Abstract
Aging decreases sleep quality by disrupting the molecular machinery that regulates the circadian rhythm. However, we do not fully understand the mechanism that underlies this process. In Drosophila, sleep quality is regulated by precisely timed patterns of spontaneous firing activity in posterior DN1 (DN1p) circadian clock neurons. How aging affects the physiological function of DN1p neurons is unknown. In this study, we found that aging altered functional parameters related to neural excitability and disrupted patterned spike sequences in DN1p neurons during nighttime. We also characterized age-associated changes in intrinsic membrane properties related to spike frequency adaptations and synaptic properties, which may account for the unstructured spike patterns in aged DN1p neurons. Because Slowpoke binding protein (SLOB) and the Na+/K+ ATPase β subunit (NaKβ) regulate clock-dependent spiking patterns in circadian networks, we compared the subcellular organization of these factors between young and aged DN1p neurons. Young DN1p neurons showed circadian cycling of HA-tagged SLOB and myc-tagged NaKβ targeting the plasma membrane, whereas aged DN1p neurons showed significantly disrupted subcellular localization patterns of both factors. The distribution of SLOB and NaKβ signals also showed greater variability in young vs. aged DN1p neurons, suggesting aging leads to a loss of actively formed heterogeneity for these factors. These findings showed that aging disrupts precisely structured molecular patterns that regulate structured neural activity in the circadian network, leading to age-associated declines in sleep quality. Thus, it is possible to speculate that a recovery of unstructured neural activity in aging clock neurons could help to rescue age-related poor sleep quality.
Highlights
Aging influences many physiological processes, including sleep (Bliwise, 1993)
Most research has focused on the clock neuron firing rate, and we do not know if aging influences the temporal structural pattern of clock neuron firing
We focused on posterior DN1 (DN1p) neurons because of their contributions to sleep regulation
Summary
Aging influences many physiological processes, including sleep (Bliwise, 1993). Agedependent declines in the physiological function control the circadian and homeostatic regulation of sleep (Cajochen et al, 2006; Pace-Schott and Spencer, 2011). We do not fully understand how aging influences clocks to regulate sleep. The molecular mechanism of circadian clock systems changes with age, reducing sleep quality Aging influences the circadian clock neuronal activity patterns (Nakamura et al, 2015, 2016). This mechanism could underlie how aging clocks regulate sleep
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