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Study leader: Prof. B.H. HarveyAssisting study leader: Dr. M. Möller-WolmaransCollaborators: Dr. G. WegenerM.Sc. Student: Dewald E. Coutts
Behavioral, neuroendocrine and neurochemical
studies on agomelatine in social isolation reared rats
Depression
INTRODUCTION
Depression – not a single neurotransmitter disorder, but represents a continuum of environmental, genetic and neurochemical determinants that occupy a distinct role.
Chronic psychosocial & environmental stressors play a role in development.
Many overlapping symptoms as well as biological mechanisms characterize mood disorders.
There are many promising hypothesis of depression and antidepressant action:
Harvey et al., 2008; Fone & Porkess, 2008
INTRODUCTION
Hypothesis
Monoamines Neurotrop
hic factors
HPA-axis & corticoster
oneGABA-glutam
ate signalin
g
Circadian
rhythms
Oxidative stress & Immune-inflammat
ory dysfunctio
n
INTRODUCTION
The monoamine hypothesis:
Postulates that depression is caused by deficits in monoamine function (5-HT, NA & DA).
Deficits may be restored by MAOI’s, TCA’s and SSRI’s.
Clinical evidence suggests that serotonergic ADs are less effective. SSRI’s induce cognitive and emotional blunting with improvements in anhedonia often the last group of symptoms to remit.
Berton et al., 2006; Krishnan et al., 2008; Machado-Vieira et al., 2009
Watson & Breedlove
INTRODUCTION
Neurotrophin hypothesis: BDNF
Stress decreases BDNF in the hippocampus and dentate gyrus partly due to glucocorticoid release and partly other mechanisms such as an increase in serotonin and glutamate transmission.
Evidence linking BDNF and depression has been obtained from studies
Nestler et al., 2002; Harvey et al., 2003; Savitz & Drevets 2009; Naert et al., 2011
INTRODUCTION
BDNF
Stress Increased activity of the HPA-axis
Production of inflammatory cytokines
Increased secretion of glucocorticoids
Atrophy & death of neurons
Nestler et al., 2002; Harvey et al., 2003
STRESS
BDNF
Sprouting of 5-HT fibers, accelerate regrowth
Modifies HPA-axisNaert et al., 2011; Souêtre et al., 1989Hsiao et al., 2010; Doane et al., 2013
INTRODUCTIONCircadian rhythm hypothesis:
80 % of depressed patients suffer from insomnia.
It clear that altered circadian rhythm is a core biological manifestation of depression and neuroendocrine abnormalities.
These alternations in cortisol secretion have been related to HPA-axis hyper-activity.
The nucleus accumbens, amygdala and certain hypothalamic nuclei are critical in regulating circadian rhythms and are abnormal in depressed patients
Soria & Urretavizcaya, 2009; McClung, 2013
Recovered ControlDepressed
Sleepperiod
7 911131517192123 7 9 1113531
37.2
37.0
36.8
36.6
36.4
36.2
36.0
BODY TEMPERATURE (°C)
20
40
60
80
100
6 9 12 15 18 21 24 3 6 9
Sleep
PLASMA MELATONIN(pg/ml)
Clock Time
PLASMA CORTISOL(ng/ml)
Sleep
20
70
120
170
220
6 9 12 15 18 21 24 3 6 9
Circadian rhythms in depression
Souetre E. et al Am J Psychiatry. 1988; 145:1133-7
Reduced amplitude
Phase shifted
Clock Time Clock Time
Melchitzky et al., 2010
INTRODUCTION
HPA-axis hypothesis:
Activation of the HPA-axis is a mechanism by which the brain reacts to acute and chronic stress and is controlled by the hippocampus and amygdala.
What is especially relevant is that elevated levels of glucocorticoids under prolonged and severe stress may damage hippocampal neurons and explains hippocampal shrinkage
Nestler et al., 2002; Savitz & Drevents, 2009
INTRODUCTION
Hippocampus Hypothalamus
Anterior Pituitary
Adrenal Cortex
Cortisol
CRH
ACTH
Immune system
Thyroid
T3
T4
TRH
TSH
BDNF reducedNeurogenesis
reduced
Nestler et al., 2002; Savitz & Drevets, 2009
INTRODUCTION Immune-inflammatory hypothesis: Immune-inflammatory dysfunction and oxidative stress
are important components in depression and are known to evoke monoaminergic changes.
Changes in nitric oxide-cyclic guanosine monophosphate, altered kynurenine metabolism are known pro-oxidative mechanisms.
