Histamine and Serotonin Lecture Flashcards Preview

Pharm Unit 2 MJC > Histamine and Serotonin Lecture > Flashcards

Flashcards in Histamine and Serotonin Lecture Deck (21)
1

What AA is histamine synthesized from?

Histidine

2

Describe the release and storage of histamine?

It is released as it is made, large amounts dont tend to build up

3

What histamine degradation product can be measured in the urine?

N-methylimidazole acetic acid

4

Where are the largest concentrations of histamine found? (areas of body)

Skin, lungs, GI and nasal mucosa, and blood
so sites that are potential for tissue injury

5

What two cells principally produce and store histamine?

Mast cells and basophils

6

What mediates histamine release form mast cells?

Calcium

7

What type of G-proteins are the H1 and H2 receptors coupled to? and where are they distributed?

H1 - Gq - smooth muscle, endothelium, brain
H2 - Gs - Gastric mucosa, cardiac muscle, mast cells, brain

8

What are the principle physiological effects of histamine on the cardiovascular system?

-Immediate fall in blood pressure due to peripheral vasodilation (H1 and H2)
- increase in vascular permeability causing edema and loss of plasma from circulation (H1)
- Increased contractility and heart rate (H2...minor effect in humans)

9

What effect does histamine have on bronchiolar smooth muscle, which receptor mediates this?

Bronchoconstriction (H1)

10

What effects does histamine have on the GI tract?

-contraction of intestinal smooth muscle; diarrhea (H1)
- Stimulates gastric acid, pepsin, and intrinsic factor secretion (H2 receptors)

11

What effect does histamine have on the nervous system?

Stimulant of sensory nerve endings: Pain (dermis) and itching (epidermis) (H1)
H3 receptors function as autoreceptors in the CNS and histamine fn as a neurotransmitter

12

What is a physiological antagonist to histamine that has opposite effects on smooth muscle through different receptors?

Epinephrine

13

What are some general side effects from antihistamine H1 antagonist drugs?

Sedation and atropine like effects

14

What product in the urine can be used to measure serotonin levels?

5-hydroxyindolacetic acid (5-HIAA)

15

What amino acid is serotonin made from? What is the rate limiting enzyme

Tryptophan
Tryptophan hydroxylase

16

Describe the distribution of Serotonin in the body?

GI - tract 90%
platelets - 8%
CNS - 2% raphe nuclei of brain stem

17

What are the effects of serotonin on the GI tract?

Contraction of smooth muscle (increase tone and facilitate peristalisis)
Carcinoid syndrome

18

What are the effects of serotonin on the cardiovascular system?

1 powerful vasoconstrictor in smooth muscle; vasodilator in skeletal muscle.
2 Activation of chemoreceptor nerve endings to cause reflex bradycardia
3 platelet aggregation

19

What are the effects of serotonin on the PNS and CNS?

CNS- mood, food intake, sleep, pituitary secretions
PNS - Stimulate nociceptive sensory nerve endings

also have autoreceptor actions

20

In general what receptors do ergot alkaloids function on?

both classes have both agonist and antagonist actions at serotonin and alpha adrenergic and some dopamine receptor

21

What effects do ergot alkaloids have on the CNS, vascular smooth muscel, and uterine smooth muscle

CNS - powerful hallucinogens
Vascular Smooth Muscle - blood vessel constriction
Uterine smooth muscle - prolonged contractions at high dose