Abstracts / Journal of Physiology - Paris 99 (2006) 245–278 271

doi:10.1016/j.jphysparis.2005.12.064

Popov, V.I., Medvedev, N.I., Rogachevskii, V.V., Ignat’ev, D.A., Stewart,M.G., Fesenko, E.E., 2003. Three-dimensional organization ofsynapses and astroglia in the hippocampus of rats and groundsquirrels: new structural and functional paradigms of the synapsefunction. Biofizika 48, 289–308.

Popov, V.I., Deev, A.A., Klimenko, O.A., Kraev, I.V., Kuz’minykh, S.B.,Medvedev, N.I., Patrushev, I.V., Popov, R.V., Rogachevskii, V.V.,Khutsian, S.S., Stewart, M.G., Fesenko, E.E., 2004. Three-dimensionalreconstruction of synapse and dendritic spines in the hippocampus ofrats and ground squirrels: new paradigms of the structure and functionof a synapse. Zh Vyssh. Nerv. Deiat. Im. I.P. Pavlova. 54, 120–129.

D-Serine and glutamatergic neurotransmission in rat

vestibular system

Julien Puyal b, Jean-Pierre Mothet c, Danielle Dememes d,

Jacqueline Raymond a, Marie-Therese Nicolas a

a Universite Montpellier 2, 34095 Montpellier Cedex 05,

Franceb IBCM, University of Lausanne, Switzerlandc CNRS UPR9040, 91198 Gif-sur-Yvette Cedex, Franced INM, INSERM U583, 34295 Montpellier, France

E-mail address: jraymond@univ-montp2.fr (J. Raymond)

To conduct informations in the vestibular system eitherin the peripheral end organs or in the vestibular nuclei(VN), the main excitatory neurotransmitter is the gluta-mate which can act through ionotropic and metabotropicreceptors. Our previous studies have shown first the timingof the expression of the glutamate receptors during postna-tal development and second, their involvement in develop-mental plasticity.

Recently, it has been demonstrated that D-serine, anamino acid present in mammal central nervous system(CNS) is the endogenous ligand of glycine site of NMDAreceptors. D-Serine works in concert with glutamate to acti-vate post-synaptic NMDA receptors. D-Serine could regu-late these receptors and could participate in synapticplasticity related to LTP. D-Serine is synthetized in astro-cytic glial cells, by serine racemase and degraded by D-amino acid oxidase (DAAO). Therefore, in the vestibularsystem, D-serine could play a role in the maturation ofthe glutamatergic synapse in the VN as well as in theperipheral sensory end organ. By immunocytochemis-try and confocal microscopy, we investigated if D-serine,serine racemase and DAAO are present in the vestibularsystem.

In the peripheral end organs, D-serine is present in thesupporting cells localized on afferent nerve fibers whichaccording to some data, are equivalent to glial cells in theCNS. But D-serine as well as serine racemase and DAAOare also present in transitional cells, which are epithelialcells highly involved in K+ recycling.

In the VN, we established spatiotemporal relationshipsamong D-serine, serine racemase and DAAO during rat

postnatal development. From birth to P21, high levels ofD-serine were detected in glial cells. The drop of D-serinein adult corresponded to an increasing level of DAAO,which has been shown to have a very high concentrationin the brainstem. The levels of D-serine, serine racemaseand DAAO and their immunocytochemical patterns frombirth to adult may indicate that, in the mature VN, glycinemight be an endogenous ligand of NMDA receptors as inthe adult cerebellum. In the immature VN glutamatergicsynapses, activation of NMDA receptors would occurthrough mechanisms involving the release of D-serine fromastrocytes, suggesting a role for astrocytic D-serine inNMDA receptor-mediated synaptogenesis.

doi:10.1016/j.jphysparis.2005.12.065

The carbamates that inhibit acetylcholinesterase

by combined type exhibit a calcium antagonistic activity

and low toxicity

Alexei Redkozubov, Iurii Ivanov

Institute of Physiologically Active Compounds,

Russian Academy of Sciences, Chernogolovka,

142432, Moscow District, Russia

E-mail address: redkozub@ipac.ac.ru (A. Redkozubov)

Two series of carbamates, o-carbamoyl acylhydroxy-moylchlorides and phenyl esters of N-substituted carb-amine acid, have been examined as inhibitors ofacetylcholinesterase as well as calcium antagonists. Thecarbamates from both series inhibited in vitro a partiallypurified acetylcholinesterase (AChE) from human redblood cells. Carbamates of the first series, the N-alkyl-and N,N-dialkylcarbamates of oximes inhibited AChE byprogressive kinetics type while the N,N-methylphenylcar-bamates of this series inhibited AChE by combined type:both with progressive and non-progressive kinetics. Thelatter exhibited calcium antagonistic activity via inhibitionof the Ca2+-induced contraction of the K+-depolarised iso-lated rat ileum preparation as well as by blocking of thevoltage-dependent L-type Ca2+ channels in rat cultured cer-ebellar granule neurons. They had lower acute toxicity onmice and weaker spasmogenic effect on intestine relativeto their high anti-AChE activity; manifesting a paradoxicaltoxic effect at moderate doses. All of the phenyl esters of N-substituted carbamine acid inhibited AChE by both mech-anisms exhibiting Ca2+-antagonistic activity as well. TheCa2+-antagonistic activity of the phenyl esters of N-substi-tuted carbamine acid correlated highly with their efficiencyin inhibiting AChE by non-progressive kinetics but notwith efficacy of the enzyme inhibition with progressivekinetics. It is suggested that one of the carbamate-bindingsites, of both AChE and the Ca2+-channel, may have sim-ilar structure and that the physiological effects of the dou-ble-acting carbamates are based on balance of their efficacy

272 Abstracts / Journal of Physiology - Paris 99 (2006) 245–278

in inhibiting AChE and potency as Ca2+-channel anta-gonists.

