We report that the oxytocin-mediated neuroprotective γ-aminobutyric acid (GABA) excitatory-inhibitory shift during delivery is abolished in the valproate and fragile X rodent models of autism. During delivery and subsequently, hippocampal neurons in these models have elevated intracellular chloride levels, increased excitatory GABA, enhanced glutamatergic activity, and elevated gamma oscillations. Maternal pretreatment with bumetanide restored in offspring control electrophysiological and behavioral phenotypes. Conversely, blocking oxytocin signaling in naïve mothers produced offspring having electrophysiological and behavioral autistic-like features. Our results suggest a chronic deficient chloride regulation in these rodent models of autism and stress the importance of oxytocin-mediated GABAergic inhibition during the delivery process. Our data validate the amelioration observed with bumetanide and oxytocin and point to common pathways in a drug-induced and a genetic rodent model of autism.

Epileptic encephalopathies are severe brain disorders with the epileptic component contributing to the worsening of cognitive and behavioral manifestations. Acquired epileptic aphasia (Landau-Kleffner syndrome, LKS) and continuous spike and waves during slow-wave sleep syndrome (CSWSS) represent rare and closely related childhood focal epileptic encephalopathies of unknown etiology. They show electroclinical overlap with rolandic epilepsy (the most frequent childhood focal epilepsy) and can be viewed as different clinical expressions of a single pathological entity situated at the crossroads of epileptic, speech, language, cognitive and behavioral disorders. Here we demonstrate that about 20% of cases of LKS, CSWSS and electroclinically atypical rolandic epilepsy often associated with speech impairment can have a genetic origin sustained by de novo or inherited mutations in the GRIN2A gene (encoding the N-methyl-D-aspartate (NMDA) glutamate receptor α2 subunit, GluN2A). The identification of GRIN2A as a major gene for these epileptic encephalopathies provides crucial insights into the underlying pathophysiology.

Synaptic vesicle fusion in brain synapses occurs in phases that are either tightly coupled to action potentials (synchronous), immediately following action potentials (asynchronous) or as stochastic events in the absence of action potentials (spontaneous). Synaptotagmin-1, -2 and -9 are vesicleassociated Ca 2+ -sensors for synchronous release. Here we found that Double C2 domain (Doc2) proteins act as Ca 2+ -sensors to trigger spontaneous release. Although Doc2 proteins are cytosolic, they function analogously to synaptotagmin-1 but with a higher Ca 2+ -sensitivity and superior in vitro fusion-efficiency. Doc2 proteins bound to SNARE-complexes in competition with synaptotagmin-1. Thus, different classes of multiple C2 domain-containing molecules trigger synchronous versus spontaneous fusion, which suggests a general mechanism for synaptic vesicle fusion triggered by the combined actions of SNAREs and multiple C2 domain-containing proteins.Neurotransmitter release is triggered by a rise in intracellular Ca 2+ , which activates sensors that subsequently trigger vesicle fusion. Synchronous release, the fastest mode of neurotransmission, involves the Ca 2+ sensors synaptotagmin-1, -2 or -9 which are anchored in the vesicle membrane and contain two cytoplasmic C2 domains that bind phospholipids in a Ca 2+ -dependent manner and interact with the soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) complex (1-5). Synaptotagmin-1-deficient neurons lack synchronous release but display an increase in spontaneous release (6-9) except in autapses (1, 10), suggesting a distinct mechanism for spontaneous release. Spontaneous release occurs in the absence of action potentials and is largely Ca 2+ -dependent (12-16), although truly Ca 2+ -independent fusion may also exist (11). Doc2a and Doc2b are soluble proteins that contain C2 domains with high similarity to synaptotagmins (17). They are expressed in nerve terminals and interact with the secretory * To whom correspondence should be addressed. sander.groffen@cncr.vu.nl and sascha.martens@univie.ac.at.. 3 current address: Max F. Perutz Laboratories, University of Vienna, Dr. Bohr-Gasse 9/3, Austria 8 These authors contributed equally to this work The authors declare no conflicting interests. Europe PMC Funders Group Role of Doc2b and Ca 2+ in spontaneous synaptic releaseWe generated Doc2b −/− mice by deleting the promoter and exon 1 of the Doc2b gene ( fig. S1) (23). Doc2b −/− mice did not express the remaining exons and lacked Doc2b immunoreactivity. Doc2b −/− mice were viable and fertile without gross abnormalities. Other proteins implicated in neurotransmitter secretion were expressed at normal levels ( fig. S1D).Compensatory ectopic expression of Doc2a was not detected in Doc2b-deficient brains by in situ hybridization and the Doc2a protein level was unchanged ( fig. S1). Doc2a −/− Doc2b −/− double knock-out (DKO) mice were also viable, fertile and indistinguishable with regard to gross anatomy. To study neurotransmission and synaptic plasticity ...

