GABA

Definition

GABA, or gamma-aminobutyric acid, is the primary inhibitory neurotransmitter in the mammalian central nervous system. It functions to reduce neuronal excitability, promoting a calming effect and playing a crucial role in the regulation of various neurological processes.

5 Must Know Facts For Your Next Test

1. GABA is synthesized from the amino acid glutamate by the enzyme glutamic acid decarboxylase (GAD).
2. GABA acts on two main types of receptors: GABA$_{A}$ and GABA$_{B}$, which have different mechanisms of action and physiological effects.
3. GABA$_{A}$ receptors are ligand-gated ion channels that, when activated, allow the influx of chloride ions, leading to hyperpolarization and reduced neuronal excitability.
4. GABA$_{B}$ receptors are G-protein coupled receptors that, when activated, inhibit the release of neurotransmitters and reduce neuronal firing through the opening of potassium channels.
5. Disruption of the GABA system has been implicated in various neurological and psychiatric disorders, including epilepsy, anxiety, and sleep disorders.

Review Questions

• Describe the role of GABA in the regulation of neuronal excitability within the central nervous system.
  • GABA is the primary inhibitory neurotransmitter in the mammalian central nervous system. It functions to reduce neuronal excitability by binding to GABA$_{A}$ receptors, which are ligand-gated ion channels. When GABA binds to these receptors, it allows the influx of chloride ions, leading to hyperpolarization of the cell membrane and a decreased likelihood of the neuron firing an action potential. This inhibitory effect of GABA is crucial for the regulation of various neurological processes, such as maintaining a balance between excitation and inhibition, modulating neuronal firing patterns, and preventing the occurrence of hyperexcitable states, like those observed in epilepsy.
• Explain the differences between the GABA$_{A}$ and GABA$_{B}$ receptors and their respective mechanisms of action.
  • GABA acts on two main types of receptors: GABA$_{A}$ and GABA$_{B}$. GABA$_{A}$ receptors are ligand-gated ion channels that, when activated by GABA, allow the influx of chloride ions, leading to hyperpolarization and reduced neuronal excitability. In contrast, GABA$_{B}$ receptors are G-protein coupled receptors that, when activated, inhibit the release of neurotransmitters and reduce neuronal firing through the opening of potassium channels. The distinct mechanisms of action of these two receptor types result in different physiological effects, with GABA$_{A}$ receptors mediating the fast, phasic inhibition and GABA$_{B}$ receptors mediating the slower, more prolonged inhibition of neuronal activity.
• Analyze the potential implications of disruptions in the GABA system and how they may contribute to the development of various neurological and psychiatric disorders.
  • Disruption of the GABA system has been implicated in the pathogenesis of several neurological and psychiatric disorders. For example, in epilepsy, a decrease in GABA-mediated inhibition can lead to the occurrence of hyperexcitable neuronal states and the development of seizures. Similarly, imbalances in the GABA system have been associated with anxiety disorders, where reduced GABA-mediated inhibition may contribute to the heightened neuronal excitability and emotional dysregulation observed in affected individuals. Additionally, alterations in the GABA system have been linked to sleep disorders, as GABA plays a crucial role in the regulation of sleep-wake cycles. Understanding the precise mechanisms by which disruptions in the GABA system can lead to the manifestation of these neurological and psychiatric conditions is an active area of research, as it may inform the development of targeted therapeutic interventions.

Related terms

Neurotransmitter: A chemical substance that is released at the end of a nerve fiber and transmits the nerve impulse to another nerve, muscle, or organ.

Inhibitory Neurotransmitter: A neurotransmitter that decreases the likelihood of the receiving neuron firing an action potential, reducing neuronal excitability.

GABA Receptor: A protein complex located on the surface of neurons that binds to GABA, leading to the opening of chloride ion channels and a hyperpolarization of the cell membrane.