L9 - Neurotransmitter

Question 1

What is an Agonist, Partial agonist and Antagonist?

Answer 1

1. can bind to, and activate, the receptor
2. binds and activates the receptor, but with reduced efficacy compared to agonist
3. binds to, but cannot activate, receptor; occupies the natural ligand site so it cannot bind

Question 2

What is an Allosteric modulator?

Answer 2

Binds the receptor at a different site to alter how receptor responds to ligand.

Question 3

Nicotinic Acetylcholine Receptor - ligand-gated ion channel characteristics?

Answer 3

Five subunits (2α, β, δ, ε, γ) arranged to form a pore.

Pentamer

2ACh bind 2α subunits to open channel

Na+ (and K+) flow down their electrochemical gradient
o Na in K out

Question 4

Classical NT’s

Answer 4

Acetylcholine
Dopamine
Serotonin (5-hydroxytryptamine)
Adrenaline (epinephrine)
Noradrenaline (norepinephrine)
Histamine
L-Glutamic acid
γ-amino-butyric acid (GABA)

Question 5

Neuropeptides (small proteins up to 100 aa)

Answer 5

Slower acting/first to evolve

Substance P (pain)
Endorphins 
Enkephalins
Vasopressin
Oxytocin (love)

Question 6

Other NT’s

Answer 6

NO (gas/freely moves across membrane/receptor inside cell)

Adenosine

ATP

Question 7

Identification of a Neurotransmitter (5)

Answer 7

1. synthesised by the neuron
2. present in synaptic terminal at sufficient concentrations
3. released on presynaptic stimulation
4. Exogenous application to postsynaptic cell evokes a response
5. Mechanism exists for its removal from synaptic cleft

Question 8

Three main classes of NT’s

Answer 8

1. Amino acids: e.g. glutamate; glycine; γ-aminobutyric acid (GABA) (synaptic vesicles, 50 nm)
2. Amines: e.g. acetylcholine (ACh); dopamine; noradrenaline; serotonin (5-HT) (synaptic vesicles)
3. Peptides: e.g. enkephalin; substance P; neuropeptide Y (dense-core secretory granules, 100 nm)

Question 9

Functions of AA NT’s (2)

Answer 9

o Glutamate – excitatory

o GABA – inhibitory

Question 10

Functions of Amines NT’s (3)

Answer 10

o Acetylcholine – neuromuscular junction, brain
• Fast acting

o Dopamine – movement
• Slower

o	Serotonin (= 5-HT) – sleep, appetite, arousal
•	Slower

Question 11

Functions of peptide NT’s

Answer 11

o Enkephalin - opiate

o Substance P – pain

Question 12

Role of Choline acetyltransferase

Answer 12

Synthesis of ACh - coenzyme acetyl-CoA to choline.

1 step reaction

Question 13

Removal of neurotransmitter from the synaptic cleft (3)

Answer 13

Diffusion

Reuptake

Enzyme degradation

Question 14

Difference of inotropic and metabotropic ACh receptors and examples

Answer 14

inotropic receptors = ion channel pore vs meta = G-protein

1. Nicotine: Fast
2. Muscatine: Slow

Question 15

GPCR effector signalling (GTP-binding protein)

Answer 15

Neurotransmitter activation of a GPCR at the postsynaptic membrane activates a specific G-protein.

Leads to downstream effects

Question 16

4 types of Glutamate receptors

Answer 16

1. AMPA: Glutamate to opon (Na influx)
2. NMDA: Glutamate + Depol ( Ca+Na influx)
3. Kainate
4. mGluR: only metabotropic

Question 17

GABAa (3) inhibitory

Answer 17

Ionotropic

Increase Cl

Slow

Question 18

GABAb (3) inhibitory

Answer 18

Metabotropic

Increase K
Decrease Ca

Slow