Abstract
Extended sleep improves sustained attention and reduces sleep pressure in humans. Downregulation of adenosine A1 receptor (A1R) and modulation of the neurotrophic factor insulin growth factor-1 (IGF-I) in brain structures controlling attentional capacities could be involved. In the frontal cortex and hippocampus of rats, we measured adenosine A1R and IGF-I protein concentrations after photoperiod-induced sleep extension. Two groups of twelve rats were adapted over 14 days to a habitual (CON) 12:12 light–dark (LD) schedule and an extended (EXT) 16:8 LD schedule. IGF-I content was also measured in plasma, liver, and skeletal muscle. In EXT, compared to CON rats, A1R content in the frontal cortex was significantly lower (p < 0.05), while IGF-I content was higher (p < 0.001), and no significant change was observed in the hippocampus. IGF-I content in plasma and muscle was higher (p < 0.001 and p < 0.01), while it was lower in liver (p < 0.001). The absolute weight and weight gain were higher in EXT rats (p < 0.01). These data suggest that 14 days under a 16:8 LD photoperiod respectively down- and upregulated cortical A1R and IGF-I levels. This photoperiod induced an anabolic profile with increased weight gain and circulating and muscular IGF-I levels. An extension of sleep duration might favor cerebral and peripheral anabolism, which may help attentional and physical capacities.
Highlights
There is plenty of evidence indicating that sleep is crucial and is an important component of human life
We initially suggested that upregulation of the neurotrophic factor insulin-like growth factor (IGF-I) and/or downregulation of adenosine A1 receptor (A1R) may represent the physiological mechanisms of such benefits [6]
We showed that, in healthy men, six nights of sleep extension were without significant effects on mRNA levels of A1R and adenosine A2A receptor (A2AR) in leukocytes at baseline, during sleep deprivation, and during recovery [8]
Summary
There is plenty of evidence indicating that sleep is crucial and is an important component of human life. It has been described that neuronal activity drives IGF-I transport into the central nervous system through the stimulation of matrix metalloproteinase-9 (MMP-9), leading to cleavage of IGFBP-3 (that renders IGF-I free) and interaction with the membrane cargo protein transporter lipoprotein-related receptor 1 (LRP1) [22] It is mainly the growth hormone (GH) that regulates IGF-I; thereby, many actions of GH are mediated via IGF-I. The present study was conducted to characterize the effects of 14 days under extended photoperiods (LD 16:8) on protein content of A1R and IGF-I in two rat brain areas, the frontal cortex and hippocampus. The mean IGF-I concentration in the liver of EXT rats was significantly lower compared to CON (p
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