Neurobiology 7

Question 1

What two categories can neuromodulators be divided into?

Answer 1

Wide projecting.

Local projecting.

Question 2

Give two examples of wide projecting neuromodulators.

Answer 2

Acetylcholine.

Dopamine

Question 3

Give two examples of local projecting neuromodulators.

Answer 3

Many peptides (somatostatin). 
Adenosine.

Question 4

What do neuromodulators typically act through?

Answer 4

GPCRs - signalling via second messengers/protein kinases.

Question 5

What is volume transmission?

Answer 5

When local neuromodulators are not released at a specific synapse, but instead diffuse to influence a group of neurons.

Question 6

Where is dopamine synthesised?

Answer 6

Substantia nigra and the ventral tegmental area (VTA) - dopamine neurons found in clusters in these areas of brain stem.

Question 7

Do dopamine neurons typically have long or short axons?

Answer 7

Long

Question 8

Where is noradrenaline synthesised?

Answer 8

In the locus ceruleus.

Question 9

Briefly describe dopamine synthesis.

Answer 9

L-DOPA is produced from L-tyrosine by tyrosine hydroxylase. This is converted to dopamine by DOPA decarboxylase.

Question 10

What does DOPA decarboxylase require as a coenzyme?

Answer 10

pyridoxal phosphate.

Question 11

What does monoamine oxidase do?

Answer 11

It is the transporter that puts dopamine into vesicles.

Question 12

What genes must be switched on to make a dopamine neuron?

Answer 12

Tyrosine hydroxylase, DOPA decarboxylase and the monoamine oxidase genes

Question 13

Briefly describe adrenaline synthesis.

Answer 13

Dopamine beta-hydroxylase catalyses the production of noradrenaline from dopamine.
Phenylethanolamine N-methyltransferase catalyses the conversion of noradrenaline to adrenaline.

Question 14

Is dopamine used in volume (non-synaptic) transmission?

Answer 14

Yes.

Question 15

What do dopamine neurons look like in the brain (striatum)?

Answer 15

The axon splits at the striatum to form a huge axonal cloud.

Question 16

What regions of the brain do the dopamine neurons in the SN project to?

Answer 16

Project into the midbrain to the striatum and neocortex.

Question 17

Give examples of dopamine neurons functions.

in CNS

Answer 17

Control blood flow to brain.
Motor control - initiates voluntary responses.
Behaviour control.

Question 18

Give examples of dopamine neurons functions outside the CNS.

Answer 18

D1 dopamine receptor mediated renin secretion in the kidney.
Dopamine reduces gap junction communication between neurons in response to light intensity - helps retina switch from rod to cones.

Question 19

Name the two main types of dopamine GPCRs

Answer 19

D1-like (including D1 and D5)

D2-like (including D2, 3 and 4).

Question 20

What type of receptor is D1 and where is found?

Answer 20

Excitatory and is expressed in the adrenal cortex.

Question 21

What does an excitatory signal to the D1 receptor do?

Answer 21

Stimulates the adrenal cortex to produce cAMP via the activation of a G protein. Results in activation of PKA and a phosphatase inhibitor - causing ion channels to be phosphorylated.

Question 22

What type of receptor is D2?

Answer 22

An inhibitory receptor.

Question 23

What does the combination of D1 and D2 allow for?

Answer 23

Fluid motor responses.

Question 24

What does shortage of dopamine result in? (symptoms wise)

Answer 24

Indecisive personality and difficulty with body movement.

Question 25

What is Parkinson’s disease treated with?

Answer 25

L-DOPA - can cross blood-brain barrier.

converted to dopamine in brain

Question 26

What symptoms does excess dopamine cause?

Answer 26

More arousal to the motivational signal - leads to ADD and possible schizophrenia.