The MCH nerve has been regarded as a nerve that promotes appetite, but in recent years, it has been reported that it is also involved in sleep-wake regulation.Using mice, the researchers conducted experiments to activate MCH nerves using optogenetic and chemo-genetic techniques that can manipulate the activity of specific nerves. It was discovered that activity was suppressed.

　Therefore, when we investigated how the activity of the MCH nerve changes with sleep and wakefulness, (3) MCH nerve that is active during wakefulness, (XNUMX) MCH nerve that is active during REM sleep, and (XNUMX) during wakefulness and REM sleep. It was found that there are three types of MCH nerves that are active in both.Furthermore, experiments to evaluate the memory ability of mice after activating or suppressing MCH neural activity were conducted in each of the novel object recognition test and the contextual fear conditioning test. In both tests, MCH neural activity was activated. Then, it turned out that the erasure of the memory proceeded.Conversely, suppression improved memory retention, but this result was only seen when MCH neural activity was suppressed during REM sleep.In other words, it was suggested that the MCH nerve, which is active during REM sleep, suppresses the nerve activity of the hippocampus and erases memory.

　Our sleep rhythm generally repeats light sleep, REM sleep, before waking up.The memory erasure by the MCH nerve that is active during REM sleep, which was revealed this time, seems to be one of the causes for immediately forgetting the contents of the dream just before waking up.

　In addition, from the experimental results that the memory of contextual fear conditioning was erased by the activation of the MCH nerve, if this mechanism is applied, the memory of the experience with strong fear remains as a trauma. Post-traumatic stress disorder ( Treatment of PTSD) may also be possible.

Paper information:[Science] REM sleep-active MCH neurons are involved in forgetting hippocampus-dependent memories