Exam 3 Flashcards
Two competing theories of depression
Monoamine Depletion Theory and the receptor sensitivity hypothesis
Due to the widespread nature of mood disorders, many studies focus on the role of these pathwasy
Diffuse modulatory systems
Bipolar disorder is also called
manic-depressive disorder
Depression is the leading cause of
suicide
This is the Milder form of depression
dysthymia
Mood v emotion
Mood = predominant emotional state over time
Emotion- transient response
Mood disorders are characterized by
1) feeling emotional state is no longer under control
2) fluctuates spontaneously with no link to stressful events
Mood disorders have a general tendency
towards progression
early episodes precipitated by psychosocial stress, but later ones happening spontaneously
Key evidence supporting monoamine depletion theory f depression:
1) Reserpine– block VMAT2 transporter and depletes serotonin levels, which causes depression
2) Tricyclic Antidepressants– inhibit SERT/NET, thus increasing amount of NT in the synapse and prolonging its effect
3) MAOI (monoamine oxidase inhibitors)– inhibit a degradation enzyme for monoamine
How to increase 5-HT in brain?
Eat more tryptophan!
How to increase NE in the brain?
administer L-Dopa
Evidence against monoamine depletion hypothesis (3):
1) Administering 5-HT via a high tryptophan diet and administering NE via L-Dopa does not improve depression
2) Depletion of 5-HT or NE does not lead to depression
3) Time lag between antidepressant treatment and relief– while these drugs act quickly to increase monoamine levels, therapeutic effects are only seen after several week
How to reduce 5-HT in brain?
remove tryptophan from diet
How to reduce NeE in brain
low doses of TH (tyrosine hydroxylase) inhibitor– rate limiting step
Monoamines are involved in the maintenance of antidepressant response
when patients are successfully treated with either 5-HT or NE selective reuptake inhibitors, they become vulnerable to depletion of the corresponding monoamine
a2 adrenergic receptor
Is an inhibitory autoreceptor (presynaptic)
Treatment of 5-HT1A agonist
-autoreceptor on soma of serotonin neurons
reduces the response time to SSRIs
Sustained elevation of monoamine levels by chronic anti-dep treatment leads to
continued activation of postsynaptic monoamine receptors and eventua down-regulation of postsynaptic receptors
Chronic antidepressant treatment ______ beta adrenergic receptors *leads to what hypothesis?
down regulates
This leads to hypothesis that b-AR upregulation leads to depression
Problems with b-AR hypothesis (3)
1) Not all antidepressants lead to upregulation of b-AR
2) Timedelay of down-regulation effect is fast (so doesn’t explain why antideps take weeks)
3) b-AR antagonists are not good antideps
Conflciting evidence of b-AR receptors
b-AR antagonists are not good anti-depressants and b-AR agonists sometimes have antidepressant effects
Chronic antidep treeatment induces _______ of 5-HT2A receptors
*leads to what hypothesis?
down-regulation
5HT2A upreguilation leads t o depression
Problems with 5HT2A receptor hypothesis
1) Not all antideps increase 5-HT2A
2) Time delay of down regulation is faster than effect on antidep
3) Electroconvulsive seizure therapy which is effective for depression, actually upregulates 5-HT2A
3) 5-HT2A antagonists are not good anti-depressants
____________ are the substrats of second messenger-dependent protein kinases. What causes an alteration in activity of these?
transcription factors
phosphorylation by kinases (like PkA)
What is CREB?
a transcription factor that when phosphorylated, binds to the CRE and initiates transcription
Gs pathway
Activation of Gs-coupled receptors
Stimulation of adenylyl cyclase
Elevation of intracellular cAMP
Activation of PKA
Increased transcriptional activity of CREB
Regulation of target genes (like BDNF and TrkB)
Chronic antidepressant treatment leads to upregulation of ________ via CREB
BDNF and TrkB
Antidep treatment leads to downregulation of (_ and _), which demonstrates
5HT7 and b1-AR
supports the idea that sustained activation of these receptors leads to a sustained activation of cAMP cascade
Gq coupled 5-HT and NE receptors
5-HT2A, 2C
a1-AR
Gq pathway
Activation of Gq-coupled 5-HT and NE receptors (5-HT2A,2C, a1-AR) Release of Ca2+ from intracellular stores Activation of CaMK Increased transcriptional activity of CREB
Up-regulation of the CREB cascade suggests that genes containing ______ can be targets for antidepressant treatment.
Cre (cAMP response element)
Role of neurotrophic factors (like BDNF)
- critical to differentiation and development of immature neurons
- required for the survival and functioning of neurons in the adult nervous system
activation of glucocorticoid
receptors leads to suppression of
_____________.
CREB mediated gene transcription and thus levels of BDNF in the brain
chronic stress and glucocorticoid administration causes
down regulation of BDNF in hippocampus and atrophy of hippocampal pyramidal neurons
Findings that support the idea that BDNF is the target for antidepressant treatment (3)
hc, stress, time course
1) Chronic treatment of antidepressants upregulates BDNF in HC
2) antidep treatment blcoks stress-induced downregulation of BDNF in HC
3) time course and regional distribution of BDNF corrsponds to that of CREB by antidepressant treatment
Antidepressant treatment leads to increase in BDNF which leads to
1) increased arborization
2) increased synaptic efficiency
3) decrease depression in animal models where BDNF is injected
4) increased neurogenesis
Pathways of stress in BDNF
Elevation of glucocorticoids
Down-regulation of BDNF
Atrophy and damage of hippocampal neurons
Reduction of the hippocampal feedback inhibition of the HPA axis (leads back to 1 in a vicious cycle)
Depression