Test 2 Sympathetic Nervous System Flashcards
The preganglionic neurons of the sympathetic nervous system are _______
while the postganglionic neurons are _________
In the sympathetic nervous system
Preganglionic are SHORT
Postganglionic are LONG
The primary neurotransmitter at the terminal synapse in the
sympathetic nervous system
is
Norepinephrine
**NE **is stored in __________
Once in the synaptic cleft, NE interacts with receptors and initiates a _______ ______ response
The NE then dissociates and is taken back up by the ________ neuron
Some of the NE is broken down by ________
**NE **is stored in lysosomes
Once in the synaptic cleft, NE interacts with receptors and initiates a second messenger response
The NE then dissociates and is taken back up by the presynaptic neuron
Some of the NE is broken down by Monoamine Oxidase (MAO)
The receptors found in the sympathetic nervous system are adrenergic receptors
When stimulated, which one causes
Vasodilation
Mydriasis
Alpha-1
Agonist: Phenylephrine
Antagonist: Prazosin
The receptors found in the sympathetic nervous system are adrenergic receptors.
When stimulated, which one causes:
Sedation
Analgesia
Alpha-2
Agonists: Xylazine and Detomidine
Antagonists: Yohimbine and Atipamezole
The receptors found in the sympathetic nervous system are adrenergic receptors.
When stimulated, which one causes:
** + Inotropy**
+Chronotropy
Beta-1
Agonists: Dobutamine, Dopamine
Antagonists: Atenolol, Metoprolol
The receptors found in the sympathetic nervous system are adrenergic receptors.
When stimulated, which one causes:
Bronchodilation
Uterine relaxation
Beta-2
Agonists: Salbutamol, Clenbuterol
Antagonists: Propanolol
The receptors found in the sympathetic nervous system are adrenergic receptors.
When stimulated, which one causes:
Lipolysis
Beta-3
Endogenous substances that serve as hormones and neurotransmitters
Catecholamines
Activates all adrenergic receptors
A catecholamine
Solution for injection
Can be given IV, IM, SC, but NOT PO
Will not cross the BBB
Used in Tx of cardiac arrest, anaphylaxis
Epinephine
- Do not use in glaucoma, shock, or tachycardias*
- Cannot use with some anesthetics*
A catecholamine
Agonist at Alpha receptors and Beta-1 receptors
Injectable, IV
More potent vasoconstriction than Epinephrine
Can cause a baroreceptor response (reflex vagal bradycardia)
Norepinephrine
Avoid extravasation, potential for tissue damage
A catecholamine
Precursor to NE
Acts directly and indirectly on Alpha and Beta-1 receptors, and Dopamine receptors
Injection, IV
Very short half-life
Different doses act on different parts of the body
Dopamine
Avoid extravasation, potential tissue damage
Synthetic catecholamine
Nonselective Beta-1 and Beta-2 agonist
Injectable
Tx of **bradyarrhythmias **and acute bronchoconstriction
Increases myocardial oxygen consumption
Decreases peripheral vascular resistance
Isoproterenol
Can cause tachycardia
Synthetic catecholamine
Beta-1 agonist with weak Beta-2 and Alpha-1 activity (cancel out)
Injectable, very short half life
Used as a positive inotrope
May increase cardiac blood flow and oxygen demand
Dobutamine
Caution with increased myocardial oxygen demand (after cardiac infarction)
Selective alpha-1 agonist (beta-1 agonist at high doses)
Oral, Injectable, Intranasal, Ophthalmic
Tx sytemically hypotension/shock
Tx locally vasoconstriction
Tx locally on the eye mydriatic
Can be used to Dx Horner’s Syndrome (sympathetic lesion)
Phenylephrine
Caution when using systemically. Systemic effects in small patients using topical and in large patients with repeated doses
Selective alpha-2 agonist, ophthalmic med
Reduces aqueous humor formation
With chronic use, increases uveoscleral outflow
May have a protective effect on the retina and optic nerve
Mydriasis may occur, though not potent
Used as an adjunct to treat glaucoma
FEW adverse effects in animals
Brimonidine
In humans, can increase eyelash growth
Agonists at Beta-1,2, and especially Beta-3 receptors
Referred to as “partitioning agents” to reduce fat deposition and *increase muscle *
in late finishing meat animals
Ractopamine and Zilpaterol
Selective Beta-2 agonist
Oral, Aerosol, or Solution for Nebulization
Poor oral absorption, very high pKa, very good mucosal absorption via inhalation
Used in horses and cats to treat asthma
Albuterol/ Salbutamol
Selective Beta-2 agonist
Available as a vet approved oral syrup for use in equines
NOT permitted in food animals
Sometimes used to Tx equine dystocia
Clenbuterol
Selective Beta-2 agonist
Minimal beta-2 effects, and no alpha effects
Tx for bronchoconstriction due to asthma or COPD
Used more in small animals
