Autonomic Pharmacology Quiz

Autonomic Pharmacology

• Drugs targeting the entire autonomic nervous system affect both sympathetic and parasympathetic systems.
• Nicotinic ACh receptors are present at synapses between pre- and post-ganglionic neurons in both systems.
• Skeletal muscle AChRs are pentameric, while ANS AChRs have 2-7 subunits.
• Hexamethonium is a non-competitive antagonist of nicotinic AChRs. It blocks all autonomic effects, but has many side effects.

Drugs Targeting Parasympathetic Nervous System

• Postganglionic parasympathetic neurons use muscarinic ACh receptors to affect organs.
• Muscarinic ACh receptors are G-protein coupled receptors (7 transmembrane domains).
• Five types of muscarinic receptors exist (M1-M5).
• M1 receptors are in the stomach and salivary glands (Gq).
• M2 receptors are in cardiac muscle (Gi).
• M3 receptors are in smooth muscles and glands (Gq).

Muscarinic Agonists/Parasympathomimetics

• These drugs activate muscarinic receptors, mimicking parasympathetic stimulation.
• Effects include decreased heart rate, vasodilation, smooth muscle contraction (gut/respiratory), salivation, and tearing.

Muscarinic Antagonists

• These drugs block muscarinic receptors, opposing parasympathetic effects.
• Uses include asthma treatment (ipratropium/tiotropium), increasing heart rate, widening pupils, treating bladder issues, and motion sickness.
• Pilocarpine is an example and is used in glaucoma treatment.

Drugs Targeting Sympathetic Nervous System

• Sympathetic postganglionic neurons use noradrenaline (NA).
• Adrenoceptors are G-protein coupled receptors (5 types).
• α1 receptors cause smooth muscle contraction (vasoconstriction, etc.).
• α2 receptors also cause contraction and inhibit NA release.
• β1 receptors increase heart rate and contractility.
• β2 receptors relax smooth muscle (e.g., bronchi, blood vessels).
• β3 receptors stimulate lipolysis and relax smooth muscle (e.g., bladder).

Adrenoceptor Agonists (Sympathomimetics)

• Used in vasoconstriction, nasal decongestion, hypertension treatment, and facial erythema.

Adrenoceptor Antagonists (Alpha-blockers)

• Used in hypertension and benign prostatic hyperplasia.

β-Adrenoceptor Antagonists (Beta-blockers)

• Used in angina, cardiac arrhythmias, heart failure, hypertension, anxiety and glaucoma.

Drugs Affecting Catecholamine Regulation

• Noradrenaline (NA) is synthesized from tyrosine.
• NA is stored in vesicles and released in the synapse.
• The action of NA is terminated by reuptake via the Noradrenaline transporter (NAT).
• Some NA is broken down by monoamine oxidase (MAO).

NAT Inhibitors

• Inhibit noradrenaline reuptake to increase its effect on the synapse.
• Examples include desipramine and cocaine.

MAO Inhibitors

• Inhibit the breakdown of noradrenaline, increasing its levels.
• Side effects include hypotension, weight gain, restlessness, insomnia and 'cheese reaction' (hypertensive crisis with cheese).

Sympathetic Amines

• Structurally similar to NA, they are transported into neurons, displacing NA and causing similar effects.
• Examples include amphetamines, ephedrine, tyramine.

Test your knowledge on autonomic pharmacology, focusing on drugs impacting the sympathetic and parasympathetic nervous systems. This quiz includes information about nicotinic and muscarinic receptors, their functions, and the drugs that affect them. Understand the mechanisms of action and clinical implications of various autonomic drugs.