Acetylcholine - PNS - SNS - receptors

major NT of PNS - found in all PREganglionic fibers - found in all POSTganglionic PARAsympathetic fibers nicotinic and muscarinic

DSA- Pharmacology Autonomics Flashcards by Priscilla Vu

Neurotransmitters of ANS (5)

Acetylcholine
Norephinephrine
Epinephrine
Dopamine
Co-transmitters

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Acetylcholine

PNS
SNS
receptors

major NT of PNS

found in all PREganglionic fibers
found in all POSTganglionic PARAsympathetic fibers

nicotinic and muscarinic

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Norepinephrine

- receptors

major NT of SNS

found in majority of POSTganglionic SYMpathetic fibers

catecholamine

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Epinephrine

synthesis
receptor

only occurs in adrenal medulla

depolarization of preganglionic sympathetic neuron (cholinergic)

nicotinic
catecholamine

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Dopamine

- receptor

precursor to NE and Epi

synthesized in cytoplasm of neurons

has actions in CNS and renal vascular smooth muscle

catecholamine

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Co-transmitters (4)

ATP

Neuropeptide Y

Substance P

Vasoactive intestinal Peptide (VIP)

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Cholinergic Neurotransmission components steps

Synthesis of ACh
Storage of ACh
Release of AcH
Binding to cholinergic receptors
Termination of acetylcholine signaling

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Synthesis of ACh

Choline transporter transport choline into neuron

Choline + AcoA (choline acetyletransferae (ChAT))-> ACh

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Storage of ACh

ATPase-dependent ACH vesicular transporter puts ACh into vesicles

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Release of Ach

AP-> depolarization causes Ca2+ voltage gated channels to open -> Ca2+ enter neuron -> vesicle go to cell membrane -> SNARE protein complex fuse vesicle into membrane ( VAMPS, SNAPS)

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Binding of ACh to cholinergic neurons

- effects

Ach diffused into synaptic cleft adn bind to nAChR

activation of release of Epi, NE
smooth muscle contraction
glandular secretion
decrease heart rate

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Termination of acetylcholine signaling

Acetylcholinesterase (AChE) cleaves ACh into acetate and choline

ACh-> choline + acetate

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Botulin Toxin

prevent ACh vesicle from being released into synaptic cleft

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Vesamicol

prevent storage of AcH in neuron

- ATPase-dependent ACH vesicular transporter

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Hemicholinium

prevent choline from reuptake into neuron

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location
structural feature
mechanism

ACh receptor

Location: CNS, ganglia

structure: Gq

Mechanism: activation PLC, DAG, IP3

location
structural feature
mechanism

ACh receptor

Location: heart, nerve , smooth muscle

structure: Gi

Mechanism: inhibit AC, activate K channel

location
structural feature
mechanism

ACh receptor

Location: Glands, smooth muscle, endothelium

structure: Gq

Mechanism: activation PLC, DAG, IP3

location
structural feature
mechanism

ACh receptor

Location: CNS

structure: Gi

Mechanism: inhibit AC/ CAMP,
activate K channel

location
structural feature
mechanism

ACh receptor

Location: CNS

structure: Gq

Mechanism: activate PLC, IP3, DAG

location
structural feature
mechanism

ACh receptor

Location: skeletal muscle, NMJ

structure: ligand-gated ion channel

Mechanism: Na/K depolarizing ion channels

location
structural feature
mechanism

ACh receptor

Location: Postganglionic cell body, CNS, dendrite

structure: ligand-gated ion channel

Mechanism: Na/K depolarizing ion channels

adrenergic transmission

catecholamines

Synthesis of catecholamines

Tyrosine is transported into nerve terminal

Adrenal medulla

storage of catecholamines

Vesicular monamine transporter (VMAT2) in cytoplasm Tyrosine-> DOPA-> DA

Reserpine

drug that inhibits VMAT2 | -leads to depletion of catecholamines from sympathetic nerve

Release of catecholamines

Ca2+ influx in adrenal medulla-> release ACh and bind with nAChR on chromaffin cells

Binding of catecholamines to adrenergic receptors

bind to alpha or beta receptor - stimulatory or inhibitory - glycogenesis, gluconeogenesis, relaxation, etc

Termination of catecholamin signaling ( 2)

1. NET (norephinephrine transporter) and DAT (dopamine transporter) reuptake and store in vesicles via VMAT2 2. Diffusion and uptake at extraneuronal sites via transporter ENT, OCT1, OCT2 by two enzymes - monoamine oxidase (MAO): - Catechol-o-methyltransferase (COMT: in liver

Cocaine

inhibit NE reuptake into neuron

Alpha 1 receptors | -effects

contraction of SM vasoconstriction glandular SM secretion pupil dilation uterine contraction

B2 receptors | -effects

stimulate relaxation of all SM tracheal and bronchial SM relaxation uterine SM relaxation intestinal SM relaxation vasodilation

Muscarinic receptor | - effect

contraction of all SM contraction of iris sphincter muscle contraction of bladder, interstinal SM, DECREASE HR ACh/ NO stimulation

EDRF (Nitric Oxide)

short lived vasodilator - in response to an AP, parasympathetic neurons release ACh _> activate mAChR -> produce NO-> go to blood vessel to cause relaxation

Parasympathetic (cholinergic) effects

1. salivation 2. Lacrimination 3. Pupil constriction 4. decrease HR 5. Uriniation 6. Increased secretions 7. Increase GI motility

Sympathetic (adrenergic) effects

1. pupil dilation 2. increase HR 3. Urinary retention 4. decreased secretion 5. decreased GI motility

Baroreceptor Reflex

1. increase BP (Phenylephrine) - Increase baroreceptor - increase PNS - decrease SNS 2. decrease BP - decrease baroreceptors - decrease PNS - increase SNS