Distortion Correction and Denoising of Light Sheet Fluorescence Images.

Light Sheet Fluorescence Microscopy (LSFM) has emerged as a valuable tool for neurobiologists, enabling the rapid and high-quality volumetric imaging of mice brains. However, inherent artifacts and distortions introduced during the imaging process necessitate careful enhancement of LSFM images for optimal 3D reconstructions. This work aims to correct images slice by slice before reconstructing 3D volumes. Our approach involves a three-step process: firstly, the implementation of a deblurring algorithm using the work of K. Becker; secondly, an automatic contrast enhancement; and thirdly, the development of a convolutional denoising auto-encoder featuring skip connections to effectively address noise introduced by contrast enhancement, particularly excelling in handling mixed Poisson-Gaussian noise. Additionally, we tackle the challenge of axial distortion in LSFM by introducing an approach based on an auto-encoder trained on bead calibration images. The proposed pipeline demonstrates a complete solution, presenting promising results that surpass existing methods in denoising LSFM images. These advancements hold potential to significantly improve the interpretation of biological data.

The Internal Conduit System of the Swine Inverted Lymph Node.

Lymph nodes (LN) are the crossroad where naïve lymphocytes, peripheral antigens and antigen presenting cells contact together in order to mount an adaptive immune response. For this purpose, LN are highly organized convergent hubs of blood and lymphatic vessels that, in the case of B lymphocytes, lead to the B cell follicles. Herein take place the selection and maturation of B cell clones producing high affinity antibodies directed against various antigens. Whereas the knowledge on the murine and human LN distribution systems have reached an exquisite precision those last years, the organization of the antigens and cells circulation into the inverted porcine LN remains poorly described. Using up to date microscopy tools, we described the complex interconnections between afferent lymphatics and blood vessels, perifollicular macrophages, follicular B cells and efferent blood vessels. We observed that afferent lymphatic sinuses presented an asymmetric Lyve-1 expression similar to the one observed in murine LN, whereas specialized perifollicular sinuses connect the main afferent lymphatic sinus to the B cell follicles. Finally, whereas it was long though that mature B cells egress from the inverted LN in the T cell zone through HEV, our observations are in agreement with mature B cells accessing the efferent blood circulation in the efferent, subcapsular area. This understanding of the inverted porcine LN circuitry will allow a more accurate exploration of swine pathogens interactions with the immune cells inside the LN structures. Moreover, the mix between similarities and differences of porcine inverted LN circuitry with mouse and human normal LN shall enable to better apprehend the functions and malfunctions of normal LN from a new perspective.

Substantial outcome improvement using a refined pilocarpine mouse model of temporal lobe epilepsy.

Systemic pilocarpine treatment is one of the most reliable means of inducing temporal lobe epilepsy (TLE). However, the traditional pilocarpine injection protocol using mice was associated with a high death rate, possibly because of cardiorespiratory collapse following status epilepticus (SE). To prevent this, we developed a modified procedure of pilocarpine SE induction, which included a single injection of a moderate dose of caffeine during the induction phase. That new protocol was based on the use of young male mice as well as on a refined Racine's scale. Using that protocol, we report a substantially increased survival rate, thus enabling the generation of a large cohort of mice that exhibited cardinal histological (e.g., mossy fiber sprouting) and electrophysiological (e.g., chronic interictal events and ictal seizures) characteristics associated with TLE. In conclusion, our refined caffeine- and pilocarpine-based protocol substantially improves the outcome of the reliable pilocarpine mouse model of TLE.

A new RNA-DNA interaction required for integration of group II intron retrotransposons into DNA targets.

Mobile group II introns are site-specific retrotransposable elements abundant in bacterial and organellar genomes. They are composed of a large and highly structured ribozyme and an intron-encoded reverse transcriptase that binds tightly to its intron to yield a ribonucleoprotein (RNP) particle. During the first stage of the mobility pathway, the intron RNA catalyses its own insertion directly into the DNA target site. Recognition of the proper target rests primarily on multiple base-pairing interactions between the intron RNA and the target DNA, while the protein makes contacts with only a few target positions by yet-unidentified mechanisms. Using a combination of comparative sequence analyses and in vivo mobility assays we demonstrate the existence of a new base-pairing interaction named EBS2a-IBS2a between the intron RNA and its DNA target site. This pairing adopts a Watson-Crick geometry and is essential for intron mobility, most probably by driving unwinding of the DNA duplex. Importantly, formation of EBS2a-IBS2a also requires the reverse transcriptase enzyme which stabilizes the pairing in a non-sequence-specific manner. In addition to bringing to light a new structural device that allows subgroup IIB1 and IIB2 introns to invade their targets with high efficiency and specificity our work has important implications for the biotechnological applications of group II introns in bacterial gene targeting.

