GABA (also known as gamma-aminobutyric acid) is the brain's primary inhibitory neurotransmitter; it decreases the likelihood that a particular neuron will fire. It works by opening ion channels that allow chloride ions to flood into the neuron.

How do chloride ions make a neuron less likely to fire? Well, remember that most neurons have a resting potential of about -70 mV--that is, the voltage inside the neuron is 70 mV less that the voltage outside the neuron. If that potential changes to about -60 mV or so, the neuron will fire. Now, excitatory neurotransmitters (like acetylcholine) make positive ions flow into the neuron, raising the potential closer to that -60 mV threshold. If chloride ions (which are negative) flow in, the resting potential will move further away from the threshold (say, down to -90 mV). You'll therefore need lots more excitatory neurotransmitter to get the neuron up to -60.

Benzodiazepines (drugs like Valium and Xanax) are GABA agonists.

A common inhibitory neurotransmitter. When released, gamma-amino butyric acid interacts with receptors controlling ion channels which allow an increase in the number of negative ions inside the post synaptic cell.
Overall, the membrane potential of the post synaptic cell is hyper-polarised, and taken further away from its threshold voltage.

Also know as

• 4 amino butanoic acid
• gamma-amino-butanoic acid

Formula: C₄ H₉ N₁ O₂