Pharmacology of Adrenergic and Cholinergic Receptors

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Questions and Answers

Which of the following drugs is a β1 selective agonist?

Dobutamine (correct)

Salbutamol

Propranolol

Phenylephrine

What is the effect of β2 selective agonists on blood vessels?

Vasoconstriction

No effect on blood vessels

Vasodilation (correct)

Depends on the dose of the drug

Which of the following is an α antagonist?

Propranolol

Phentolamine (correct)

Hexamethonium

Atropine

What is the mechanism of action of receptor agonists?

they mimic the action of transmitters Signup and view all the answers

Which of the following drugs is used for congestive heart failure and cardiogenic shock?

Dobutamine Signup and view all the answers

What is the therapeutic application of β2 selective agonists?

Treatment of asthma Signup and view all the answers

What is the effect of Botulinum toxin on the release of neurotransmitter ACh?

Prevents release Signup and view all the answers

What is the therapeutic application of ephedrine?

Nasal decongestion and asthma Signup and view all the answers

What is the mechanism of action of cocaine?

Re-uptake inhibitor Signup and view all the answers

What is the effect of alpha (α) receptors on blood vessels?

Vasoconstriction Signup and view all the answers

What is the therapeutic application of galanthamine?

Alzheimer's disease Signup and view all the answers

What is the effect of phenelzine on neurotransmission?

Inhibits the enzymatic inactivation of NA Signup and view all the answers

What is the primary mechanism of action of cocaine in noradrenergic neurotransmission?

Inhibition of reuptake Signup and view all the answers

Which of the following receptors is responsible for smooth muscle contraction in blood vessels?

Alpha 1 receptor Signup and view all the answers

What is the effect of isoprenaline on peripheral resistance?

Decreases peripheral resistance Signup and view all the answers

Which of the following drugs is a selective alpha 2 agonist?

Clonidine Signup and view all the answers

What is the therapeutic application of salbutamol?

Treatment of asthma Signup and view all the answers

Which of the following enzymes is responsible for the degradation of noradrenaline?

Monoamine oxidase (MAO) Signup and view all the answers

What is the effect of noradrenaline on peripheral resistance?

Increases peripheral resistance Signup and view all the answers

Which of the following receptors is responsible for smooth muscle relaxation in the respiratory tract?

Beta 2 receptor Signup and view all the answers

What is the mechanism of action of phenelzine?

Inhibition of monoamine oxidase Signup and view all the answers

Which of the following drugs is a selective beta 1 agonist?

Dobutamine Signup and view all the answers

Study Notes

Adrenergic Receptors and Neurotransmission

Adrenergic receptors are classified into two types: alpha (α) and beta (β)
α receptors: NA > A > Isoprenaline
β receptors: Isoprenaline > A > NA
α receptors are further divided into α1 and α2, and β receptors into β1, β2, and β3
Each subtype has a different second messenger response

Neurotransmitter Release and Re-uptake

Neurotransmitter release: ACh, NA, tyramine, ephedrine, and amphetamine promote release
Re-uptake inhibitors: cocaine, imipramine; inhibit uptake 1, increase NA effect
Uses: cocaine (local anaesthetic), imipramine (depression)
Side effects: cocaine (drug dependence), imipramine (atropine-like effects)

Inhibitors of Enzymatic Inactivation

ACh esterase inhibitors: galanthamine; inhibit ACh esterase in synaptic cleft, prolong ACh action
MAO inhibitors: phenelzine; inhibit monoamine oxidase in presynaptic terminal, increase stored pool
Uses: galanthamine (Alzheimer's disease), phenelzine (depression)
Side effects: phenelzine (cheese reaction)

Adrenergic Transmission and Receptors

Noradrenaline receptors: α1, α2, β1, β2, β3
α1: inositol triphosphate (IP3), diacylglycerol (DAG)
α2: ↓ cAMP
β1: ↑ cAMP
β2: ↑ cAMP
β3: unknown

Structure-Activity Relationships (SAR)

Increase size of substituents on N atom: potent β agonists, less affinity for UT1 and MAO
Addition of α-methyl group: α selective, resistant to MAO, still susceptible to UT1
Removal of β -OH: greatly reduced interaction with α and β receptors
Substitute or replace catechol -OH groups: not degraded by COMT, still susceptible to UT1

Adrenergic Receptors in Peripheral Tissues

Cardiovascular system: α receptors (smooth muscle contraction), β receptors (smooth muscle relaxation)
Heart: β1 receptors (+ve chronotrophic and inotrophic effects)
Eye: α receptors (radial papillary dilation muscle), β receptors (ciliary muscle relaxation)
Respiratory tract: β2 receptors (bronchial muscle relaxation, bronchodilation)
Gastrointestinal tract: α receptors (presynaptic on cholinergic terminals, ↓ release of ACh), β receptors (smooth muscle relaxation)

Adrenergic Agonists and Antagonists

Receptor agonism (mimics action of NorAdr): NorAdr, α phenylephrine, methoramine (α1), Clonidine, α-methyl-NorAdr (α2), isoprenaline, Adr (β), prenalterol (β1), salbutamol, terbutaline (β2)
Receptor antagonism (blocks action of NorAdr): atropine (M antagonist), phentolamine (α antagonist), propranolol (β antagonist)

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Description

Test your knowledge of adrenergic and cholinergic receptors, including agonists and antagonists, and their effects on the body. Learn about the different types of receptors and their responses to various drugs. Assess your understanding of pharmacology and its applications in medicine.