How does the brain develop differently to support nocturnality in some mammals, but diurnality in others? To answer this, one might look to the suprachiasmatic nucleus (SCN), which is entrained by light via the retinohypothalamic tract (RHT). However, because the SCN is more active during the day in all mammals ...

The suprachiasmatic nucleus is the master circadian clock and resets the peripheral clocks via various pathways. Glucocorticoids and daily feeding are major time cues for entraining most peripheral clocks. However, recent studies have suggested that the dominant timing factor differs among organs and tissues. In our current study, we reveal ...

Melatonin concentration in plasma reaches high levels during the night and synchronizes body rhythms with the photoperiod. Previous evidence obtained in cultured cells suggests that melatonin synchronizes cytoskeletal re-arrangements at nocturnal plasma concentration. In this study, we determined the amount of microtubules and microfilaments in the rat hippocampus as an ...

Aims: The spontaneously hypertensive stroke prone rat (SHRSP) is a potential animal model of human lacunar stroke, but there is little information on SHRSP small vessel pathology, especially in young rats. We investigated the structural changes that occur in cortical and subcortical vessels and adjacent tissue in SHRSP before, during ...

Punch-drunk syndrome (PDS) refers to a pathological condition in which higher brain dysfunction occurs in a delayed fashion in boxers who have suffered repeated blows to the head. However, the underlying mechanisms remain unknown. This study attempted to elucidate the mechanism of higher brain dysfunction observed following skull vibration in ...

The role of radial glia cells (RGCs) as neural progenitors and as guides for migrating neurons is well established, whereas their precise contribution to adult hippocampal neurogenesis remains less understood. To precisely study the properties of hippocampal RGCs under normal conditions in vitro, here we acquired the hippocampal RGCs of ...

The secretory profile of growth hormone (GH) is sexually dimorphic in rats. In male transgenic (TG) rats expressing human GH (hGH) that we generated, the circulating levels of both hGH and endogenous GH are flattened with no male-type pulsatility. To elucidate the regulatory role of episodic GH profile on the ...

In seasonal climatic regimes, animals have to deal with changing environmental conditions. It is reasonable to expect that seasonal changes are reflected in animal overall energetics. The relation between daily energy expenditure (DEE) and seasonally variable ecological determinants has been studied in many free-living small mammals; however with inconsistent results. ...

The aim of the current study was to investigate the effects of triamcinolone acetonide (TA) upon the expression and phosphorylation of growth-associated protein 43 (GAP 43) in the retinas of oxygen-induced retinopathy (OIR) rats. Oxygen-induced retinopathy was induced by exposing Sprague-Dawley rats to hyperoxia (80% oxygen) from postnatal (P) days ...

Circadian rhythms in behavior and physiology change as female mammals transition from one reproductive state to another. The mechanisms responsible for this plasticity are poorly understood. The suprachiasmatic nucleus (SCN) of the hypothalamus contains the primary circadian pacemaker in mammals, and a large portion of its efferent projections terminate in ...

We studied the effects of adverse conditions such as constant light (LL) on the circadian rhythm of malate (MDH, EC 1.1.1.37) and lactate (LDH, EC 1.1.1.27) dehydrogenase activities of the testes of male Wistar rats on postnatal day 28 (PN28), anxiety-like behavior (elevated plus-maze test) at PN60 and sexual behavior ...

The present study was performed to investigate changes of cytosolic and mitochondrial calpain activities, and effects of intravitreously injected calpain inhibitor on photoreceptor apoptosis in Royal College of Surgeon's (RCS) rats. Time courses of activities for both cytosolic and mitochondrial calpains and amount of calpastatin in RCS rat retina were ...

A decrease in the nighttime release of the pineal hormone melatonin is associated with aging and chronic diseases in animals an humans. Melatonin has a protective role in type 2 diabetes; however, its synthesis itself is affected in the disease. The aim of this study was to detect crucially impaired ...

