Agonists and Antagonists

• Agonists stimulate receptors, while antagonists inhibit them.

Nicotinic Receptors

• Stimulation: Nicotine acts as a muscle relaxant and affects the central nervous system (CNS).
• Nicotine patches assist individuals dealing with nicotine addiction by delivering gradually decreasing doses, this helps to minimize withdrawal symptoms.
• Inhibition: Not clinically applicable.

Muscarinic Receptors

• Stimulation: Pilocarpine induces muscle contraction and helps manage glaucoma by contracting the ciliary muscle and facilitating fluid drainage.
• Inhibition: Atropine inhibits secretions in small doses, elevates heart rate in moderate doses, and reduces gastrointestinal motility in large doses.

Alpha-1 Receptors

• Found in: Smooth muscles
• Stimulation: Pseudoephedrine and Phenylephrine cause vasoconstriction, reduce swelling of mucous membranes, and decrease secretions.
• Inhibition: Tamsulosin relaxes smooth muscle in the bladder and prostate to improve urine flow; it also reduces blood pressure due to vasodilation.

Alpha-2 Receptors

• Found in: Brain and periphery
• Stimulation: Clonidine reduces CNS outflow for ADHD treatment and lowers blood pressure and heart rate.
• Inhibition: Has limited clinical use.

Beta-1 Receptors

• Found on: The heart and kidneys
• Stimulation: Dobutamine increases heart rate, force of heart contraction, and speed of conduction between SA and AV nodes.
• Inhibition: Metoprolol, is a selective B blocker, that acts on Beta-1 receptors to reduce blood pressure and heart rate.

Beta-2 Receptors

• Found on: The lungs
• Stimulation: Albuterol induces bronchodilation.
• Inhibition: Propranolol, a nonselective B blocker, affects both Beta-2 and Beta-1 receptors, lowering blood pressure but can also cause bronchoconstriction.

Catecholamines and Adrenergic Receptors

• Epinephrine and Norepinephrine stimulate alpha- and beta-receptors on target organs, leading to increased heart rate and vasoconstriction for improved blood flow to essential organs.
• Dopamine's effects are dose-dependent, targeting arteries in the kidneys, heart, and brain.
• Inhibition: Not clinically applicable.

Agonists stimulate receptors. Antagonists inhibit them. Nicotinic receptors are stimulated by Nicotine which acts as a muscle relaxant and affects the central nervous system. Muscarinic receptors are stimulated by Pilocarpine to induces muscle contraction and helps manage glaucoma.