Dentate Granule Cells Recruited in the Home Environment Display Distinctive Properties.

The dentate granule cells (DGCs) play a crucial role in learning and memory. Many studies have described the role and physiological properties of these sparsely active neurons using different behavioral contexts. However, the morpho-functional features of DGCs recruited in mice maintained in their home cage (without training), considered as a baseline condition, have not yet been established. Using fosGFP transgenic mice, we observed ex vivo that DGCs recruited in animals maintained in the home cage condition are mature neurons that display a longer dendritic tree and lower excitability compared with non-activated cells. The higher GABAA receptor-mediated shunting inhibition contributes to the lower excitability of DGCs activated in the home environment by shifting the input resistance towards lower values. Remarkably, that shunting inhibition is neither observed in non-activated DGCs nor in DGCs activated during training in virtual reality. In short, our results suggest that strong shunting inhibition and reduced excitability could constitute a distinctive neural signature of mature DGCs recruited in the context of the home environment.

In Utero Administration of Drugs Targeting Microglia Improves the Neurodevelopmental Outcome Following Cytomegalovirus Infection of the Rat Fetal Brain.

Congenital cytomegalovirus (CMV) infections represent one leading cause of neurodevelopmental disorders. Recently, we reported on a rat model of CMV infection of the developing brain in utero, characterized by early and prominent infection and alteration of microglia-the brain-resident mononuclear phagocytes. Besides their canonical function against pathogens, microglia are also pivotal to brain development. Here we show that CMV infection of the rat fetal brain recapitulated key postnatal phenotypes of human congenital CMV including increased mortality, sensorimotor impairment reminiscent of cerebral palsy, hearing defects, and epileptic seizures. The possible influence of early microglia alteration on those phenotypes was then questioned by pharmacological targeting of microglia during pregnancy. One single administration of clodronate liposomes in the embryonic brains at the time of CMV injection to deplete microglia, and maternal feeding with doxycyxline throughout pregnancy to modify microglia in the litters' brains, were both associated with dramatic improvements of survival, body weight gain, sensorimotor development and with decreased risk of epileptic seizures. Improvement of microglia activation status did not persist postnatally after doxycycline discontinuation; also, active brain infection remained unchanged by doxycycline. Altogether our data indicate that early microglia alteration, rather than brain CMV load per se, is instrumental in influencing survival and the neurological outcomes of CMV-infected rats, and suggest that microglia might participate in the neurological outcome of congenital CMV in humans. Furthermore this study represents a first proof-of-principle for the design of microglia-targeted preventive strategies in the context of congenital CMV infection of the brain.

Mouse subthalamic nucleus neurons with local axon collaterals.

The neuronal population of the subthalamic nucleus (STN) has the ability to prolong incoming cortical excitation. This could result from intra-STN feedback excitation. The combination of inducible genetic fate mapping techniques with in vitro targeted patch-clamp recordings, allowed identifying a new type of STN neurons that possess a highly collateralized intrinsic axon. The time window of birth dates was found to be narrow (E10.5-E14.5) with very few STN neurons born at E10.5 or E14.5. The fate mapped E11.5-12.5 STN neuronal population included 20% of neurons with profuse axonal branching inside the nucleus and a dendritic arbor that differed from that of STN neurons without local axon collaterals. They had intrinsic electrophysiological properties and in particular, the ability to generate plateau potentials, similar to that of STN neurons without local axon collaterals and more generally to that of classically described STN neurons. This suggests that a subpopulation of STN neurons forms a local glutamatergic network, which together with plateau potentials, allow amplification of hyperdirect cortical inputs and synchronization of the STN neuronal population.

Crystal structures of a group II intron lariat primed for reverse splicing.

The 2'-5' branch of nuclear premessenger introns is believed to have been inherited from self-splicing group II introns, which are retrotransposons of bacterial origin. Our crystal structures at 3.4 and 3.5 angstrom of an excised group II intron in branched ("lariat") form show that the 2'-5' branch organizes a network of active-site tertiary interactions that position the intron terminal 3'-hydroxyl group into a configuration poised to initiate reverse splicing, the first step in retrotransposition. Moreover, the branchpoint and flanking helices must undergo a base-pairing switch after branch formation. A group II-based model of the active site of the nuclear splicing machinery (the spliceosome) is proposed. The crucial role of the lariat conformation in active-site assembly and catalysis explains its prevalence in modern splicing.

