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MHeNS, School for Mental Health and Neuroscience
Simultaneous Versus Solitary Pharmacological Manipulation of NMDA- and AMPAreceptors: Effects of New Drugs on Contextual Learning and its Extinction
Vignisse JulieA,B, Steinbusch H.W.M.A, Griegoriev V.C, Bettendorff L.B, Bolkunov A.C, Nunes J.D, Bachurin S.C and Strekalova T.A,D
D
CONCLUSIONS
Study design
o A concomitant low affinity NMDA receptor blockade and AMPA stimulation enhance memory
The effects of new drugs on NMDA receptors were studied on isolated cortical neurons that
contained a population of NMDA receptors; NMDA solutions of 1-100 μΜ containing 7 μΜ of
glycine were applied to activate the receptor. The effects of tested compounds on the stimulation of
AMPA receptors were investigated on isolated Purkinje neurons using partial receptor agonist
kainic acid (KA), which induces AMPA-receptor mediated currents while evoking relatively low
receptor desensitization. The effects of IPAC 1-3 and 5, dimebon, positive modulator of AMPA
receptor QXX and memantine on learning were studied in (A) the step-down avoidance task and in
(B) a fear conditioning paradigm. Dimebon has been reported to have pro-cognitive effects in
these models2,4 and was used as an independent positive control.
o Mono-drugs replicate the properties of bifunctional drugs at ten-fold higher doses
o Multi-target memory enhancers have a high potential for clinical implications
BACKGROUND
The development of novel memory enhancers for treating cognitive deficits associated with
neurological and psychiatric disorders remains a primary focus of study in central nervous system
research. Glutamatergic system has been identified as a central element in this purpose. Indeed,
low-affinity blockade of NMDA-receptors or potentiation of AMPA-receptors have been reported to
result in memory enhancement but the administration of many of them presents problems with their
side-effects1. Therefore, developping molecules that combine procognitive effects of NMDA lowaffinity receptor blocker and AMPA positive modulator while decreasing their adverse effects is of the
most importance. Bifunctional drug therapy targeting distinct receptor signalling systems can
generate increased efficacy at lower concentrations compared to monofunctional therapy.
0
(A) Step-down
Avoidance
Administration of
drug or vehicle
0
(B) Extinction
of Fear
Conditioning
+ 15 min
+1h
+ 24 h
Training
Recall
session 1
Recall
session 2
+ 24 h
+ 3 min
+ 10 min
Extinction procedure
Training Recall
Administration
session of drug/vehicle
Recall of
extinction
The present study aimed to compare the mnemotropic potency of molecules that have bifunctional
activity (a concomitant effect on the NMDA- and AMPA–receptors) against monofunctional drugs:
the low-affinity NMDA receptor blocker memantine and the positive AMPA receptor modulator QQX.
New bio-isosteric analogues of MK-801 (IPAC 1-5) were synthesized and designed to have
bifunctional activity. Low-affinity NMDA blockade was achieved by introducing greater flexibility into
the molecule, and AMPA receptor stimulation was produced by introduction of a sulfamidecontaining derivative of isothiourea in the structure. Dimebon, a weak antagonist (IC50=10 µM) of
NMDA-receptor2 and a positive modulator of AMPA receptors at low concentrations (1-20 µM)3, has
revealed memory enhancing properties in in vivo studies2,4 which are suggested to be due to its
interaction with other neuromediatory systems and mechanisms in additional to glutamatergic2.
1) IPAC 5 was used as a drug of superior concomitant effects on
both NMDA and AMPA receptors
(A)
O
N
N
H
H3C
+
H2N
QQX
S N
H3C
CH
NH 3
CH3
N
H2O
N
H
Cl
H3C
N
N
H
S N
H
N
CH3
H3C
CH MeOH, 4050°C
NH 3
CH3
S N
N
CH3
H3C
CH
NH 3
CH3
Non competitive blockade of
NMDA-R
S N
2
(B)
R1-N=C=S
+
R
2
R
N
H
3
Et2O, r.t.
R
1
H
N
S
Potentiation of AMPA-R in %
from control,
dose of maximal effects
and range of effective doses
N
N
H
H
N
CH3
3
H3C
CH
NH 3
CH3
R4Hal
acetone, r.t.
R
1
R
N
N
R
4
S
R
3
IPAC-2-5
[email protected]
www.unimaas.nl/mhens
QXX 5
Dim
IPAC-1
IPAC-2
IPAC-3
IPAC-5
#
#
100
#
*
*
*
50
0
Figure 2. Effects of bio-isosteric analogues of MK-801 on contextual learning in the step-down
avoidance test. Mice treated with memantine at a dose of 5 mg/kg or dimebon or IPAC-5 revealed significant
increase in the latency of step down 1 h (*p<0.05) and 24 h after training (#p<0.05) as compared with
respective control groups, suggesting that the administration of these drugs enhances both short-term and
long-term memories in this task. No such effects were observed in animals treated by memantine at a dose of
1 mg/kg, QXX, IPAC-1, IPAC-2 or IPAC-3. Each column represents the mean ± SEM. Experimental groups:
Con: saline-treated control; DMSO: DMSO-treated control; Mem 1 or 5: memantine (1 mg/kg or 5 mg/kg);
Dim: dimebon (1 mg/kg); QXX- (5 mg/kg), IPAC-1- (1 mg/kg), IPAC-2- (0.5 mg/kg), IPAC-3- (1 mg/kg),
IPAC-5 (0.5 mg/kg)- treated group.
