EMA Review of Isatuximab in Combination with Pomalidomide and Dexamethasone for the Treatment of Adult Patients with Relapsed and Refractory Multiple Myeloma.

Isatuximab is a monoclonal antibody that binds to the human CD38 antigen. On May 30, 2020, a marketing authorization valid through the European Union (EU) was issued for isatuximab in combination with pomalidomide and dexamethasone (IsaPd) for the treatment of adult patients with relapsed and refractory (RR) multiple myeloma (MM). The recommended dose of isatuximab was 10 mg/kg, administered intravenously weekly at cycle 1 and then biweekly in subsequent 28-day cycles. Isatuximab was evaluated in a phase III, open-label, multicenter, randomized trial that randomly allocated IsaPd versus pomalidomide plus dexamethasone (Pd) to adult patients with RR MM. The primary endpoint of the trial was progression-free survival, as assessed by an independent review committee, which was superior for the IsaPd arm (hazard ratio, 0.596; 95% confidence interval, 0.436-0.814; p = .001) compared with the Pd arm. Treatment with IsaPd led to higher incidences of treatment-related adverse events (AEs), grade ≥ 3 AEs, and serious AEs compared with Pd treatment. Most frequently observed AEs that occurred more often in the IsaPd arm were infusion-related reactions, infections, respiratory AEs, neutropenia (including neutropenic complications), and thrombocytopenia. The aim of this article is to summarize the scientific review of the application leading to regulatory approval in the EU. IMPLICATIONS FOR PRACTICE: Isatuximab was approved in the European Union, in combination with pomalidomide and dexamethasone, for the treatment of patients with multiple myeloma who have already received therapy but whose disease did not respond or relapsed afterward. The addition of isatuximab resulted in a clinically meaningful and significant prolongation of the time from treatment initiation to further disease relapse or patient's death. The safety profile was considered acceptable, and the benefit-risk ratio was determined to be positive.

Blinatumomab for Acute Lymphoblastic Leukemia: The First Bispecific T-Cell Engager Antibody to Be Approved by the EMA for Minimal Residual Disease.

On November 15, 2018, the Committee for Medicinal Products for Human Use (CHMP) recommended the extension of indication for blinatumomab to include the treatment of adults with minimal residual disease (MRD) positive B-cell precursor acute lymphoblastic leukemia (ALL). Blinatumomab was authorized to treat relapsed or refractory B-precursor ALL, and the change concerned an extension of use. On March 29, 2018, the U.S. Food and Drug Administration (FDA) granted accelerated approval to blinatumomab to treat both adults and children with B-cell precursor ALL who are in remission but still have MRD. On July 26, 2018, the CHMP had originally adopted a negative opinion on the extension. The reason for the initial refusal was that although blinatumomab helped to reduce the amount of residual cancer cells in many patients, there was no strong evidence that it led to improved survival. During the re-examination, the CHMP consulted the scientific advisory group. The CHMP agreed with the expert group's conclusion that, although there was no strong evidence of patients living longer, the available data from the main study (MT103-203) indicated a good durable response to blinatumomab, with an overall complete response rate for the primary endpoint full analysis set (defined as all subjects with an Ig or T-cell receptor polymerase chain reaction MRD assay with the minimum required sensitivity of 1 × 10-4 at central lab established at baseline [n = 113]) as 79.6% (90/113; 95% confidence interval, 71.0-86.6), with a median time to complete MRD response of 29.0 days (range, 5-71). Therefore, the CHMP concluded that the benefits of blinatumomab outweigh its risks and recommended granting the change to the marketing authorization. The Committee for Orphan Medicinal Products, following reassessment, considered that significant benefit continued to be met and recommended maintaining the orphan designation and thus 10 years market exclusivity (the Orphan Designation is a legal procedure that allows for the designation of a medicinal substance with therapeutic potential for a rare disease, before its first administration in humans or during its clinical development). The marketing authorization holder for this medicinal product is Amgen Europe B.V. IMPLICATIONS FOR PRACTICE: Immunotherapy with blinatumomab has excellent and sustainable results, offering new hope for patients with minimal residual disease-positive acute lymphoblastic leukemia, a disease with poor prognosis. New recommendations and change of practice for treatment of this patient group are detailed.

