Neurotransmitters Flashcards

1
Q

Classify neurotransmitters according to structure & function

A

S, amino acids, biogenic amines, neuropeptides & others
F, excitatory, inhibitory or both

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2
Q

Mention methods of inactivation of neurotransmitters and therapeutic application

A

Reuptake, SSRI
Hydrolysis, MAO inhibitors

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3
Q

Mention the principal excitatory and principal inhibitory NT and their method of removal

A

E, glutamate, reuptake
I, GABA, converted to succinate semialdehyde by GABA-T, then oxidized to succinate which is used in Krebs cycle.

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4
Q

Describe formation of GABA

A

Derived from glutamic acid by glutamic acid decarboxylase enzyme and pyridoxal phosphate is required as a coenzyme.

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5
Q

Describe function, origin and fate of glycine

A

Major inhibitory NT
Can be synthesized from serine by serine hydroxymethyltransferase, removed by reuptake through high-affinity transporters.

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6
Q

Write equations of synthesis & degradation of Ach

A

S, Acetyl CoA + choline —ChAT—-> Ach + CoA
D, Ach—-AChE—>acetate + choline

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7
Q

…..is the precursor of catecholamines, while the enzyme directly producing dopamine is …….

A

Tyrosine
Dopa-decarboxylase

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8
Q

…..is the rate-limiting step of CA synthesis

A

Tyrosine hydroxylase

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9
Q

The enzyme catalyzing formation of NE ……, While that catalyzing formation of E

A

Dopamine beta-hydroxylase
Phenyl-ethanolamine N-methyl-transferase

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10
Q

Fates of catecholamines

A

1- Active uptake by sympathetic nerve endings
2- Catabolism to biologically inactive products by MAO & COMT
D to homovanillic acid
NE & E to vanillylmandelic acid

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11
Q

GR: Occurrence of Parkinson’s & mention a lab result

A

Due to insufficient production of dopamine as a result of idiopathic loss of dopamine-producing cells in the brain.
Decreased HVA in urine

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12
Q

…..is used to treat Parkinson’s

A

L-DOPA

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13
Q

Justify the addition of carbidopa to L-dopa

A

It is an inhibitor of dopa-decarboxylase and reduced the decarboxylation of L-dopa in peripheral tissues thus allowing higher concentration of the precursor to reach the brain.

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14
Q

Alpha-methyl dopa mechanism

A

Competitive inhibition of DOPA decarboxylase

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15
Q

Mention drug treatment of pheochromocytoma and mechanism

A

Alpha-methyl tyrosine
Competes with tyrosine for enzyme tyrosine hydroxylase

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16
Q

Mechanism and use of MAOI

A

In the neuron MAOIs inactivate the enzyme and thus increase levels of NE & serotonin
Antidepressant action

17
Q

Functions of serotonin

A

In CNS: NT, mood, appetite, temp reg, source of melatonin in the pineal body
Stimulate smooth muscle contraction (VC)
Imp for GIT motility

18
Q

Describe synthesis and degradation of serotonin

A
  1. Tryptophan is hydroxylated in a tetrahydrobiopterin-requiring reaction catalyzed by tryptophan hydroxylase producing 5-hydroxytryptophan
  2. 5-hydroxytryptophan is decarboxylated to serotonin
    Deg is by MAO producing 5-hydroxyindolacetic acid
19
Q

Write a short note on carcinoid tumour

A

Arise from argentaffin cells, characterizied by increase production of serotonin dec in niacin causing pellagra and inc 5-HIAA in urine.

20
Q

SSRI used as ….

A

Antidepressants

21
Q

Functions of melatonin

A

Stimulates immune system, antioxidant, involved in sleep regulation
It follows a circadian rhythm

22
Q

Mention conditions which can cause melatonin deficiency

A

-Cigarettes, caffeine, stress
-Antidepressents & BBs
Level dec as we age

23
Q

Histamine synthesis is catalyzed by ….

A

Histidine decarboxylase enzyme

24
Q

Functions of histamine

A
  1. Allergic & inflammatory reactions & gastric acid secretion
  2. Arousal, wakefulness & electrographic arousal
  3. VD
25
Q

Synthesis of NO

A

From L-arginine by the action of nitric oxide synthase enzyme

26
Q

Physiological functions of NO

A
  1. VD of cerebral, coronary and muscular arteries
  2. Dec GIT & urogenital motility
  3. Release of hormones from hypothalamus
  4. It is produced by macrophges, monocytes and neutrophils to kill mircoorganisms
27
Q

Pharmacological functions of NO

A

Nitroglycerin for angina
NO inhalation for pulmonary VD, to treat pulmonary HTN & high-altitude pulmonary edema

28
Q

The two steps of serotonin formation from tryptophan

A

Hydroxylation
Decarboxylation

29
Q

The two steps of melatpnin formation from serotonin

A

Acetylation
Methylation