UC Berkeley finds sleep-growth hormone feedback loop in mice — ScienceDaily
Researchers at the University of California, Berkeley, found in mice that sleep stimulates the release of growth hormone, while this hormone, through feedback, affects the neuronal mechanisms of awakening. The work, published in the journal Cell, is described by ScienceDaily.
The scientists focused on the hypothalamus, a region of the brain involved in regulating hormone production and the sleep-wake cycle. They studied neurons that produce growth hormone-releasing hormone (GHRH), as well as two types of neurons that produce somatostatin. GHRH promotes growth hormone secretion, while somatostatin suppresses it.
Neuronal activity during sleep
The experiments were conducted in mice using electrodes implanted in the brain, optical stimulation of individual neurons, and methods for tracing connections between cells. During REM sleep, the activity of neurons associated with both GHRH and somatostatin increased. Despite the opposing effects of these signaling systems, their coordinated activity was accompanied by increased growth hormone release.
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During non-REM sleep, the activity of somatostatin-producing neurons decreased, weakening the inhibitory effect. At the same time, the activity of neurons associated with GHRH increased moderately. This combination also promoted growth hormone secretion.
Feedback with awakening
The researchers also found that growth hormone affects the locus coeruleus, a region of the brainstem associated with alertness, attention, and cognitive functions. As hormone levels gradually rose during sleep, it stimulated neurons in this region and facilitated the transition to wakefulness.
Growth hormone is important not only for development during childhood: it supports muscle and bone tissue, regulates the use of stored fat, and affects glucose levels. The authors note that the findings may provide a basis for further research into sleep disorders associated with metabolic and neurological diseases. At the same time, the mechanisms were established in experiments on mice, so their effects in humans still need to be tested separately.
