BIOPSYCH 03/04

Overview of Drug Interaction with Neurons

• Understanding the Basics

  • How drugs enter the body and affect the neural processes.

  • Focus on the interaction between drugs and neurotransmitters.

Mechanisms of Drug Action

1. Neurotransmitter Production

   • Some drugs increase neurotransmitter synthesis, leading to elevated levels.

   • Example: Treatment for Parkinson's disease involves drugs enhancing dopamine production.

   • Some drugs block neurotransmitter production, decreasing availability.

2. Neurotransmitter Storage

   • Drugs can influence the amount of neurotransmitter stored in synaptic vesicles.

   • Historical Example: Reserpine, a blood pressure medication, depleted neurotransmitters and resulted in increased suicide rates, leading to it being withdrawn.

3. Neurotransmitter Release

   • Drugs can affect how much neurotransmitter is released during synaptic transmission.

   • Stimulants often enhance release rates, increasing the effect on target neurons.

4. Neurotransmitter Binding

   • Some drugs interfere with receptor binding:

     • Drugs can block receptors, preventing neurotransmitter action (e.g., Botox, which uses botulism toxin to paralyze muscle contractions).

     • Other drugs can mimic neurotransmitters and activate receptors, like nicotine.

5. Reuptake and Breakdown

   • Some drugs inhibit reuptake mechanisms, leading to prolonged neurotransmitter action in the synapse.

   • Example: SSRIs block the reuptake of serotonin, increasing its availability and effect on mood disorders.

Addiction and Dependence

• Key Definitions:

  • Addiction: Continued use of a substance despite negative consequences; can be psychological or physiological.

  • Dependence: Physical adaptation to a substance, leading to withdrawal symptoms when not taking the drug.

• Dopamine's Role in Addiction:

  • Dopamine is critical for pleasure and reward; most addictive drugs affect dopamine pathways.

  • Addictive behaviors are often linked to the brain areas that process dopamine.

Environmental and Biological Influences on Addiction

• Studies show a combination of biological predisposition and environmental factors contribute to addiction.

• Example: Studies in mice demonstrate how genetic factors influence alcohol preference based on environmental exposure.

Tolerance and Withdrawal

• Tolerance:

  • Refers to the body's adaptation to a drug, requiring more of it to achieve the same effect, results in physiological changes.

• Withdrawal:

  • Symptoms that occur when a dependent individual stops using the substance; can be psychological (e.g., cravings) or physical (e.g., shaking).

• Impact of Environment on Overdose Risk:

  • Changing environments during drug use can disrupt the body's preparatory responses, increasing overdose risk.

  • Example: Musicians often overdose in unfamiliar settings due to lack of environmental cues that prepare their bodies for drug use.

Summary of Neuron Signals

• Signal Propagation: Action potentials involve voltage-gated channels opening in response to electrical signals, allowing ions like sodium to enter the neuron and propagate the signal.

• Neurotransmitter Release: Triggered by calcium entry through voltage-gated channels, leading to exocytosis of neurotransmitters into the synapse.

• Post-synaptic Effect: Neurotransmitters bind to receptors on the post-synaptic neuron, leading to potential further depolarization and propagation of the signal.

Historical Context of Drug Use

• Drugs often follow a pattern of being banned and later becoming accepted based on evolving social, political, and health perspectives.

• Propaganda throughout history has impacted public perception of drug use and its associated risks.