GAMMA AMINO BYUTRIC ACID (GABA)

It is an inhibitory neurotransmitter

SYNTHESIS OF GABA

- formed by decarboxylation of glutamate by the action of enzyme glutamate decarboxylase present at the nerve terminal in the brain

GABA is taken by the nerve terminal using a GABA transporter or a vesicular trIonotropic receptoransporter

REUSE of GABA

GABA is metabolized to succinate by the process of transamination

Action of GABA

it binds to the following receptors

• GABA a

• GABA b

• GABA c

Ionotropic receptors - ligand-binding receptors that respond through an ion chanal

metabotropic receptors - g protein-coupled receptors that respond by activating metabolic pathway. GABA a and GABA c are ionotropic - They hyperpolarize cell by the influx of chlorine GABA b -

• metabotropic, they are inhibitory

• They produce fast reaction by

  • Promoting potassium influx

  • Inhibiting the influx of calcium ions

  • Inhibits action of acetyl cyclase

  • Increases influx of chloride ions

CLINICAL PHYSIOLOGY

• Long term low-level stimulation of GABA receptors reduces noise produced by neuron discharge and improves the signal to noise ratio in the brain

• Benzodiaphine is a group of drugs that stimulate GABA and acts as antianxiety, anticonvulsant and sedative.

• Vigabatrin, an antiepileptic inhibitor of GABA transaminase

• Pyridoxine deficiency is a rare disease in which the vitamin is not available for the synthesis of GABA. It usually presents as frequent seizures during infancy that are resistant to treatment with anticonvulsants but responds very well to vitamin supplementation.