Bioavailability is TERRIBLE in equines
Terbutaline
Beta-2 agonist
Acts as a peripheral vasodilator and causes uterine relaxation
Sometimes used as a tocolytic in cattle
Isoxsuprine
This group of drugs is typically used for their CNS effects
for “Behavioral Therapy”
Indirect Acting Sympathomimetics
- Clomipramine (tricyclic antidepressants)*
- Fluoxetine (SSRIs)*
- Selegeline (MAOIs)*
________ blocks NE reuptake
while
________ increases NE release
-
Cocaine blocks NE reuptake
while
Amphetamine increases NE release
This mixed acting sympathomimetic
primarily acts indirectly through increased release of NE in the
bladder neck/urethra. It also has direct alpha-1 agonist activity
Oral, Tablets, Extended Release, Oral Solution
Used mostly in small animals (canines) to treat urinary incontinence due to
urethral sphincter hypotonus
<em>Estrogens</em><em>may increase expression of alpha-1 receptors in the urinary sphincter, so you can see synergism</em>
Phenylpropanolomine
Side effects include: Restlessness, urinary retention, tachycardia, hypertension, anorexia
This mixed acting sympathomimetic causes indirect release of NE (primary action)
Has some direct alpha-1 and beta activation
It can cause vasoconstriction, cardiac stimulation, bronchodilation, urinary sphincter contraction, and mydriasis
It is not used pharmacologically at this time, but can be a component in some
herbal therapies (Ma Huang)
Ephedrine/ Pseudoephedrine
This direct acting sympatholytic drug
is a non-specific alpha antagonist that binds irreversibly to the receptor
Oral, capsule forms
Takes a few days to see a clinical response
Most commonly used in **small animals **to treat **urinary retention **by relaxing internal smooth muscle sphincter
and can be combined with benzodiazepines to relax the skeletal muscles
Used to manage pheochromocytoma perioperatively and manage hypertension
Phenoxybenzamine
- Can cause excessive alpha-blockade leading to hypotension and tachycardia*
- May cause miosis, changes in intraocular eye pressure, or GI signs*
This direct acing sympatholytic is an alpha-1 antagonist
Oral, and capsular form
Commonly used to treat urinary retention by relaxing smooth muscle sphincter
Compared to phenoxybenzamine, this drug may have greater effect, faster onset,
but potentially greater cardiovascular effects
Prazosin
This group of drugs are beta-adrenergic antagonists
and will generally
decrease cardiac rate and contractility.
They are used to treat tachycardias
Beta-Blockers
- Propanolol*
- Timolol*
- Metoprolol*
- Atenolol*
- Esmolol*
- Sotalol*
STAMPE
Out of all the beta-blockers (beta-adrenergic antagonists)
Which ones are non-selective?
Propanolol
Timolol
Sotalol
This drug has been used in the treatment of methylxanthine (chocolate) toxicity
and is longer lasting than other beta-blockers
Metoprolol
What 2 drugs have been used to treat methylxanthine (chocolate) toxicity?
Propanolol
and
Metoprolol
Which beta-blocker is used ophthalmically in the treatment of
glaucoma, and as a preventitive in the contralateral eye?
Timolol
Because beta-blockers can cause an increase in airway resistance and bronchospasm, which beta-blocker would you use preferentially in the treatment of an animal with asthma?
Atenolol
Has beta-1 selectivity, so less effect on beta-2 receptors in the lungs
Which beta-blocker is membrane stabilizing?
Propanolol
This beta-blocker has very short duration of action
and lacks any membrane-stabilizing effects. It is used to test patients for
sensitivity to beta-blocker therapy
Esmolol
This beta-blocker is a Class III Antiarrythmic and less potent than propanolol.
It acts like an anti-arrhythmic by prolonging the duration of cardiac action potentials and refractory period
Unlike any other beta-blocker, it is used to manage ventricular tachyarrhythmias
Sotalol!
This is the only indirect acting sympatholytic
Blocks monoamine transporters thus reducing NE uptake into vesicles
This leads to reduced storage of NE and mediator depletion
Used as a calming agent for equines for long-term stall rest
Reserpine
________ is the main inhibitory neurotransmitter in the CNS
GABA
THIS IS VERY IMPORTANT! KNOW THIS!
What are the 6 cotransmitters which are responsible for fine tuning the effects
of autonomic activity on tissues
ATP
VIP
GnRH
GABA
Serotonin
Dopamine
What is NANC transmission?
Non-Adrenergic Non-Cholinergic transmission
Occurs and NO acetylcholine or epinephrine is needed!
The most important of these is NO (Nitric Oxide)
potent smooth muscle relaxant that causes vasodilation
This is the most important agent of NANC transmission
and is a potent smooth muscle relaxant that causes vasodilation
NITRIC OXIDE!!!
