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Sympathetic Nervous System (SNS)
Controls fight-or-flight physiological responses.
Catecholamines
Hormones like epinephrine and norepinephrine.
Non-catecholamines
Agents lacking hydroxyl groups on benzene ring.
Adrenergic Receptors
Receptors mediating sympathetic nervous system responses.
Direct-acting Agonists
Bind and activate adrenergic receptors directly.
Indirect-acting Agonists
Increase norepinephrine and epinephrine levels.
Dual-acting Agonists
Exhibit both direct and indirect actions.
Epinephrine
Primary catecholamine for emergency situations.
Norepinephrine
Key neurotransmitter in sympathetic nervous system.
Phenylephrine
Non-catecholamine used as a decongestant.
Isoproterenol
Synthetic catecholamine for bronchodilation.
Dopamine
Precursor to norepinephrine and epinephrine.
Tyrosine Hydroxylase (TH)
Converts tyrosine to dopa in synthesis pathway.
Dopa Decarboxylase
Converts dopa to dopamine in neurons.
Dopamine β-Hydroxylase
Converts dopamine to norepinephrine.
Phentolamine N-methyltransferase
Converts norepinephrine to epinephrine.
Substance P
Neurotransmitter involved in pain transmission.
Adverse Effects
Negative reactions to sympathomimetic agents.
Cardiovascular Actions
Effects on heart rate and blood pressure.
Respiratory Actions
Effects on bronchial muscle relaxation.
MAO Inhibitors
Prevent breakdown of norepinephrine.
COMT Inhibitors
Inhibit catecholamine metabolism.
Clinical Uses
Applications of sympathomimetic agents in medicine.
Adrenergic receptors
G protein coupled receptors mediating sympathetic effects.
Epinephrine
Binds α1, α2, β1; treats allergic reactions.
Norepinephrine
Precursor to epinephrine; controls blood pressure.
Dopamine
Binds dopamine receptors; affects α1, β1 receptors.
Direct-acting agonists
Bind directly to adrenergic receptors.
Isoproterenol
Synthetic agonist; primarily β receptor activity.
Dobutamine
Primarily β1 agonist; increases cardiac output.
Phenylephrine
Selective α1 agonist; causes vasoconstriction.
Clonidine
α2 agonist; reduces sympathetic outflow.
Indirect-acting agonists
Promote norepinephrine release without direct binding.
Tyramine
Releases stored norepinephrine; found in aged foods.
Amphetamine
Stimulates release of norepinephrine; increases alertness.
Cocaine
Inhibits norepinephrine reuptake; increases sympathetic effects.
Mixed acting agonists
Activate receptors via direct binding and norepinephrine release.
Ephedrine
Mixed agonist; stimulates both α and β receptors.
Mechanism of action
Agonists activate receptors, influencing second messenger systems.
Second messenger systems
IP3/DAG and cAMP mediate adrenergic receptor actions.
Adenylate cyclase
Enzyme activated by G proteins; increases cAMP.
Vasodilation
Widening of blood vessels; occurs with β receptor stimulation.
Vasoconstriction
Narrowing of blood vessels; occurs with α receptor stimulation.
G protein
Mediates signal transduction from receptor activation.
Catechol-O-methyltransferase (COMT)
Enzyme that inactivates catecholamines like norepinephrine.
Monoamine oxidase (MAO)
Enzyme that breaks down neurotransmitters including norepinephrine.
Attention deficit hyperactivity disorder (ADHD)
Low norepinephrine levels may contribute to its development.
Cleakage
Leakage of substances into tissue.
Adverse Effects
Negative reactions like anxiety and arrhythmias.
Catecholamine
A class of neurotransmitters including dopamine.
Dopamine
Precursor to norepinephrine in noradrenergic nerves.
Parkinson's Disease
Caused by lack of dopamine in the brain.
Shock Syndrome
Hemodynamic imbalance due to various medical conditions.
β-Adrenoceptors
Receptors that respond to catecholamines like dopamine.
Chronotropic Effects
Changes in heart rate due to stimulation.
Inotropic Effects
Changes in heart contractility due to stimulation.
D1 and D2 Receptors
Dopamine receptors involved in renal vasodilation.
α-Adrenergic Receptors
Receptors that increase vascular resistance when stimulated.
Isoprenaline
Non-selective beta adrenergic receptor agonist.
Heart Block
Interruption of electrical conduction in the heart.
Adams-Stokes Attacks
Transient loss of consciousness due to heart issues.
Glycogenolysis
Breakdown of glycogen to glucose in the liver.
Oxymetazoline
α1- and α2-agonist used for nasal decongestion.
Vasoconstriction
Narrowing of blood vessels to reduce blood flow.
Ephedrine
Alpha and beta-adrenergic agonist from ephedra plant.
Hypotension
Abnormally low blood pressure condition.
Renin-Angiotensin-Aldosterone System
Hormonal system regulating blood pressure and fluid balance.
Nasal Decongestant
Medication to relieve nasal congestion.
Sympathomimetic Drug
Mimics effects of the sympathetic nervous system.
Injection Site Necrosis
Tissue death at the site of injection.
Adrenergic receptors
Receptors activated by catecholamines like norepinephrine.
α-1 receptors
Cause vasoconstriction and increase blood pressure.
β-1 receptors
Increase heart rate and contractility.
β-2 receptors
Induce bronchodilation in the lungs.
Ephedrine
Stimulates α and β receptors, increases norepinephrine release.
Pseudoephedrine
A decongestant acting primarily on α receptors.
Tyramine
Monoamine that induces catecholamine release.
Blood-brain barrier (BBB)
Prevents certain substances from entering the brain.
Monoamine oxidase inhibitors (MAOIs)
Prevent breakdown of monoamines, increasing their levels.
Cheese effect
Hypertensive crisis from tyramine with MAOIs.
Tyramine-rich foods
Include cheese, chocolate, and fermented products.
Amphetamine
Promotes wakefulness, used for ADHD and narcolepsy.
Vesicular monoamine transporter (VMAT2)
Transports monoamines into vesicles in neurons.
Catechol-O-methyltransferase (COMT)
Enzyme that metabolizes catecholamines in circulation.
Cocaine
CNS stimulant, local anesthetic, and vasoconstrictor.
Norepinephrine reuptake
Process of norepinephrine being reabsorbed into neurons.
Central nervous system (CNS)
Part of the nervous system including the brain and spinal cord.
Adverse effects of cocaine
Include headaches, seizures, and cardiovascular issues.
Absorption of cocaine
60-80% absorbed via oral or nasal routes.
Indirect sympathomimetic action
Stimulates sympathetic nervous system indirectly.
MAO metabolism
Breaks down monoamines in the liver.
Hypertensive crisis
Severe increase in blood pressure due to drug interactions.
CNS disorders
Conditions affecting the brain and spinal cord.
Therapeutic uses of amphetamine
Treats ADHD and narcolepsy.
Norepinephrine (NE)
A neurotransmitter involved in arousal and alertness.