Out-of-hospital Times Using Helicopters Versus Ground Services for Emergency Patients.

OBJECTIVE: Minimizing out-of-hospital time reduces morbidity and mortality in patients with severe trauma, acute coronary syndrome, or acute stroke. Our objective was to compare out-of-hospital times by helicopter versus ground services when the estimated time of arrival on the scene was over 20 minutes. METHODS: We proposed a retrospective observational monocentric study following 2 cohorts. The helicopter group and the ground group included patients with severe trauma, acute coronary syndrome, or acute stroke transported by helicopter or ground services. RESULTS: Two hundred thirty-nine patients were included; 118 were in the ground group, and 121 were in the helicopter group. Distances for the helicopter group were higher (62.1 ± 22.5 km vs. 27.6 ± 10.4 km, P < .001). When distances were over 35 km, the helicopter group was faster. We identified distance, need for surgery, and intensive care hospitalization as 3 predicting factors for choosing helicopters over ground modes of transport. CONCLUSION: In cases of severe trauma, acute coronary syndrome, or acute stroke, emergency medical helicopter transport can be chosen over ground transport when patients are in a severe state and when the distance is further than 35 km from the hospital.

The European Medicines Agency Review of Carfilzomib for the Treatment of Adult Patients with Multiple Myeloma Who Have Received at Least One Prior Therapy.

On November 19, 2015, a marketing authorization valid through the European Union was issued for carfilzomib in combination with lenalidomide and dexamethasone for the treatment of adult patients with multiple myeloma (MM) who have received at least one prior therapy.In a phase III trial in patients with relapsed MM, median progression-free survival (PFS) for patients treated with carfilzomib in combination with lenalidomide and dexamethasone (CRd) was 26.3 months versus 17.6 months for those receiving lenalidomide and dexamethasone alone (hazard ratio = 0.69; 95% confidence interval, 0.57-0.83; one-sided log-rank p value < .0001). The most frequently observed toxicity (grade ≥3, treatment arm vs. control arm) in the phase III trial included neutropenia (29.6% vs. 26.5%), anemia (17.9% vs. 17.7%), thrombocytopenia (16.8% vs. 12.3%), pneumonia (12.5% vs. 10.5%), fatigue (7.7% vs. 6.4%), hypertension (4.6% vs. 2.1%), diarrhea (3.8% vs. 4.1%), and respiratory tract infection (4.1% vs. 2.1%).The objective of this article is to summarize the scientific review of the application leading to regulatory approval in the European Union. The scientific review concluded that the gain in PFS of 8.7 months observed with the combination of CRd was considered clinically meaningful and was supported by a clear trend in overall survival benefit, although the data were not mature. The delay in disease progression appeared superior to available alternatives in the setting of relapsed MM at the time of the marketing authorization of carfilzomib. Therefore, given the overall accepted safety profile, which was considered manageable in the current context, the benefit risk for CRd was considered positive. IMPLICATIONS FOR PRACTICE: Carfilzomib (Kyprolis) was approved in the European Union in combination with lenalidomide and dexamethasone for the treatment of adult patients with multiple myeloma who have received at least one prior therapy. The addition of carfilzomib to lenalidomide and dexamethasone resulted in a clinically meaningful and statistically significant improvement of progression-free survival compared with lenalidomide and dexamethasone, which was supported by a clear trend in overall survival benefit, although the data were not mature. At the time of the marketing authorization of carfilzomib, the delay in disease progression appeared superior to available alternatives in the setting of relapsed multiple myeloma. In terms of safety, the overall accepted safety profile was considered manageable.