Ng et al., 2008; Garcia-Cazorla et al., 2008; Maes et al., 2011; Wegener et al., 2010; Dhir & Kulkarni, 2011; Von Gall et al., 2002
Monoamines
Trophic factors: (BDNF)
Exitotoxicit
y: Glutamate
Inflammation
IDOTRP
QUIN
KYNANeuro
degenerative Neuro
ProtectiveNMDA-
Ragonist NMDA-R
antagonist
Stressful
stimulus
Glutamate release
Pro-inflammat
ory cytokines
NOS-activation
Accumulation of nitrosactive/oxidative mediators
O-
H2O2 2H2
O
SOD
GSH-Px
NO ONNO-
GSH GSSHStructure damage
LPxMDA-relea
se
Ng et al., 2008; Garcia-Cazorla et al., 2008; Maes et al., 2011; Wegener et al., 2010; Dhir & Kulkarni, 2011; Von Gall et al., 2002
AGOMELATINE
Primary node of action
Mechanism
Anxiolytic
Devoid of 5-HT side effects
C Munoz, Servier; Banasr et al., 2006; Racagni et al., 2011
MT1MT2
5-HT2C
The Biological Clock
Mignot E. et al. Nat Neurosci. 2002; 5:1071-5 Turek FE, et al. Arch Neurol. 2001.
Biological, physiological, and behavioral parameters
Suprachiasmatic nuclei (SCN)(Anterior hypothalamus)
SCN 5HT PVN Pineal
Retina
Sleep regulating centreseg. RN, dl-hypothal
Peripheral clocks
Melatonin
Other zeitgebers, egwork schedules
AGOMELATINE These actions have a fundamental effect on frontal cortical
function and as a result on all contributing factors of depression.
Beneficial effects can be attributed to its fronto-cortical DAergic properties and lack of 5-HTergic actions.
Banasr et al., 2006; Racagni et al., 2011; C. Munoz, Servier; Sansone & Sansone. 2010
RECEPTORS The expression of 5-HT2C and MT1 receptors also show a diurnal
rhythmicity in the SCN & HPC. SCN targets in the hypothalamus modulates brain stem monoamine nuclei.
This implying that monoamines are indirectly affected by changes in the SCN.
MT1 & MT2
Hardeland et al., 2011; Millan et al., 2003; De Barardis et al., 2011; Tardito et al., 2012; Racagni et al., 2011; McClung, 2013; Harvey & Slabbert ,2014
Stahl SM. Circuits in Psychopharmacology. In: Stahl’s Essential Psychopharmacology. Neuroscientific Basis and Practical Application. C Cambridge University Press, Cambridge. Third Edition 2008.Chapter 7:195-222.
ANIMAL MODELS Exposing humans or animals to early-life adverse events, such
as maternal separation or isolation, profoundly affects brain development and leads to psychiatric disorders.
The use of animal models: Animal models are needed to identify new drug targets, and in
evaluating causative or mechanistic hypotheses regarding depression.
Early-life SIR of rat pups is known to produce late-life bahavioral and biological changes with the neurodevelopmental hypothesis of depression.Face
validityConstruct
validityPredictive
validityReproduces
clinical symptoms
Theoretical rational
regarding illness
Predict a given response
Fone & Porkess 2008; Pryce & Klause, 2013; Toua et al., 2010; Möller et al., 2011; Möller et al., 2013a
ANIMAL MODELS
SIR Model
Reversed with an AD and an antipsychotic
Behavioral level: Neurophobia Aggression Cognitive rigidity Impaired
sensorimotor + social interaction
Neuro-biological level: Reduced PFC volume Decreased cortical &
hippocampal synaptic plasticity
Monoaminergic deficits
Möller et al., 2013a,b; Giannantonio & Martinotti, 2012
ANIMAL MODELS
In our hands this model demonstrated excellent validity for modeling the neurobiology and behavioral profile for schizophrenia, while other laboratories have established its relevance for depression.
To the best of our knowledge, the ability of agomelatine to reverse SIR-induced bio-behavioral changes has not been undertaken.
Möller et al., 2013a, 2013b; Heidbreder et al., 2000
MY PROJECT
MY PROJECT
Biological rhythms
Immune-inflammatory
Redox-, Resilience
pathways
SIR Behavioral, Endocrine Neurochemi
cal analysisAgomelati
ne
RESEARCH PROBLEM
Antidepressant efficacy is disappointing – 55-60% effective
Treatments have restricted actions on monoaminergic systems.
Circadian rhythm plays a major role to ensure optimal functioning.