No abstract

In conditions of facilitated synaptic release, CA3/CA1 synapses generate anomalously slow NMDA receptor-mediated EPSCs (EPSC(NMDA)). Such a time course has been attributed to the cooperation of synapses through glutamate spillover. Imitating a natural pattern of activity, we have applied short bursts (2-7 stimuli) of high-frequency stimulation and observed a spike-to-spike slow-down of the EPSC(NMDA) kinetics, which accompanied synaptic facilitation. It was found that the early component of the EPSC(NMDA) and the burst-induced late component of the EPSC(NMDA) have distinct pharmacological properties. The competitive NMDA antagonist R-(-)-3-(2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid (D-CPP), which has higher affinity to NR2A than to NR2B subunits and lowest affinity at NR2D subunits, significantly slowed down the decay rate of the afterburst EPSC while leaving the kinetics of the control current unaffected. In contrast, ifenprodil, a highly selective NR2B antagonist, and [+/-]-cis-1-[phenanthren-2yl-carbonyl]piperazine-2,3-dicarboxylic acid (PPDA), a competitive antagonist that is moderately selective for NR2D subunits, more strongly inhibited the late component of the afterburst EPSC(NMDA). The receptors formed by NR2B and (especially) NR2D subunits are known to have higher agonist sensitivity and much slower deactivation kinetics than NR2A-containing receptors. Furthermore, NR2B is preferentially and NR2D is exclusively located on extrasynaptic membranes. As the density of active synapses increases, the confluence of released glutamate makes EPSC decay much longer by activating more extrasynaptic NR2B- and NR2D-subunit-containing receptors. Long-term potentiation (LTP) induced by successive rounds of burst stimulation is accompanied by a long-term increase in the contribution of extrasynaptic receptors in the afterburst EPSC(NMDA.)

Tuberous sclerosis complex (TSC), caused by dominant mutations in either TSC1 or TSC2 tumour suppressor genes is characterized by the presence of brain malformations, the cortical tubers that are thought to contribute to the generation of pharmacoresistant epilepsy. Here we report that tuberless heterozygote Tsc1+/− mice show functional upregulation of cortical GluN2C-containing N-methyl-D-aspartate receptors (NMDARs) in an mTOR-dependent manner and exhibit recurrent, unprovoked seizures during early postnatal life (

We report that half striatal cholinergic interneurons are dual transmitter cholinergic and GABAergic interneurons (CGINs) expressing ChAT, GAD65, Lhx7, and Lhx6 mRNAs, labeled with GAD and VGAT, generating monosynaptic dual cholinergic/GABAergic currents and an inhibitory pause response. Dopamine deprivation increases CGINs ongoing activity and abolishes GABAergic inhibition including the cortico-striatal pause because of high [Cl−]i levels. Dopamine deprivation also dramatically increases CGINs dendritic arbors and monosynaptic interconnections probability, suggesting the formation of a dense CGINs network. The NKCC1 chloride importer antagonist bumetanide, which reduces [Cl−]i levels, restores GABAergic inhibition, the cortico-striatal pause-rebound response, and attenuates motor effects of dopamine deprivation. Therefore, most of the striatal cholinergic excitatory drive is balanced by a concomitant powerful GABAergic inhibition that is impaired by dopamine deprivation. The attenuation by bumetanide of cardinal features of Parkinson’s disease paves the way to a novel therapeutic strategy based on a restoration of low [Cl−]i levels and GABAergic inhibition.

No abstract