Lecture 8 Flashcards
Transmitter systems (17 cards)
What are the five major classes of neurotransmitters?
What defines fast neurotransmission?
- Acts via ligand-gated ion channels (ionotropic receptors)
- Millisecond to second response
- Examples: GABAA, AMPA, NMDA, nAChR, 5-HT₃
What defines slow neurotransmission?
- Acts via G-protein coupled receptors (metabotropic)
- Seconds to minutes response
- Examples: GABAB, mGluR, dopamine, serotonin (except 5-HT₃), mAChR
What are the six key steps of neurotransmission?
- Synthesis (from precursors)
- Storage (in vesicles via transporters)
- Release (Ca²⁺-dependent exocytosis)
- Receptor action (binds to post/pre-synaptic receptors)
- Reuptake (via high-affinity transporters)
- Degradation (enzymatic breakdown)
What determines whether a neurotransmitter is excitatory or inhibitory?
The type of receptor it binds to and the resulting ion conductance (cation = excitatory, anion = inhibitory)
Give examples of inhibitory neurotransmitters.
- GABA (all receptors)
- Glycine
- Dopamine (D₂)
- Serotonin (5-HT₁)
- ACh (M₂)
- Histamine (H₃, H₄)
- Noradrenaline (α₂)
Give examples of excitatory neurotransmitters.
- Glutamate
- Dopamine (D₁)
- Serotonin (5-HT₂–7)
- ACh (nAChR, M₁, M₃)
- Histamine (H₁, H₂)
- Noradrenaline (α₁, β)
What are the main drug targets in neurotransmission?
• Receptors (ionotropic, metabotropic)
• Ion channels
• Transporters
• Enzymes
• DNA/RNA
What are the types of receptor-targeting drugs?
• Agonist: Activates receptor
• Antagonist: Blocks receptor
• Allosteric modulator: Enhances or inhibits receptor response
What is an orthosteric receptor binding site?
Primary recognition site for an endogenous substance; where agonists/antagonists bind
What is an allosteric receptor binding site?
A separate binding site where positive/negative allosteric modulators bind to alter receptor activity
What are the types of transporter-targeting drugs?
• Substrate: Mimics endogenous substance
• Inhibitor: Blocks transporter
What are the types of ion channel-targeting drugs?
• Modulators - Increase/decrease ion channel opening.
• Blockers - Bind to and block the ion channel.
What are the types of enzyme-targeting drugs?
• False substrate: Mimics natural substrate
• Inhibitor: Blocks enzyme
• Pro-drug: Activated by enzyme
What is the precursor for dopamine and noradrenaline?
L-tyrosine → L-DOPA → dopamine → noradrenaline
What is the precursor for serotonin (5-HT)?
L-tryptophan → 5-hydroxytryptophan → serotonin
How is acetylcholine synthesised and degraded?
- Synthesised from choline + acetyl-CoA via choline acetyltransferase
- Degraded in the synapse by acetylcholinesterase into choline + acetate
- Choline reabsorbed to be recycled
