Dopamine - Expanded

Question 1

What compound is the precursor to dopamine?

Answer 1

L-DOPA.

Question 2

How can dopaminergic neurones be identified electrophysiologically?

Answer 2

They can be seen to exhibit tonic/burst firing.

Question 3

Which inputs control the firing of dopaminergic neurones?

Answer 3

Inputs from the cortex (Glu), SNr (GABA), Raphe (5HT), Locus coeruleus (NA).

Question 4

How does the firing of dopaminergic neurones change when they are assayed in brain slices?

Answer 4

They tick over at a rate of 6 times per second as they have lost their inputs so have lost their burst fire potential.

Question 5

How is dopamine released at classical synapses?

Answer 5

By calcium-dependent exocytosis.

Question 6

Name the three central dopaminergic pathways.

Answer 6

The nigrostriatal system, the mesolimbic/mesocortical pathways, and the tuberohypophyseal system.

Question 7

Where do the nerves of the nigrostriatal system originate from and where do they link to?

Answer 7

The nerves of the nigrostriatal system originate in the A9 cell group of the substantia nigra and link to the corpus striatum.

Question 8

What functions is the nigrostriatal system involved in?

Answer 8

Motor control and motor planning.

Question 9

What does a loss of dopamine in the nigrostriatal system lead to?

Answer 9

Loss of movement (akinesia) or reduced movement (dyskinesia).

Question 10

In animal experiments, what do unilateral 6-OH dopamine legions result in?

Answer 10

Contralateral turning, the animal turns towards the lesioned site.

Question 11

Parkinson’s disease is associated with a deficiency in which central dopaminergic pathway?

Answer 11

Nigrostriatal.

Question 12

Where do the nerves of the mesolimbic/mesocortical systems originate from and where do they link to?

Answer 12

The nerves of the mesolimbic/mesocortical systems originate from the A10 nerve group in the ventral tegmental area ad link to the nucleus accumbens, amygdala, and cortex.

Question 13

What are the mesolimbic and mesocortical pathways responsible for?

Answer 13

They are responsible for motivation, behavioural control, cognition, and addiction.

Question 14

What is the result of a large amount of dopamine in the mesolimbic/mesocortical systems?

Answer 14

Stereotyped repetitive behaviours indicative of psychosis or schizophrenia.

Question 15

What is a common side effect of over administration of parkinson’s medication?

Answer 15

Schizophrenic symptoms due to an increase of dopamine in the mesolimbic/mesocortical systems.

Question 16

Symptoms of what disease can be seen in schizophrenic patients given an excess of dopamine receptor antagonists?

Answer 16

Parkinson’s.

Question 17

Where do the nerves of the tubero-hypophyseal system originate from and where do they link to?

Answer 17

The nerves of the tubero-hypophyseal system originate in the A12 nerve group of the arcuate nucleus of the hypothalamus and link to the medial eminence and the pituitary gland.

Question 18

Which neurotransmitter controls hormone release from the anterior pituitary gland?

Answer 18

Dopamine.

Question 19

What hormone does dopamine inhibit the release of?

Answer 19

Prolactin.

Question 20

What hormone does dopamine increase the release of?

Answer 20

Growth hormone.

Question 21

How do anti-psychotic D2 antagonists cause gynecomastia (breast development in men) and male lactation?

Answer 21

They prevent dopamine from inhibiting prolactin release.

Question 22

Where does dopamine also act to cause nausea and vomiting?

Answer 22

The chemo-receptor trigger zones in the medulla.

Question 23

Where does dopamine act to cause dilation of blood vessels?

Answer 23

Vascular smooth muscle.

Question 24

How does reserpine act to prevent dopamine from being converted to noradrenaline?

Answer 24

It blocks dopamine uptake into vesicles.

Question 25

What is the main mechanism for dopamine signal termination?

Answer 25

Re-uptake in synaptic terminals by specific dopamine transporters.

Question 26

What illicit drug blocks dopamine reuptake?

Answer 26

Cocaine.

Question 27

What enzymes enzymatically degrade dopamine? What is it degraded into?

Answer 27

MAO, COMT, and aldehyde dehydrogenase. It is degraded into dihydroxyphenyl acetic acid (DOPAC) and homovanillic acid (HVA)

Question 28

DOPAC and HVA are excreted in the urine, what can this be used as a measure of?

Answer 28

Dopamine release.

Question 29

What form of receptors are all dopamine recetors?

Answer 29

Metabotropic; GPCRs.

Question 30

What are the two types of dopamine receptors?

Answer 30

D1 like and D2 like.

Question 31

What cellular effect does activation of D1 like dopamine receptors have?

Answer 31

An increase in adenylate cyclase activity leading to an increase in cAMP.

Question 32

What cellular effect does activation of D2 like dopamine receptors have?

Answer 32

A decrease in the activity of adenylate cyclase leading to a decrease in cAMP. This leads to an increase in potassium ion influx and a decrease in cellular calcium ion concentration.

Question 33

What is the potency of dopamine to D1 like receptors?

Answer 33

Low.

Question 34

What is the potency of dopamine to D2 like receptors?

Answer 34

High.

Question 35

Which two types of dopamine receptors are the most common?

Answer 35

D1 and D2.

Question 36

Where are D1 and D2 dopamine receptors found most commonly?

Answer 36

In all terminal fields.

Question 37

Where are D3 and D4 dopamine receptors found most commonly?

Answer 37

In limbic areas.

Question 38

Where are D5 dopamine receptors only found?

Answer 38

In the hippocampus, hypothalamus, and thalamus.

Question 39

What conditions can be treated by targeting dopaminergic pathways?

Answer 39

Schizophrenia, ADD, drug dependence, endocrine dysfunctions, movement disorders (Parkinson’s).