Session 3a - Neurotransmitters

Question 1

Describe the structure of a typical neuron?

Answer 1

From top to tail:
Dendrites receiving information from adjacent neurones,
Cell body or ‘soma’ containing the organelles (including the nucleus, nissyl substance etc..) and cytoplasm,
Axon - which transmits the signal down
Myelin Sheath etc…/ insulation
Terminal branches

Question 2

What are the two main neurotransmitters for depressive disorders?

Answer 2

Nor-adrenaline
Serotonin

(Other neurotransmitters important in psychiatric conditions include: Dopamine, Acetylcholine, GABA and Glutamate)

Question 3

What are the main functions of ‘Nor-Adrenaline’ in the brain?

Answer 3

Mood
Suggests a role in behaviour (arousal and attention)
Implication in memory functions

Question 4

Where is Nor-Adrenaline made?

Answer 4

Nor-Adrenaline is made in the ‘locus coeruleus’ in the brainstem, and then transported to several areas of the cortex.

Question 5

Once released into the synaptic cleft, the neurotransmitter Nor-Adrenaline binds to what receptors?

What roles to the types of receptors play?

Answer 5

Adrenoreceptors: specifically alpha 1 and 2, beta 1 and 2.

Beta receptors in the brain is not very clear, however alpha receptors play a role in arousal and mood

Question 6

The synthesis of Nor-Adrenaline is complex: without having to name the enzymes, can you name the products of synthesis?
Note: the first substrate is an amino acid.

Answer 6

Tyrosine - (L)Dopa - Dopamine - NorAdrenaline - (Adrenaline)

Question 7

Nor Adrenaline, once acted on adrenoreceptors, must be recycled and or degraded. Uptake systems 1 and 2 help the uptake on the molecule; but what is the enzyme (present in the pre synaptic knob) that degrades NA?

Answer 7

MAO

MonoAmine Oxidase.

Question 8

Evidence of nor-adrenaline being implicated in the causation of depression:
AMPT (alpha-methyl-P-tyrosine) inhibits Tyrosine to L-Dopa. In doing so, what symptoms are experienced?

Answer 8

increased: sleep, anger, and depressive symptoms
decreased: calmness
These are typical symptoms of depressed patients.

Question 9

State two major types of anti-depressive drugs:

Answer 9

1. Tricyclic anti-depressants
2. SNRI’s (Serotonin Noradrenaline re-uptake inhibitors)
3. SSRI’s (Selective serotonin re-uptake inhibitors)
4. MAOi’s (MonoAmineOxidase Inhibitors)

All these serve to keep either serotonin and/or NA in the synaptic cleft as long as possible so they can have maximal effect on the pre/post synaptic receptors.

(Reserpine is another drug that depletes the nerve ends of nor adrenaline)

Question 10

Serotonin (5HT) has major functions in the brain. Can you state 3?

Answer 10

Sleep, Impulse Control, Appetite, or Mood (SIAM)

Question 11

Where specifically is Serotonin produced?

Answer 11

5HT is produced in the brain stem, specifically the Raphe nuclei. It is then transported to cortical areas and the limbic system.

Question 12

Serotonin is synthesised is a multi step fashion, can you state the products of syntheses?
The first product is an amino acid.

Answer 12

Tryptophan - 5 hydroxy tryptophan (5-HTP) - Serotonin (5HT)
(- N Acetyl serotonin - Melatonin)

Question 13

There are many serotonergic receptors that aren’t required to know.

Answer 13

YAY!

Question 14

Reasons for implicating serotonin in depression:
Studies have found that 5HIAA (a metabolite in depression) is depleted in the CSF of depressed patients. What other substance is shown to be low as well?
(Pre-cursor for Serotonin)

Answer 14

Tryptophan

Question 15

What effects can dopamine have on the body?

Answer 15

Dopamine can release a feeling of pleasure and in ‘drive’
(this is also the same effect cocaine and amphetamines can elicit)
Electro-Convulsive therapy has an effect on the dopamine system. Dopamine is also the main neurotransmitter implicated in schizophrenia.

Question 16

The Mono-Amine Hypothesis of depression focuses on the role of which 3 neurotransmitters?

Answer 16

Serotonin (5HT), Nor-Adrenaline and Dopamine.

Question 17

Neurotransmitters can change in mania. State what happens to levels of Noradrenaline

Answer 17

Levels are increased.

Serotonin levels inconsistent

Question 18

Dopamine agonists can cause manic symptoms in patients. What effect do antipsychotics have on levels of dopamine?

Answer 18

Antipsychotics block dopamine receptors, and thus have anti-manic/ depressive properties

Question 19

State the most commonly used mood stabiliser?
What is its effects on the body (2)?
When would you use Mood Stabilisers, and with what other drugs?

Answer 19

Lithium
1. Positive effect on BDNF (Brain Derived Neurotrophic Factor) transcription. I.e. something that helps nerves grow.
2. Possible positive effect on Serotonin production
With Anti-depressants, you raise the mood of the patient, to then give them a mood stabiliser to stabilise a positive mental state.

Question 20

What is the most important INHIBITORY neurotransmitter in the brain?
To what receptors do GABA bind to?
Upon binding of GABA to these receptors, what ion is the permeability increased to?
What other molecules do GABA receptors have affinity for? (3)

Answer 20

GABA
GABA (A) and (B) receptors
Chloride ions
Alcohol, Benzodiazepines and steroids (or barbiturates)

Question 21

Classify what sort of receptors GABA A and B are:

Answer 21

GABAa: ion channels. If the receptor is activated, the membrane permeability for Cl- increases, and this has an inhibitory effect on the neuron.
GABAb: receptors are second messenger receptors.