```markdown # Neuropharmacology Neuropharmacology examines how drugs alter nervous system function by interacting with neural signaling pathways. It focuses on drug effects on neurons, synapses, neurotransmitters, and receptors, with applications in treating neurological/psychiatric disorders and understanding substance abuse. ## Drug-Receptor Interactions Drugs modulate signaling primarily by binding to receptors: - **Agonists** mimic neurotransmitters, activating receptors (e.g., nicotine mimicking acetylcholine at nicotinic receptors). - **Antagonists** block receptors, preventing neurotransmitter binding (e.g., haloperidol blocking dopamine D₂ receptors in schizophrenia). - **Inverse agonists** suppress baseline receptor activity. ## Neurotransmitter-Specific Mechanisms Drugs target neurotransmitter systems: 1. **Dopamine**: - *Amphetamines* increase dopamine release. - *Antipsychotics* (e.g., risperidone) antagonize D₂ receptors. 2. **Serotonin (5-HT)**: - *SSRIs* (e.g., fluoxetine) inhibit reuptake, prolonging 5-HT activity in synapses. 3. **GABA**: - *Benzodiazepines* (e.g., diazepam) enhance GABA’s inhibitory effects by binding to GABA_A receptors. 4. **Glutamate**: - *Ketamine* blocks NMDA receptors, inducing anesthesia. ## Pharmacokinetics & Pharmacodynamics - **Pharmacokinetics**: Governs drug absorption, distribution (e.g., crossing the blood-brain barrier), metabolism, and excretion. Lipophilicity affects brain penetration. - **Pharmacodynamics**: Explores dose-response relationships, efficacy (max effect), and potency (dose required for effect). ## Key Drug Actions - **Reuptake Inhibitors**: Prevent neurotransmitter recycling (e.g., cocaine blocking dopamine reuptake). - **Enzyme Inhibitors**: Reduce neurotransmitter breakdown (e.g., MAO inhibitors increasing monoamine levels). - **Modulators**: Alter receptor sensitivity (e.g., ethanol enhancing GABA_A receptor function). ## Clinical Relevance - Drugs restore imbalances: L-DOPA replenishes dopamine in Parkinson’s; donepezil inhibits acetylcholine breakdown in Alzheimer’s. - Side effects arise from non-target receptor binding (e.g., antipsychotics causing movement disorders via extrastriatal D₂ blockade). ```

5: Ethics in research

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