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Acetylcholine Functional Properties
- Used by motor neuronsin spinal cord - NMJ for voluntary movement : excitatory effect
- Used by ANS
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Acetylcholine Biosynthesis
- Choline + Acetyl‐CoA -->ACh + Coenzyme A
- Enzyme: Choline acetyltransferase (ChAT)
- Limiting step: free choline concentration
- Release from vesicles viadepol --> Ca dependent exocytosis
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Acetylcholine Degredation
At synaptic cleftby AChE
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Acetylcholine Receptors
- Nicotinic: ligand-gated ionchannels in NMJ, autonomic ganglia & some CNS neurons
- agonist = nicotine; antagonist =curare; targeted in MG
- Muscarinic: localized in smooth muscle, heart, glands, brain
- agonist = muscarin; antagonist =atropine; activation is coupled to G-proteins
- Neuronal-type R: autonomic ganglia
- antagonist =hexamethonium (ganglion block)
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Acetylcholine Notes
- ACh release inhibited by botulinumtoxin & stimulated by black widow spider venom
- Lambert-Eaton affects Ca channels & prevents ACh release
- Physostigmine is a drug that inhibits AChE to keep ACh in cleft; treat MG
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Dopamine (catecholamine) Functional Properities
Located in substantianigra, VTA, & hypothalamus
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Dopamine (catecholamine) Biosynthesis
- L-Tyrosine --> (via TH, BH4) L-DOPA --> (via AAAD, VitB6) Dopamine
- Tyrosine hydroxylase (TH) is rate limiting enzy
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Dopamine (catecholamine) Degredation
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Dopamine (catecholamine) Receptors
- G-protein coupled
- D1 & D5 activate cAMP(excitatory)
- D2 & D3, D4 inactivate cAMP(inhibitory)
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Dopamine (catecholamine) Notes
- Used in Parkinson’s & Schizophrenia Tx
- Drug of abuse
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Norepinephrine (catecholamine) Functional Properties
Located in locus cereleus & brainstem
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Norepinephrine (catecholamine) Biosynthesis
- Dopamine --> NE
- Enzyme: DBH
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Norepinephrine (catecholamine) Degredation
MAO-A
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Norepinephrine (catecholamine) Receptors
GPCR
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Norepinephrine (catecholamine) Notes
Amphetamine blocks reuptake of dopamine & NE
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Epinephrine/Adrenaline (catecholamine) Functional Properities
Located in locus cereleus & brainstem
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Epinephrine/Adrenaline (catecholamine) Biosynthesis
Dopamine --> (via DBH) NE --> (via SAM) Epi
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Epinephrine/Adrenaline (catecholamine) Degredation
MAO-A
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Epinephrine/Adrenaline (catecholamine) Receptors
GPCR
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Serotonin/ 5HT Functional Properties
Located in raphe nuclei
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Serotonin/ 5HT Biosynthesis
Tryptophan --> (via tryptophan hydroxylase & BH4) 5-hydroxytryptophan --> (via AAAD) Serotonin (5HT)
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Serotonin/ 5HT Degredation
MAO-A
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Serotonin/ 5HT Receptors
- Cation permeable
- agonist = sumatriptan
- antagonist = ondansetron
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Serotonin/ 5HT Notes
- Mood control, sleep, pain, temp.
- Precursor for melatonin
- Implicated in depression, anxiety, migraines
- Activation induces vomiting
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Histamine Functional Properities
- Diamine NT w/ neurons located in tuberomamillary nucleus of hypothalamus
- projects diffusely
- arousal
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Histamine Biosynthesis
L-Histadine --> (via HDC) Histamine
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Histamine Degradation
Histamine methyltransferase (HMT)
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Histamine Receptors
- H3 receptors are agonist for treating eating disorders & pain
- H1 receptor antagonists can treat allergies, cross BBB --> cause drowsiness
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Histamine Notes
Arousal, pain threshold, gut secretion, allergic rxn
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ATP, Adenosine Functional Properities
- Purinergic NT in the brain
- ATP is converted to adenosine
- Adenosine produces vasodilation
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ATP, Adenosine Receptors
- G-protein coupled receptors
- A1 are inhibitory in CNS; antagonized by caffiene
- A2A antagonizes the effect of dopamine D2 receptors
- A2A & A2B --> vasodilation
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ATP, Adenosine Notes
Lesh-Nyhan syndrome is caused by mutations in purine salvage pathway HGPRT
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