3) IPAC 5 (0.5 mg/kg) and QXX (5 mg/kg), but not memantine
(5 mg/kg) facilitate extinction of contextual memory
(A) Extinction of Contextual Fear Conditioning
80
60
*
40
*
*
20
IPAC-3
Con
IPAC-5
Mod ↓
High ↓↓
High ↑↑
High ↑↑
Mod ↓
Mod ↑
High ↓↓
Mod ↑
1.2±0.15
n.a.
21.4±1.58
3.2±0.47
0.8±0.11
High ↓↓
High ↑↑
0.4±0.07
and
21.2±2.15
n.a.
230%
0.01-0.1 µM
150 %
0.5 µM
148 %
0.5 µM
1050%
30 µM
1.10-5-0.01 µM
0.001– 1.0 µM
0.5 – 1.0 µM
0.02 - 1.0 µM
1.0 – 30 µM
Table 1 : Magnitudes of electrophysiological mono- and bi-functional effects of QXX, Memantine and
new bio-isoteric analogs of MK-801 (IPAC 1-5) on AMPA- and NMDA-receptors. Freshly isolated neurons
from 9-16-day-old rat pups were used for the patch-clamp technique. NMDA-receptor mediated currents were
studied in cortical slices. AMPA-receptor mediated currents were studied in Purkinje neurons of the cerebellum3.
Arrows indicate the effects of drugs on NMDA- and AMPA-receptors: „high‟ (↓↓) or „moderate‟ (↓) blockade and
„high‟ (↑↑) or „moderate‟ (↑) positive modulation.
REFERENCES
1 Gonda, Curr. Pharm Des. 2012;18(12):1558-67.
2 Bachurin & al., Ann N Y Acad Sci. 2001;939:425-35.
3 Grigoriev, Dranyi & Bachurin, Bull Exp Biol Med. 2003;136(5):474-7.
4 Vignisse & al., Prog Neuropsychopharmacol Biol Psychiatry 2011;35(2):510-22.
School for Mental Health and Neuroscience
Div. Neuroscience
T +3143 388 4110
F +3143 367 1096
80
60
40
20
0
Con
210%
0.001 µM
DMSO Mem 5 QXX 1 QXX 5 Dim IPAC-1 IPAC-2 IPAC-3 IPAC-5
(B) Contextual Freezing Before Dosing
100
HHal
Figure 1 : The synthesis of five tested bio-isosteric analogues of MK-801. (A) Routes of synthesis of IPAC-1; (B)
Routes of synthesis of IPAC-2-5 compounds (radicals in the formulas: IPAC-2: R1 = Ph, R2 = Bn, R3 = Me, R4 = Bn, Hal =
Br. IPAC-3: R1 = Bn, R2 = H, R3 = H, R4 = 2-Cyclohexenyl, Hal = Br; IPAC-5: R1 = All, R2 = Bn, R3 = H, R4 = Et, Hal = I).
Correspondence to:
Dr Tatyana Strekalova
IPAC-2
IPAC-1
2
R
Mem 5
150
Potency to affect NMDA and/or
AMPA receptors
Blockade of NMDA–R: IC50 (µM)
Cl
NaBH4
R
N
IPAC-1
Memantine
Cl
CH3
Mem 1
0
Potentiation of AMPA-R
H3C
DMSO
100
RESULTS
Cl
Con
+ 48 h
INTRODUCTION
H3C
200
Percent of time
spent with freezing, s
C
Percent of time spent
with freezing, %
B
B
1h
24
h
B
1h
24
h
B
1h
24
h
B
1h
24
h
B
1h
24
h
B
1h
24
h
B
1h
24
h
B
1h
24
h
B
1h
24
h
B
1h
24
h
Department of Neurosciences, MHeNS, Maastricht University, Netherlands
Bioenergetics And Cerebral Excitability Unit, GIGA-Neurosciences, University of Liege, Liège, Belgium
IPAC, Russian Academy of Sciences, Chernogolovka/Moscow , Russia
Center of Environmental Biology, Faculty of Sciences, Lisbon University, Lisbon, Portugal;
Latency of step down, s
A
2) IPAC 5 (0.5 mg/kg) and Memantine (5 mg/kg), but not QQX
(5 mg/kg) enhance the acquisition of the step-down avoidance
task
DMSO Mem 5 QXX 1 QXX 5 Dim IPAC-1 IPAC-2 IPAC-3 IPAC-5
Figure 3: Effects of bio-isosteric analogues of MK-801 on extinction of contextual freezing in a fearconditioning paradigm. (A) During recall of memory extinction trials, the percentage of time spent in freezing
was decreased in mice treated with QXX at a dose of 5 mg/kg, with IPAC-5 and with dimebon (versus respective
control group, *p<0.05) suggesting that these drugs facilitated fear memory extinction. Groups treated with
memantine (5 mg/kg), QXX at a dose of 1 mg/kg, IPAC-1, IPAC-2, and IPAC-3 showed no changes in freezing
behaviour during a recall of extinction session. (B) During a recall session of fear conditioning, before dosing, all
groups showed similar freezing rates. Each column represents the mean ± SEM. Symbols are as in Figure 2
except for QXX 1 or 5: QQX (1 or 5 mg/kg) - treated group.
AKNOWLEDGEMENTS
This study was supported by Internationale Stichting Alzheimer Onderzoek (ISAO) grant N 09501 to T.S.
(International Foundation on Alzheimer’s disease research, the Netherlands), by the Royal Netherlands
Academy of Arts and Sciences (KNAW) and by the Fonds pour la formation à la Recherche dans l'Industrie et
dans l'Agriculture (FRIA) to J.V. Authors are grateful to Dr Alexei Proshin for providing us new compounds
used in this study.
Maastricht University - address
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