Eicosanoids and Melatonin
How does circadian rhythm relate to melatonin?
-it is controlled by endogenous pacemaker in suprachiosmatic nucle -environmental lighting alters time of circadian rhythem of melatonin secretion -melatonin secretion starts after darkness and peaks at 2-4 am then decreases
What biological functions can be affected by melatonin?
-sleep (affects speed of falling asleep and quality of sleep) -cardiac rhythm -mood sexual maturation and reproduction (changes in hours of darkness/season linked to repro activity -may affect puberty, sex steroid production and ovarian function -cancer -immune response -aging
What is melatonin's veterinary imporance?
-use in dogs with Alopecia X -decreases anxiety and seizure activity -sedation in-coordination in short term side effects
Prostanoids derived from AA have how many double bonds?
2
Prostanoids derived from EPA have how many double bonds?
3
Leukotrienes derived from AA have how many double bonds?
4
Leukotrienes derived from EPAs have how many double bonds?
5
A subscript after the name of an eicosanoids denotes what?
The number of double bonds it has
Some functions of Prostanoids are what?
autocrine, paracrine, mediated by specific receptors, mediate inflammation and other physiological actions
What stimulates melatonin production and how?
darkness -retinal photoreceptors release NE activating receptors in the pineal gland which stimulates conversion of serotonin to melatonin
Eicosanoids
group of signaling molecules made by the oxidation of 20 carbon EFAs
Paracrine
hormone acts on a nearby cell
Aracidonic Acid is involved in what cellular functions?
inflammation, immunity, CNS
Omega 3 EFAs
less inflammatory
What inhibits melatonin and how?
light -retinal photoreceptor cells are hyperpolarized which inhibits NE release
Autocrine
local hormones that act on the same cell that secretes them
How does melatonin affect tumor growth?
melatonin inhibits tumorigenesisa caused by carcinogens
Eicosapentaenoic Acid (EPA)
omega 3 FA with 5 double bonds
Aracidonic Acid (AA)
omega 6 FA with 4 double bonds
Omega 6 EFAs
pro inflammatory
Anatomical source of melatonin
produced by the pineal gland in center of brain behind 3rd ventricle
What subclasses fall within Postanoids?
prostaglandins, prostacyclins, and thromboxanes
Prostanoids
released and oxygenated by "cyclo-oxygenase" -subclasses are prostaglandins, prostacyclins, and thromboxanes
Leukotrienes
released and oxygenated by "lipo-oxygenase"
PGE3 function
smooth muscle contraction, bronchoconstriction, pain, heat, and fever
Darkness has what effect on melatonin?
stimulates it
PGF Alpha function
uterine contraction
TXA2 function
vasoconstriction, stimulates platelet aggregation
PGI2 function
vasodilation, inhibits platelet aggregation
