar rats were divided into 4 groups (t en per group): controls, rats exposed to continuous light, exposed to continuous light plus treated with captopril (100 mg/kg/24 h) and exposed to continuous light plus treated with melatonin (10 mg/kg/24 h). Systolic blood pressure (SBP) and collagen type I and III in the media of thoracic aorta were me asured. Continuous light induced hypertension and fibrotic rebuilding of the aorta in terms of enhancement of collagen I and III concentration in the aortic media. Both captopril and melatonin prevented SBP rise and reduced collagen III concentration in the aorta. However, only melatonin reduced collagen I and the sum of collagen I and III in the aortic tissue. We conclude that in continuous light-induced hypertension, administration of melatonin, along with SBP reduction, decreases collagen I and III concentration in the aorta. It is suggested that antifibrotic effect of melatonin may reduce the stiffness of the aorta and small arteries and beneficially influence the nature of the pulse wave and peripheral vascular resistance., K. Repová-Bednárová ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Under continuous light (LL) of low intensity (up to 2.0 lux), the free-running period of the blow fly activity rhythm lengthened for flies whose initial τDD was less than about 25 h, but shortened for longer-period flies. Light intensity above about 2.0 lux led to an overt behavioural arrhythmicity. A comparison of phases of the oscillation after LL as a function of phases before LL, however, indicated that the oscillation continued its motion even though overt behaviour was arrhythmic. As the intensity during LL increased to 48 lux, phases after LL became centred on a narrow range close to CT 12. Extended periods of brighter light are considered to have two effects: (a) an exogenous "masking" effect occurring at intensities greater than about 2.0 lux, and (b) at intensities between about 2.0 and 48 lux, a gradual resetting of the covert oscillator to CT 12. Between 2.0 and 48 lux, therefore, the circadian oscillation governing locomotor activity in C. vicina continues its motion despite the superficial arrhythmicity in behaviour.