Therapeutic target in mood disorders = disrupted circadian rhythm
Optimal AD treatment should act as a resynchronizer
Agomelatine's action involves resynchronizing of circadian rhythms (via regulation of 5HT vs. melatonergic activity in SCN) plus a direct effect on frontal NA/DA release (via 5HT2c antag) plus an indirect action by modifying monoamine release in brain stem (via re-entrainment of biological rhythms). However the exact actions still requires clarification
Melatonin is an antioxidant with recent clinical evidence suggesting the same for agomelatine.
Nestler et al., 2002; Mairesse et al., 2012; Morley-Fletcher et al., 2011; Molteni et al., 2013
AIMS & OBJECTIVES
Face Validity Construct validity
Predictive validity
Reversal of behavioral, neuroendocrine and neurochemical disturbances with antidepressant
• Agomelatine
Monoamine disturbances
Dyregulation of the HPA-axis (corticosterone)
Oxidative stress & Immune-inflammatory dysfunction
Altered kynurenine metabolism
Cognitive changes
Anhedonia
Anxiety Depressive-like
behaviour
How the above actions of agomelatine compares to that of melatonin (MT1 & MT2 agonist) and S32006 (5-HT2C antagonist). And reversing agomelatine’s effects with a melatonin antagonist or
worsening the manifestations.
RESEARCH METHODOLOGY:
ANIMALS
Male Sprague-Dawley rats (300-350g; Vivarium, North West University) randomly allocated to groups – 12 rats/group
PND 21 the animals will be randomized to SIR (1 animal/cage) or social rearing (3-4 animals/cage) for 8 weeks
Animals will be handled according to the code of ethics in research (ethical approval will be obtained for this study).
Möller et al., 2013a
RESEARCH METHODOLOGY:
DRUG TREATMENT
All drugs will be of the highest grade provided by Servier.
Drug treatment will take place during the final 14 days of rearing:
Treatment will be given s.c. at 16h00 in the afternoon.
Treatments
Chronic Agomeltine
40mg/kg
Chronic S32006 (5-HT2C
antagonist)10mg/kg
Chronic Melatonin40mg/kg
Chronic S22153 MT1 & MT2 antagonist20mg/kg
Möller et al ., 2012a; Möller et al., 2013a; Molteni et al., 2013; Schmelting et al., 2014; C Munoz, Servier; Norman et al., 2012; Papp et al., 2010; Mairesse et al., 2012
RESEARCH METHODOLOGY:
STUDY DESIGN
6 Weeks
11 12 13 14
PND 21
Treatment period: 14 days
Expt 1
Behavioral studies
SIR group
Social group
Behavioral Studies
FST & OFTSPT NO
R
RESEARCH METHODOLOGY:
STUDY DESIGN
14
Neurochemical and Neuroendocrine studies
12 Rats per groupThus 240 rats in total
PND 21
6 Weeks
Treatment period: 14 days
Expt 2Neuroendocrine & neurochemical studies
Social group
SIR group
RESEARCH METHODOLOGY:BEHAVIORAL STUDIES
Beh
avio
ral
Stud
ies
Sucrose Preference
TestAnhedonia
Novel Object Recognition
Cognitive impairment
Open Field Test
Forced Swim Test
Depressive-like
symptoms & Anxiety
Möller et al., 2013; Harvey et al., 2010; Lieberberg et al., 2010
RESEARCH METHODOLOGY:BEHAVIORAL STUDIES
Assessment of anhedonia:This is a significant component of depression. Anhedonia will be assessed using the sucrose preference test (SPT) on day 11 & 12.
• Beginning of test, animals will be singly housed for 48h. • 2 Bottles will be available in each cage (200ml sucrose &
200ml tap water)
Preferences will be measured as follows:• Sucrose consumption• Water consumption• Total liquid (sucrose & water)
At the end of the 48h, the bottles will be removed, consumption noted and the animals returned to their previous housing conditions.
Brenez Sáenz, Villagra & Fornaguera Trias, 2006
RESEARCH METHODOLOGY:BEHAVIORAL STUDIES
Cognitive assessmentNovel object recognition will be evaluated on day 13 as an expression of declarative recognition memory.
• Rats will be exposed to a 5-min habituation session in the NOR box, followed by experimental trails where each rat will be exposed to 2 identical objects for 5 min.
• Rats will be returned to their home cages for a 1.5h inter-trail interval.
• Box will be cleaned, both items removed and replaced with 1 identical familiar object and a novel unfamiliar object.
