1. Molecular mechanism underlying Depression: The
relationship between serotonin system and glutamate
system in mouse cortical neurons and HT22 cells
Adiba SHABNAM
2015
4. DEPRESSION
A common psychiatric
disorder characterized
by low mood, loss of
pleasure, sleep and
appetite changes, poor
concentration and
suicidal tendency
Depression
5. Why to study depression?
• Most common psychiatric
disorder
• All age group affected (max.
40-59 yrs)
• Women are more at risk
• Lifetime prevalence 16.2 %
(USA)
• Only 20 % people experience
the symptoms of depression.
• Maximum global burden of
disease in 2030 (WHO, 2008)
6. Causes of depression
• Genetic or hereditary
• Biochemical - monoamine
• Endocrine factors
• psychological factors
8. Involvement of Cortex in depression
Abnormal metabolism in the prefrontal cortex in various mood disorders
9. Involvement of Hippocampus in depression
Reduced Hippocampal volume (Bremner et al, 2000,Lange et al, 2004; Macmaster et al, 2007;Brien et
al 2004, Sheline et al 1995 )
Chronic stress selectively reduces
hippocampal volume in rats: a
longitudinal MRI study (Lee, 2009)
12. Serotonin theory
• Most widely accepted hypothesis
• Depletion of 5-HT in depressed patients
• Antidepressants like SSRI inhibits its re-uptake and
increases its concentration in the synaptic cleft.
LIMITATIONS
• Not all depressed patients (50%) responds to 5-HT
agonists and SSRI. (Mahar et al, 2014)
• Delayed onset of effect (2 weeks)
• A reduction in 5-HT level does not precipitate in
depressive phenotype in healthy individuals
14. Glutamate
TheoryofDepression
• Increased plasma glutamate level in
depression (Altamura et al)
• Ketamine and mGlu2/3 R antagonist -
antidepressant
• 5-HT1A R stimulation by ketamine &
mGlu2/3 R antagonist (Fukumoto et al,
2014)
17. Glutamatergic theory
Mechanism of action of
Ketamine
AMPA-R activation
mTOR signalling pathway
activated in prefrontal cortex
GluR1, Synapsin, spine density
Synaptogenesis
BDNF translation
Kavalali, 2012
18. Glutamate system also has antidepressant
effect
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19. GABA
TheoryofDepression
• Overlapping anxiety and depression circuit (kalueff, 2007)
• GABA implicated in SSRI action (Mohler, 2012)
• Alteration of GABA-A R in depression (Fatemi, 2013)
20. 5HT1A & 5HT2A/2C receptors in depression
5HT1A R
•5HT-1a R agonists (8-OH-DPAT) produce antidepressant like
effect (Cryan, 2005).
•5HT-1A auto-receptor desensitize with antidepressant drugs.
•Presynaptic 5HT1A R (autoreceptor): risk for depression
•Postsynaptic 5HT1A R : produce antidepressant effect
•5HT-1A R mediates ketamine effect (Fukumoto et al, 2014)
5HT2A R
• Antidepressant drugs block 5-HTA R mediated responses
(Celada et al, 2004)
• Treatment with 5-HT2A/2C R agonist DOI caused increase
release of glutamate in the cortex blocked by pretreatment
with 5HT2A R antagonist (Scruggs, 2003)
21. Objective of the experiment
Investigation of the effect
of 5-HT1A agonist and 5-
HT 2A/2C agonist on m-
RNA expression of
AMPA-R (GluR1, GluR2,
GluR3,GluR4), GABA-
Aα1 and BDNF
22. 5HT 2A/2C agonist
5HT,BDNF
Group II mGluR
antagonist
NMDA-R antagonist
AMPA-R activation
mTOR signaling BDNF,
Synaptogenesis
Antidepression
GABA-A R
5HT1A agonist
Mechanism of Depression
23. Experiment
m-RNA expression of GluR1, GluR2,
GluR3, GluR4, BDNF, GABA-A R
5-HT 1A agonist
(8-OH-DPAT)
5-HT 2A/2C agonist
(DOI)
26. Drug Addition: Serotonin Agonist
8-OH-DPAT and DOI at 4 different concentrations
8-OH DPAT
(0 nM)
8-OH DPAT
(1nM)
8-OH DPAT
(10nM)
8-OH DPAT
(100nM)
DOI
(0 nM)
DOI
(1 nM)
DOI
(10 nM)
DOI
(100 nM)
After 4 hours
39. Conclusion • Decreased mRNA expression
of GluR1 and increased
mRNA expression of GluR2
by 8-OH-DPAT
• Decreased mRNA expression
of GluR3 and BDNF by 8-OH-
DPAT
• Increased mRNA expression
of GluR3 and BDNF by DOI
• No amplification of GluR1,
GluR2, GluR4, GABA-Aα1.
SHORTFALLS
• Manual error ?
• defective primers ? (>1 year)
• cDNA of HT-22 cells got
modified.Interaction between
GluR and cDNA of HT22 cells
