c-Fos Expression in the Brains of Behaviorally “Split” Hamsters in Constant Light: Calling Attention to a Dorsolateral Region of the Suprachiasmatic Nucleus and the Medial Division of the Lateral Habenula

Tavakoli-Nezhad, Mahboubeh; Schwartz, William J.

doi:10.1177/0748730405278443

Cited by 37 publications

(36 citation statements)

References 61 publications

(60 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…First, the bifurcated bouts could derive from oscillators within versus outside the SCN (Abe et al, 2001), similar to those involved in food- and light-entrained oscillators (Mendoza, 2007; Stephan, 2002); alternatively, comparable to LL-induced split rhythms, the left and the right SCN may become temporally dissociated (de la Iglesia et al, 2000; Yan et al, 2005). Third, functional compartments delineated by dorsal/ventral or core/shell of the SCN may become temporally dissociated, as in free-running and entrained oscillations in T22 rats (de la Iglesia et al, 2004), or the LL-induced split hamsters (Tavakoli-Nezhad and Schwartz, 2005; Yan et al, 2005). Finally, cells even within SCN subregions may cycle with a distribution of peak phases to produce bimodality at the population level.…”

Section: Discussionmentioning

confidence: 99%

“…In DD, the core region lacks detectable rhythms in clock gene expression, and some neurons lack circadian rhythms in electrical activity (Hamada et al, 2001; Jobst and Allen, 2002). In split hamsters housed in LL, however, neurons in the core region are reorganized and show robust rhythms in antiphase to that in the shell (Yan et al, 2005; Tavakoli-Nezhad and Schwartz, 2005). Following ablation of the core, the remaining SCN cannot sustain behavioral rhythms as measured by wheel-running activity, drinking, and gnawing (Kriegsfeld et al, 2004; LeSauter and Silver, 1999), indicating a specialized role of these cells in maintaining clock function (Antle et al, 2003; Antle et al, 2007).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Reorganization of Suprachiasmatic Nucleus Networks under 24-h LDLD Conditions

2010

View full text Add to dashboard Cite

The suprachiasmatic nucleus (SCN), locus of the master circadian clock in the brain, is comprised of multioscillator neural networks that are highly plastic in responding to environmental lighting conditions. Under a 24-h light:dark:light:dark (LDLD) cycle, hamsters bifurcate their circadian locomotor activity such that wheel running occurs in each of the 2 daily dark periods with complete inactivity in between. In the present study, we explored the neural underpinning of this behavioral bifurcation. Using calbindin (CalB)–containing cells of the SCN as a regional marker, we characterized PER1 and c-FOS expression in the core and shell SCN subregions. In LD-housed animals, it is known that PER1 and c-FOS in the core and shell region are in phase with each other. In contrast, in behaviorally bifurcated animals housed in LDLD, the core and shell SCN exhibit antiphase rhythms of PER1. Furthermore, cells in the core show high FOS expression in each photophase of the LDLD cycle. The activation of FOS in the core is light driven and disappears rapidly when the photophase is replaced by darkness. The results suggest that bifurcated activity bouts in daytime and nighttime are associated with oscillating groups of cells in the core and shell subregions, respectively, and support the notion that reorganization of SCN networks underlies changes in behavioral responses under different environmental lighting conditions.

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Reorganization of Suprachiasmatic Nucleus Networks under 24-h LDLD Conditions

2010

View full text Add to dashboard Cite

show abstract

“…(F) New networks of SCN oscillators are seen under unusual environmental conditions. In the behaviorally split animal, the left and right SCN are in antiphase, and within each SCN, the core and shell of each SCN are in antiphase (Tavakoli-Nezhad and Schwartz 2005;Yan et al 2005). (G) SCN network organization may resemble a small-world network with mostly local connections between nodes and with a few long-distance connections.…”

