Chemistry of Behavior Flashcards
What do both endogenous neurotransmitters and exogenous drugs have in common?
They both have the ability to bind to receptor molecules and cause (or prevent) events in the postsynaptic neuron
What is the criteria for a neurotransmitter?
- Exist in presynaptic terminal
- Capable of being produced by the presynaptic cell
- Released during an AP
- Recognized by receptors on the postsynaptic membrane
- Substance produces changes in postsynaptic cell
- Blocking release of substance prevents presynaptic activity from affecting postsynaptic cell
What are some common neurotransmitters?
- Acetylcholine (ACh)
- Dopamine (DA)
- Norepinephrine (NE)
- Serotonin (5-HT)
- Glutamate (GLU)
- GABA
Acetylcholine is responsible for what functions?
- Muscle contraction
- Cognitive processing
How was acetylcholine discovered?
In 1921: Famous experiment by Otto Loewi
“Vagusstoff”
NTs first found in PNS
Describe the key characteristics of Nicotinic?
- Activated by nicotine
- Found in brain and striated muscles
Describe the key characteristics of muscarinic.
- Activated by muscarine
- Found in brain, cardiac muscles of heart, smooth muscles
Which common neurotransmitters are monoamines?
- Dopamine
- Norepinephrine
- Serotonin
What functions is dopamine associated with?
- Motor function
- Reward (and addiction)
- ‘Higher’ cognitive processing
What is one approach a scientist can take to understand dopamine function?
Optogenetics
What functions is norepinephrine associated with?
- Role in regulating sympathetic nervous system (Fight or Flight)
- Arousal
What role is serotonin (5-Ht) associated with?
- Mood
- Sleep
- Higher cognitive processes
Which common neurotransmitters diffuse modulatory systems?
- Acetylcholine
- Dopamine
- Norepinephrine
- Serotonin
True or False:
Core of each system is small
True
True or False:
Core is deep in the brain but projects to cortex
True
True or False:
Each neuron influences many others
True
Axon of one neuron may contact more than 100,000 postsynaptic neurons spread across the brain
Which common neurotransmitters have lots of neurons all over the brain?
- Glutamate
- GABA
What functions is glutamate associated with?
- Learning and memory
- Excitatory
What is the most abundant neurotransmitter?
Glutamate
What function is GABA associated with?
Inhibition
How do neurotransmitters affect the postsynaptic cell?
By binding to receptor molecules
Neurotransmitters can have different effects based on…
the receptor subtype to which they bind
What is a receptor subtype?
Any type of receptor having functional characteristics that distinguish it from other types of receptor for the same neurotransmitter
GABAa, GABAb, and GABAc all bind to GABA making them…
GABA receptors
What makes GABAa, GABAb, and GABAc different receptor subtypes?
GABA has a different effect when it binds to each subtype
What are the key characteristics of GABAa?
- Inhibitory
- Ionotropic
- Directly opens Cl- channels
- Prevent seizure activity
What are the key characteristics of GABAb?
- Inhibitory
- Metabotropic
- Lead to K+ channels opening
- Lead to a greater degree of hyper polarization than GABAa
What are the key characteristics of GABAc?
- Inhibitory
- Ionotropic
- Directly open Cl- channels (channels stay open longer than GABAa channels)
- Important in the functioning of the retina
True or False:
There are more neurotransmitters than receptor types.
False
Many more receptor types than neurotransmitters
_______ bind to receptors.
Neurotransmitters
Postsynaptic effect will depend on the function of the …
particular receptor subtype to which the neurotransmitter binds
Is GABA an endogenous or exogenous substance?
Endogenous substance
What is binding affinity?
Degree of chemical attraction between a ligand and a binding site
Can exogenous substances bind to the same receptor sites as endogenous substances?
Yes - more variability in specificity of binding
What is efficacy?
Propensity of the ligand to activate the receptor to which it is bound
What do we classify drugs based on?
The way they affect the postsynaptic neuron relative to the effect of an endogenous neurotransmitter on the same receptor
What are drug classification categories?
- Agonist
- Inverse agonist
- Antagonist
What does an agonist do?
It has the same effect as a neurotransmitter.
High efficacy.
Inhibitory effect.
What does an inverse agonist do?
Opposite effect than the neurotransmitter that would normally bind to the receptor.
High efficacy.
Excitatory effect.
If neurotransmitter causes an EPSP, an inverse agonist causes an ____.
IPSP
What does an antagonist do?
Lack of effect - drug does not activate the receptor and may block receptor site so neurotransmitter can’t act.
Low efficacy.
What is a competitive substance?
A substance that binds to identical site as neurotransmitter
What is a noncompetitive substance?
A substance that binds to a different part of the receptor site
How likely is it that the drug will bind to a receptor?
Affinity
How will the drug act at the receptor?
- Agonist
- Inverse agonist
- Antagonist
Efficacy
Is the drug binding to the same site as an endogenous neurotransmitter would?
Competitive vs. Noncompetitive
True or False:
Drugs can affect whether neurons have neurotransmitters to release
True
Transmitter production
What effects can drugs have on the soma?
Inhibit NT synthesis
What effects can drugs have on the axon?
Block transport down the axon
What effects can drugs have on the axon terminal?
Inhibit storage in vesicles
True or False:
Drugs can affect parts of the transmission process?
True
transmitter release
What effect can drugs have on the transmission process near the axon hillock of the presynaptic neuron?
Inhibit AP
ex: block voltage-gated Na+ channels
What effect can drugs have on the transmission process near the axon terminal?
Mess with feedback through autoreceptors
What effect can drugs have on the transmission process near the axon hillock of the postsynaptic neuron?
Affect chemical transmission
ex: block voltage-gated Ca2+ channels or encourage NT release
What does cannabis target?
CB-1 and CB-2 receptors for endocannabinoids
Where are CB-1 and CB-2 receptors found?
on presynaptic axon terminals
What category do the CB-1 and CB-2 receptors fall under?
Metabotropic receptors
How does cannabis act?
It is an agonist.
It effects voltage-gated Ca2+ channels
It often inhibits inhibition (via GABA)
What parts of the nervous system does cannabis effect?
- Basal ganglia (movement)
- Cerebellum (movement)
- Cerebral cortex (higher cognitive function)
- Hypothalamus (appetite)
- Hippocampus (learning, memory, stress)
- Spinal cord (peripheral sensation including pain)
- Medulla (nausea/vomiting chemoreceptor trigger zone)
True or False:
Drugs can affect what happens in the synaptic cleft.
True
Transmitter clearance
How do drugs affect what happens in the synaptic cleft?
Inhibit reuptake or degradation: more transmitter in the synapse
What does cocaine target?
Transporter molecules for reuptake of monoamines
How does cocaine act?
Prevents reuptake, leaving NTs in synapse for extended time
Experience a high (extreme pleasure)
What does cocaine block?
The dopamine transporter
How do drugs get into the system?
- Ingestion
- Inhalation
- Peripheral injection
- Central injection
What barrier must drugs pass in order to get into the system?
The blood-brain barrier
Separates the CNS from circulatory system
What does the brain do to reduce the effects of drugs?
Maintenance of homeostasis - drug alters normal functioning and neurons can react to this
What is metabolic tolerance?
Increased efficiency clearing drug out of body
What is functional tolerance?
Change within neurons that decrease effectiveness
Tolerance can lead to…
- Cross tolerance
- Withdrawal symptoms
How can a cell contract an agonist?
Down-regulation
How can a cell counteract an antagonist?
Up-regulation