The European Medicines Agency Review of Decitabine (Dacogen) for the Treatment of Adult Patients With Acute Myeloid Leukemia: Summary of the Scientific Assessment of the Committee for Medicinal Products for Human Use.

UNLABELLED: : On September 20, 2012, a marketing authorization valid throughout the European Union (EU) was issued for decitabine for the treatment of adult patients aged 65 years and older with newly diagnosed de novo or secondary acute myeloid leukemia (AML) who are not candidates for standard induction chemotherapy. Decitabine is a pyrimidine analog incorporated into DNA, where it irreversibly inhibits DNA methyltransferases through covalent adduct formation with the enzyme. The use of decitabine was studied in an open-label, randomized, multicenter phase III study (DACO-016) in patients with newly diagnosed de novo or secondary AML. Decitabine (n = 242) was compared with patient's choice with physician's advice (n = 243) of low-dose cytarabine or supportive care alone. The primary endpoint of the study was overall survival. The median overall survival in the intent-to-treat (ITT) population was 7.7 months among patients treated with decitabine compared with 5.0 months for those in the control arm (hazard ratio [HR], 0.85; 95% confidence interval [CI], 0.69-1.04; p = .1079). Mature survival data after an additional year of follow-up were consistent with these results, with a median overall survival of 7.7 months in patients treated with decitabine and 5.0 months in the control arm (HR, 0.82; 95% CI, 0.68-0.99; p = .0373). Secondary endpoints, including response rates, progression-free survival, and event-free survival, were increased in favor of decitabine when compared with control treatment. The most common adverse drug reactions reported during treatment with decitabine are pyrexia, anemia, thrombocytopenia, febrile neutropenia, neutropenia, nausea, and diarrhea. This paper summarizes the scientific review of the application leading to approval of decitabine in the EU. The detailed scientific assessment report and product information (including the summary of product characteristics) for this product are available on the EMA website (http://www.ema.europa.eu). IMPLICATIONS FOR PRACTICE: Acute myeloid leukemia (AML) remains an area of significant unmet need, especially in older patients. Older patients and those with comorbidities are often considered ineligible for standard induction therapy, and outcome for these patients is poor. Decitabine has favorable effects in terms of overall survival, which were considered clinically meaningful in the context of a manageable toxicity profile and after consideration of the lack of therapeutic alternatives for these patients. Decitabine is widely used in the treatment of AML in patients aged >60 years, as per current guidelines, including the European LeukemiaNet and the U.S. National Cancer Comprehensive Network.

Biosimilars: what clinicians should know.

Biosimilar medicinal products (biosimilars) have become a reality in the European Union and will soon be available in the United States. Despite an established legal pathway for biosimilars in the European Union since 2005 and increasing and detailed regulatory guidance on data requirements for their development and licensing, many clinicians, particularly oncologists, are reluctant to consider biosimilars as a treatment option for their patients. Major concerns voiced about biosimilars relate to their pharmaceutical quality, safety (especially immunogenicity), efficacy (particularly in extrapolated indications), and interchangeability with the originator product. In this article, the members and experts of the Working Party on Similar Biologic Medicinal Products of the European Medicines Agency (EMA) address these issues. A clear understanding of the scientific principles of the biosimilar concept and access to unbiased information on licensed biosimilars are important for physicians to make informed and appropriate treatment choices for their patients. This will become even more important with the advent of biosimilar monoclonal antibodies. The issues also highlight the need for improved communication between physicians, learned societies, and regulators.

Ultrasound guidance for radial arterial puncture: a randomized controlled trial.

