L12 - drugs affecting SNS II Flashcards
What are the indirect sympathomimetics drugs?
Amphetamine, Ephedrine, Tyramine
Effects of indirect sympathomimetics
increase the availability of noradrenaline/adrenaline to stimulate adrenergic receptors, and there is no interaction between the drug and receptor
Chemical structure similar to NA/A
Bronchodilatation (beta 2 adrenoceptor mediated action)
Enter terminals by uptake 1
Increase mean arterial BP (alpha 1 adrenoceptor mediated action)
Inhibit NA uptake 1
Increase heart rate and force (beta 1 adrenoceptor mediated action)
Displace NA/adrenaline from storage vesicles
Decrease gut motility (alpha 1 adrenoceptor mediated action)
Effects of cocaine
Blocks the reuptake of NA by blocking the reuptake transporter (NET, DAT and SERT)
Impramine
- Blocks the reuptake of NA
- Sodium channel blocker (contributes to cardio toxicity)
- Anti-muscarinic
- Anti-histamine
Direct sympathomimetics
Drugs that have direct agonist action on adrenergic receptors
Smooth muscle
Noradrenaline>Adrenaline>Isoprenaline
Cardiac muscle
Isoprenaline>Adrenaline>Noradrenaline
Isoprenaline
a medication used for the treatment of bradycardia (slow heart rate)
What are adrenoceptors?
They are a class of G protein-coupled receptors that are targets for the catecholamines, especially noradrenaline and adrenaline
For heart, noradrenaline acts on which type of receptors? (from sympathetic fibres)
Presynaptic alpha 2, postsynaptic beta 1
For other tissues, noradrenaline acts on which type of receptor? (from sympathetic fibres)
Presynaptic alpha 2, postsynaptic alpha 1
For most tissues (in severe situation), NA/Adrenaline from adrenal medulla, acts on what receptor?
Extra synaptic beta 2
Where is alpha 1 receptor located?
It is located at the postsynaptic in all tissues except for the HEART
Where is alpha 2 receptor located?
It is located at the presynaptic, wide spread distribution (all tissues) (inhibition of transmitter release) - -ve feedback control
Where is beta 1 receptor located?
It is located at the postsynaptic of the heart - increase rate and force of contraction)
Where is beta 2 receptor located?
It is located at non-synaptic sites
Effects of beta 2 receptor
1) Bronchial smooth muscle relaxes (bronchiodilatation)
2) Some vascular smooth muscle relaxes (but vasodilation in skeletal muscle, coronary and hepatic arterioles, some veins)
3) liver (glycogen mobilisation)
Effects of alpha 2 receptor
1) Vascular smooth muscle contracts (vasoconstriction, reduced blood flow, increased blood pressure)
2) Longitudinal muscle of GI tract relaxes, anal sphincter contracts (reduced motility, constipation)
3) eye radical contraction (pupil dilates)
4) Salivary glands - secretion of thick saliva
5) Liver - glycogen mobilisation
6) Vas deferens contracts - ejaculation
