Autonomic NS Pharmacology Flashcards
What two types of nerves make up the peripheral NS?
Somatic Nerves
Autonomic Nerves
What is the function of somatic nerves?
Movement of skeletal muscles
What is the function of autonomic nerves?
Motor function of internal organs
- Motility of GI tract, bladder
- Dilation of pupils
What two systems make up the autonomic NS?
Sympathetic (Adrenergic)
Parasympathetic (Cholinergic)
What neurotransmitters and receptors are involved in the sympathetic NS?
Epinephrine 80% & NE 20% (adrenal medula)
Norepinephrine (nerves)
Ach (sweat glands - ONLY EXCEPTION)
Dopamine (renal, D1 receptors)
Adrenergic receptors
- Alpha 1, Alpha 2
- Beta 1, Beta 2, Beta 3 (not clinically significant)
What neurotransmitters and receptors are involved in the parasympathetic NS?
Acetylcholine
Muscarinic receptors
- M1, M2, M3
What is miosis and which NS is it involved in?
Constrict pupils
Parasympathetic autonomic NS
What is mydriasis and what NS is it involved in?
Dilate pupils
Sympathetic autonomic NS
What are 8 pharmacologically relevant functions of the PANS?
- Miosis (CN III)
- Lacrimation (CN VII)
- Salivation (CN IX)
- Decreased HR (CN X)
- Broncho-constriction
- Stimulates GI motility & secretion
- Contracts bladder & Relaxes sphincter
- Erection
What are 9 pharmacologically relevant functions of the SANS?
- Mydriasis
- Increased HR & Contractility
- Bronchodilation
- Arteriolo-constriction
- Inhibits GI motility & secretion
- Stimulates adrenals
- Stimulates glucose release
- Relaxes bladder & contracts sphincter
- Ejaculation
__________ is the neurotransmitter at the autonomic ganglia.
Acetylcholine
Where are a1 receptors found?
Blood vessels
Pupils dilators
Intestinal & bladder sphincters
Liver
What are the agonist actions of a1?
Vasoconstriction Mydriasis Increased intestinal & bladder tone Increased glycogenolysis Decreased renin
What are the antagonist actions of a1?
Relaxation of vascular smooth muscle
Vasodilation
Relaxation of the prostate capsule
Where are a2 receptors found?
Presynaptic sympathetic neurons
What are the agonist actions of a2?
Decreased sympathetic outflow Decreased insulin release Decreased lipolysis Decreased aqueous humor production Increased platelet aggregation
Where are B1 receptors found?
Heart
What are the agonist actions of B1?
Increased HR & contractility
Increases renin release
Increased lipolysis
What are the antagonist actions of B1?
Decreased HR & contractility
Where are B2 receptors found?
Lungs
Blood vessels
Liver
Pancreas
What are the 8 agonist actions of B2?
- Vasodilation
- Bronchodilation
- Increased lipolysis
- Increased insulin release
- Increased glycogenolysis
- Increased aqueous humor production
- Increased K+ cellular uptake
- Decreased uterine tone (tocolysis)
What are the antagonist actions of B2?
Bronchoconstriction
Decreased K+ cellular uptake
Decrease aqueous humor production
Sympathomimetic Drugs
Adrenergic Agonists
Drugs that MIMIC the activity of the SNS
Define Direct-Acting Agonists.
Exert their effect by DIRECTLY BINDING to alpha, beta, or dopaminergic receptors and mimicking the effects of endogenous catecholamines.
Define Indirect-Acting Agonists.
Enhance the effects of Epi & NE by inhibiting their reuptake or degradation.
Define Mixed-Action Agonists.
Work by directly binding to receptors & releasing NE from its stores.
What are non-selective adrenergic agonists?
Are mainly natural catecholamines (CA)
Only available as injections
Theoretically work on all adrenergic receptors
Epi
NE
Dopamine
What are selective adrenergic agonists?
Are mainly synthetic CAs and non-CAs.
Selectivity is not absolute, it is lost with high doses.
a1-selective: Oxymetazoline & phenylephrine
a2-selective: Clonidine
B1-selective: Dobutamine
B2-selective: SABA (albuterol) & LABA (formoterol)
B3-selective: Mirabegron
What are 2 examples of indirect-acting adrenergic agonists?
Cocaine
Amphetamines
What are 2 examples of mixed-action adrenergic agonists?
Ephedrine
Pseudoephedrine
Cathecholamines
- Oral usability
- Duration of action
- CNS penetration
Cathecholamines
- Oral usability: INEFFECTIVE
- Duration of action: SHORT
- CNS penetration: POOR
Non-Cathecholamines
- Oral usability
- Duration of action
- CNS penetration
Non-Cathecholamines
- Oral usability: EFFECTIVE
- Duration of action: LONG
- CNS penetration: GOOD
How does epinephrine interact with a1 receptors?
Can activate almost all adrenergic receptors hence, it is the treatment of choice for anaphylactic shock
a1 stimulation → vasoconstriction → ↑BP & ↓ edema
How does epinephrine interact with B1 receptors?
B1 stimulation → ↑HR & contractility → ↑CO (used for cardiac arrest caused by asystole)
How does epinephrine interact with B2 receptors?
B2 stimulation → Bronchodilation (sometimes used for emergency treatment of bronchospasms)
How does NE interact with adrenergic receptors?
At therapeutic doses, NE mainly stimulates
a1 receptors → vasoconstriction → ↑BP
Its use is more limited than epi, helps in cases of profound hypotension & shock
How does dopamine function in LOW DOSES?
In low doses, it stimulates
D1 receptors → renal vasodilation
How does dopamine function in MODERATE DOSES?
In moderate doses, it stimulates
B1 receptors → cardiac stimulation
How does dopamine function in HIGH DOSES?
In high doses, it simulates
a1 receptors → vasoconstriction
When treating shock, which is preferred: Dopamine or NE?
Dopamine is preferred to NE because of its effect on renal vasculature when used in low doses
What are 2 examples of a1-selective drugs?
Oxymetazoline: Used as eyedrops for red eye
Phenylephrine: Nasal decongestants, OTC old treatments; can ↑BP & precipitate angina
