Light‐induced c‐Fos Expression in the Mouse Suprachiasmatic Nucleus: Immunoelectron Microscopy Reveals Co‐localization in Multiple Cell Types

Castel, Mona; Belenky, Michael; Cohen, S.; Wagner, Shlomo; Schwartz, William J.

doi:10.1111/j.1460-9568.1997.tb00762.x

Cited by 53 publications

(43 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Estimates of the size and identity of this population of light-responsive cells range from 20 to 40% of SCN cells and vary depending on the assay used [electrophysiology (Sawaki, 1979;Meijer et al, 1986;Aggelopoulos and Meissl, 2000) or IEG expression (Earnest et al, 1993;Silver et al, 1996;Castel et al, 1997;Aioun et al, 1998)]. The present study shows that 1 hr after a brief light pulse, most GFP cells (in the CalB::GFP mouse) in the SCN express Fos.…”

Section: Discussionmentioning

confidence: 72%

Phenotype Matters: Identification of Light-Responsive Cells in the Mouse Suprachiasmatic Nucleus

et al. 2004

View full text Add to dashboard Cite

Section: Discussionmentioning

confidence: 72%

Phenotype Matters: Identification of Light-Responsive Cells in the Mouse Suprachiasmatic Nucleus

et al. 2004

View full text Add to dashboard Cite

“…Assuming that the primary and secondary retinal inputs have analogous roles in the hamster and rat SCN, the CaBP-ir subnucleus is in an ideal anatomical location to receive unprocessed as well as precoded information about environmental photic conditions and relay it to other structures. It has been demonstrated that GRP-ir (hamster) and VIP-ir neurons (hamster, rat, and mouse) SCN express the immediate early gene c-fos in response to photic stimulation Aïoun et al, 1998;Castel et al, 1998). While some of these subpopulations receive direct retinal input (axo-somatic or axodendritic), others, such as VIP-ir neurons in the hamster, might be activated in an indirect manner (axo-axonal input onto dendritic processes; see Fig.…”

Section: Discussionmentioning

confidence: 99%

Retinal Innervation of Calbindin-D28K Cells in the Hamster Suprachiasmatic Nucleus: Ultrastructural Characterization

et al. 2000

View full text Add to dashboard Cite

The authors have described a subregion of the hamster hypothalamic suprachiasmatic nucleus (SCN) containing cells that are immunopositive for the cytosolic calcium-binding protein, Calbindin-D 28K (CaBP). Several lines of evidence indicate that this region may constitute the site of the pacemaker cells that are responsible for the regulation of circadian locomotor rhythms. First, 79% of the CaBP-immunoreactive (ir) neurons express Fos in response to photic stimulation, indicating that they are close to or part of the input pathway to pacemakers. Second, at the light microscopy level, retinal terminals innervate the CaBP subnucleus. Finally, destruction of this subnucleus renders animals arrhythmic in locomotor activity. In this study, the authors examined the ultrastructural relationship between cholera toxin (CTβ) labeled retinal fibers and the CaBP-ir subregion within the hamster SCN. CTβ-ir retinal terminals make primarily axo-somatic, symmetric, synaptic contacts with CaBP-ir perikarya. In addition, retinal terminals form synapses with CaBP processes as well as with unidentified profiles. There are also complex interactions between retinal terminals, CaBP perikarya, and unidentified profiles. Given that axo-somatic synaptic input has a more potent influence on a cell's electrical activity than does axo-dendritic synaptic input, cells of the CaBP subregion of the SCN are ideally suited to respond rapidly to photic stimulation to reset circadian pacemakers.Keywords calcium-binding proteins; calbindin-D 28K ; CaBP; pacemaker; suprachiasmatic nucleus; retinal terminals; electron microscopy; circadian rhythmsThe suprachiasmatic nucleus (SCN) of the hypothalamus is the site of the putative circadian clock in mammals (see Klein et al., 1991). The circadian system regulates the periodicity of many rhythmic responses in mammals including rest-wake cycles (see Moore-Ede et al., 1982), electrical activity, and neuropeptide levels (Inouye, 1996), to name a few. In the absence of exogenous stimuli, the circadian clock oscillates with a periodicity that is close to 24 h. The circadian timing system also has the capacity to entrain or synchronize the organism to the exogenous geo-solar cycle. The primary neural substrate responsible for the © 2000 Sage Publications, Inc.Correspondence to: Maria-Teresa Romero. transduction of exogenous photic stimuli is the retinohypothalamic tract (RHT), a monosynaptic pathway projecting from the retina to the SCN (Card and Moore, 1991;Moore, 1996). A secondary pathway, the geniculo-hypothalamic tract, also provides photic input to the circadian pacemaker. Photic information is integrated in the SCN to produce a stable phase relationship between physiological and behavioral activity and the environmental light-dark cycle (Meijer, 1991). While it is clear that the SCN is the site of the circadian pacemaker, the precise identity of retinorecipient cells that mediate entrainment remains to be elucidated. NIH Public AccessWe recently described cells immunopositive for Calbindin-D 28K (...