Abnormal Development of Glutamatergic Synapses Afferent to Dopaminergic Neurons of the Pink1(-/-) Mouse Model of Parkinson's Disease.

In a preceding study, we showed that in adult pink1(-/-) mice, a monogenic animal model of Parkinson's disease (PD), striatal neurons display aberrant electrical activities that precede the onset of overt clinical manifestations. Here, we tested the hypothesis that the maturation of dopaminergic (DA) neurons of the pink1(-/-) substantia nigra compacta (SNc) follows, from early stages on, a different developmental trajectory from age-matched wild type (wt) SNc DA neurons. We used immature (postnatal days P2-P10) and young adult (P30-P90) midbrain slices of pink1(-/-) mice expressing the green fluorescent protein in tyrosine hydroxylase (TH)-positive neurons. We report that the developmental sequence of N-Methyl-D-aspartic acid (NMDA) spontaneous excitatory postsynaptic currents (sEPSCs) is altered in pink1(-/-) SNc DA neurons, starting from shortly after birth. They lack the transient episode of high NMDA receptor-mediated neuronal activity characteristic of the immature stage of wt SNc DA neurons. The maturation of the membrane resistance of pink1(-/-) SNc DA neurons is also altered. Collectively, these observations suggest that electrical manifestations occurring shortly after birth in SNc DA neurons might lead to dysfunction in dopamine release and constitute an early pathogenic mechanism of PD.

Activating the branch-forming splicing pathway by reengineering the ribozyme component of a natural group II intron.

When assayed in vitro, group IIC self-splicing introns, which target bacterial Rho-independent transcription terminators, generally fail to yield branched products during splicing despite their possessing a seemingly normal branchpoint. Starting with intron O.i.I1 from Oceanobacillus iheyensis, whose crystallographically determined structure lacks branchpoint-containing domain VI, we attempted to determine what makes this intron unfit for in vitro branch formation. A major factor was found to be the length of the helix at the base of domain VI: 4 base pairs (bp) are required for efficient branching, even though a majority of group IIC introns have a 3-bp helix. Equally important for lariat formation is the removal of interactions between ribozyme domains II and VI, which are specific to the second step of splicing. Conversely, mismatching of domain VI and its proposed first-step receptor in subdomain IC1 was found to be detrimental; these data suggest that the intron-encoded protein may promote branch formation partly by modulating the equilibrium between conformations specific to the first and second steps of splicing. As a practical application, we show that by making just two changes to the O.i.I1 ribozyme, it is possible to generate sufficient amounts of lariat intron for the latter to be purified and used in kinetic assays in which folding and reaction are uncoupled.

[Innovative immunotherapies of respiratory allergic diseases]. / Immunothérapies innovantes des maladies allergiques respiratoires.

Allergen immunotherapy (AIT) is an effective method in the treatment of respiratory allergic diseases (asthma, rhinitis and conjunctivitis). In addition to reducing symptoms, AIT can alter the course of allergic disease and remains efficient long after it has been discontinued by inducing specific tolerance to the allergen. In current clinical practice, immunotherapy is administered by subcutaneous or sublingual routes. The duration of efficacy is 7 to 12 years. It can prevent the development of both asthma and sensitization to new allergens. Despite recent progresses, other approaches are needed, especially for allergies (atopic dermatitis, food allergies). The new AIT improvement approaches involve the use of adjuvants or recombinant allergies, peptides and new routes of administration.

Glutamatergic synaptic currents of nigral dopaminergic neurons follow a postnatal developmental sequence.

