Neurotransmitter Metabolism

Question 1

neuropeptides are synthesized from

Answer 1

large precursors, which are proteolytically processed to produce smaller active peptides.

Question 2

how is the rate limiting step in synthesis of catecholamines controlled?

Answer 2

by feedback inhibition and membrane depolarization mechanisms.

Question 3

the 2 basic categories of neurotransmitters are?

Answer 3

neuropeptides and small N containing molecules

Question 4

examples of small N containing molecules are

Answer 4

glutamate, aspartate, g-aminobutyric acid (GABA), glycine, acetylcholine, dopamine, norepinephrine, epinephrine, serotonin, and histamine.

Question 5

where are neuropeptides synthesized?

Answer 5

in the CNS

Question 6

how do endorphins work

Answer 6

bind to opioid receptors and block pain signals

Question 7

how are small N containing neurotransmitters synthesized

Answer 7

from amino acids, intermediates of glycolysis and the TCA cycle, and O2 in the cytoplasm of the presynaptic terminal.

Question 8

where are catcholamines found

Answer 8

few are in the cytosol, majority are in the storage vesicles

Question 9

how are catecholamines drawn into the storage vesicles?

Answer 9

In the vesicles, the catecholamines exist in a complex with ATP and acidic proteins known as chromogranins.

Question 10

how are catecholamines degraded?

Answer 10

• re-uptake and diffusion away from synapse

- degradation enzymes (MAO, COMT) are in the pre-synaptic terminal

Question 11

MAO is found

Answer 11

on outer mitochondrial membrane

Question 12

there are 2 kinds of MAO enzymes ?

Answer 12

• MAO-A: deaminates norepinephrine and serotonin

- MAO-B:acts on a wide spectrum of phenylethylamines

Question 13

list the metabolism of histamine

Answer 13

histamine is produced both by mast cells and by certain neuronal fibers.

• mast cells: They are prevalent in the thalamus, hypothalamus, dura mater, leptomeninges, and choroid plexus
• Histaminergic neuronal cell bodies in the human are found in the tuberomammillary nucleus of the posterior basal hypothalamus. The fibers project into nearly all areas of the CNS, including the cerebral cortex, the brainstem, and spinal cord.

Question 14

how is Ach inactivated/

Answer 14

acetylcholinesterase, which is a serine esterase that forms a covalent bond with the acetyl group.
- it is inhibited by neurotoxins like Sarin