Mood Altering Drugs Flashcards
What drug is a tricyclic antidepressant?
amitriptyline
What are the 3 SSRIs?
- sertraline
- fluoxeline
- paroxetine
What are the “newer antidepressants”?
- bupropion
- trazodone
- duloxetine
- venlafaxine
What benzodiazepine is sometimes used as an antidepressant?
alprazolam
What are the main MAOIs?
- selegiline
2. tranylcypromine
What 4 drugs are used to treat bipolar disorder?
- lithium
- valproate
- carbamazepine
- atypical anti-psychotics
What is the biogenic amine hypothesis?
How was it derived?
Mood disorders are caused by abnormally low levels of monoamines [specifically NE and 5HT].
This theory was derived because reserpine which decreased NE caused depression in some individuals
Both TCAs and MAOIs increase the level of neurotransmitters in the synapse. How do they differ in MOA?
TCAs prevent reuptake, while MAOIs inhibit degradation
What is the mechanism of a1 receptors?
What is the effect on serotonergic neurons?
they couple to GPCR that activates PLC which breaks down PIP–>IP3, DAG
IP3–> Ca release
DAG–> activates PKC
On serotonergic neurons, it stimulates firing and enhances 5HT release
What is the mechanism of a2 receptors? What is the effect on serotonergic neurons? noradrenergic neurons?
they inhibit adenylyl cyclase –> reduced cAMP
presynaptic noradrenergic neurons –> inhibit NE release
synaptic terminal serotonergic–> inhibit 5HT release
What is the mechanism of B1 receptors?
increase cAMP–> excitatory
Where is more than 90% of the body’s 5HT located?
Periphery in platelets, mast cells, enterochromaffin cells of GI.
In the CNS where is 5HT released?
Where is NE released?
both are released from neural projections from the brainstem
NE- locus ceruleus
5HT- raphe nucleus
How is serotonin synthesized?
- tryptophan—tyrosine hydroxylase–> 5-hydroxytryphtophan
- decarboxylase –> 5HT
- MAO–> HIAA
How is dopamine and NE synthesized?
- tyrosine —tyrosine hydroxylase–>DOPA
- decarboxylase–> dopamine
- DBH–> NE
- MAO–> dihydromandelic acid
- VMA–> COMT
Describe the 5HT1a receptor.
Inhibitory or excitatory?
Where in the CNS are they found?
Auto or heteroreceptors?
inhibitory causing:
- decrease in cAMP
- opening of K channels
They are found in:
- raphe nuclei where they are autoreceptors for negative feedback
- hippocampus, amygdala, frontal cortex as postsynaptic heteroreceptors.
What is believed to be the major factor in precipitating serotonin syndrome?
activation of 5HT1a heteroreceptors [inhibitory] in the hippocampus, lateral septum, entorhinal, amygdala and frontal cortex
Describe 5HT1d receptors.
Is it inhibitory or excitatory?
Auto or heteroreceptors?
It depresses cAMP levels when activated.
It is autoreceptors on serotonergic synpapses that provide negative feedback.
Describe 5HT2a receptors.
Excitatory or inhibitory?
Where are they found?
They activate GCPR, increase PLC–>IP3, DAG–>excitatory
They are found in the hypothalamus and in the periphery [platelet aggregation, smooth muscle contraction]
Describe 5HT3 receptors.
How are they distinct from the other serotonin receptors in terms of structure?
Why are they of clinical importance?
They are ligand-gated ion channels rather than GPCR.
They are of importance because they are believed to be the cause of the uncomfortable side effects of anti-depressants –>nausea,vomiting from brainstem system
What serotonin receptor is responsible for triggering nausea and vomiting response due to increased serotonin due to anti-depressant use?
5HT3
In synaptic vesicles, there is often peptides co-packaged with neurotransmitters. What are examples of the co-packaged nerotransmitter/neuropeptide pairs?
In these pairs, where do the neurotransmitters come from?
- NE or Epi with enkaphelins
- 5HT with substance P
The neutrotransmitters do NOT come from synthesis in the ER and transport in the golgi
INSTEAD
1. dopamine and 5HT are transported through the synaptic vesicle membrane
2. NE is synthesized in the synaptic vesicle
How do glutamate and GABA enter synaptic vesicles?
How does this differ from Ach and monoamines?
Glut and GABA enter via electrochemical gradient
Ach and monoamines enter via pH gradient
What is the principle mechanism of inactivating neurotransmitters after their release?
Because of this, what are the major targets of most currently used antidepressants [and many anxiolytics and stimulants]?
Reuptake so presynaptic monoamine transporters are the target
DAT–> dopamine
SERT–> serotonin
NET–> NE
What drug/substance inhibits DAT, NET and SERT?
cocaine
What is the biological basis for antidepressant action?
After the antidepressant is started,
- synaptic monoamine levels decrease due to neg feedback on autoreceptors [5HT1a, HT1d]
- inhibitory autoreceptors gradually get down-regulated and synaptic monoamine again rises
- post-synaptic excitatory receptors are also down-regulated, but to a lesser degree so you still get desired effects
What is the key problem of the bioamine hypothesis for depression?
Antidepressants have immediate effects on synaptic monoamine levels, but therapeutic benefits are not manifested for weeks [2-4]
What is the transcriptional regulation model of antidepressants?
Anti-depressants induce increase in neurotransmitter level that activates signal transduction, upregulating factors that trigger synthesis of new proteins.
- B1 on 5HT4-7 increase cAMP–> activate CREB
- a1 on 5HT2 increases Ca and PKC –> change gene transcription
It is thought that this leads to an increase in BDNF
What is the neurotrophic factor hypothesis of antidepressants?
Stress and depression downregulate brain derived neurotrophic factor BDNF causing atrophy of neurons especially in the hippocampus.
It is thought that antidepressants inhibit MAPK phosphatase that turns off ERK-P that usually converts to BDNF
How does TCA differ from the antipsychotic phenothiazine?
How does this change the function of the drug?
Instead of a Sulfur on the middle ring, it has 2 carbons.
This results in the inability to block dopamine receptors but gained ability to block monoamine reuptake