L7 - NT identification and proof of function

Question 1

what are the 7 criteria for a neurotransmitter

Answer 1

1. mimics nerve response (if used to stimulate tissue)
2. has synthesis pathway in nerve
3. has storage mechanism in nerve
4. has a release mechanism from nerve (often Ca2+ dependant)
5. specific receptors targeted and activated
6. quick action
7. action ceases quickly (enzyme degradation/reuptake)

Question 2

describe the process of establishment of Noradrenaline as a neurotransmitter

Answer 2

1. studies found that aq extracts of the adrenal medulla caused:
   
   • increased rate and force of contraction in isolated
     frog heart
   • increased b.p of anaesthetised dog
2. studies found that the effects of adrenal extract similar to SNS stimulation - was later found that it was closer to PNS

Question 3

what evidence was there to support that NA was the NT in PNS

Answer 3

1. fluorescence spec showed sympathetic nerves release nor adrenaline
2. electron microscopy showed presence of NA storage vesicles
3. bioassays showed NA release was Ca2+ dependant
4. NA synthesised in nerve from tyrosine
5. NA has specific receptors (a B adrenoreceptors)

Question 4

what enzyme degrades NA in the synapse

Answer 4

monoamine oxidase

Question 5

what evidence supports that NA acts on more than one receptor?

Answer 5

differing agonist affinities (PA2)

differing transduction

Question 6

what is uptake 1?

Answer 6

uptake back into presynaptic neuron

Question 7

what is uptake 2

Answer 7

degradation of NT by enzymes in cleft

Question 8

why is identification of neurotransmitters important

Answer 8

1. changes in NT may be important in understanding disease mechanisms
2. allows development of specific drugs

Question 9

importance of identifying NA as a NT

Answer 9

development of several treatments for diseases such as:

• hypertension (B blockers)
• heart failure (B blockers)

Question 10

example of an a blocker

Answer 10

prazosin