PHAR: Introduction to Neurotransmitters

Question 1

What are 6 neurotransmitters that were looked at as example?

Answer 1

1. Acetylcholine
2. Noradrenaline
3. 5-hydroxytryptamine (serotonin)
4. Dopamine
5. Glutamate
6. GABA (γ-aminobutyric acid)

Question 2

What are the 2 main receptor types of neurotransmitters?

Answer 2

• G-protein-coupled receptors (GPCRs).
• Ligand-gated ion channels.

Question 3

Is Glutamate excitatory or inhibitory?

Answer 3

Primary EXCITATORY neurotransmitter in the CNS.

Question 4

Where is glutamate most abundant?

Answer 4

• Cortex.
• Basal ganglia.
• Sensory pathways.

Question 5

• What are the 4 main glutamate receptor subtypes?
• Which are ligand-gated and which are GPCR?

Answer 5

• 3 ligand-gated Na⁺/Ca²⁺ channels:
  
  • NMDA (GluN).
  • AMPA (GluA).
  • Kainate (GluK).
• 1 G-protein-coupled receptor:
  
  • Metabotropic (mGluR).

Question 6

Is γ-Aminobutyric Acid (GABA) an inhibitory or excitatory neurotransmitter?

Answer 6

GABA is the primary INHIBITORY neurotransmitter in the CNS.

Question 7

• What are the 2 main GABA receptor subtypes?
  
  • Ligand-gated or GPCR?

Answer 7

• 1 x Ligand-gated Cl^- channel:
  
  • GABA_A receptor (Cl^- channel opening → hyperpolarisation)
• 1 x G-protein-coupled receptor:
  
  • GABA_B receptor (inhibits activity of adenylyl cyclase).
    
    • Adenylyl cyclase plays a regulatory role for cells (converts ATP to cAMP)

Question 8

Which 2 neurotransmitters are amino acids?

Answer 8

• Glutamate.
• GABA.

Question 9

Is acetylcholine excitatory or inhibitory?

Answer 9

Mostly EXCITATORY neurotransmitter, can be INHIBITORY.

Question 10

What are the 2 main acetylcholine receptor subtypes?

Answer 10

• Nicotinic (nACh receptors) - all excitatory
  
  • Ligand-gated Na⁺/Ca²⁺ channels.
• Muscarinic (mACh receptors) - some excitatory, some inhibitory (don’t need to know which)
  
  • G-protein coupled receptors.

Question 11

What is the role of acetylcholine?

Answer 11

• Widespread in CNS.
• Main peripheral transmitter of parasympathetic system and motor neurons.

Question 12

Which are the 3 main neurotransmitters from the monoamine group?

Answer 12

• Noradrenaline (norepinepherine).
• Dopamine.
• Serotonin/5-hydroxytrypatmine (5-HT).

Question 13

Where are NA neurons mainly located?

Answer 13

• Locus coeruleus. Sends axons to:
  
  • Cortex
  • Hippocampus
  • Cerebellum
  • Spinal cord

Main peripheral transmitter of sympathetic nervous system.

Question 14

What does the locus coeruleus mediate?

Answer 14

• Arousal.
• Sleep.
• Anxiety.
• Mood.

Question 15

What do α-adrenoceptors in the medulla regulate?

Answer 15

Blood pressure.

Question 16

What are the 2 main noradrenaline receptor types?

Answer 16

• G-protein coupled receptors.
  
  • α-adrenoceptors - excitatory.
  • β-adrenoceptors - most are inhibitory.

Question 17

What are the 3 main dopamine pathways in CNS and what do they control?

Answer 17

• Nigrostriatal.
  
  • ​​​​Motor control (associated with Parkinson’s disease).
• Mesolimbic/mesocortical.
  
  • ​Emotion, reward, arousal (associated with addiction and psychosis).
• ​Tuberohypophyseal.
  
  • ​Prolactin secretion (associated pituitary system).

Question 18

What are the receptors of dopamine?

Answer 18

• G-protein coupled receptors
  
  • D1, D5 - stimulate adenylyl cyclase.
  • D2, D3, D4 - inhibit adenylyl cyclase.

Question 19

What is the common name for 5-hydroxytryptamine (5-HT)?

Answer 19

Serotonin.

Question 20

Where are 5-hydroxytyptamine neuron bodies mainly located?

Answer 20

Raphe nuclei (pons-medulla), project axons to:

• Cortex.
• Hippocampus.
• Basal ganglia.
• Limbic system.
• Hypothalamus.

Question 21

What are the 5-hydroxytryptamine receptor subtypes?

Answer 21

• G-protein coupled receptors:
  
  • 5-HT₁ - inhibitory
  • 5-HT₂ - excitatory
• Ligand-gated cation channel:
  
  • 5-HT₃ - excitatory

Question 22

What are the 5-Hydroxytryptamine (serotonin) receptors associated with?

Answer 22

• 5-HT₁ - inhibitory - antidepressant, lowering appetite.
• 5-HT₂ - excitatory - agitation, hallucinations.
• 5-HT₃ - excitatory - nausea.

5-hydroxytryptamine also regulates:

• Nociception.
• Temperature.
• Blood pressure.

Question 23

What are 3 mechanisms neurotransmitter related drugs are put into therapeutic practice?

Answer 23

• Regulating neurotransmitter abundance (e.g. SSRI antidepressants).
• Activating a receptor (e.g. beta-adreneoceptor agonists in asthma).
• Inhibiting a receptor (e.g. 5HT3 receptor antagonists for nausea).

Question 24

Describe the process of glutamate being deactivated to glutamine.

Answer 24

• When glutamate has interacted with the receptor may be taken back up, or may be taken up to adjacent astrocytes where it undergoes deactivation by the process glutamate → glutamine.
• Astrocyte ejects it from the cell and can be used for other metabolic purposes.
• Neurone can reverse process to restore glutamate.

Question 25

Why are Na⁺/Ca²⁺ channels excitatory?

Answer 25

• Rush of cations into cell.
• Increase of membrane polarity.
• Brings membrane potential closer to zero.
• Depolarisation occurs → excitatory response.