The role of calcium ions in circadian rhythm of suprachiasmatic nucleus neuron activity in rat hypothalamic slices

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 rhythmicity on PRL surges by disrupting this loop. Because lesion of the locus coeruleus (LC) abolishes PRL surges and these neurons receive SCN projections, we investigated the role of SCN rhythmicity in the LC neuronal circadian rhythm as a possible component of the circadian mechanism regulating PRL surges. Cycling rats on proestrous day and estradiol-treated ovariectomized rats received injections of antisense or random-sequence deoxyoligonucleotide cocktails for clock genes ( Per1, Per2, and Clock) in the SCN, and blood samples were taken for PRL measurements. The percentage of tyrosine hydroxylase-positive neurons immunoreactive to Fos-related antigen (FRA) was determined in ovariectomized rats submitted to the cocktail injections and in a 12:12-h light:dark (LD) or constant dark (DD) environment. The antisense cocktail abolished both the proestrous and the estradiol-induced PRL surges observed in the afternoon and the increase of FRA expression in the LC neurons at Zeitgeber time 14 in LD and at circadian time 14 in DD. Because SCN afferents and efferents were probably preserved, the SCN rhythmicity is essential for the magnitude of daily PRL surges in female rats as well as for LC neuronal circadian rhythm. SCN neurons therefore determine PRL secretory surges, possibly by modulating LC circadian neuronal activity.

Download Full-text

Effect of suprachiasmatic nucleus lesion on circadian dentin increment in rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.2001.280.5.r1364 ◽

2001 ◽

Vol 280 (5) ◽

pp. R1364-R1370 ◽

Cited By ~ 30

Author(s):

Mie Ohtsuka-Isoya ◽

Haruhide Hayashi ◽

Hisashi Shinoda

Keyword(s):

Circadian Rhythm ◽

Fourier Analysis ◽

Suprachiasmatic Nucleus ◽

Constant Light ◽

Maxillary Incisors ◽

The Brain

Mammalian dentin universally shows circadian increments. However, little is known about the mechanism of this phenomenon. The purpose of the present study was to investigate the role of the suprachiasmatic nucleus (SCN) in the generation of circadian rhythm in dentin increment. Rats underwent lesion of the SCN by electrodes and were maintained under constant light to examine whether the circadian increment free runs. The rats were injected with nitrilotriacetato lead to chronologically label the growing dentin. Two weeks after the operation, maxillary incisors and the locations of lesions in the brain were examined histologically. A harmonic (Fourier) analysis was performed to examine the densitometric pattern of the dentin increments to determine their periodicity. In rats with a completely lesioned SCN, ultradian increments, but no circadian increments, were observed in the dentin. Alternatively, in rats with an intact or only partially lesioned SCN, circadian increments persisted or were only temporarily disturbed. These results suggest that the SCN plays an important role in the generation of the circadian dentin increment in rats.

Download Full-text

Circadian Rhythm Disturbances in Mood Disorders: Insights into the Role of the Suprachiasmatic Nucleus

Neural Plasticity ◽

10.1155/2017/1504507 ◽

2017 ◽

Vol 2017 ◽

pp. 1-28 ◽

Cited By ~ 52

Author(s):

Chelsea A. Vadnie ◽

Colleen A. McClung

Keyword(s):

Circadian Rhythm ◽

Circadian Rhythms ◽

Mood Disorders ◽

Suprachiasmatic Nucleus ◽

External Environment ◽

Brain Regions ◽

Common Symptom ◽

Peripheral Tissues ◽

Environmental Perturbations

Circadian rhythm disturbances are a common symptom among individuals with mood disorders. The suprachiasmatic nucleus (SCN), in the ventral part of the anterior hypothalamus, orchestrates physiological and behavioral circadian rhythms. The SCN consists of self-sustaining oscillators and receives photic and nonphotic cues, which entrain the SCN to the external environment. In turn, through synaptic and hormonal mechanisms, the SCN can drive and synchronize circadian rhythms in extra-SCN brain regions and peripheral tissues. Thus, genetic or environmental perturbations of SCN rhythms could disrupt brain regions more closely related to mood regulation and cause mood disturbances. Here, we review clinical and preclinical studies that provide evidence both for and against a causal role for the SCN in mood disorders.

Download Full-text

Chronobiological features of primary headaches and the role of melatonin in the regulation of biological rhythms

Medical Council ◽

10.21518/2079-701x-2019-1-33-38 ◽

2019 ◽

pp. 33-38

Author(s):

E. M. Evdokimova ◽

M. G. Poluektov ◽

G. R. Tabeyeva

Keyword(s):

Circadian Rhythm ◽

Cluster Headache ◽

Suprachiasmatic Nucleus ◽

Seasonal Pattern ◽

Biological Rhythms ◽

Primary Headaches ◽

Melatonin Secretion ◽

Clinical Observations

Frequency is considered as a key sign of the course of some forms of primary headaches (PH). One of the most prominent representatives is the hypnical and cluster headache, which predetermined their name. Clinical observations demonstrate a clear circadian rhythm and seasonal pattern of cluster headache (CH) and migraine (M) attacks. In accordance with modern concepts, the phenomenon of the periodicity of painful episodes of a number of forms of primary headaches is associated with dysfunction of the suprachiasmatic nucleus of the hypothalamus, the main pacemaker of biological rhythms. The connection of PH with chronopathology is confirmed by revealing the disturbances of melatonin secretion in CH and M. Melatonin has proven to be effective in treatment of these PH.

Download Full-text

Mitochondrial matrix calcium ions regulate energy production in myocardium: A cytochemical study

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100134429 ◽

1990 ◽

Vol 48 (2) ◽

pp. 166-167

Author(s):

W.A. Jacob ◽

R. Hertsens ◽

A. Van Bogaert ◽

M. De Smet

Keyword(s):

Energy Metabolism ◽

Calcium Ions ◽

Energy Production ◽

Regulation Of Respiration ◽

Free Calcium ◽

Mitochondrial Matrix ◽

Cytochemical Study ◽

Nmr Techniques

In the past most studies of the control of energy metabolism focus on the role of the phosphorylation potential ATP/ADP.Pi on the regulation of respiration. Studies using NMR techniques have demonstrated that the concentrations of these compounds for oxidation phosphorylation do not change appreciably throughout the cardiac cycle and during increases in cardiac work. Hence regulation of energy production by calcium ions, present in the mitochondrial matrix, has been the object of a number of recent studies.Three exclusively intramitochondnal dehydrogenases are key enzymes for the regulation of oxidative metabolism. They are activated by calcium ions in the low micromolar range. Since, however, earlier estimates of the intramitochondnal calcium, based on equilibrium thermodynamic considerations, were in the millimolar range, a physiological correlation was not evident. The introduction of calcium-sensitive probes fura-2 and indo-1 made monitoring of free calcium during changing energy metabolism possible. These studies were performed on isolated mitochondria and extrapolation to the in vivo situation is more or less speculative.

Download Full-text