Circadian Rhythms of Perineuronal Nets and Somatostatin: Relationship to Growth Hormone and Sleep Associated with Memory Consolidation



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ABSTRACT How memory is stored and processed during sleep, a phenomenon called memory consolidation, remains unclear. Perineuronal Nets (PNNs), which are structures that form around neurons and regulate synapses, and growth hormone, which also regulates synapses, may provide a critical clue into this process. Contrary to what was thought, new research suggests that PNNs are modified during sleep, allowing for memory consolidation. I investigated the circadian rhythm of PNN composition, and the effect of sleep deprivation on PNNs and growth hormone. Animals were sacrificed every 4 hours across the 24-hour cycle, or following sleep deprivation and their brains were sliced and stained. PNN composition was determined using a microscope. Results showed a rhythmic variation in PNN composition everywhere with a decrease in number during the night, supporting the idea that PNN decreases allow for memories to be consolidated. Sleep deprivation prevented this decrease and the normal increase in growth hormone. I investigated somatostatin, a neuropeptide involved in anxiety regulation and growth hormone inhibition and found it varied over the circadian rhythm. Increasing our knowledge of PNNs and their function can aid understanding and treatment of diseases including Schizophrenia, Alzheimer’s disease and PTSD. Future studies can look at human brains with this disease.