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Pharmacology > 5 - HT / Serotonin > Flashcards

5 - HT / Serotonin Flashcards

1
Q

What is serotonin synthesised from?

A

From tryptophan by tryptophan hydroxylase and an ubiquitous carboxylase.

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2
Q

What does degradation of serotonin occur by?

A

Monoamine oxidase

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3
Q

What does degradation by monoamine oxidase form?

A

5-hydroxyindoleacetic acid (5-HIAA)

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4
Q

Where is endogenous 5-HT found?

A

Enterochromaffin cells & enteric nerves on wall of intestine: gastric peristalsis & emptying
Platelets: aggregation, haemostasis, alter local vascular supply
They get loaded with 5-HT as they pass through intestinal circulation where there is high concentration storage, release and uptake of 5-HTs
CNS: act as a neurotransmitter

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5
Q

Effect of 5-HT on GIT

A

Gut peristalsis and secretion, gastric emptying

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6
Q

Effect of 5-HT on platelets

A

Platelet aggregation

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7
Q

What is the effect of 5-HT on blood vessels?

A

Vasodilation (eg. arterioles by causing endothelial cells to release NO & inhibit noradrenaline release)
Vasoconstriction (eg. large vessels)

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8
Q

What is the effect of 5-HT on cardiac muscle?

A

Direct increase rate and force

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9
Q

What is the effect of 5-HT on chemoreceptors?

A

Indirectly mediated bradycardia (vagus8) and vasodilation

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10
Q

Receptor subtype of GIT for 5-HT?

A

5-HT2/5-HT3
5-HT4

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11
Q

Receptor subtype of Platelets for 5-HT?

A

5-HT2

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12
Q

Receptor subtype of blood vessels for 5-HT?

A

5-HT1
5-HT1/5-HT2

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13
Q

Receptor subtype of cardiac muscle for 5-HT?

A

5-HT4

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14
Q

Receptor subtype of chemoreceptors for 5-HT?

A

5-HT3

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15
Q

Agonist of 5-HT1 ( decrease cAMP)

A

5-carboxamido tryptamine (5-CT) – vasoconstriction

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16
Q

Antagonist of 5-HT1

A

Ergotamine (PA) – ergot alkaloid drug with anti-migraine effect due to constriction of the intracranial extra-cerebral blood vessels

17
Q

Agonist of 5-HT(1A)

A

Buspirone (PA) - treat GAD

18
Q

Antagonist of 5-HT(1A)

A

Methysergide (PA)

19
Q

Agonist of 5-HT(1B) and 5-HT(1D) and effect

A

Sumatriptan – reduces vascular inflammation associated with migraine

20
Q

Agonist of 5-HT(1F) and effect

A

Lasmiditan – investigational drug for treatment of acute migrane, might have fewer side-effects compared to triptans

21
Q

Agonist of 5-HT2A-C (↑ IP3) and effect

A

α-methyl 5-HT (αMS) – acts on 5-HT2 to cause vasodilation, has longer half-life as not metabolized by MOA and no CNS effects as –OH group reduces its ability to cross BBB.
LSD – psychedelic drug

22
Q

Antagonist of 5-HT2A-C (↑ IP3) and effect

A

Methysergide (PA) – prophylactic but no longer recommended due to retroperitoneal fibrosis.

23
Q

Agonist of 5-HT2C (mostly in brain) and effect

A

Lorcaserin – weight-loss drug with CNS effects

24
Q

Agonist of 5-HT3 and effect

A

2-methyl 5-HT

25
Q

Antagonist of 5-HT2C (mostly in brain) and effect?

A

Pizotifen – preventative drug to reduce frequency of recurrent migraine
Acts on 5-HT2A as well

26
Q

Antagonist of 5-HT3 (channel) and effect

A

Ondansetron & Tropisetron – antiemetic drugs, particularly for controlling severe nausea & vomiting that occurs with many forms of cancer chemotherapy.

27
Q

Agonist of 5-HT4 (↑ cAMP) and effect

A

5-methoxytryptamine (5-MT) – cardiac stimulant effects
Tegaserod – promote gastric emptying/alter peristalsis, increase colon activity

28
Q

Antagonist of 5-HT4 (↑ cAMP) and effect

A

Tropisetron blocks this receptor as well

29
Q

Ergotism defn

A

The effect of long-term ergot poisoning, traditionally due to the ingestion of the alkaloids produced by the Claviceps purpurea fungus that infects rye and other cereals.

30
Q

NANC receptor peptides

A
  • Kinins
  • Angiotensin II
  • Endothelins
31
Q

Kinins effects (2)

A

B1: arterial (vein) constrict
B2: arteriolar (venule) dilation (NO) – increase capillary permeability

32
Q

Angiotensin effects (2)

A

AT1: arteriolar constriction, aldosterone release
AT2: catecholamine release

33
Q

Endothelins

A

ET(A) & ET(B) (Bosentan is a competitive ET antagonist used in the treatment of pulmonary artery hypertension (PAH), by constricting pulmonary blood vessels)

34
Q

Other NANC receptor peptides (3)

A

Y1-6 receptors: Neuropeptide Y (NPY)
VPAC1,2 receptors: Vasoactive intestinal polypeptide (VIP)
Neurokinin receptors, NK1-3: Substance P

Pharmacology (4 decks)

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