Test 2 Sympathetic Nervous System Flashcards by Preeti Gulve

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

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The primary neurotransmitter at the terminal synapse in the

sympathetic nervous system

Norepinephrine

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**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)

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The receptors found in the sympathetic nervous system are adrenergic receptors

When stimulated, which one causes

Vasodilation

Mydriasis

Alpha-1

Agonist: Phenylephrine

Antagonist: Prazosin

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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

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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

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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

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The receptors found in the sympathetic nervous system are adrenergic receptors.

When stimulated, which one causes:

Lipolysis

Beta-3

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Endogenous substances that serve as hormones and neurotransmitters

Catecholamines

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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*

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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

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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

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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

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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)

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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

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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

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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

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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

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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

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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

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Terbutaline

Beta-2 agonist

Acts as a peripheral vasodilator and causes uterine relaxation

Sometimes used as a tocolytic in cattle

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Isoxsuprine

This group of drugs is typically used for their CNS effects

for “Behavioral Therapy”

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Indirect Acting Sympathomimetics

Clomipramine (tricyclic antidepressants)*
Fluoxetine (SSRIs)*
Selegeline (MAOIs)*

________ blocks NE reuptake

while

________ increases NE release

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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>}

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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 ## Footnote *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!!!

Test 2 Sympathetic Nervous System Flashcards

(41 cards)