The suprachiasmatic nucleus (SCN) of the hypothalamus is the central pacemaker that controls circadian rhythms in mammals. In diurnal grass rats (Arvicanthis niloticus), many functional aspects of the SCN are similar to those of nocturnal rodents, making it likely that the difference in the circadian system of diurnal and nocturnal ...

Circadian rhythms in behavior and physiology are very different in diurnal and nocturnal rodents. A pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus is responsible for generating and maintaining circadian rhythms in mammals, and cellular and molecular rhythms within the SCN of diurnal and nocturnal rodents are very ...

OBJECTIVE: To investigate the effects of different electromagnetic fields on some haematochemical parameters of circadian rhythms in Sprague-Dawley rats. METHODS: The study was carried out in 18 male and 18 female rats in good health conditions exposed to 50 Hz magnetic sinusoid fields at the intensity of 1000 microT, 100 ...

Studies of the hypothalamic-pituitary-adrenal (HPA) axis and the hypothalamic-pituitary-testicular (HPT) axis have revealed a reciprocal relationship between these two endocrine pathways. In rats, for example, disruption of the HPT axis alters the circadian secretion of corticosterone. Stress, on the other hand, can have varying effects on testosterone secretion in both ...

Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the HD gene. Besides psychiatric, motor and cognitive symptoms, HD patients suffer from sleep disturbances. In order to screen a rat model transgenic for HD (tgHD rats) for sleep-wake cycle dysregulation, we monitored their circadian activity ...

The continuing worldwide epidemic of retinopathy of prematurity (ROP), a leading cause of childhood visual impairment, strongly motivates further research into mechanisms of the disease. Although the hallmark of ROP is abnormal retinal vasculature, a growing body of evidence supports a critical role for the neural retina in the ROP ...

In rats, limited daytime wheel access suppresses feeding over the subsequent night [Lattanzio SB, Eikelboom R. Wheel access duration in rats: I. effects on feeding and running. Behav Neurosci 2003; 117:496-504.]. This phenomenon is known as the wheel-induced feeding suppression (WIFS). The classic antipsychotic, chlorpromazine, can minimize the severity of ...

Albino Sprague-Dawley rats are known to undergo photoreceptor degeneration after exposure to constant light, but the molecular mechanism(s) by which the photoreceptors degenerate is not fully understood. We hypothesized that cytotoxic oxysterols are generated in situ in the retina under such conditions and may be involved in the degenerative mechanism. ...

Hypertensive TGR(mRen2)27 (TGR) rats represent a strain with genetically upregulated renin-angiotensin-aldosterone system. Simultaneously with development of hypertension, a daily profile in blood pressure (BP) inverts and in mature TGR rats BP is higher during the lighttime (L) than the darktime (D). Physiological mechanisms of inverted BP rhythm generation are not ...

Independently, chronic protein malnutrition and aging have been shown to affect locomotor activity (LA) and body temperature (BT) rhythms in mammals. The objective of the present study was to ascertain the combined effects of these two factors by examining period, entrainment and other circadian parameters between LA and BT rhythms. ...

Mammalian species can be defined as diurnal or nocturnal, depending on the temporal niche during which they are active. Even if general activity occurs during nighttime in nocturnal rodents, there is a patchwork of general activity patterns in diurnal rodents, including frequent bimodality (so-called crepuscular pattern, i.e., dawn and dusk ...

The effects of chronic treatment with the antioxidant hormone melatonin on degeneration of serotonergic fibers were studied in the striatum and olfactory tubercle of the zitter rat, which shows a loss-of-function mutation of the glycosylated transmembrane protein attractin. In these animals, serotonergic fibers in the striatum and olfactory tubercle undergo ...

The most widespread models to study blindness, rats and mice, have retinas containing less than 3% cones. The diurnal rodent Arvicanthis niloticus retina has around 35% cones. Using ERG recordings, we studied retina function in this species. Several features differed from that reported in rats and mice: (a) fivefold larger ...