UNLABELLED: STUDY OBJECTIVE AND BACKGROUND: Arterial puncture for blood gas analysis is a frequent procedure and could be difficult in the emergency setting. The aim of the study was to compare ultrasonographically guided arterial radial puncture vs conventional sampling. MATERIALS AND METHODS: This is a prospective, randomized study. The inclusion criteria are all patients needing arterial blood gas at admission in the emergency unit. The exclusion criteria are the following: Hallen test positive, local sepsis, local trauma, known sever local arteriopathy, refusal of consent by the patient, participation in another study, and cardiac arrest. Patients were randomized into 2 groups: radial arterial puncture obtained through an ultrasonographically guided technique (group 1) or radial arterial puncture by conventional method (group 2). The main objective is the number of attempts after enrollment. The secondary objectives are time to success, patient satisfaction and pain, and physician satisfaction. Immediate complications were collected. Groups were compared with nonparametric analysis. RESULTS: The data were usable for 72 of 74 patients included. Lung disease (acute exacerbation of chronic obstructive pulmonary disease and pneumonia) at 45% (n = 32) and suspicion of pulmonary embolism in 31% (n = 22) were the most common reasons. Demographics data were comparable in the 2 groups. In group 1, the number of attempts significantly increased (2.35 [1-3] vs 1.66 [1-2] [P = .017]), and the sample was 2.4 times longer (132 seconds [50-200] vs 55 [20-65] [P < .01] by standard method). There was no significant difference in terms of pain (visual analog scale [VAS], 3.6 [2-5] for both groups [P = .743]), patient satisfaction (VAS, 7.2 [5-9] vs 6.8 [5-9] [P = .494]), and physician satisfaction (VAS, 6.0 [3.5-8] vs 6.9 [5-9] [P = .233]). No immediate complications were found in the 2 groups. CONCLUSION: Ultrasonographically guided arterial puncture increases the number and duration of implementations. This technique, however, does not alter the patient's pain, the number of immediate complications, or patient and physician satisfaction.

p21-Activated kinase 3 (PAK3) protein regulates synaptic transmission through its interaction with the Nck2/Grb4 protein adaptor.

Mutations in the p21-activated kinase 3 gene (pak3) are responsible for nonsyndromic forms of mental retardation. Expression of mutated PAK3 proteins in hippocampal neurons induces abnormal dendritic spine morphology and long term potentiation anomalies, whereas pak3 gene invalidation leads to cognitive impairments. How PAK3 regulates synaptic plasticity is still largely unknown. To better understand how PAK3 affects neuronal synaptic plasticity, we focused on its interaction with the Nck adaptors that play a crucial role in PAK signaling. We report here that PAK3 interacts preferentially with Nck2/Grb4 in brain extracts and in transfected cells. This interaction is independent of PAK3 kinase activity. Selective uncoupling of the Nck2 interactions in acute cortical slices using an interfering peptide leads to a rapid increase in evoked transmission to pyramidal neurons. The P12A mutation in the PAK3 protein strongly decreases the interaction with Nck2 but only slightly with Nck1. In transfected hippocampal cultures, expression of the P12A-mutated protein has no effect on spine morphogenesis or synaptic density. The PAK3-P12A mutant does not affect synaptic transmission, whereas the expression of the wild-type PAK3 protein decreases the amplitude of spontaneous miniature excitatory currents. Altogether, these data show that PAK3 down-regulates synaptic transmission through its interaction with Nck2.

The European Medicines Agency review of cabazitaxel (Jevtana®) for the treatment of hormone-refractory metastatic prostate cancer: summary of the scientific assessment of the committee for medicinal products for human use.

On March 17, 2011 the European Commission issued a marketing authorization valid throughout the European Union for Jevtana® (Sanofi-Aventis, Paris, France) for the treatment of patients with hormone-refractory metastatic prostate cancer previously treated with a docetaxel-containing regimen. The active substance of Jevtana® is cabazitaxel acetone solvate, an antineoplastic agent that acts by disrupting the microtubular network in cells. The recommended dose of cabazitaxel is 25 mg/m2 administered as a 1-hour i.v. infusion every 3 weeks in combination with oral prednisone or prednisolone, 10 mg, administered daily throughout treatment. In the main study submitted for this application, a 2.4-month longer median overall survival time and a 30% lower risk for death were observed for cabazitaxel, compared with mitoxantrone. The most common side effects with cabazitaxel were anemia, leukopenia, neutropenia, thrombocytopenia, and diarrhea. This paper summarizes the scientific review of the application leading to approval in the European Union. The detailed scientific assessment report and product information, including the summary of product characteristics, are available on the European Medicines Agency Web site (http://www.ema.europa.eu).

