TLO 10.5 Drug Mechanisms and Targets

Drug Target Molecules and Mechanisms

• Carrier Molecules (Transporters): Proteins that move substances across cell membranes, including neurotransmitters, glucose, amino acids, and ions.
• Agonist: Drug that binds to a transporter, enhancing its activity, increasing molecule transport.
• Antagonist: Drug that blocks or inhibits transporter activity, preventing substance movement.
• Example (SSRIs): Block serotonin transporter, preventing serotonin reuptake, increasing serotonin levels.

Enzymes

• Description: Biological catalysts speeding up chemical reactions, involved in metabolism, neurotransmitter breakdown, and hormone regulation.
• Agonist: (Less common) Drugs that enhance enzyme activity.
• Antagonist: (Common) Drugs that inhibit enzymes, reducing molecule production or modifying processes.
• Example (ACE inhibitors): Inhibit angiotensin-converting enzyme, lowering blood pressure.

Ion Channels

• Description: Membrane proteins allowing ions (e.g., sodium, potassium, calcium) to pass into or out of cells, critical for nerve transmission, muscle contraction, and homeostasis.
• Agonist: Drug that increases ion channel activity, allowing more ion flow.
• Antagonist: Drug that blocks or inhibits ion channels, preventing ion flow.
• Example (Calcium Channel Blockers): Block calcium ion flow into smooth muscle cells, leading to vasodilation (widening of blood vessels).

Receptors

• Description: Proteins on or inside cells that bind to specific molecules (ligands) like hormones, neurotransmitters, or drugs, mediating biological effects.
• Types:
  • G protein-coupled receptors (GPCRs): Involved in neurotransmitter and hormone signaling.
  • Ion channel-linked receptors: Directly control ion flow.
  • Nuclear receptors: Found inside cells, regulate gene expression interacting with hormones.
• Agonist: Drug binding to a receptor, activating it; mimicking natural ligand to trigger a response.
• Antagonist: Drug binding to a receptor but not activating it, blocking receptor, preventing endogenous ligand/agonist binding.
• Example (Beta-adrenergic Receptors):
  • Agonist (Salbutamol): Causes bronchodilation (widening of airways), treating asthma.
  • Antagonist (Propranolol): Blocks adrenaline effects, reducing heart rate and blood pressure.

Agonist vs. Antagonist

• Agonist: Molecule activating a receptor, ion channel, enzyme, or transporter, producing a biological response.
• Antagonist: Molecule binding, but not activating target; blocking natural ligand or agonist action.

TLO 10.5. DESCRIBE THE MAIN DRUG TARGET MOLECULES (CARRIER MOLECULES, ENZYMES, ION CHANNELS AND RECEPTORS) AND HOW DRUGS ACT ON THE TARGETS (USING THE TERMS AGONIST AND ANTAGONIST)