Circadian Rhythm ; Social Behavior ; Suprachiasmatic Nucleus

No abstract available.
Animals ; Rats* ; Suprachiasmatic Nucleus* ; Vasoactive Intestinal Peptide*

Mammals synchronize their circadian activity primarily to the cycles of light and darkness in the environment. Circadian rhythm is controlled by the central clock in the hypothalamic suprachiasmatic nucleus (SCN) and the peripheral clocks in various tissues. More importantly, the central clock can integrate photic/nonphotic signals to generate rhythmic outputs, and then drive the slave oscillators in peripheral tissues through neuroendocrine and behavioral signals. Human reproductive activities, as some other physiological functions, are controlled by the biological clocks. Accumulating lines of epidemiological and genetic evidence indicate that disruption of circadian clock can be directly involved in multiple pathological processes, including infertility. In this review, we mainly discuss the presence of a circadian clock in reproductive tissues and its roles in follicles development, ovulation, spermatogenesis, fertilization and embryo implantation, etc. As the increased shift work and assisted reproductive technologies possibly disrupt circadian rhythmicity to impact reproduction, the importance of circadian rhythms should be highlighted in the regulation of reproductive process.
Animals ; Biological Clocks ; Circadian Rhythm ; Hypothalamus ; Light ; Reproduction ; Suprachiasmatic Nucleus

Circadian clock is an internal autonomous time-keeping system, including central clocks located in the suprachiasmatic nucleus (SCN) and peripheral clocks. The molecular circadian clock consists of a set of interlocking transcriptional-translational feedback loops that take the clock-controlled genes 24 h to oscillate. The core mechanism of molecular circadian clock is that CLOCK/BMAL1 dimer activates the transcription of cryptochromes (CRYs) and Periods (PERs), which act as transcriptional repressors of further CLOCK/BMAL1-mediated transcription. In addition to this basic clock, there is an additional sub-loop of REV-ERBα and RORα regulating the transcription of BMAL1. Approximately 80% protein-coding genes demonstrate significant rhythmicity. The earth rotation is responsible for the generation of the daily circadian rhythms. To coordinate metabolic balance and energy availability, almost all organisms adapt to the rhythm. Studies have shown that circadian clock integrating with metabolic homeostasis increases the efficiency of energy usage and coordinates with different organs in order to adapt to internal physiology and external environment soon. As the central organ of metabolism, the liver performs various physiological activities nearly all controlled by the circadian clock. There are multiple interactive regulation mechanisms between the circadian clock and the regulation of liver metabolism. The misalignment of metabolism with tissue circadian is identified as a high-risk factor of metabolic diseases. This article reviews the recent studies on circadian physiological regulation of liver glucose, lipid and protein metabolism and emphasizes oscillation of mitochondrial function. We also take an outlook for new methods and application of circadian clock research in the future.
CLOCK Proteins ; Circadian Clocks/genetics* ; Circadian Rhythm ; Liver ; Suprachiasmatic Nucleus

No abstract available.
Animals ; Rats* ; Receptor, Nerve Growth Factor* ; Suprachiasmatic Nucleus*

The distributions and morphological characteristics of neurons displaying immunoreactivity to the catecholamine synthetic enzymes, tyrosine hydroxylase[TH], dopamine-beta-hydroxylase[DBH], and phenyletha-nolamine-N-methyltransferase[PNMT] were examined in the adjacent sections of the diencephalon of the striped field mouse [Apodemus agrarius coreae].Only TH-, and no DBH- or PNMT-immunoreactive neurons were found in the diencephalon. In the preoptic area, TH-immunoreactive neurons were found in the anterior preoptic nucleus of Loo[APN], periventricular preoptic nucleus, medial preoptic nucleus, lateral preoptic nucleus and suprachiasmatic nucleus. In the hypothalamus, TH-immunoreactive neurons were found in theparaventricular hypothalamic nucleus, periventricular gray, retrochiasmatic area,anterior hypothalamic nucleus of anterior hypothalamic area and retrochiasmatic region of the hypothalamus. In the rostral tuberal region of the hypothalamus, TH-immunoreactive neurons were found in the paraventricular nucleus, periventricular gray and arcuate nucleus. In the midtuberal region of the hypothalamus, TH-immunoreactive neurons were found in the paraventricular nucleus, dorsomedial hypothalamic nucleus, zona incerta and arcuate nucleus. In the caudal tuberal region of the hypothalamus, dorsal hypothalamic nucleus, posterior hypothalamic complex and arcuate nucleus.
Animals ; Anterior Hypothalamic Nucleus ; Arcuate Nucleus ; Diencephalon* ; Dopaminergic Neurons* ; Dorsomedial Hypothalamic Nucleus ; Hypothalamus ; Immunohistochemistry ; Mice ; Neurons ; Paraventricular Hypothalamic Nucleus ; Preoptic Area ; Subthalamus ; Suprachiasmatic Nucleus ; Tyrosine

