The sympathetic nervous system€¦ · Sympatholytics. Sympathomimetics. o Cardiovascular system o...
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The sympathetic nervous system
Transcript of The sympathetic nervous system€¦ · Sympatholytics. Sympathomimetics. o Cardiovascular system o...
The sympathetic nervous system
α-receptors
α1-receptor smooth muscle contraction
vasoconstriction
mydriasis
α-receptors
α2-receptor
inhibition of neurotransmitter release (NA!)
Neurotransmission
NA
NA
NAα2
α2-agonists
NA
NA
NA
α2
XYLAZINE
α-receptors
α2-receptor
GI-relaxation
inhibition of insulin release
β-receptors
β1-receptor
cardiac effects (positive inotropic, chronotropic)
β2-receptor
vasodilatation
bronchodilatation
uterus relaxation
(β3-receptor
lipolysis in fat tissue)
Synthesis of catecholamines
Drugs acting on the
sympathetic nervous system
1. Sympathomimetics
2. Sympatholytics
Sympathomimetics
o Cardiovascular system o positive chronotropico positive inotropic o vasoconstriction (α1-agonists)o vasodilatation (β2-agonists)
Pharmacological effects
β1-agonisták
o Gastrointestinal systemo smooth muscle relaxationo GI atony
o Respiratory systemo bronchodilatation, decreased bronchial secretion
o Urinary bladdero increased sphincter-constriction (α1-receptor)
o Eyeo mydriasis (iris radial muscles) o increase in aqueous humor production
Pharmacological effects
Nonspecific sympathomimetics
Active substances
Adrenaline (epinephrine)
noncspecific (mainly β1 and β2 receptors)
α-receptors in higher dosage
cardiac effect
arrhytmogenic!
blood pressure?
indications:
- cardiac stop
- severe bronchoconstriction
- anaphylaxia
- local vasoconstriction (haemorrhages)
- increase in duration of local anaesthetics
Ca, Fe: 0.02 mg/kg intratracheal, IV.
Active substances
Noradrenaline (norepinephrine)
nonspecific (mainly β1 and α1 receptors)
cardiac effect
blood pressure is significantly increased!
indications (rare):
- hypotension
Active substances
Dopamine
low dose D1-receptors (kidney!) 2-5 µg/kg
medium dose β1-receptors (heart!) 5-10 µg/kg
high dose α1-receptors (pressor) 10-20 µg/kg
indications
Specific sympathomimetics
β-adrenoceptor agonists
Dobutamine
mainly β1 receptors
cardiac effect
indications:
- cardiogenic shock (IV. infusion)
Isoproterenol
only β receptors (β1 and β2 )
heart+bronchi+muscle vessels
indications?
β2 agonists (clenbuterole, salbutamole, terbutaline, salmeterole, isoxsuprine etc.)
mainly β2 receptors
bronchodilatation
uterus relaxation
higher dosage β1 receptorscardiac effect
clenbuterole 4:1
salbutamole 650:1
salmeterole 50000:1
side effects!
β-adrenoceptor agonists
β2 agonists
indications: horse RAO
feline asthma
bronchitis, bronchopneumonia
tracheal hypoplasia
tracheal collapse
earlier…
dosage: clenbuterole horse 1-3 µg/kg PO.
salbutamole 100-200 µ/cat
360-720 µg/horse
β-adrenoceptor agonists
Phenylephrine
mainly α1-receptors vasoconstriction
used rarely
local and systemic usage
α-adrenoceptor agonists
Allergy, cold
Hypotension, shock (?)?)
Xylometazoline, oxymetazoline, naphazoline, tetryzoline
mainly α1-receptors vasoconstriction
local usage
α-adrenoceptor agonists
Phenylpropanolamine
mainly α1-receptors urinary bladder sphincter constriction!
per os usage (empty stomach)
side effects
Ephedrine
nonspecific, direct and indirect effects
tachyphylaxis
CNS
allergy, incontinence (p.o.)
Amphetamine
α-adrenoceptor agonists
α2-agonists
SEDATO-HYPNOTICS (see later)
xylazine, detomidine, medetomidine, romifidine
α-adrenoceptor agonists
Sympatholytics
Nonspecific α-antagonists
Phenoxybenzamine (urethra sphincter relaxation)
long duration of action
Phentolamine
Tolazoline
α1-antagonists
prazosine, doxasozine (urethra sphincter relaxation)
α2-antagonists
atipamezole, yohimbine
α-adrenoceptor antagonists
Nonspecific β-antagonistsPropranololeTimolole
SIDE EFFECTS
Specific β1-antagonistsMetoprololeAtenolole
β-adrenoceptor antagonists
