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Probing the neuron connections of anxiety and sleep

By Tim Sandle     Jul 5, 2017 in Health
Tokyo - When someone is anxious sleeplessness is a common side-effect. But why is this? Researchers have been investigating the underlying mechanisms in the brain that link insomnia to anxiety.
The study comes from the University of Tsukuba’s Sleep Institute and it investigates the role that brain neuron splay with anxiety and difficulties with sleeping. The researchers have detected neurons that function to connect emotions and sleep.
It is well established that significant changes to the surrounding environment or responses to dangers lead to shifts in behavior, leading most mammals including humans to adopt a vigilant state. This, in turn, leads to changes to physiological conditions which are related to modulation of autonomic and endocrine functions.
The brain region affected is the bed nucleus of the stria terminalis, which forms part of the extended amygdala. The activity of the bed nucleus of the stria terminalis correlates with anxiety in response to threat monitoring and helps to regulate its activity in response to acute stress. This part of the brain also controls endocrine and autonomic reactions in response to events, which take the form of emotions like anxiety and fear.
Further investigations by the Japanese researchers found that excitation of specific GABAergic neurons in stria terminalis during sleep in mice led to the mice entering a wakefulness state without the normal bodily changes that are involved with ‘waking up’. Ordinarily chemicals called orexins (neuropeptides) are involved; in the case of the research, these chemicals were by-passed.
The researchers also found that prolonged excitation of GABAergic neurons by what is termed a ‘chemogenetic method’ triggered a longer-lasting wakefulness state. This, however, could be blocked by administering an orexin receptor blocker called DORA 22 in advance. Chemogenetics is used to understand the relationship between brain activity and behavior and it describes the processes by which macromolecules can be engineered to interact with previously unrecognized small molecules.
Discussing the significance of all this, the researchers write that the bed nucleus of the stria terminalis region of the brain and the associated GABAergic neurons can play a role in sleeping and waking. In other words, extreme emotional states stemming from anxiety can by-pass the normal chemical reactions involved in going to sleep and waking up, accounting for sleep disruption with those who are suffering from high levels of anxiety or similar emotive stress.
It is hoped the research will help with developing drugs and drug targets to address anxiety disorder as well as different sleep disorders. The research findings are reported to The Journal of Neuroscience. The accompanying research paper is titled “Excitation of GABAergic neurons in the bed nucleus of the stria terminalis triggers immediate transition from non-rapid eye movement sleep to wakefulness in mice.”
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