Supported by a RFBR grant (# 04-04-49515).

doi:10.1016/j.jphysparis.2005.12.066

Fig. 1. Alteration of synoptic properties by KARAP/DAP 12 mutation.(A) Enhanced LTP in KD75 mice. (B) Diminution of GluR1. GluR2 andTrkB (gp 145) in post-synapic densities.

Regulation of synaptic properties by the microglial protein

DAP12/KARAPAnne Roumier a,1, Catherine Bechade a,1,

Jean-Christophe Poncer b,1, Karl-Heinz Smalla c,

Elena Tomasello d, Eric Vivier d, Eckart D. Gundelfinger c,

Antoine Triller a, Alain Bessis a

a INSERM U497 Ecole Normale Superieure, 75005 Paris,

Franceb INSERM EMI0224 75013 Paris, Francec Leibniz Institute for Neurobiology, Magdeburg, Germanyd Centre d’Immunologie de Marseille, Luminy, France

E-mail addresses: aroumier@wotan.ens.fr (A. Roumier),bechade@wotan.ens.fr (C. Bechade)

Several proteins are expressed in both immune and ner-vous systems. However, their putative non-immune func-tions in the brain remain poorly understood. DAP12/KARAP is a transmembrane polypeptide associated withcell-surface receptors in hematopoeitic cells (Tomaselloet al., 1998). Its mutation in human induces Nasu–Hakoladisease, characterized by presenile dementia and demyelin-ization (Paloneva et al., 2000). Synaptic defects have beenproposed to account for the early onset of some dementia.We thus hypothesized that DAP12/KARAP may impactsynaptic function. In mice deficient for DAP12/KARAPfunction (named KD75), LTP was enhanced (Fig. 1A),and synaptic glutamate receptors were altered withAMPARs being more permeable to calcium. This lastresult was confirmed by biochemical analysis : in mutants,GluR2 expression was decreased only in the post-synapticdensities (PSD) but not in the whole membrane fraction,demonstrating specific impairment of synaptic receptoraccumulation (Fig. 1B). Alteration of BNDF/TrkB signal-ing in mutants was demonstrated by the dramatic decreaseof synaptic TrkB (Fig. 1B), with no change in other regula-tory or scaffolding proteins. This decrease of synaptic TrkBwas also observed by immunocytochemistry in culturedhippocampal neurons. Finally, DAP12/KARAP wasdetected only in microglia at perinatal stages, and neverin neurons, astrocytes or oligodendrocytes.

DAP12/KARAP may thus alter microglial physiology,and subsequently synaptic function and plasticity througha novel microglia–neuron interaction. We are currentlyinvestigating by microarray analysis the factors involvedin this link.

1 These authors contributed equally to the work.

doi:10.1016/j.jphysparis.2005.12.067

Paloneva, J., Kestila, M., Wu, J., Salminen, A., Bohling, T., Ruotsalainen,V., Hakola, P., Bakker, A.B., Phillips, J.H., Pekkarinen, P., Lanier,L.L., Timonen, T., Peltonen, L., 2000. Loss-of-function mutations inTYROBP (DAP12) result in a presenile dementia with bone cysts. Nat.Genet., 25357–25361.

Tomasello, E., Olcese, L., Vely, F., Geourgeon, C., Blery, M., Moqrich,A., Gautheret, D., Djabali, M., Mattei, M.G., Vivier, E., 1998. Genestructure, expression pattern, and biological activity of mouse killercell activating receptor-associated protein (KARAP)/DAP-12. J. Biol.Chem. 273, 34115–34119.

Otoferlin, defective in DFNB9 human deafness, is a synaptic

protein of sensory hair cells involved in exocytosis

Isabelle Roux a, Saaid Safieddine a, Koulm Guillaumie b,Regis Nouvian c, M’hamed Grati a,d, Philippe Rostaing e,

Jean-Pierre Hardelin a, Antoine Triller e, Tobias Moser c,

Francois Darchen b, Christine Petit a

a INSERM U587, Institut Pasteur, Paris, Franceb Institut de Biologie Physico-Chimique Paris, Francec Department of Otolaryngology, University of Gottingen,

Germanyd NIDCD, Bethesda, MD 20892, USAe INSERM U497, Ecole Normale Superieure, Paris, France

E-mail addresses: iroux@pasteur.fr (I. Roux),ssafiedd@pasteur.fr (S. Safieddine)

The molecular components underlying the high tempo-ral precision and sustained neurotransmitter release ofthe auditory inner hair cell (IHC) ribbon synapse are stillunknown. The elucidation of the molecular mechanismsgoverning these functional features is a major challenge,especially as the small number of IHCs in the cochlea pre-cludes the use of standard biochemical and moleculargenetics techniques. Thus, the identification of genes