1. Psychoactive Drugs & The Brain

2. Psychoactive Substances & The Brain
Psychoactive substances enter the bloodstream via oral administration, inhalation, smoking, or injection
Psychoactive substances must somehow move from the blood to the brain in order for central nervous system effects to occur

3. How Do Substances Get From Blood Vessels to Brain?
Brain structured to protect itself
Cells lining blood vessels traveling into brain are tightly-packed together
Materials do not cross easily between brain and blood
Pramod Dash, UT Medical School (Figures 11.a & 11.b)
Substances do not easily get through between cells, unless small enough
Not all drug particles are small enough to fit between cells
Drug access to brain depends on a variety of access pathways
The protective structure of blood vessels in brain = Blood-Brain Barrier

4. How Substances Get from Blood Vessels to Brain
Substances must be small enough, and/or
Substances must be fat-soluble
Substances can have help from carriers
Substances can have help from other substances that bind on receptors
Some areas of blood-brain barrier are weaker than others

5. Once Drugs Access Brain Tissue, Then What?
Neurons
Received most research attention
Focus of HEA150
Glial cells
Receiving more research attention
Appear to have important supportive roles (blood- brain barrier, e.g.)

6. Neuron Neuron is a nervous system cell
Dendrites receive electrical information
Soma/cell body processes electrical information
Axon sends electrical information down neuron
End of axon is terminal, which can translate electrical message into chemical message

8. Communication Between & Among Neurons
Neurons do not physically connect
Communication occurs in space between neurons: the synapse
When electrical impulse travels down axon of one neuron, a chemical is released, a neurotransmitter
Image source: Neurevolution.net: Chronicling the Cognitive Revolution in Neuroscience

9. Communication Between & Among Neurons
Neurotransmitter binds to specific receptors in target neuron, like “lock and key”
The “capture” of neurotransmitter continues electrical communication
Neurotransmitter may excite target neuron
Neurotransmitter may inhibit target neuron
Source: NIDA

10. Communication Between & Among Neurons
After the neurotransmitter connects to receptor, most is removed and returned: reuptake
How Transmission Works (NIDA)

11. Communication Between & Among Neurons is Complicated
Target neuron (postsynaptic neuron) can be excited or inhibited
Adjacent neurons can affect excitation or inhibition of postsynaptic neuron
Dozens of neurotransmitters
Dopamine
Serotonin
GABA
Glutamate
Norepinephrine
Many receptor types, working with specific neurotransmitters
Neurotransmitter Chart (Zak Fallows, MIT)

12. Effects of Psychoactive Substances on Neuronal Communication - Example #1
Psychoactive substances can cause a release or increased release of neurotransmitter from a neuron (agonists) Source: BCSworthpublishers.com

13. Effects of Psychoactive Substances on Neuronal Communication – Example #2
Psychoactive substances can prevent a neuron from releasing, or reduce the release of, neurotransmitter (antagonist) Source: BCSworthpublishers.com

14. Effects of Psychoactive Substances on Neuronal Communication – Example #3
Psychoactive substances can block the reuptake of a neurotransmitter
Cocaine (NIDA)
Methamphetamine (two ways to affect communication, MedXclusive Learning)

15. Effects of Psychoactive Substances on Neuronal Communication – Examples
For study on your own (optional)
Agonist and antagonist examples (apehrlichman.com)

16. Mouse Party (University of Utah)
Ecstasy
LSD
Marijuana
Heroin
Alcohol
Cocaine
Methamphetamine