Feeding schedules that limit food availability to a set time of day are powerful synchronizers of the rhythms of expression of the circadian clock protein Period 2 (PER2) in the limbic forebrain in rats. Little is known, however, about the mechanisms that mediate the effect of such timed restricted feeding ...

PURPOSE: To check differences in visual function between Wistar (albino) and Long-Evans (pigmented) rats. METHODS: The animals were born in our facilities and reared under identical light conditions avoiding bright light. Visual electrophysiology was performed at the ages of 1.5, 4, 7 and 10 months (electroretinography, ERG) and at 1.5 ...

Although circadian rhythms of males and females are different in a variety of ways in many species, their mechanisms have been primarily studied in males. Furthermore, rhythms are dramatically different in diurnal and nocturnal animals but have been studied predominantly in nocturnal ones. In the present study, we examined rhythms ...

Housing laboratory animals under lighting conditions that more closely mimic the natural environment may improve their wellbeing. This study examined the effects of dim light or a long-night photocycle on resting heart rate (HR) of rats and their HR responses to acute procedures. Male and female Sprague-Dawley (SD) and spontaneously ...

Adverse cardiovascular events in humans occur with a day/night pattern, presumably related to a daily pattern of behaviours or endogenous circadian rhythms in cardiovascular variables. Healthy humans possess a scale-invariant/fractal structure in heartbeat fluctuations that exhibits an endogenous circadian rhythm and changes towards the structure observed in cardiovascular disease at ...

Relatively little is known about the function of the biological clock and its efferent pathways in diurnal species, despite the fact that its major transmitters and neuronal connections are also conserved in humans. The mammalian biological clock is located in the hypothalamic suprachiasmatic nuclei (SCN). Several lines of evidence suggest ...

BACKGROUND: Melatonin, the primary hormone of the pineal gland, is a known modulator of various physiological processes. The aim of this study was to evaluate the role of melatonin in the pathogenesis of hypertension in rats with metabolic syndrome and to assess whether melatonin supplementation prevents the development of hypertension ...

Two respiration-related rhythm generators, the pre-Bötzinger complex inspiratory and the parafacial pre-inspiratory rhythm generators, have been identified in the medulla of rodents that produce intrinsic periodic bursts. Although both generators can be independently active under specific conditions, they interact as a coupled oscillator system to regulate the respiratory rhythm. Here, ...

PURPOSE: The authors investigated photopic electroretinographic changes during degeneration in the Royal College of Surgeons (RCS) and transgenic P23H rhodopsin rat models, including the cellular origins of a large corneal-negative component that persists in the RCS rat. METHODS: Photopic and scotopic electroretinograms (ERGs) were recorded from dystrophic RCS (RCS-p(+)/Lav) rats ...

Variation in circadian rhythms and nocturnality may, hypothetically, be related to or independent of genetic variation in photoperiodic mediation of seasonal changes in physiology and behavior. We hypothesized that strain variation in photoperiodism between photoperiodic F344 rats and nonphotoperiodic Harlan Sprague Dawley (HSD) rats might be caused by underlying variation ...

PURPOSE: To investigate the effects of citicoline on upregulated clusterin and retinal damage induced by kainic acid (KA). METHODS: KA was injected into the vitreous of rats. Effects of systemic citicoline treatments were estimated by measuring the thickness of the various retinal layers, immunoblotting, and immunohistochemical techniques. RESULTS: One day ...

Restricted feeding schedules (RFS) are a potent Zeitgeber that uncouples daily metabolic and clock gene oscillations in peripheral tissues from the suprachiasmatic nucleus (SCN), which remains entrained to the light-dark cycle. Under RFS, animals develop food anticipatory activity (FAA), characterized by arousal and increased locomotion. Food availability in nature is ...

