Histamine, Serotonin, and Their Antagonists

Question 1

Histamine

Answer 1

amine formed by decarboxylation of the amino acid histidine. stored throughout the body in mas cells and basophils

Question 2

where is largest histimine concentration found?

Answer 2

skin, lungs, GI and nasal mucosa, and blood. rich at sites of potential tissue injury

Question 3

mast cell histamine release

Answer 3

exocytotic process that requires energy and intracellular Ca. stimuli are antigens and anaphylatoxins, certain basic drugs, and chemical or mechanical injury

Question 4

cardiovascular action of histamine

Answer 4

immediate fall in blood pressure due to peripheral vasodilation (H1 and H2). increase in vascular permeability causing edema and plasma loss (H1), and direct cardiac effects of increased contractility, heart rate (H2)

Question 5

bronchiolar smooth muscle action of histamine

Answer 5

bronchoconstriction (H1). hyperreaction in asthmatics

Question 6

gastrointestinal tract action of histamine

Answer 6

contraction of intestinal smooth muscle, diarrhea (H1). stimulates gastric acid, pepsin, and intrinsic factor secretion (H2 receptors)

Question 7

nervous system action of histamine

Answer 7

stumulant of sensory nerve endings: Pain and itching (H1). three subtypes have been found in the CNS. H3 receptors are presynaptic autoreceptors on histaminergic neurons that mediate feedback inhibition of the synthesis and release of histamine

Question 8

H1 antagonist general properties

Answer 8

rapid absorption through oral administration, widely distributed through body, rapidly metabolized, many non-prescription time release preps in combination with analgesics and decongestants, many actions not ascribable to H1 blockade

Question 9

clinical uses of H1 antagonists

Answer 9

allergic reactions, motion sickness, nausea and vomiting of pregnancy, sleep aids

Question 10

H2 receptor antagonists mechanism

Answer 10

compete at H2 receptors on basolateral membrane of parietal cells. blocks gastric acid secretion in response to all stimuli, but reduction in nocturnal acid secretion is much more pronounced than meal-stimulated acid secretion.

Question 11

clinical uses for H2 receptor antagonists

Answer 11

dyspepsia, duodenal and gastric ulcers, hypersecretory conditions

Question 12

storage and release of serotonin (5-HT)

Answer 12

released by mechanical and neuronal stimuli, and reserpine

Question 13

serotonin receptors

Answer 13

at lease seven types of serotonin receptors (5-HT 1-7). most are G protein coupled, but 3 is a ligand gated ion channel and others may be too

Question 14

pharmacological actions of 5-HT on GI tract

Answer 14

GI tract: contraction of smooth muscle, carcinoid syndrome (tumors that release large amounts of 5-HT)

Question 15

pharm actions of 5-HT on cardiovasc

Answer 15

cardiovasc system: vasoconstrictor in smooth muscle, vasodilator in heart and skeletal muscle. activates chemoreceptor nerve endings to cause reflex bradycardia. platelet aggretgation

Question 16

pharm actions of 5-HT on nervous system

Answer 16

periph: stimulates nociceptive sensory nerve endings (itch and ain). activates chemosensitive endings located in coronary vascular bed.

Central: receptors in brain involved in mood, food, sleep, regulation of pituitary secretions. Presynaptic activation of 5-Ht 1A or 1D receptors inhibits raphe cell firing or serotonin release

Question 17

ergot alkaloids

Answer 17

nitrogen containing compounds produced by a fungus that infects grain. produces dementia, vasospasm, abortion.

Question 18

pharm of ergot alkaloids

Answer 18

powerful hallucinogens, action on dopamine receptor suppresses prl secretion from pituitary cells. bascular smooth muscle blood vessel constriction. uterine smooth muscle contracture at high doses