As a consequence of the Earth's rotation, almost all organisms experience day and night cycles within a 24-hr period. To adapt and synchronize biological rhythms to external daily cycles, organisms have evolved an internal time-keeping system. In mammals, the master circadian pacemaker residing in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus generates circadian rhythmicity and orchestrates numerous subsidiary local clocks in other regions of the brain and peripheral tissues. Regardless of their locations, these circadian clocks are cell-autonomous and self-sustainable, implicating rhythmic oscillations in a variety of biochemical and metabolic processes. A group of core clock genes provides interlocking molecular feedback loops that drive the circadian rhythm even at the single-cell level. In addition to the core transcription/translation feedback loops, post-translational modifications also contribute to the fine regulation of molecular circadian clocks. In this article, we briefly review the molecular mechanisms and post-translational modifications of mammalian circadian clock regulation. We also discuss the organization of and communication between central and peripheral circadian oscillators of the mammalian circadian clock.
Brain ; Circadian Clocks ; Circadian Rhythm ; Hypothalamus, Anterior ; Mammals ; Protein Processing, Post-Translational ; Suprachiasmatic Nucleus

Most organisms have adapted to a circadian rhythm that follows a roughly 24-hour cycle, which is modulated by both internal (clock-related genes) and external (environment) factors. In such organisms, the central nervous system (CNS) is influenced by the circadian rhythm of individual cells. Furthermore, the period circadian clock 2 (Per2) gene is an important component of the circadian clock, which modulates the circadian rhythm. Per2 is mainly expressed in the suprachiasmatic nucleus (SCN) of the hypothalamus as well as other brain areas, including the midbrain and forebrain. This indicates that Per2 may affect various neurobiological activities such as sleeping, depression, and addiction. In this review, we focus on the neurobiological functions of Per2, which could help to better understand its roles in the CNS.
Brain ; Central Nervous System ; Circadian Clocks* ; Circadian Rhythm ; Depression ; Hypothalamus ; Mesencephalon ; Neurotransmitter Agents ; Prosencephalon ; Suprachiasmatic Nucleus

Circadian rhythms orchestrate biochemical and physiological processes in living organisms to respond the day/night cycle. In mammals, nearly all cells hold self-sustained circadian clocks meanwhile couple the intrinsic rhythms to systemic changes in a hierarchical manner. The suprachiasmatic nucleus (SCN) of the hypothalamus functions as the master pacemaker to initiate daily synchronization according to the photoperiod, in turn determines the phase of peripheral cellular clocks through a variety of signaling relays, including endocrine rhythms and metabolic cycles. With aging, circadian desynchrony occurs at the expense of peripheral metabolic pathologies and central neurodegenerative disorders with sleep symptoms, and genetic ablation of circadian genes in model organisms resembled the aging-related features. Notably, a number of studies have linked longevity nutrient sensing pathways in modulating circadian clocks. Therapeutic strategies that bridge the nutrient sensing pathways and circadian clock might be rational designs to defy aging.
Aging ; metabolism ; pathology ; Animals ; Circadian Clocks ; Humans ; Suprachiasmatic Nucleus ; metabolism ; pathology

The role of neuropeptides in the central nervous system (CNS) has received increasing attention. Numerous peptide molecules are found in the mammalian CNS and many of them are thought to act as either neurotransmitters or neuromodulators. The neuropeptides found in high concentration in the hypothalamus include vasopressin (VP), vasoactive intestinal polypeptide, somatostatin, and oxytocin. The main approches to assess the involvement of neuropeptides can be focused on functions affecting the aging of the brain. Morphological aging of the CNS has been characterized by degenerative changes of fiber connections and cell loss, although degeneration does not always occur to the same extent throughout various parts of the brain and, moreover, varies for different cell types. Despite of many studies in VP containing neurons , there exist discrepancies in results about the changes of aged rat brain. The aim of the present study is, therefore, to investigative possible changes in the number and morphology of VPimmunoreactive neurons with aging in each area of the hypothalmus of the aged rats. As a result, the number of VP-immunoreactive neurons was decreased in hypothalamus nucleus of aged group. Especially, in VP-immunoreactive neurons of hypothalamus, the size of neuronal cell body and nuclei in aged group is larger than in young group and the fiber density of immunoreactivity neurons of median eminance (ME) in aged group is stronger than in young group. But, the total number of VP-immunoreactive neurons in the suprachiasmatic nucleus (SCN) of the aged group is larger than in the young group. These studies indicate the involvement of VP-immunoreactive neurons in aging process of hypothalamus, and aging process may affect the synthesis of VP in the neurons of hypothalamic nuclei. Whereas, in VP expression, aging process induces an enlargement of the cell size of surviving neurons to compensate.
Aging ; Animals ; Brain ; Cell Size ; Central Nervous System ; Hypothalamus* ; Neurons* ; Neuropeptides ; Neurotransmitter Agents ; Oxytocin ; Paraventricular Hypothalamic Nucleus ; Rats* ; Somatostatin ; Suprachiasmatic Nucleus ; Supraoptic Nucleus ; Vasoactive Intestinal Peptide ; Vasopressins