The spontaneous activity pattern of adult dopaminergic (DA) neurons of the substantia nigra pars compacta (SNc) results from interactions between intrinsic membrane conductances and afferent inputs. In adult SNc DA neurons, low-frequency tonic background activity is generated by intrinsic pacemaker mechanisms, whereas burst generation depends on intact synaptic inputs in particular the glutamatergic ones. Tonic DA release in the striatum during pacemaking is required to maintain motor activity, and burst firing evokes phasic DA release, necessary for cue-dependent learning tasks. However, it is still unknown how the firing properties of SNc DA neurons mature during postnatal development before reaching the adult state. We studied the postnatal developmental profile of spontaneous and evoked AMPA and NMDA (N-Methyl-D-aspartic acid) receptor-mediated excitatory postsynaptic currents (EPSCs) in SNc DA neurons in brain slices from immature (postnatal days P4-P10) and young adult (P30-P50) tyrosine hydroxylase (TH)-green fluorescent protein mice. We found that somato-dendritic fields of SNc DA neurons are already mature at P4-P10. In contrast, spontaneous glutamatergic EPSCs show a developmental sequence. Spontaneous NMDA EPSCs in particular are larger and more frequent in immature SNc DA neurons than in young adult ones and have a bursty pattern. They are mediated by GluN2B and GluN2D subunit-containing NMDA receptors. The latter generate long-lasting, DQP 1105-sensitive, spontaneous EPSCs, which are transiently recorded during this early period. Due to high NMDA activity, immature SNc DA neurons generate large and long lasting NMDA receptor-dependent (APV-sensitive) bursts in response to the stimulation of the subthalamic nucleus. We conclude that the transient high NMDA activity allows calcium influx into the dendrites of developing SNc DA neurons.

Early hypersynchrony in juvenile PINK1(-)/(-) motor cortex is rescued by antidromic stimulation.

In Parkinson's disease (PD), cortical networks show enhanced synchronized activity but whether this precedes motor signs is unknown. We investigated this question in PINK1(-)/(-) mice, a genetic rodent model of the PARK6 variant of familial PD which shows impaired spontaneous locomotion at 16 months. We used two-photon calcium imaging and whole-cell patch clamp in slices from juvenile (P14-P21) wild-type or PINK1(-)/(-) mice. We designed a horizontal tilted cortico-subthalamic slice where the only connection between cortex and subthalamic nucleus (STN) is the hyperdirect cortico-subthalamic pathway. We report excessive correlation and synchronization in PINK1(-)/(-) M1 cortical networks 15 months before motor impairment. The percentage of correlated pairs of neurons and their strength of correlation were higher in the PINK1(-)/(-) M1 than in the wild type network and the synchronized network events involved a higher percentage of neurons. Both features were independent of thalamo-cortical pathways, insensitive to chronic levodopa treatment of pups, but totally reversed by antidromic invasion of M1 pyramidal neurons by axonal spikes evoked by high frequency stimulation (HFS) of the STN. Our study describes an early excess of synchronization in the PINK1(-)/(-) cortex and suggests a potential role of antidromic activation of cortical interneurons in network desynchronization. Such backward effect on interneurons activity may be of importance for HFS-induced network desynchronization.

[The implementation gap in asthma prevention and control?]. / Prévenir et contrôler l'asthme, quels sont les obstacles ? Comment les surmonter ?

Asthma and allergic diseases generally start early in life and persist throughout life but, for reasons we do not yet understand, they sometimes appear later Prevention, early diagnosis and treatment of these major chronic respiratory diseases is a recognized priority for EU public health policy and for the United Nations. As factors favoring allergy (rapid urbanization, pollution, climate change and infections) are not expected to change in the foreseeable future, it is crucial to develop, strengthen and optimize prevention and treatment. We have developed tools to control asthma but are still unable to prevent children from developing asthma and allergic diseases. This article examines what works and what does not, and analyzes the "missing links" between the creation and effective implementation of a prevention program, otherwise known as the implementation gap.

Stochastic loss of silencing of the imprinted Ndn/NDN allele, in a mouse model and humans with prader-willi syndrome, has functional consequences.

Genomic imprinting is a process that causes genes to be expressed from one allele only according to parental origin, the other allele being silent. Diseases can arise when the normally active alleles are not expressed. In this context, low level of expression of the normally silent alleles has been considered as genetic noise although such expression has never been further studied. Prader-Willi Syndrome (PWS) is a neurodevelopmental disease involving imprinted genes, including NDN, which are only expressed from the paternally inherited allele, with the maternally inherited allele silent. We present the first in-depth study of the low expression of a normally silent imprinted allele, in pathological context. Using a variety of qualitative and quantitative approaches and comparing wild-type, heterozygous and homozygous mice deleted for Ndn, we show that, in absence of the paternal Ndn allele, the maternal Ndn allele is expressed at an extremely low level with a high degree of non-genetic heterogeneity. The level of this expression is sex-dependent and shows transgenerational epigenetic inheritance. In about 50% of mutant mice, this expression reduces birth lethality and severity of the breathing deficiency, correlated with a reduction in the loss of serotonergic neurons. In wild-type brains, the maternal Ndn allele is never expressed. However, using several mouse models, we reveal a competition between non-imprinted Ndn promoters which results in monoallelic (paternal or maternal) Ndn expression, suggesting that Ndn allelic exclusion occurs in the absence of imprinting regulation. Importantly, specific expression of the maternal NDN allele is also detected in post-mortem brain samples of PWS individuals. Our data reveal an unexpected epigenetic flexibility of PWS imprinted genes that could be exploited to reactivate the functional but dormant maternal alleles in PWS. Overall our results reveal high non-genetic heterogeneity between genetically identical individuals that might underlie the variability of the phenotype.

