Melatonin and Eicosanoids

Question 1

Which hormone’s major role is regulation of sleep and wakefulness?

Answer 1

melatonin

Question 2

Where is melatonin produced?

Answer 2

pineal gland

Question 3

Melatonin is synthesized from ____, with _____ as an intermediate.

Answer 3

tryptophan, serotonin

Question 4

Secretion of melatonin is regulated by what?

Answer 4

light

Question 5

Secretion of melatonin is stimulated by?

Answer 5

darkness

Question 6

Can blind people still have light-induced suppression of melatonin?

Answer 6

yes

Question 7

The circadian rhythm of melatonin secretion is controlled by?

Answer 7

endogenous pacemaker in the supra-chiasmatic nucleus

Question 8

True or false: Melatonin increased until 1-3 years old, and then declines with age.

Answer 8

True

Question 9

Melatonin regulates/affects what?

Answer 9

• sleep
• circadian rhythm
• mood
• sexual maturation and reproduction
• may have anti-inflammatory effects on immune system
• may have beneficial effects on cancer
• aging

Question 10

Melatonin activates what receptors?

Answer 10

MT1 and MT2

Question 11

How can melatonin be used in veterinary medicine?

Answer 11

• treat Alopecia X in dogs since it may decrease GnRH, which decreases LH/FSH effects on adrenal androgen precursors
• decreases anxiety and seizure activity
• minimal short term side effects include sedation and incoordination

Question 12

What are Eicosanoids?

Answer 12

group of signaling molecules synthesized by oxidation of 20-carbon essental fatty acids

Question 13

Omega-3 EFAs yield what?

Answer 13

eicosapentaenoic acid

Question 14

Omega-6 EFAs yield what?

Answer 14

arachidonic acid

Question 15

Prostaglandins A-I differ in what?

Answer 15

substituents on the cyclopentane ring

Question 16

What is the major function of eicosapentaenoic acid cascade?

Answer 16

to dampen inflammatory effects of arachidonic acid prostanoids

Question 17

What are the overall effects of arachidonic acid cascade?

Answer 17

• stimulate inflammatory responses
• modulate pain and fever
• reproductive functions
• inhibit gastric acid secretion
• blood pressure regulation
• platelet activation/inhibition

Question 18

The arachidonic acid cascade forms?

Answer 18

• prostanoids (prostaglandins, prostacyclins, thromboxanes)
• leukotrines
• lipoxins

Question 19

The eicosapentaenoic acid cascade forms?

Answer 19

mostly prostanoids

Question 20

Cats can’t convert linoleic acid to arachidonic acid, why?

Answer 20

due to low delta 6-desaturase enzyme

Question 21

What releases arachidonic acid from phospholipids in cell membrane?

Answer 21

phospholipase A2

Question 22

Arachidonic acid will be oxygenated by?

Answer 22

• cyclooxygenase (COX1 and COX2) to mke prostanoids
• lipooxygenase (5LOX) to make leukotrines

Question 23

What are the dietary precursors of arachidonic acid?

Answer 23

• linoleic acid
• gamma linoleic acid

Question 24

PGE2 has what actions?

Answer 24

• smooth muscle contraction
• bronchoconstriction
• pain
• heat
• fever

Question 25

What NSAIDs will inhibit COX1 and COX2?

Answer 25

• aspirin
• carprofen (rimadyl)
• flunixin (banamine)
• phenylbutazone
• ibuprofen
• naproxen

Question 26

What NSAIDs will inhibit only COX2?

Answer 26

• firocoxib (prevacox)
• deracoxib (deramaxx)
• meloxicam (metacam)
• piroxicam
• celecoxib (Celebrex)

Question 27

What is the action of NSAIDs?

Answer 27

inhibit prostanoid formation to decrease inflammation, redness, swelling, pain, heat

Question 28

PGI2 has what actions?

Answer 28

• vasodilation
• inhibits platelet aggregation

Question 29

TXA2 has what actions?

Answer 29

• vasoconstriction
• stimulates platelet aggregation

Question 30

What are characteristics of prostanoids derived from arachidonic acid?

Answer 30

• local hormones with autocrine or paracrine function
• short half life
• mediated by specific receptors
• mediate inflammation (except for lipoxins)