Serotoninergic fine-tuning of the excitation-inhibition balance in rat visual cortical networks.

Fundamental brain functions depend on a balance between excitation (E) and inhibition (I) that is highly adjusted to a 20-80% set point in layer 5 pyramidal neurons (L5PNs) of rat visual cortex. Dysregulations of both the E-I balance and the serotonergic system in neocortical networks lead to serious neuronal diseases including depression, schizophrenia, and epilepsy. However, no link between the activation of neuronal 5-hydroxytryptamine receptors (5-HTRs) and the cortical E-I balance has yet been reported. Here we used a combination of patch-clamp recordings of composite stimulus-locked responses in L5PN following local electrical stimulations in either layer 2/3 or 6, simultaneous measurement of excitatory and inhibitory conductance dynamics, together with selective pharmacological targeting and single-cell reverse transcriptase-polymerase chain reaction. We show that cortical serotonin shifts the E-I balance in favor of more E and we reveal fine and differential modulations of the E-I balance between 5-HTR subtypes, in relation to whether layer 2/3 or 6 was stimulated and in concordance with the specific expression pattern of these subtypes in pyramidal cells and deep interneurons. This first evidence for the functional segregation of 5-HTR subtypes sheds new light on their coherent functioning in polysynaptic sensory circuits.

The European Medicines Agency Review of Tafasitamab in Combination With Lenalidomide for the Treatment of Adult Patients With Relapsed/Refractory Diffuse Large B-cell Lymphoma.

Tafasitamab is a humanized monoclonal antibody that binds to the CD19 antigen, which is expressed in tumor cells from patients with diffuse large B-cell lymphoma (DLBCL). On June 24, 2021, a positive opinion for a conditional marketing authorization was issued by the European Medicines Agency (EMA)'s Committee for Medicinal Products for Human Use (CHMP) for tafasitamab, in combination with lenalidomide, for the treatment of adult patients with relapsed or refractory DLBCL who are ineligible for autologous stem cell transplantation. Tafasitamab was evaluated in the phase 2 single-arm, multicenter, open-label L-MIND clinical trial. The primary endpoint of this trial was objective response rate (ORR). The best ORR, achieved at any time during the study, was 56.8% (95% confidence interval: 45.3%-67.8%), and the median duration of response was 34.6 months (95% confidence interval: 26.1-not reached). The most frequently reported adverse events by system organ class were infections and infestations (72.8%; grade ≥3: 29.6%), blood and lymphatic system disorders (65.4%; grade ≥3: 56.8%), gastrointestinal disorders (64.2%; grade ≥3: 2.5%), and general disorders and administration site conditions (58.0%; grade ≥3: 8.6%). The aim of this article is to summarize the scientific review of the application which led to the positive opinion by the CHMP.

Characterization of the Barley Net Blotch Pathosystem at the Center of Origin of Host and Pathogen.

