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INTRODUCTION The newly established Synaptic Neurobiology Laboratory investigates how cells in the brain communicate with each other and their local environment. The goal is to understand how neurons communicate with each other under both normal and pathological circumstances. Through collaborations with current research groups at the Institute, the Laboratory aims to further strengthen research into schizophrenia, depression and autism. Through their activation and modulation, nerve cells (neurons) are able to transmit electrical signals and release chemicals called neurotransmitters at junctions between nerve cells (synapses). These connections enable nerve cells to communicate with each other to form interconnected circuits, the basis of all higher brain functions including movement, learning, memory and consciousness. HIGHLIGHTS The role of astrocytes as a cause of mental illness While approximately 10% of the brain consists of neurons, responsible for movement and thinking, the rest is made up of supportive cells called glial cells. Scientists have always believed that astrocytes, a type of glial cell known for its distinctive star like shape, only provide mechanical and metabolic support for neurons, by maintaining the environment in the brain. However, our research (presently funded by the NHMRC) demonstrates that astrocytes actively regulate neuronal activity and may have important roles to play in learning and memory, as well as neurological and mental disorders. Using electrophysiological techniques newly established at the Mental Health Research Institute (MHRI), we are beginning to understand how these important cells modulate neurons and their synaptic connections in the brain. Networks of astrocytes in the brain have been linked to mental illnesses such as schizophrenia and bipolar disorder. Although the biological mechanism responsible is not known, it is most likely linked to the ability of astrocytes to take up and release brain chemicals like glutamate, serotonin, dopamine and D-serine that in turn modulate synaptic connections.
In particular, the amino acid D-serine has been directly linked to schizophrenia and depression. D-serine is synthesized from L-serine by an enzyme almost exclusively found in brain astrocytes. Upon release from astrocytes, it acts as a co-activator of a type of neurotransmitter receptor called an NMDA glutamate receptor. NMDA glutamate receptors have been implicated in the ‘glutamate hypofunction hypothesis’ of schizophrenia. Drugs that block NMDA glutamate receptors in the brain cause schizophrenic-like symptoms such as social withdrawal and impaired short-term memory and language functions, whist partial activators (agonists) of NMDA glutamate receptor ameliorate schizophrenia. Thus, astrocytes have untapped therapeutic potential in neuropsychiatric disorders such as schizophrenia. In the future, drugs or other treatment strategies targeted at glial cells rather than neurons may help relieve these mental disorders and their burden on the community.
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