Biogenic Amines- Histamine and Serotonin

Question 1

How is histamine is synthesized?

Answer 1

histidine with histidine carboxylase

Question 2

What are the functions of histamine?

Answer 2

1. growth and regeneration
2. neurotransmission
3. regulator of microcirculation
4. defense mechanisms (stored in mast cells in skin and lungs)

Question 3

When is histamine released in response to tissue injury?

Answer 3

Histamine is released following tissue injury
inflammatory response
mechanical injury
thermal
radiant
chemical- insect venoms, drugs

Question 4

What is the mechanism of histamine?

Answer 4

binding to specific histamine receptors

Question 5

What are the vascular effects of histamine?

Answer 5

1. constricts larger vessels, dilate smaller vessels, can cause pooling of blood at injury site
2. causes endothelial cell leakage and edema- “wheal”
3. “triple response” to injected histamine

Question 6

What are the neuronal effects of histamine?

Answer 6

1. stimulate sensory neurons- itch, pain

2. CNS- increase alertness

Question 7

What are the smooth muscle effects of histamine?

Answer 7

1. constrict bronchioles- bronchoconstriction

2. constricts intestinal muscle- diarrhea

Question 8

What is the exocrine secretion effect of histamine?

Answer 8

1. stimulates bronchial, salivary, digestive secretions

Question 9

What is the mechanism of antihistamine?

Answer 9

block the histamine receptor (H1 + H2)

Question 10

H1 blockers physiologic targets?

Answer 10

1. central nervous system
2. drying of mucous membranes
3. peripheral nervous system
4. smooth muscle dilator

Question 11

H1 blocker central nervous system effects?

Answer 11

1. sedative (some can be excitatory in children and elderly)
2. antinausea
3. antiemetic

Question 12

H1 blocker drying of mucous membranes effects?

Answer 12

due to blockage of H1 receptors- possibly also animuscarinic effects

Question 13

H1 blocker peripheral nervous system effects?

Answer 13

local anesthetic

Question 14

H1 smooth muscle dilator effects?

Answer 14

1. bronchial smooth muscle dilator

2. can inhibit secretion of interleukins and other inflammation mediators

Question 15

H2 blockers- physiologic target?

Answer 15

gastric secretion

Question 16

H2 gastric secretion effects?

Answer 16

histamine is required to stimulate H+ secretion from parietal cells- blockade of H2 receptors causes decreased H+ secretion

Question 17

Therapeutic indication for first generation H1 antihistamines?

Answer 17

treatment of allergic responses

Question 18

What kind of treatment of allergic responses?

Answer 18

dermatoses
    urticaria (itching)
    insect stings + bites
allergic rhinitis and allergic conjunctivitis
    decrease congestion, sneezing

Question 19

What are antihistamines NOT of value treating?

Answer 19

asthma or “common cold”

Question 20

What else are antihistamines good for?

Answer 20

antiemetic, antinauseant (motion sickness)

sedatives (Nytol)- contain diphenhydramine (Benedryl)

Question 21

First generation H1 blockers mechanism of action?

Answer 21

can act on both peripheral and central histamine (H1) receptors