Net blotch (NB) is a major disease of barley caused by the fungus Pyrenophora teres f. teres (Ptt), and P. teres f. maculata (Ptm). Ptt and Ptm infect the cultivated crop (Hordeum vulgare) and its wild relatives (H. vulgare ssp. spontaneum and H. murinum ssp. glaucum). The main goal of this research was to study the NB-causing pathogen in the crop center of origin. To address this, we have constructed a Ptt (n = 15) and Ptm (n = 12) collection isolated from three barley species across Israel. Isolates were characterized genetically and phenotypically. Aggressiveness of the isolates was determined based on necrotrophic growth rate on detached leaves of barley. In addition, isolates were genetically characterized by the mating type, followed by phylogenetic analysis, clustering them into seven groups. The analysis showed no significant differentiation of isolates based on either geographic origin, host of origin or form (Ptt vs. Ptm). Nevertheless, there was a significant difference in aggressiveness among the isolates regardless of host species, geographic location or sampling site. Moreover, it was apparent that the isolates derived from wild hosts were more variable in their necrotrophic growth rate, compared to isolates sampled from cultivated hosts, thereby suggesting that NB plays a major role in epidemiology at the center of barley origin where most of the diversity lies. Ptm has significantly higher necrotrophic and saprotrophic growth rates than Ptt, and for both a significant negative correlation was found between light intensity exposure and growth rates.

NMDA receptor-dependent function and plasticity in inhibitory circuits.

NMDA receptors have been known to play a central role in long-term potentiation at glutamatergic synapses in principal cells for thirty years. In contrast, their roles in the development and activity-dependent plasticity of synapses in inhibitory circuits have only recently begun to be understood. Progress has, to a great extent, been hampered by the extensive diversity of GABAergic cell types in the CNS. However, anatomical, immunohistochemical and electrophysiological methods have allowed distinct types to be identified, with the result that consistent patterns of synaptic plasticity have begun to emerge. This review summarizes recent evidence on the role of NMDA receptors in the development and plasticity of GABAergic synapses on principal cells and of glutamatergic synapses on identified interneurons. A major challenge is to understand how NMDA receptors affect the routing of information in healthy inhibitory circuits, and how changes in NMDA receptor function may contribute to altered circuit function in disorders such as schizophrenia. This article is part of the Special Issue entitled 'Glutamate Receptor-Dependent Synaptic Plasticity'.

Hospital out-lying through lack of beds and its impact on care and patient outcome.

BACKGROUND: When medical wards become saturated, the common practice is to resort to outlying patients in another ward until a bed becomes free. OBJECTIVES: Compare the quality of care provided for inpatients who are outlying (O) in inappropriate wards because of lack of vacant beds in appropriate specialty wards to the care given to non outlying (NO) patients. METHODS: We propose a matched-pair cluster study. The exposed group consisted of inpatients that were outliers in inappropriate wards because of lack of available beds. Non-exposed subjects (the control group) were those patients who were hospitalized in the ward that corresponded to the reason for their admission. Each patient of the exposed group was matched to a specific control subject. The principal objective was to prospectively measure differences in the length of hospital stays, the secondary objectives were to assess mortality, rate of re-admission at 28 days, and rate of transfer into intensive care. RESULTS: 238 were included in the NO group, 245 in the O group. More patients in the O group (86% vs 76%) were transferred into a ward with prescription completed. O patients remained in hospital for 8 days [4-15] vs 7 days [4-13] for NO patients (p = 0.04). 124 (52%) of the NO patients received heparin-based thromboembolic prevention during their stay in hospital vs 104 (42%) of the O patient group (p = 0.03). 66 (27%) O patients were re-admitted to hospital within 28 days vs 40 (17%) NO patients (p = 0.008). CONCLUSION: O patients had a worse prognosis than NO patients.

The V-ATPase membrane domain is a sensor of granular pH that controls the exocytotic machinery.

Several studies have suggested that the V0 domain of the vacuolar-type H(+)-adenosine triphosphatase (V-ATPase) is directly implicated in secretory vesicle exocytosis through a role in membrane fusion. We report in this paper that there was a rapid decrease in neurotransmitter release after acute photoinactivation of the V0 a1-I subunit in neuronal pairs. Likewise, inactivation of the V0 a1-I subunit in chromaffin cells resulted in a decreased frequency and prolonged kinetics of amperometric spikes induced by depolarization, with shortening of the fusion pore open time. Dissipation of the granular pH gradient was associated with an inhibition of exocytosis and correlated with the V1-V0 association status in secretory granules. We thus conclude that V0 serves as a sensor of intragranular pH that controls exocytosis and synaptic transmission via the reversible dissociation of V1 at acidic pH. Hence, the V-ATPase membrane domain would allow the exocytotic machinery to discriminate fully loaded and acidified vesicles from vesicles undergoing neurotransmitter reloading.

