The suprachiasmatic nucleus (SCN) of the hypothalamus is the principal hp HSTNN-UB11 laptop battery endogenous pacemaker in the mammalian brain, responsible for internal biological rhythms ([Antle and Silver, 2005] and [Morin and Allen, 2006]), including motor activity, body temperature, food intake, hormonal secretion and immune factors daily variation. Environmental light is the main factor responsible for SCN entrainment, and reaches the SCN via the retinohypothalamic tract, targeting especially oscillator cells in the so-called “core” of the nucleus. Core SCN cells communicate with oscillators lying in the so-called “shell”, located mainly dorsally in the SCN, that in turn projects outside the nucleus (Antle and Silver, 2005).
Circadian modulation of immunological factors, including daily variation of natural killer cells and T-lymphocytes and release of their cytokine products, is well documented (see, for example, [Opp, 2005], [Arjona and Sarkar, 2005] and [Hayashi et al., 2007]). Information on the effect of immune factors on the biological clock hp HSTNN-UB11 laptop battery is instead more limited, although acute exposure to inflammatory mediators has been reported to affect neurons of the rodent SCN in vivo and in vitro (Robertson et al., 2000; [Lundkvist et al., 2002], [Marpegán et al., 2005] and [Sadki et al., 2007]). In addition, subcutaneous interferon- administration to mice for 6 days leads to loss of the SCN ability to drive endogenous rhythms (Ohdo et al., 2001). The mouse SCN also shows a circadian time-dependent response to systemic acute injections of the endotoxin lipopolysaccharide (LPS) (Marpegàn et al., 2005), which is a toxic and soluble component of the Gram-negative bacterial cell wall.
SCN function, including its response to photic hp HSTNN-UB11 laptop battery stimulation, was found to be impaired in a chronic neuroinflammatory condition, represented by experimental infection in rats with Trypanosoma brucei (Peng et al., 1994; Lundkvist et al., 2005). This parasite is the causative agent of African trypanosomiasis or sleeping sickness in humans, a severe disease hallmarked in its advanced stage by disruption of the sleep/wake cycle and sleep structure. However, the relationship between biological clock functioning and chronic inflammation remains to be ascertained. We here examined in mice whether chronic LPS administration affects the SCN response to light as evaluated by Fos induction. The Fos protein is encoded by the immediate early gene c-fos, which acts as coupling factor between external photic stimulation and intracellular signalling pathways of circadian clock cells. Fos is a marker of neuronal activity whose expression in the SCN has been shown to be correlated with both light input and the behavioural output of the biological clock (see, for example, [Capotto and Guido, 2000] and Morin hp HSTNN-UB11 laptop battery and Allen, 2006 L.P. Morin and C.N. Allen, The circadian visual system, 2005, Brain Res. Rev. 51 (2006), pp. 1–60. Abstract | Article | PDF (1645 K) | View Record in Scopus | Cited By in Scopus (42)[Morin and Allen, 2006]).
