PSYCHOPHARMACOLOGY FINAL STUDY_ GUIDE
Module 5a: Anxiolytics I GABA
● 2 inhibitory NTs: GABA & glycine
● GABA only manufactured by GABAergic neurons
● Synthesis: glutamate → GABA via glutamic acid decarboxylase (GAD)
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PSYCHOPHARMACOLOGY FINAL STUDY_ GUIDE
Module 5a: Anxiolytics I GABA
● 2 inhibitory NTs: GABA & glycine
● GABA only manufactured by GABAergic neurons
● Synthesis: glutamate → GABA via glutamic acid decarboxylase (GAD)
● Drugs allylglycine, thiosemicarbazide & 3-mecaptoproprionic acid block GABA synthesis
○ → leads to convulsions
● GABA important in regulating brain excitability Vesicularization & Reuptake
● Vesicular GABA transporter (VGAT) = vesicular inhibitory AA transporter (VIAAT)
○ Also in neurons that use glycine as NT
● VMAT- DA, NE & 5-HT
● 3 reuptake transporters on membranes of neurons & glia: GAT-1,GAT-2, GAT-3
○ GAT-1 & 2 expressed in neurons & astrocytes
○ GAT-3 only in astrocytes
○ GAT-1 @ nere terminals of GABAergic neurons- important for GABA reuptake
■ Tiagabine: selective GAT-1 inhibitor, elevates extracellular GABA & enhances GABA transmission (especially in cortex & hippocampus)
● Gabitril (tiagabine): used for treatment-resistant partial seizures
● Enzymatic breakdown of GABA: GABA→ succinate semialdehyde via GABA aminotransferase (GABA-T)
○ Glutamate is a by product (can be used to resynthesize GABA)
○ Some glutamate taken up by astrocyes → glutaminase (via glutamine synthetase)--> GABAergic neuron → glutamate (via glutaminase)
● Vigabatrin (sabril): irreversible inhibitor of GABA-T used to treat epilepsy
○ Prevents degradation of synaptic GABA
○ May lead to constriction of visual field b/c GABAergic neurons in retina
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