Upload
domina-petric
View
47
Download
0
Embed Size (px)
Citation preview
Effects of
sympathomimetic
drugs on the
cardiovascular
system
Domina Petric, MD
2
Type of
adrenergic
receptor
Tissue Effects on the tissue
α1 Smooth musculature of
innervated blood vessels
Contraction
Dilator pupillae muscle Contraction
(mydriasis)
Smooth musculature of hair
pilomotors
Contraction
Heart Increased strength of
contraction
α2 Postsynaptic in the brain Multiple effects
Thrombocytes Agregation
Adrenergic and cholinergic
presynaptic endings
Inhibition of
neurotransmitters
release
Fat cells Lipolysis inhibition
3
Type of
adrenergic
receptor
Tissue Effects on the tissue
β1 Heart, juxtaglomerular cells Increased strength
and speed of
contraction,
increased renin
release
β2 Smooth musculature of bronchi,
uterus and blood vessels
Relaxation
Sceletal muscles Increased potassium
uptake
Liver Activation of
glycogenolysis
β3 Fat cells Activation of lipolysis
“
4
Type of
adrenergic
receptor
Tissue Effects on the tissue
D1 Smooth muscles Dilatation of blood
vessels
D2 Nerve endings Modulation of
transmitters release
Effects of α1 receptors activation
➝ These receptors are widely distributed in thevasculature.
➝ Their activation causes arterial and venouscontraction.
➝ Clean α1-receptor agonists increase peripheralarterial resistance and decrease capacity of veins.
➝ Increase of blood pressure causes reflexbradicardia.
➝ Reflex bradicardia is due to activation ofbaroreceptors.
➝ Venous inflow is increased.
5
6
Alfa-receptor agonist MIDODRINE can be used to treat orthostatic hypotension.
In the blood vessels of skin and abdominal organs there are mostly alfa-receptors
so constriction is a consequence of adrenaline and noradrenaline release.
Blood vessels in sceletal muscles have both alfa and beta adrenergic receptors so
release of adrenaline and noradrenaline can cause both contriction and vasodilatation.
Blood vessels in the nasal mucosa have alfa-receptors. That is why sympathomimetics
are used as nasal decongestans (local vasoconstriction).
These receptors are present in all bloodvessels.
Their activation causes vasoconstriction when used locally (very fast intravenous infusion or high oral dose).
Systemic use of α2-receptors agonists causesboth central α2-receptorsactivation and peripheralα2-receptors activation.
Effects of α2-receptors activation
Activation of centralα2-receptors causesdecrease ofsympathetic tonus and lowers bloodpressure.
α2-agonists are therefore used as sympatholytics intreatment ofhypertension.
7
Effects of β-receptors activation
Activation ofβ-receptorsin the heartincreasesheartcontractilityand heartfrequency.
Activation ofβ2-receptorson theperipherycausesvasodilatationin some bloodvessels.
Sympathomimetics effects in the heart1) Positive inotropic effect:
increase of intrinsic heartactivity. Contraction is stronger, relaxation is faster.
2) Positive chronotropic effect: increase of heart frequency.
3) Positive dromotropic effect: increase of conduction speedin the atrioventricular node.
4) Positive bathmotropic effect: increased excitability of theheart.
8
Effect of dopamine receptors activation
Intravenous aplication of dopamine
causes vasodilatation of renal, visceral,
coronary and cerebral arterioles via
activation of D1-receptors.
Activation of D1-receptors in renal blood
vessels can increase natriuresis.
Activation of presynaptic D2-receptors
inhibits noradrenalin release.
Dopamine activates β1-receptors in the
heart.
9
Effect of dopamine receptors activation
10
Low dose ofdopaminedecreasesperipheralresistance.
When givenin highspeed
infusionactivates α-receptors.
High speedinfusion ofdopamine
mimicsaffects of
noradrenaline.
Activation of α-receptors causesvasoconstriction,
including renalvasoconstriction.
DOPAMINE