Cholinergic and Adrenergic Drugs- drug list midterm

Cholinergic Agonists

• Acetylcholine (ACh) directly activates both muscarinic and nicotinic receptors.
• Muscarine specifically activates all muscarinic receptors.
• Pilocarpine selectively activates muscarinic receptors.
• Bethanechol activates muscarinic receptors.
• Nicotine selectively activates nicotinic receptors.
• Physostigmine is an intermediate-acting acetylcholinesterase (AChE) inhibitor.
• Echothiophate is a long-acting AChE inhibitor.

Cholinergic Antagonists

• Atropine blocks the activation of muscarinic receptors.
• Trimethaphan blocks nicotinic receptors in autonomic ganglia (Nn), inhibiting both sympathetic and parasympathetic nervous systems.
• D-Tubocurarine blocks nicotinic receptors at the neuromuscular junction (Nm), preventing muscle contraction.

Adrenergic Agonists

• Norepinephrine (NE) primarily acts on α1, α2, and β1 receptors, mimicking sympathetic nervous system activity.
  • β1 receptor activation increases heart rate and contractility, leading to increased blood pressure.
  • α1 receptor activation in the eye causes pupil dilation and vasoconstriction.
  • α2 receptor activation in adrenergic nerve terminals in the CNS decreases sympathetic outflow.
  • α1 = α2, β1>β2 activity
• Epinephrine acts on α1, α2, β1, and β2 adrenoceptors, all of which are linked to G-protein second messenger systems.
  • α1=α2, β1= β2
  • α1 activation increases IP3/DAG.
  • α2 activation decreases cAMP.
  • β1, β2, and β3 activation increases cAMP.
• Phenylephrine is a direct-acting α1 adrenergic agonist with much greater affinity for α1 receptors than α2 receptors.
  • Activates α1 receptors in blood vessels, causing vasoconstriction.
  • Vasoconstriction triggers the baroreceptor reflex, increasing parasympathetic activity and decreasing sympathetic activity.
• Clonidine is an α2 adrenergic agonist, with much greater affinity for α2 receptors than α1 receptors.
  • α2>>α1
  • Used to treat opioid withdrawal, pain, hypertension, glaucoma, and diarrhea.
  • Causes relaxation in the CNS.
  • Causes relaxation in the eye, decreasing aqueous humor production and intraocular pressure.
  • In the context of diarrhea, α2 activation decreases acetylcholine (ACh) release, leading to decreased M3 activation.
• Dobutamine has a greater affinity for β1 receptors over β2 receptors.
  • Activates β1 receptors, increasing heart rate and force of contraction.
  • The baroreceptor reflex monitors blood pressure, increasing PSNS activity and decreasing SNS activity, leading to vasodilation
• Isoproterenol has equal affinity for β1 and β2 receptors.
  • In the heart, it increases contraction.
  • In blood vessels within skeletal muscles, it causes relaxation.
  • In the bronchi, it promotes relaxation.
• Albuterol primarily acts on β2 receptors.
  • Causes relaxation in the bronchi, GI tract, bladder, and uterus by relaxing smooth muscle.
• Tyramine is an indirect-acting sympathomimetic.
  • It is normally metabolized by monoamine oxidase.
  • Increases norepinephrine (NE) release, which can be toxic and lead to sympathetic excess.
  • Tyramine and norepinephrine are taken up by the same receptor, and tyramine can block norepinephrine uptake.
• Amphetamine is an indirect-acting sympathomimetic.
  • Increases the level of norepinephrine at the synapse, increasing activity of multiple receptors.
• Cocaine is an indirect-acting sympathomimetic.
  • Prevents the re-uptake of norepinephrine.

Adrenergic Antagonists

• Prazosin selectively blocks α1 receptors.
  • Blocks α1 receptors activated by Norepinephrine or epinephrine.
  • Leads to relaxation in blood vessels in organs and skin.
  • Can cause the baroreceptor reflex response, decreasing BP, decreasing PSNS and increase SNS.
• Yohimbine selectively blocks α2 receptors.
  • Blocks α2 receptors activated by Norepinephrine or epinephrine.
  • Inhibits α2, causing relaxation in the GI tract.
• Metoprolol selectively blocks β1 receptors.
  • Blocks β1 receptors leading to relaxation in the heart and decreases heart rate and force of contraction.
  • Inhibition of β1 can trigger the baroreceptor reflex response, decreases BP, decreased PSNS and increase SNS.
• Propranolol non-selectively blocks both β1 and β2 receptors, affecting multiple areas.
  • Heart: Causes relaxation.
  • Eye: Causes relaxation, decreasing production of aqueous humor.
  • Blood vessels: Causes constriction (mediated by blocking β2 receptors).
  • Bronchi: Causes constriction (mediated by blocking β2 receptors).
  • GI tract: Causes constriction (increases motility when blocking β2).
  • Bladder: Contracts the bladder.
• Butoxamine selectively blocks β2 receptors.
  • blocks the β2 receptors that are activated by Norepinephrine or epinephrine

Overview of cholinergic and adrenergic agonists and antagonists. Includes mechanisms of action and receptor targets for drugs like acetylcholine, atropine, norepinephrine.