A study was conducted of acute intoxication of infant and adult Wistar rats with fluoroacetamide (FAA), an inhibitor of oxidative metabolism. FAA was administered orally to adult rats at 1/2 LD(50) and subcutaneously to infant rats at LD(100) or 1/10 LD(50). Electrocardiogram (ECG), respiration and motor activity were registered for ...

Melatonin not only plays a major role in the regulation of circadian rhythms, but is also involved in antioxidative defense and immunomodulation. Circulating melatonin levels are derived primarily from the pineal gland while other sources of melatonin have also been reported. Here, we show for the first time that astrocytes ...

This study investigates the release characteristics of atrial natriuretic peptide (ANP) from young (10 weeks) and old (22 months) rat atrium. Levels of ANP release from samples of atrium were studied by organ perifusion. Rats were exposed to light:dark (LD) cycles of 12:12 or 18:6 and sacrificed at different zeitgeber ...

The nature of the circadian signal from the suprachiasmatic nucleus (SCN) required for prolactin (PRL) surges is unknown. Because the SCN neuronal circadian rhythm is determined by a feedback loop of Period (Per) 1, Per2, and circadian locomotor output cycles kaput (Clock) gene expressions, we investigated the effect of SCN ...

Multiple extracardiac stimuli, such as workload and circulating nutrients (e.g., fatty acids), known to influence myocardial metabolism and contractile function exhibit marked circadian rhythms. The aim of the present study was to investigate whether the rat heart exhibits circadian rhythms in its responsiveness to changes in workload and/or fatty acid ...

PURPOSE: To investigate the protective effect of intravitreal injection of basic fibroblast growth factor-impregnated nanoparticles (bFGF-NPs) against photoreceptor degeneration in Royal College of Surgeons (RCS) rats. METHODS: Three-week-old RCS rats received intravitreal injection of PBS, blank NPs, bFGF (2.5 microg), or bFGF-NPs (2.5 microg). Eyes were assessed by morphologic, immunohistochemical, ...

Retinal degenerative conditions increase susceptibility to light damage, but rapid retinal degeneration (RD) models show less susceptibility to cyclic dim light. We investigated whether constant blue light (BL) exposure can eliminate the residual visual responses in a comparatively rapid RD rat model. Pigmented rhodopsin mutant S334ter line-3 rat pups (21 ...

PURPOSE: To investigate the inheritance of susceptibility to oxygen-induced retinopathy in the rat with the use of formal backcross analysis. METHODS: Neonatal offspring of inbred albino Fischer 344 (F344) and pigmented Dark Agouti (DA) crosses and F1xF344 and F1xDA backcrosses were exposed to alternating 24-hour cycles of hyperoxia (80% oxygen ...

AIM: To investigate whether the circadian expression of central clock genes and angiotensin II type 1 (AT1) receptors was altered in sinoaortic-denervated (SAD) rats. METHODS: Male Sprague-Dawley rats underwent sinoaortic denervation or a sham operation at the age of 12 weeks. Four weeks after the operation, blood pressure and heart ...

We have reported that after rats were acclimated to heat for about 5 h daily at a fixed time, the pattern of day-night variations of core temperature (T(cor)) altered, i.e., their T(cor) fell, especially during the period when they had previously been exposed to heat. The suprachiasmatic nucleus (SCN) of ...

Melatonin is an indoleamine widely distributed in the evolution that shows a great functional versatility, playing an important role as a transmitter of photoperiodic information and exhibiting antioxidant, oncostatic, anti-aging and immunomodulatory properties. In vertebrates, this molecule is produced by the pineal gland and other extrapineal sites. The present study ...

The study of how the retina processes the photic information required for the entrainment of the circadian system is an exciting new topic in retinal neurobiology. We have recently shown that in RCS/N-rdy rats melanopsin mRNA levels are dramatically reduced (about 90%) and melanopsin immunoreactivity cannot be detected in the ...