1. Nanxin Li, et al. Science 329, 959 (2010) R1 黃泰翰 V.S. 洪成志2010.09.21
mTOR-Dependent Synapse Formation Underlies the Rapid Antidepressant Effects of NMDA Antagonists
Nanxin Li, et al.
Science 329, 959 (2010)
R1 黃泰翰 V.S. 洪成志

2. Ketamine Antagonist of Glutamate NMDA receptor
analgesia, anesthesia, sedation
Psychological effects similar to phencyclidine (PCP)
Dissociative state
Hallucination
Schizophrenia like symptoms

3. Behavior model of depression
Despair
Forced Swim Test (FST)
Learned hopelessness(LH)
Anxiety
Novelty-Suppressed Feeding Test (NSFT)

4. Forced Swim Test (FST) 1st swim for 15 mins - 24 hrs later
drug treatment - 24hrs later
2nd swim for 5 mins
Duration of Immobility

5. Learned-Helplessness (LH)
Inescapable footshock (IES)
60 footshocks,
duration: 15 s,
intershock interval: 60 s
-24hrs- drug treatment -24hrs-
Active avoidance testing
30 trials of escapable footshock
duration: 35s
Number of escape failure recorded

6. Novelty-Suppressed Feeding Test (NSFT)
food-deprived for 24hrs
placed in an open field
76.5 cm X 76.5 cm X 40 cm
food in the center
latency to feed

7. A Randomized Trial of an NMDA Antagonist in Treatment-Resistant Major Depression
Placebo controlled, double-blinded trial
18 subjects with treatment refractory MDD
A single low dose of Ketamine (0.5mg/Kg)
C. A. Zarate Jr. et al., Arch. Gen. Psychiatry 63, 856 (2006).

8. Ketamine
Signaling Pathway?
Anti-depression
effects

10. mTOR Signaling Pathway
Mammalian target of rapamycin
Rapamycin = Sirolimus
Immunosuppresant
Ubiquitous
Protein kinase
translation regulation
S6K
4E-BP

11. Translation Regulation
Protein Synthesis
Translation from mRNA
Initiation, elongation, termination
Regulation
eIF (eukaryotic initiation factor)
eEF
Ribosome

12. S6K 4E-BP S6K phosphorylates ribosomal protein S6,
component of the small, 40S ribosomal subunit.
4E-BP
eIF4E binding protein

15. Methods Ketamine Measurement Synaptoneurosome in Prefrontal Cortex
intraperitoneal injection
Measurement
Synaptoneurosome in Prefrontal Cortex

16. Ketamine (ip) induce transient, dose-dependent mTOR signaling in synaptoneurosome of PFC
10 mg/Kg
1 hr

17. ECS
Electroconvulsive seizure, imipramine, or fluoxetine did not significantly influence mTOR signaling
Chronic (21D)
Acute (1hr)

18. Ketamine
4E-BP
mTOR
S6K

20. mTOR and growth factor signaling pathway
MAPK/ERK cascade
Extracellular signal–regulated kinase
Mitogen-activated protein kinase
MAP3K -> MAP2K -> MAPK
Akt/PKB pathway
PI3K -> PDK -> Akt
C. A. Hoeffer, E. Klann, Trends Neurosci. 33, 67 (2010)

21. Ketamine transiently and dose-dependently increases pERK & pAkt
1 hr
10 mg/Kg
Ketamine transiently and dose-dependently increases pERK & pAkt

22. Pretreatment (30 mins before Ketamine): U0126 (20 nmol, ICV): inhibitors of ERK LY (20 nmol, ICV): inhibitor of PI-3k/Akt

23. Ketamine
ERK, Akt
mTOR
4E-BP
S6K

24. Glutamate receptor Ionotropic Glutamate receptor
NMDA receptor
AMPA receptor
Kainate receptor
Metabotropic Glutamate receptor

25. Antidepressant actions of ketamine & AMPA receptor
Glutamate AMPA receptor
NBQX
a selective AMPA receptor inhibitor
it attenuate the reduction in immobility time induced by ketamine
Pretreatment (10 min before Ketamine) with NBQX (10 mg/kg, ip)
S. Maeng et al., Biol. Psychiatry 63, 349 (2008).