Section: The Tissue Is the Issuementioning

confidence: 99%

Exploring Spatiotemporal Organization of SCN Circuits

Yan

Karatsoreos

LeSauter

et al. 2007

Cold Spring Harbor Symposia on Quantitative Biology

105

111

View full text Add to dashboard Cite

Suprachiasmatic nucleus (SCN) neuroanatomy has been a subject of intense interest since the discovery of the SCN's function as a brain clock and subsequent studies revealing substantial heterogeneity of its component neurons. Understanding the network organization of the SCN has become increasingly relevant in the context of studies showing that its functional circuitry, evident in the spatial and temporal expression of clock genes, can be reorganized by inputs from the internal and external environment. Although multiple mechanisms have been proposed for coupling among SCN neurons, relatively little is known of the precise pattern of SCN circuitry. To explore SCN networks, we examine responses of the SCN to various photic conditions, using in vivo and in vitro studies with associated mathematical modeling to study spatiotemporal changes in SCN activity. We find an orderly and reproducible spatiotemporal pattern of oscillatory gene expression in the SCN, which requires the presence of the ventrolateral core region. Without the SCN core region, behavioral rhythmicity is abolished in vivo, whereas low-amplitude rhythmicity can be detected in SCN slices in vitro, but with loss of normal topographic organization. These studies reveal SCN circuit properties required to signal daily time.

show abstract

“…Splitting is caused by the left and right halves of the SCN which oscillate in antiphase to each other (Mendoza et al 2009;Tavakoli-Nezhad and Schwartz 2005). Arrhythmicity results, if the neurons within the SCN decouple from each other.…”

Section: Scn and Its Networkmentioning

confidence: 99%

How Light Resets Circadian Clocks

2014

View full text Add to dashboard Cite

The daily revolutions of the earth around its axis are responsible for day and night and its annual orbit around the sun for the seasons with their fluctuations in day length. Most organisms have adapted to these diurnal and annual cycles. The strategies and mechanisms used are quite delicate and complicated.It came as a surprise that photosynthesis and many other processes are, however, additionally controlled by internal clocks. Thus, photosynthesis fluctuates not only during the daily light-dark cycle (=LD; see the List of Abbreviations and http://www.circadian.org/dictionary.html) but also when the plants are kept under LL and constant temperature (Hennessey and Field 1991). However, the period length (period for short) of this rhythmic event then deviates from exactly 24 h and is therefore called circadian (from Latin circa, about, and dies, day). If in the absence of LD and temperature cycles other 24 h time cues (also called zeitgeber, German for time giver) would control the rhythm, it should show an exact 24 h rhythm. This is not the case, demonstrating the endogenous nature of a clock that is locked to light signals (see Fig. 18.1). Spectrum of RhythmsEndogenous rhythms of organisms are not only tuned to the daily cycle of 24 h. The range of rhythms found in organisms covers ultradian (with periods of several hours to very short ones), circadian, and annual (with periods of about a year) rhythms. Other rhythms such as tidal, 14-day, and monthly ones cope with influences of the moon on the earth, mainly on the water movements of the oceans, and they are therefore found in organisms at the coasts and in the sea. Annual rhythms interact with the day-length changes during the year (see below). There are furthermore rhythms with periods covering several years. The following discussion of a "biological clock" is restricted to circadian rhythms. Even they are often not just composed of one clock type but form a "circadian system" consisting of two or more clocks with different prop- Function of Circadian ClocksThe term "clock" usually implies a time-measuring device or function. For instance, the day length (or night length) can be determined by an organism. Since day length is a function of the time of the year (long days in summer, short days in winter), it can be used to time certain events such as flowering or tuber formation of a plant or breeding of birds and mammals during the most appropriate season. These processes are denoted photoperiodism (see Chap. 19).However, a clock can also be used to set a certain temporal order. For instance, the circadian control of our sleepwake cycle ensures that we rise in the morning and fall asleep in the evening at a preferred time. Food intake and digestion are likewise controlled by this clock and gated to certain times of the day (Silver et al. 2011;Duguay and Cermakian 2009;Forsgren 1935). The circadian clock will time these events also under constant conditions. Furthermore, circadian clocks can serve as alarm clocks.

show abstract

c-Fos Expression in the Brains of Behaviorally “Split” Hamsters in Constant Light: Calling Attention to a Dorsolateral Region of the Suprachiasmatic Nucleus and the Medial Division of the Lateral Habenula

Cited by 37 publications

References 61 publications

Reorganization of Suprachiasmatic Nucleus Networks under 24-h LDLD Conditions

Reorganization of Suprachiasmatic Nucleus Networks under 24-h LDLD Conditions

Exploring Spatiotemporal Organization of SCN Circuits

How Light Resets Circadian Clocks

Contact Info

Product

Resources

About