Daily serotonin rhythms in rat brain during postnatal development and aging

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 non-photic 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 light-dark 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.

Effect of melatonin on age induced changes in daily serotonin rhythms in suprachiasmatic nucleus of male Wistar rat

“…Daily serotonin pulses in SCN were robust in 3, 4 and 6 months old age groups. These findings support our earlier finding (Jagota and Kalyani, 2008) although in brain the 5-HT rhythmicity was established only at 3 months of age in rat and 5-HT rhythmicity disintegrated at 6 months. Present study indicates early establishment of 5-HT rhythm in SCN and disintegration by 9 months.…”

“…Exogenous melatonin administration has been linked by many workers to entrainment of activity rhythms, phase shifts and synchronization of rhythmicity (Cassone et al 1986;Sack et al 1998;Revell et al 2006). We have reported recently (Jagota and Kalyani 2008) age induced changes in daily serotonin rhythmicity in rat brain. However, no information is available on age related changes in daily serotonin rhythms in SCN.…”

“…Serotonin levels were measured at various time points (ZT-0, 6, 12, 18 and 24) in the rat SCN (n = 6) as described earlier (Jagota and Kalyani 2008).…”

“…The 5-HT has been referred as modulator of aging in brain (Sibille et al 2007). We have previously reported progressive decline with age in mean 5-HT levels in brain and daily rhythmicity with disintegration at middle age (Jagota and Kalyani, 2008).…”

Involvement of Oxidative Stress in Age-Related Bone Loss

“…Male Wistar rats are often used to study the aging and age-related pathologic processes [13][14][15][16][17][18]. Therefore, young, adult, and old rats were used in the study.…”