show abstract

“…Anatomically, only a subset of all rodent SCN cells are directly retinorecipient (for review, see Lee et al, 2003a). Physiologically, estimates of photoresponsiveness range from about one-fifth (by c-Fos immunoreactivity) (Castel et al, 1997) to about one third (by electrophysiology) located in the ventrolateral subdivision of the SCN (Meijer et al, 1986(Meijer et al, , 1998. No more than about 20% of the cells in this subset can be attributed to any one identified peptidergic phenotype (Romijn et al, 1996;Castel et al, 1997), and initial work suggested that no peptidergic cell type uniformly produced photosensitive responses.…”

Section: Scn Tissue Organization and Heterogeneous Gene Expressionmentioning

confidence: 99%

The Suprachiasmatic Nucleus is a Functionally Heterogeneous Timekeeping Organ

Silver¹,

Schwartz²

2005

Methods in Enzymology

Self Cite

View full text Add to dashboard Cite

Ever since the locus of the brain clock in the suprachiasmatic nucleus (SCN) was first described, methods available have both enabled and encumbered our understanding of its nature at the level of the cell, the tissue and the animal. A combination of in vitro and in vivo approaches has shown that the SCN is a complex heterogeneous neuronal network. The nucleus is comprised of cells that are retinorecipient and reset by photic input; those that are reset by non-photic inputs; slave oscillators that are rhythmic only in the presence of the retinohypothalamic tract; endogenously rhythmic cells, with diverse period, phase and amplitude responses; and cells that do not oscillate, at least on some measures. Network aspects of SCN organization are currently being revealed, but mapping these properties onto cellular characteristics of electrical responses and patterns of gene expression are in early stages. While previous mathematical models focused on properties of uniform coupled oscillators, newer models of the SCN as a brain clock now incorporate oscillator and gated, nonoscillator elements. The Brain's Clock as a ConstructThe function of the suprachiasmatic nucleus (SCN) was discovered during the era that identified the hypothalamus as the site of several brain "centers" governing homeostaticallyregulated behaviors. Ablation of the lateral hypothalamus resulted in a significant reduction of eating behavior and weight loss, hence an eating center. Destruction of the ventromedial hypothalamus produced obesity, hence a satiety center. The opportunity to electrically self stimulate the brain was so powerful a reward that all other motivated behaviors were put aside, hence pleasure centers. And lesions of the SCN led to dramatic behavioral and physiological arrhythmicity, hence a timekeeping center.Today, most of these center constructs have fallen out of favor. For the eating center, it was realized that "specific" hypothalamic lesions damaged fibers of passage, that lesioned animals showed sensory neglect and no longer responded to afferent inputs, and that other, major consequences accompanied weight loss in addition to disrupted feeding. For the pleasure centers, once the neural network and transmitter systems involved in self stimulation were delineated, it was obvious that no single center controlled the behavior. The notion of brain centers began to lose its heuristic value, and the centrist view was even labeled a "millstone" rather than a "milestone" to progress in neurobiology (Coscina, 1976).For the SCN, such a revision has not occurred. The body of evidence identifying the nucleus as the master circadian pacemaker in mammals is multi-disciplinary in nature, and the strength of this functional localization is unsurpassed by that of any other structure in the vertebrate NIH Public Access

show abstract

Light‐induced c‐Fos Expression in the Mouse Suprachiasmatic Nucleus: Immunoelectron Microscopy Reveals Co‐localization in Multiple Cell Types

Cited by 53 publications

References 52 publications

Phenotype Matters: Identification of Light-Responsive Cells in the Mouse Suprachiasmatic Nucleus

Phenotype Matters: Identification of Light-Responsive Cells in the Mouse Suprachiasmatic Nucleus

Retinal Innervation of Calbindin-D28K Cells in the Hamster Suprachiasmatic Nucleus: Ultrastructural Characterization

The Suprachiasmatic Nucleus is a Functionally Heterogeneous Timekeeping Organ

Contact Info

Product

Resources

About