NEUROTRANSMITTER SYSTEMS

Question 1

Outline the 5 criteria for defining a Neurotransmitter

Answer 1

1) synthesis in nerve terminal
2) storage in nerve terminal vesicles
3) Ca2+ regulated release
4) Post-synaptic effect
5) Inactivation by specific mechanism

Question 2

Name the 4 chemical categories of Classical Neurotransmitters

Answer 2

Amino Acids
Derivative of AAs
Peptides
Esters

Question 3

Give examples of Amino Acid Neurotransmitters

Answer 3

Glutamate, GABA and Glycine

Question 4

Give examples of Derivative of AA Neurotransmitters

Answer 4

Dopamine, Norepinephrine, 5-HT and Histamine

Question 5

What chemical class of Neurotransmitter does Ach belong?

Answer 5

Esters

Question 6

Name the 3 classes of Atypical Neurotransmitters

Answer 6

1) Nucleotides/ Nucleosides
2) Lipid Derivatives
3) Gases

Question 7

Give an example of a Lipid Derivative Neurotransmitter

Answer 7

Endocannabinoids; are derived from membrane phospholipids. They aren’t released in vesicles. They are retro-transmitters.

Question 8

Describe the role of Glutamate in the CNS

Answer 8

Is very high conc. as its the major excitatory NT. In the synapse, glutamate is converted to glutamine by the enzyme glutamine synthase

Question 9

Describe the synthesis of GABA

Answer 9

Glutamate is converted to GABA by the enzyme Glutamic Acid Dehydrogenase (GAD), the process is highly linked with the Krebs Cycle

Question 10

describe the synthesis of ACh

Answer 10

Ach is the ester of choline and acetyl-CoA, the enzyme Choline acetytransferase (ChAT) transfers the Acetylt group from acetyl-CoA onto Choline

Question 11

Describe the degradation of ACh

Answer 11

The enzyme Acetyl cholinesterase (AChe) breaks the eser bond and produces choline and acetyl. Ache is present in the synaptic cleft

Question 12

What is the rate limiting step of Ach formation?

Answer 12

The availability of Choline, aka the rate of transport of choline into the neuron by the plasma membrane High affinity Choline Uptake System (HACU)

Question 13

What are the 3 Catecholamines?

Answer 13

Dopamine, Norepinephrine and Epinephrine

Question 14

What amino acid are the catecholamines derivatives of?

Answer 14

Tyrosine

Question 15

What is L-Dopa and how is it made?

Answer 15

The precursor of Dopamine

Tyrosine + Tyrosine Hydroxylase –> L-DOPa

Question 16

What enzyme is responsible for the formation of Dopamine?

Answer 16

AADC changes L-DOPA to Dopamine

Question 17

How is Norepinephrine synthesised from Dopamine?

Answer 17

The enzyme DBH adds a hydroxyl group to Dopamine thus producing Norepinephrine. The DBH is held in vesicles so DA is transported into a vesicle where it is changed to NE

Question 18

How is Epinephrine made?

Answer 18

The enzyme PNTM methylates NE, producing Epinephrine.

Question 19

What is the name of the enzyme responsible for the breakdown of the Catecholamines?

Answer 19

Monoamine Oxidase.

Question 20

What are the Indoleamines?

Answer 20

The NTs derived from tryptophan

Question 21

Describe the synthesis of 5-HT

Answer 21

The enzyme Tryptophan Hydroxylase converts Tryptophan to 5-HT

Question 22

What are the Imidazoles?

Answer 22

The NTs derived from Histidine.

Question 23

How is Histamine produced?

Answer 23

A single decarboxylation reaction of histidine by the enzyme Histidine Decarboxylase produces Histamine