Periventricular heterotopia in 6q terminal deletion syndrome: role of the C6orf70 gene.

Periventricular nodular heterotopia is caused by defective neuronal migration that results in heterotopic neuronal nodules lining the lateral ventricles. Mutations in filamin A (FLNA) or ADP-ribosylation factor guanine nucleotide-exchange factor 2 (ARFGEF2) cause periventricular nodular heterotopia, but most patients with this malformation do not have a known aetiology. Using comparative genomic hybridization, we identified 12 patients with developmental brain abnormalities, variably combining periventricular nodular heterotopia, corpus callosum dysgenesis, colpocephaly, cerebellar hypoplasia and polymicrogyria, harbouring a common 1.2 Mb minimal critical deletion in 6q27. These anatomic features were mainly associated with epilepsy, ataxia and cognitive impairment. Using whole exome sequencing in 14 patients with isolated periventricular nodular heterotopia but no copy number variants, we identified one patient with periventricular nodular heterotopia, developmental delay and epilepsy and a de novo missense mutation in the chromosome 6 open reading frame 70 (C6orf70) gene, mapping in the minimal critical deleted region. Using immunohistochemistry and western blots, we demonstrated that in human cell lines, C6orf70 shows primarily a cytoplasmic vesicular puncta-like distribution and that the mutation affects its stability and subcellular distribution. We also performed in utero silencing of C6orf70 and of Phf10 and Dll1, the two additional genes mapping in the 6q27 minimal critical deleted region that are expressed in human and rodent brain. Silencing of C6orf70 in the developing rat neocortex produced periventricular nodular heterotopia that was rescued by concomitant expression of wild-type human C6orf70 protein. Silencing of the contiguous Phf10 or Dll1 genes only produced slightly delayed migration but not periventricular nodular heterotopia. The complex brain phenotype observed in the 6q terminal deletion syndrome likely results from the combined haploinsufficiency of contiguous genes mapping to a small 1.2 Mb region. Our data suggest that, of the genes within this minimal critical region, C6orf70 plays a major role in the control of neuronal migration and its haploinsufficiency or mutation causes periventricular nodular heterotopia.

The mtDNA rns gene landscape in the Ophiostomatales and other fungal taxa: twintrons, introns, and intron-encoded proteins.

Comparative sequence analysis of the mitochondrial small subunit ribosomal RNA (rns) gene among species of Ophiostoma, Grosmannia, Ceratocystiopsis and related taxa provides an overview of the types of introns that have invaded this gene within the ophiostomatoid fungi. The rns gene appears to be a reservoir for a number of group I and group II introns along with intron-associated open reading frames such as homing endonucleases and reverse transcriptases. This study uncovered two twintrons, one at position mS917 where a group ID intron encoding a LAGLIDADG ORF invaded another ORF-less group ID intron. Another twintron complex was detected at position mS1247 here a group IIA1 intron invaded the open reading frame embedded within a group IC2 intron. Overall the distribution of the introns does not appear to follow evolutionary lineages suggesting the possibility of rare horizontal gains and frequent losses. Results of this study will make a significant contribution to the understanding of the complexity of the mitochondrial intron landscape, and offer a resource to those annotating mitochondrial genomes. It will also serve as a resource to those that bioprospect for ribozymes and homing endonucleases.

Subthalamic lesion or levodopa treatment rescues giant GABAergic currents of PINK1-deficient striatum.