Plasticity of inhibition.

Until recently, the study of plasticity of neural circuits focused almost exclusively on potentiation and depression at excitatory synapses on principal cells. Other elements in the neural circuitry, such as inhibitory synapses on principal cells and the synapses recruiting interneurons, were assumed to be relatively inflexible, as befits a role of inhibition in maintaining stable levels and accurate timing of neuronal activity. It is now evident that inhibition is highly plastic, with multiple underlying cellular mechanisms. This Review considers these recent developments, focusing mainly on functional and structural changes in GABAergic inhibition of principal cells and long-term plasticity of glutamateric recruitment of inhibitory interneurons in the mammalian forebrain. A major challenge is to identify the adaptive roles of these different forms of plasticity, taking into account the roles of inhibition in the regulation of excitability, generation of population oscillations, and precise timing of neuronal firing.

Target-specific expression of presynaptic NMDA receptors in neocortical microcircuits.

Traditionally, NMDA receptors are located postsynaptically; yet, putatively presynaptic NMDA receptors (preNMDARs) have been reported. Although implicated in controlling synaptic plasticity, their function is not well understood and their expression patterns are debated. We demonstrate that, in layer 5 of developing mouse visual cortex, preNMDARs specifically control synaptic transmission at pyramidal cell inputs to other pyramidal cells and to Martinotti cells, while leaving those to basket cells unaffected. We also reveal a type of interneuron that mediates ascending inhibition. In agreement with synapse-specific expression, we find preNMDAR-mediated calcium signals in a subset of pyramidal cell terminals. A tuned network model predicts that preNMDARs specifically reroute information flow in local circuits during high-frequency firing, in particular by impacting frequency-dependent disynaptic inhibition mediated by Martinotti cells, a finding that we experimentally verify. We conclude that postsynaptic cell type determines presynaptic terminal molecular identity and that preNMDARs govern information processing in neocortical columns.

Involvement of NR2A- or NR2B-containing N-methyl-D-aspartate receptors in the potentiation of cortical layer 5 pyramidal neurone inputs depends on the developmental stage.

In the cortex, N-methyl-D-aspartate receptors (NMDARs) play a critical role in the control of synaptic plasticity processes. We have previously shown in rat visual cortex that the application of a high-frequency stimulation (HFS) protocol used to induce long-term potentiation in layer 2/3 leads to a parallel potentiation of excitatory and inhibitory inputs received by cortical layer 5 pyramidal neurones without changing the excitation/inhibition balance of the pyramidal neurone, indicating a homeostatic control of this parameter. We show here that the blockade of NMDARs of the neuronal network prevents the potentiation of excitatory and inhibitory inputs, and this result leaves open to question the role of the NMDAR isoform involved in the induction of long-term potentiation, which is actually being strongly debated. In postnatal day (P)18-23 rat cortical slices, the blockade of synaptic NR2B-containing NMDARs prevents the induction of the potentiation induced by the HFS protocol, whereas the blockade of NR2A-containing NMDARs reduced the potentiation itself. In P29-P32 cortical slices, the specific activation of NR2A-containing receptors fully ensures the potentiation of excitatory and inhibitory inputs. These results constitute the first report of a functional shift in subunit composition of NMDARs during the critical period (P12-P36), which explains the relative contribution of both NR2B- and NR2A-containing NMDARs in synaptic plasticity processes. These effects of the HFS protocol are mediated by the activation of synaptic NMDARs but our results also indicate that the homeostatic control of the excitation/inhibition balance is independent of NMDAR activation and is due to specialized recurrent interactions between excitatory and inhibitory networks.