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Biogerontology (2008) 9:229234 DOI 10.1007/s10522-008-9132-z
RESEARCH ARTICLE
Daily serotonin rhythms in rat brain during postnatal development and aging
Anita Jagota D. Kalyani
Received: 19 December 2007 / Accepted: 7 February 2008 / Published online: 4 March 2008 Springer Science+Business Media B.V. 2008
Abstract Aging is characterized by progressive decline in most physiological functions. The age-related sleep disturbances have been attributed to disturbances of circadian function. Neurotransmitter serotonin plays important role in the photic and nonphotic regulation of circadian rhythms and is a precursor of melatonin, an internal zeitgeber. To understand the age induced changes in the functional integrity of circadian system, we studied daily serotonin rhythms in brain by measuring serotonin levels at variable time points in wide range of age groups such as 15 days, 1, 2, 3 (adult), 4, 6, 9, 12, 18 and 24-months old male Wistar rats. Animals were maintained under lightdark conditions (LD 12:12), 2 weeks prior to experiment. We report here, mean serotonin levels over 24 h period in brain is highest at 3 months and daily serotonin rhythmicity reliably begins at 3 months and disintegrates at middle age and beyond. The age induced changes in daily serotonin rhythmicity in brain obtained in present study will be a step towards understanding age induced disorders of circadian function.
Keywords Brain Serotonin
Aging and circadian rhythms
Introduction
The age-related decline in physiological functions (for review see Turek et al. 1995) can be due to malfunctioning of central nervous system (CNS) which may involve neuronal and synaptic loss of function and decrease in the concentration of various neurotransmitters (Slotkin et al. 2005). Aging is characterized by the disturbances of circadian function (Touitou et al. 1997; Cardinali et al. 2002; Jagota 2005). In the mammalian circadian clock function, serotonin (5-hydroxytryptamine, 5-HT) is implicated in the photic and non-photic regulation of circadian rhythms (Jiang et al. 2000). The principal pacemaker of mammalian circadian rhythms, the suprachiasmatic nucleus (SCN) (Klein et al. 1991; Jagota et al. 2000; Jagota 2006) contains one of the densest serotonergic terminal plexes of the brain (Morin 1999). The SCN regulates the production and discharge of melatonin (hormonal message for darkness) from precursor serotonin, such that melatonin levels are high at night and low during the day (Sudgen 1989; Jagota et...