10cm
10cm 10cm
10cm 10cm
10cm 10cm
10cm
RESEARCH METHODOLOGY:BEHAVIORAL STUDIES
Open field test (OFT):Test will be used to measure locomotor and anxiety activity which is a parameter used to test the general ability of the animal to move and negotiate its surrounding.
On the day of testing, rats will be placed in the OFT arena and allowed to explore the arena for 5min under low light. During this time the rat is video-taped.
Scoring: Total number of lines crossed during the session will be used as a measure of general activity, while the number of entries into the central square of the arena will provide a measurement of anxiety-like behavior.
RESEARCH METHODOLOGY:BEHAVIORAL STUDIES
Assessment of depressive-like symptoms:These symptoms will be assessed using the forced swim test (FST) on day 14. On the penultimate day of treatment, 1.e. 24h prior to the final swim test, the rats will be placed in a room to habituate for 60min after which they will be subjected to 15min of pre-swimming in transparent Perspex cylinders (30cm (d) x 40cm (h)) containing 30cm of clean water (25 ˚± 2C).
Final day of treatment, after 20min habituation in thetest room the rats will be assessed in an open field arena to determine locomotor activity.
1h later the rats will be reintroduced to the cylinders fortheir final 5min swim test.
Immobility, climbing, diving and swimming behaviorswill be recorded.
RESEARCH METHODOLOGY:BLOOD COLLECTION
After decapitation, trunk blood will be collected in pre-chilled, 4ml vacutainer tubes, plasma stored at -80 ˚C until the day of analysis.
Peri
pher
al &
N
euro
endo
cri
ne
Corticosterone ELISA Kit
Tryptophan, Kynurenine, KYNA, QA
Validated LCMS
methodSuperoxide dismutase ELISA Kit
Harvey et al., 2006; Möller et al., 2011; 2012b
RESEARCH METHODOLOGY:BRAIN DISSECTION
The brain regions will be snap frozen in liquid
nitrogen and stored at -80 º C until the day of analysis.
Molteni et al., 2013; Toua et al., 2010; Racagni et al., 2011; Paxinos & Watson, 2010; Davidson et al., 2009
RESEARCH METHODOLOGY:BRAIN DISSECTION
Bra
in
diss
ectio
n Reduced vs. oxidized glutathione analysis
Quantification using a LCMS method
Monoamine analysis5-HT, DA, NA and
their metabolites will be analysed using a
HPLC method
Lipid peroxidation analysis
Will be determined by thiobarbituric acid
(TBA) assay.Data will be expessed
as pmol malonialdehyde
formed/mg proteinMöller et al., 2011; 2013a; Harvey et al., 2008
STATISTICAL ANALYSIS:
Statistical analysis will be done with Graphpad Prism 11; SPSS® Software, under supervision of NWU statistical consultation.
Three or two-way ANOVA with Bonferroni post-hoc test will be used to model the body weight, behavioral, blood and neurochemical measurements.
Möller et al., 2013
EXPECTED OUTCOMES
We propose the following outcomes:
1. SIR will induce profound depressive-like symptoms:• Deficits in cognition• Elevated Anxiety• Anhedonia Agomelatine will reverse these symptoms The melatonin agonist may reverse some manifestations
(maybe anxiety) while the melatonin antagonist will worsen the symptoms.
The 5-HT2C antagonist may improve congnition.
2. SIR will present with elevated plasma corticosterone levels
Agomelatine will reverse this effect. Melatonin and the 5-HT2C antagonist will not reverse this
effect. Melatonin antagonist may elevate corticosterone levels.
EXPECTED OUTCOMES
3. SIR will induce reduced regional brain monoamines akin to depression
That will be reversed by agomelatine. That will not be reversed by melatonin That may be partly reversed by the 5-HT2C antagonist. The melatonin antagonist will not reverse this effect, but
worsen this reduction.
4. SIR will induce immune-redox changes: elevated QUIN, regional brain lipid peroxidation and reduced KYNA, SOD activity, and GSH:GSSG ratio, akin to depression
That will be reversed by agomelatine That will not be reversed by melatonin or the 5-HT2C
antagonist. That will be worsened by a melatonin antagonist.
TIME LINE
June 2014 Presentati
on of study and approval
Sept/Oct 2014 Behaviora
l study commences
Jan/Feb 2015 Blood &
neurochemical study commences
July-Oct 2015 Data
analysis & writing up of dissertation
Nov 2015 Submit
dissertation
July 2014 Submissio
n of ethics application
FUNDING
Study will be financed by: NRF & MRC funding awarded to BHH Cost of all drugs will be carried by Servier, Paris,
France.
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