26. NBQX blocked ketamine activation of mTOR signaling and upstream ERK & Akt

27. Ketamine
AMPA
ERK, Akt
mTOR
4E-BP
S6K

29. mTOR and synaptic protein synthesis
Presynaptic protein:
Synapsin I
Postsynaptic proteins:
PSD95, GluR1
Arc:
activity-regulated cytoskeletal-associated protein
C. A. Hoeffer, E. Klann, Trends Neurosci. 33, 67 (2010).

30. Ketamine induces intermediate (1-2 hr) but transient increase of Arc
Ketamine induces delayed (2-72 hr) increase of synaptic proteins
Pretreatment (30 min) with a selective mTOR inhibitor, rapamycin (0.2 nmol, ICV) block the effect

31. Synape Formation ?

32. Dendritic spine formation
Y. Yoshihara, M. De Roo, D. Muller, Curr. Opin. Neurobiol. 19, 146 (2009).

33. Spine density analysis
Layer V Pyramidal Cell in PFC
Tips of tuft branches approaching the pial membrane
Proximal tuft dendrites just distal to the bifurcation
Density
Head diameter
Length

34. ketamine increased spine density in distal and proximal segments of the apical tuft

36. Head diameter
Spine length

38. Excitatory postsynaptic current (EPSC)
Apical dendrites of Layer V pyramidal cells in mPFC
5-HT and Hypocretin Increase EPSCs
Restraint stress
5-HT and hypocretin-induced EPSCs decreased
Apical tuft dendritic branch length and spine density decreased
R. J. Liu, G. K. Aghajanian, Proc. Natl. Acad. Sci. U.S.A. 105, 359 (2008).

39. EPSC measurement

43. Rapamycin was infused (0
Rapamycin was infused (0.2 nmol, ICV) 30 min before ketamine (10 mg/kg, ip)
Rapid behavioral actions of ketamine require mTOR signaling

44. Infusion of rapamycin (0
Infusion of rapamycin (0.01 nmol) into the mPFC blocked the antidepressant actions of ketamine (10 mg/kg, ip) in the FST and NSFT

45. Pretreatment with inhibitors of
ERK (U0126, 20 nmol, ICV) or
PI3 kinase / Akt (LY294002, 20 nmol, ICV)
block of ketamine effects in FST and NSFT

46. Learned helpless with Inescapable Shock (IES)
Synapsin I, PSD95 and GluR1
Ketamine given 24hr after IES
Tissue collected 24 hr after ketamine
Single dose of ketamine reverse this effect
Pretreatment with rapamycin (ICV, 30 min before) block ketamine effect

47. Dose-dependent ketamine antidepressant action
FST
Low dose
10 mg/kg
high anesthetic dose
80 mg/kg
Similar with dose of ERK, Akt, and mTOR induction

48. Ketamine for Depression ?
Risk of abuse and adverse effects Ro
selective NMDA receptor subunit 2B (NR2B) antagonists
NMDA Receptor = 2 NR1 + 2 NR2
NR1: 8 subtype
NR2: 4 subtype
NR2A, NR2B, NR2C, NR2D

49. Ro 25-6981 produced rapid (24 hr before), dose-dependent antidepressant action in the FST

50. Pretreatment with rapamycin (0
Pretreatment with rapamycin (0.2 nmol, ICV) abolished the actions of Ro (10 mg/kg, ip) in FST and NSFT

51. mTOR signaling ERK and Akt signaling synaptic proteins
4E-BP1, p70S6K, mTOR
ERK and Akt signaling
synaptic proteins
Arc,
PSD95, GluR1, synapsin I

52. Conclusion Rapid antidepressant actions of ketamine
Fast activation of mTOR signaling in PFC
Rapid and sustained elevation of synapse associated proteins and spine number
Elevated 5-HT neurotransmission

53. Discussion
Rapid antidepressant therapy
mTOR signal pathway

54. Thank you for listening !