Circadian Regulation of Arousal: Role of the Noradrenergic Locus Coeruleus System and Light Exposure

Abstract

Noradrenergic LC neurons provide a circadian regulation of the sleep-wake cycle, and the maintenance of LC function depends on light exposure. Light deprivation induces a loss of noradrenergic fibers, which in turn decreases the amplitude of the sleep-wake rhythm.

Can light make us bright? Effects of light on cognition and sleep

“…However, when light exposure duration was less than a minute, the majority of effects were elicited for subcortical structures, such as the dorso-posterior thalamus and the brainstem (LC-compatible area; Vandewalle et al, 2007a,b). The overarching significance of LC-related areas in this case is due to its projections to numerous cortical sites, which favors its role as a mediator for light changes in alertness and cognitive performance (Gonzalez and Aston-Jones 2006). The thalamus, in particular, its dorsal and posterior nuclei (i.e., pulvinar), is a key structure involved in the interaction between alertness and cognition (Portas et al, 1998), and lightrelated changes in its activity can be directly implicated in enhanced alertness during light exposure.…”

“…Direct photic input to this nucleus may therefore alter ventrolateral preoptic area activity. The locus coeruleus (LC) located in dorsal tegmentum of the pons is also involved in the regulation of the sleep-wake cycle (Saper et al, 2005) regulating the amplitude of the sleep-wake circadian rhythm set by the SCN by increasing wakefulness during the active period (Gonzalez and Aston-Jones 2006). Alternatively, the acute alerting effects of light may happen through acute melatonin suppression, given that increased melatonin suppression can be associated with greater arousal and/or attenuation of the endogenous circadian drive for alertness .…”

What Keeps Us Awake?—the Role of Clocks and Hourglasses, Light, and Melatonin

“…Direct photic input to this nucleus may therefore alter VLPO activity and waking arousal levels. The LC is also involved in the regulation of the sleep-wake cycle (Saper et al, 2005b), regulating the amplitude of the sleep-wake circadian rhythm set by the SCN by increasing wakefulness during the active period (see also Section III, Gonzalez and Aston-Jones, 2006).…”

“…The importance of LC areas in this case is due to the fact that this region projects to numerous cortical sites and is, therefore, well placed to mediate lightinduced changes in alertness and cognition (Gonzalez and Aston-Jones, 2006). The thalamus, in particular its dorsal and posterior nuclei (i.e., pulvinar), is a key structure involved in the interaction between alertness and cognition (Portas et al, 1998).…”

Antidepressants and Morphological Plasticity of Monoamine Neurons

“…Gonzalez and Aston-Jones (2006, 2008 have reported that light deprivation or long-term exposure to constant darkness in rats (DD) increased apoptosis in LC neurons and decreased the number of NA boutons in the cerebral cortex. The DD rats also demonstrated increased immobility in the forced swim test.…”