- Regulating neuronal excitability
- Modulating synaptic transmission
- Influencing learning and memory
- Controlling anxiety and other emotional states
GABA-A receptors are ligand-gated ion channels. This means that they open in response to the binding of GABA, allowing chloride ions to flow into the cell. The influx of chloride ions hyperpolarizes the cell, making it more difficult to excite.
GABA-A receptors are made up of five subunits, which can be arranged in different combinations to form different receptor subtypes. There are 19 different GABA-A receptor subunits that have been identified, but only 15 of these subunits are thought to be involved in the formation of functional receptors.
The different GABA-A receptor subtypes have different properties, and they are distributed in different areas of the brain. For example, some GABA-A receptor subtypes are more abundant in the hippocampus, while others are more abundant in the amygdala.
GABA-A receptors are also affected by alcohol. Alcohol binds to GABA-A receptors and enhances the effects of GABA, which is why alcohol can have a calming effect. However, alcohol can also have a sedating effect, and it can even be fatal in high doses.
GABA-A receptors are essential for normal brain function, and they are involved in a wide range of physiological and behavioral processes. However, GABA-A receptors can also be involved in the development of diseases, such as anxiety disorders, epilepsy, and addiction.
Structure of GABA-A Receptors
GABA-A receptors are ligand-gated ion channels that are composed of five subunits, each of which is a transmembrane protein. The subunits are arranged in a ring around a central pore, which is where chloride ions flow through when the receptor is activated.
The five subunits of GABA-A receptors are named α, β, γ, δ, and ε. The α subunit is the most important subunit, and it determines the overall properties of the receptor. The β, γ, δ, and ε subunits can vary in their sequence and expression, and they can affect the sensitivity of the receptor to GABA and other drugs.
Function of GABA-A Receptors
GABA-A receptors are involved in a wide range of physiological and behavioral processes, including:
- Regulating neuronal excitability
- Modulating synaptic transmission
- Influencing learning and memory
- Controlling anxiety and other emotional states
Diseases Associated with GABA-A Receptors
GABA-A receptors are essential for normal brain function, and they are involved in a wide range of physiological and behavioral processes. However, GABA-A receptors can also be involved in the development of diseases, such as anxiety disorders, epilepsy, and addiction.
- Anxiety disorders: GABA-A receptors are involved in the regulation of anxiety. Mutations in GABA-A receptors have been linked to anxiety disorders, such as panic disorder and social anxiety disorder.
- Epilepsy: GABA-A receptors are involved in the control of seizures. Mutations in GABA-A receptors have been linked to epilepsy, and drugs that target GABA-A receptors are often used to treat seizures.
- Addiction: GABA-A receptors are involved in the reinforcing effects of drugs, such as alcohol and benzodiazepines. Drugs that target GABA-A receptors can be addictive, and they can also worsen the symptoms of addiction.
According to a recent paper published in the journal Trends in Pharmacological Sciences1, GABA-A receptors are important targets for treating both the affective and cognitive symptoms of depression. GABA-A receptors are the main receptors for GABA, the most prominent inhibitory neurotransmitter in the brain.
The paper reviews the evidence from various studies on how GABA and GABA-A receptors are involved in depression and how different drugs that modulate their function can have antidepressant effects. The authors propose possible mechanisms by which GABA-modulating treatments could help address the different aspects of depression, such as:
- Neurosteroids: These are natural hormones that act as positive modulators of GABA-A receptors, enhancing their function and increasing the inhibitory effect of GABA. Chronic stress, which is a major risk factor for depression, decreases neurosteroid signaling, impairing the inhibitory balance. Conversely, enhancing neurosteroid signaling improves behavioral outcomes and mood. For example, Brexanolone, a synthetic version of a neurosteroid, was approved by the FDA in 2019 as a treatment for peripartum depression, and has also shown efficacy in other forms of major depressive disorder2.
- Subunit-selective compounds: These are drugs that target specific subunits of the GABA-A receptor, which have different functions and distributions in the brain. By selectively activating or inhibiting certain subunits, these compounds can have more specific and beneficial effects on depression and its symptoms. For instance, alpha-5 subunit-selective inverse agonists can enhance cognitive performance and memory by reducing excessive inhibition in the hippocampus3. Alpha-2/alpha-3 subunit-selective positive allosteric modulators can reduce anxiety and stress-related behaviors by increasing inhibition in the amygdala.
- Neurogenesis: This is the process of generating new neurons in the brain, which is impaired in depression and restored by antidepressant treatments. GABA-A receptors play a key role in regulating neurogenesis, as they influence the proliferation, differentiation, migration, and survival of neural progenitor cells. Modulating GABA-A receptor function can therefore affect neurogenesis and its consequences on mood and cognition. For example, neurosteroid-induced activation of GABA-A receptors can promote neurogenesis in the hippocampus and improve depressive-like behaviors.
reference link :https://www.cell.com/trends/pharmacological-sciences/fulltext/S0165-6147(23)00136-0?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0165614723001360%3Fshowall%3Dtrue