Neurotransmission and Drugs Flashcards by Javi Bonamego

What happens when a neurotransmitter binds to a receptor?

The receptor becomes activated like a key and lock

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Ligand

a molecule that binds to a receptor

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What happens to neurotransmitters leftover in the synaptic cleft

They get destroyed by enzymes or reuptake ( reabsorption of neurotransmitter by presynaptic neurons

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How many NT are there

Dozens- 5-10 major types

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How are NT generalized

And what determines the effect

By anatomical localization
By effect (EPSP or IPSP)
The postsynaptic receptors and channels

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The most common NT found in the nervous system, found throughout the brain
Excitatory (induces EPSPs)

Glutamate
Glutamate receptors induce depolarization following NT binding
Participates in numerous processes, emphasis on learning and memory

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What are the 3 types of receptors for glutamate

AMPA (ionotropic)
NMDA (ionotropic)
mGluR (metabotropic)

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GABA

Gamma Amino Butyric Acid
Most common inhibitory NT
Causes IPSPs
Found throughout the brain
Opens either chloride channels (Cl- into cell) or potassium channels (K+ ions out of the cell)

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2 receptors for GABA

GABAA

2. GABAB

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ACh

Acetylcholine
Usually EPSPs
In brain and PNS

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What does ACh affect in the brain

Sensation, learning, and action

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What does ACh affect in the PNS

Peripheral motor neurons

Parasympathetic system

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Neuromuscular junction

A synapse between a motor neuron and a muscle fiber

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What NT is at the neuromuscular junction

ACh

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Sarin

Extremely toxic chemical weapon
Inhibitor of acetylcholinesterase ( an ACh degrader)
Causes ACh buildup, prevents muscle relaxation

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The family of Catecholamines

Adrenaline
Noradrenaline
Dopamine
Both EPSP & IPSP

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Norepinephrine

aka Noradrenaline
General function is to mobilize the brain and body for action
Sympathetic autonomic system
Produced in small structures, widespread affect
Most notably in the Locus Coeruleus

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Dopamine

Movement, reward, motivation

Produced in the Substantia Nigra and Ventral Tegmental Area

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How many families of dopamine receptors are there

D1 & D2

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Serotonin (5-HT)

Known as "happiness NT" 
Sleep, appetite
Antidepressant drugs increase serotonin
Produced in the Raphe Nuclei
Mixed EPSPs &amp; IPSPs

Opioids

Endorphin and Enkephalin
"Natural morphine"
Pain reduction, reward, euphoria
Mixed EPSPs &amp; IPSPs
Bind to opioid receptors
Synthesized following pain, exercise and laughter

Nitric Oxide

Reverse NT
Soluble gas in dendrites-generated by postsynaptic enzyme in response to NT
Leaks out of dendrite
Enters presynaptic neuron-needs no membrane receptor. Penetrates inside neuron directly
Activates presynaptic secondary messenger
Feedback

How many receptor subtypes are there for acetylcholine

2 or more (ionotropic and metabotropic)

How many receptor subtypes are there for dopamine

5 or more (metabotropic)

In 2 families (D1 vs D2)

How many receptor subtypes are there for norepinephrine

4 or more (metabotropic)

How many receptor subtypes are there for serotonin

7 or more (ionotropic and metabotropic)

How many receptor subtypes are there for glutamate

5 or more (ionotropic and metabotropic)

How many receptor subtypes are there for GABA

10 or more (ionotropic and metabotropic)

How many receptor subtypes are there for opioids

3 or more (metabotropic)

What do most psychoactive drugs act on

synapses

Agonists- Presynaptic: Postsynaptic:

Turn ON NT system (EPSP or IPSP) Release NT Activate receptors

Antagonists- Presynaptic: Postsynaptic:

Turn OFF NT system Prevent release Block receptors

Inverse agonists

Postsynaptic bind to receptors but induces opposite effect

Parkinsons disease

Reduced dopamine levels Medication: L-Dopa L-Dopa is a dopamine precursor Presynaptic agonists

Cocaine

Presynaptic agonist | Inhibits reuptake of dopamine by blocking dopamine transporter. Also blocks serotonin and norepinephrine

Amphetamine

Blocks and reverses dopamine transporter Increases levels of dopamine and norepinephrine Stimulation, euphoria, wakefulness, improved cognitive control Used in treatment of ADHD, narcolepsy, depression; athletic performance enhancer

Adderall

Prescribed combination of amphetamine and dextroamphetamine

Ritaline

Not amphetamine, but similar effect

Selective Serotonin Reuptake Inhibitors

SSRIs Block reuptake of Serotonin Commonly prescribed antidepressant: Prozac

Morphine and Heroin

Postsynaptic Agonists Activate postsynaptic opioid receptors Euphoric, pain relief Mimic endorphins, enkephalin

Synthetic Opioid Drugs

Fentanil- 50X more potent than heroin Carfentanil- 100X more potent than fentanil Pain reduction, tranquilizer darts Overdose inhibits brainstem breathing circuits

LSD (Lysergic Acid Diethylamide)

Postsynaptic agonist Hallucinogenic Drug Activates serotonin receptors

Benzodiazepines

Xanax, Valium Postsynaptic agonist Sedative, hypnotic, anxiolytic (anti-anxiety), anti-epileptic, muscle relaxant Bind to GABA receptors and facilitate GABA effects

Antipsychotic Drugs for Schizophrenia

Pimozide, haloperidol Block D2 dopamine receptors Prevent dopamine from activating

Atypical Antipsychotics

Block serotonin receptors | Still block dopamine too

Routes of administration of drugs

Oral Sniff and nasal mucosa Intravenous injection Smoke

Long-term effects | 1. Receptor-Down Regulation

Tolerance to drug -Fewer receptors to activate Withdrawal in absence -Normal NT gives lower signal

Long-term effects | 2. Neural Sensitization

Hyper responsive to drug Dopamine sensitization and addiction -Wanting vs. liking

Long-term effects | 3. Neurotoxicity

Amphetamine Kills dopamine neurons Toxic at 10X street dose