Cellular electrophysiological signatures of Parkinson's disease described in the pharmacological 6-hydroxydopamine (6-OHDA) animal models of Parkinson's disease include spontaneous repetitive giant GABAergic currents in a subpopulation of striatal medium spiny neurons (MSNs), and spontaneous rhythmic bursts of spikes generated by subthalamic nucleus (STN) neurons. We investigated whether similar signatures are present in Pink1(-/-) mice, a genetic rodent model of the PARK6 variant of Parkinson's disease. Although 9- to 24-month-old Pink1(-/-) mice show reduced striatal dopamine content and release, and impaired spontaneous locomotion, the relevance of this model to Parkinson's disease has been questioned because mesencephalic dopaminergic neurons do not degenerate during the mouse lifespan. We show that 75% of the MSNs of 5- to 7-month-old Pink1(-/-) mice exhibit giant GABAergic currents, occurring either singly or in bursts (at 40 Hz), rather than the low-frequency (2 Hz), low-amplitude, tonic GABAergic drive common to wild-type MSNs of the same age. STN neurons from 5- to 7-month-old Pink1(-/-) mice spontaneously generated bursts of spikes instead of the control tonic drive. Chronic kainic acid lesion of the STN or chronic levodopa treatment reliably suppressed the giant GABAergic currents of MSNs after 1 month and replaced them with the control tonic activity. The similarity between the in vitro resting states of Pink1 MSNs and those of fully dopamine (DA)-depleted MSNs of 6-OHDA-treated mice, together with the beneficial effect of levodopa treatment, strongly suggest that dysfunction of mesencephalic dopaminergic neurons in Pink1(-/-) mice is more severe than expected. The beneficial effect of the STN lesion also suggests that pathological STN activity strongly influences striatal networks in Pink1(-/-) mice.

Midbrain dopaminergic neurons generate calcium and sodium currents and release dopamine in the striatum of pups.

Midbrain dopaminergic neurons (mDA neurons) are essential for the control of diverse motor and cognitive behaviors. However, our understanding of the activity of immature mDA neurons is rudimentary. Rodent mDA neurons migrate and differentiate early in embryonic life and dopaminergic axons enter the striatum and contact striatal neurons a few days before birth, but when these are functional is not known. Here, we recorded Ca(2+) transients and Na(+) spikes from embryonic (E16-E18) and early postnatal (P0-P7) mDA neurons with dynamic two-photon imaging and patch clamp techniques in slices from tyrosine hydroxylase-GFP mice, and measured evoked dopamine release in the striatum with amperometry. We show that half of identified E16-P0 mDA neurons spontaneously generate non-synaptic, intrinsically driven Ca(2+) spikes and Ca(2+) plateaus mediated by N- and L-type voltage-gated Ca(2+) channels. Starting from E18-P0, half of the mDA neurons also reliably generate overshooting Na(+) spikes with an abrupt maturation at birth (P0 = E19). At that stage (E18-P0), dopaminergic terminals release dopamine in a calcium-dependent manner in the striatum in response to local stimulation. This suggests that mouse striatal dopaminergic synapses are functional at birth.

Onset of Pup Locomotion Coincides with Loss of NR2C/D-Mediated Cortico-Striatal EPSCs and Dampening of Striatal Network Immature Activity.

Adult motor coordination requires strong coincident cortical excitatory input to hyperpolarized medium spiny neurons (MSNs), the dominant neuronal population of the striatum. However, cortical and subcortical neurons generate during development large ongoing patterns required for activity-dependent construction of networks. This raises the question of whether immature MSNs have adult features from early stages or whether they generate immature patterns that are timely silenced to enable locomotion. Using a wide range of techniques including dynamic two-photon imaging, whole cell or single-channel patch clamp recording in slices from Nkx2.1-GFP mice, we now report a silencing of MSNs that timely coincides with locomotion. At embryonic stage (as early as E16) and during early postnatal days, genetically identified MSNs have a depolarized resting membrane potential, a high input resistance and lack both inward rectifying (IK(IR)) and early slowly inactivating (I(D)) potassium currents. They generate intrinsic voltage-gated clustered calcium activity without synaptic components. From postnatal days 5-7, the striatal network transiently generates synapse-driven giant depolarizing potentials when activation of cortical inputs evokes long lasting EPSCs in MSNs. Both are mediated by NR2C/D-receptors. These immature features are abruptly replaced by adult ones before P10: MSNs express IK(IR) and I(D) and generate short lasting, time-locked cortico-striatal AMPA/NMDA EPSCs with no NR2C/D component. This shift parallels the onset of quadruped motion by the pup. Therefore, MSNs generate immature patterns that are timely shut off to enable the coordination of motor programs.