Signaling pathways responsible for the rapid antidepressant-like effects of a GluN2A-preferring NMDA receptor antagonist

In a previous study we found that the preferring GluN2A receptor antagonist, NVP-AAM077, elicited rapid antidepressant-like effects in the forced swim test that was related to the release of glutamate and serotonin in the medial prefrontal cortex. In the present work we sought to examine the duration of this behavioral effect as well as the molecular readouts involved. Our results showed that NVP-AAM077 reduced the immobility in the forced swim test 30?min and 24?h after its administration. However, this effect waned 7 days later. The rapid antidepressant-like response seems to be associated with increases in the GluA1 subunit of ?-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, mammalian target of rapamycin (mTOR) signaling, glia markers such as glial fibrillary acidic protein (GFAP) and excitatory amino acid transporter 1 (EAAT1), and a rapid mobilization of intracellular stores of brain-derived neurotrophic factor (BDNF) in the medial prefrontal cortex.Acknowledgements: M.G.-S. was recipient of a contract from the Sistema Nacional de Garantía Juvenil co-funded by the European Social Fund. We also thank Novartis for the generous gift of NVP-AAM077. This work was supported by the Instituto de Salud Carlos III, Subdirección General del Evaluación y Fomento de la Investigación (FIS Grants PI13/00038 and PI16/00217) that were co-funded by the European Regional Development Fund (‘A way to build Europe’). Funding from the Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III is also acknowledged

Selective Regulation of NR2B by Protein Phosphatase-1 for the Control of the NMDA Receptor in Neuroprotection

An imbalance between pro-survival and pro-death pathways in brain cells can lead to neuronal cell death and neurodegeneration. While such imbalance is known to be associated with alterations in glutamatergic and Ca2+ signaling, the underlying mechanisms remain undefined. We identified the protein Ser/Thr phosphatase protein phosphatase-1 (PP1), an enzyme associated with glutamate receptors, as a key trigger of survival pathways that can prevent neuronal death and neurodegeneration in the adult hippocampus. We show that PP1α overexpression in hippocampal neurons limits NMDA receptor overactivation and Ca2+ overload during an excitotoxic event, while PP1 inhibition favors Ca2+ overload and cell death. The protective effect of PP1 is associated with a selective dephosphorylation on a residue phosphorylated by CaMKIIα on the NMDA receptor subunit NR2B, which promotes pro-survival pathways and associated transcriptional programs. These results reveal a novel contributor to the mechanisms of neuroprotection and underscore the importance of PP1-dependent dephosphorylation in these mechanisms. They provide a new target for the development of potential therapeutic treatment of neurodegeneration

Diastereoselectivity in the alkylation of 4-fluoroproline methyl esters

The reaction of alkylation of cis- and trans-4-fluoro-N-BOC-L-proline methyl esters has been examined by exposing their lithium enolates to a range of alkylating agents. The process showed a high degree of facial diastereoselectivity (except when methyl iodide was used as alkylating agent), invariably giving rise to products bearing the alkyl group in anti with respect to the fluorine atom. A tentative model to account for the observed stereoselectivity is also proposed

The Role of GluN2A and GluN2B Subunits on the Effects of NMDA Receptor Antagonists in Modeling Schizophrenia and Treating Refractory Depression

Paradoxically, N-methyl-D-aspartate (NMDA) receptor antagonists are used to model certain aspects of schizophrenia as well as to treat refractory depression. However, the role of different subunits of the NMDA receptor in both conditions is poorly understood. Here we used biochemical and behavioral readouts to examine the in vivo prefrontal efflux of serotonin and glutamate as well as the stereotypical behavior and the antidepressant-like activity in the forced swim test elicited by antagonists selective for the GluN2A (NVP-AAM077) and GluN2B (Ro 25-6981) subunits. The effects of the non-subunit selective antagonist, MK-801; were also studied for comparison. The administration of MK-801 dose dependently increased the prefrontal efflux of serotonin and glutamate and markedly increased the stereotypy scores. NVP-AAM077 also increased the efflux of serotonin and glutamate, but without the induction of stereotypies. In contrast, Ro 25-6981 did not change any of the biochemical and behavioral parameters tested. Interestingly, the administration of NVP-AAM077 and Ro 25-6981 alone elicited antidepressant-like activity in the forced swim test, in contrast to the combination of both compounds that evoked marked stereotypies. Our interpretation of the results is that both GluN2A and GluN2B subunits are needed to induce stereotypies, which might be suggestive of potential psychotomimetic effects in humans, but the antagonism of only one of these subunits is sufficient to evoke an antidepressant response. We also propose that GluN2A receptor antagonists could have potential antidepressant activity in the absence of potential psychotomimetic effect

GluN2A and GluN2B NMDA receptor subunits differentially modulate striatal output pathways and contribute to levodopa-induced abnormal involuntary movements in dyskinetic rats

Dual probe microdialysis was used to investigate whether GluN2A and GluN2B NMDA receptor subunits regulate striatal output pathways under dyskinetic conditions. The preferential GluN2A antagonist NVP-AAM077 perfused in the dopamine-depleted striatum of 6-hydroxydopamine hemilesioned dyskinetic rats reduced GABA and glutamate levels in globus pallidus whereas the selective GluN2B antagonist Ro 25-6981 elevated glutamate without affecting pallidal GABA. Moreover, intrastriatal NVP-AAM077 did not affect GABA but elevated glutamate levels in substantia nigra reticulata whereas Ro 25-6981 elevated GABA and reduced nigral glutamate. To investigate whether GluN2A and GluN2B NMDA receptor subunits are involved in motor pathways underlying dyskinesia expression, systemic NVP-AAM077 and Ro 25-6981 were tested for their ability to attenuate levodopa-induced abnormal involuntary movements. NVP-AAM077 failed to prevent dyskinesia while Ro 25-6981 mildly attenuated it. We conclude that in the dyskinetic striatum, striatal GluN2A subunits tonically stimulate the striato-pallidal pathway whereas striatal GluN2B subunits tonically inhibit striato-nigral projections. Moreover, GluN2A subunits are not involved in dyskinesia expression whereas GluN2B subunits minimally contribute to it. 2013 American Chemical Societ

The different effects on recognition memory of perirhinal kainate and NMDA glutamate receptor antagonism: implications for underlying plasticity mechanisms

To investigate the involvement of different types of glutamate receptors in recognition memory, selective antagonists of NMDA and kainate receptors were locally infused into the perirhinal cortex of the rat temporal lobe. Such infusion of a selective kainate receptor antagonist produced an unusual pattern of recognition memory impairment: amnesia after a short (20 min) but not a long (24 h) delay. In contrast, antagonism of perirhinal NMDA glutamate receptors by locally infused AP-5 (2-amino-5-phosphonopentanoic acid) impaired recognition memory after the long but not the short delay. For both drugs, impairment was found when the drug was present during acquisition but not when it was present during retrieval. Experiments in vitro indicate that selective antagonism of NMDA receptors containing NR2A subunits blocks perirhinal long-term potentiation (LTP), whereas antagonism of NMDA receptors containing NR2B subunits blocks long-term depression (LTD). However, recognition memory after a 24 h delay was impaired only when both an NR2A and an NR2B antagonist were infused together, not when either was infused separately. These results establish that kainate receptors have a role in recognition memory that is distinct from that of NMDA receptors, that there must be at least two independent underlying memory mechanisms in the infused region, that this region and no other is necessary for both short-term and long-term familiarity discrimination, and that perirhinal-dependent long-term recognition memory does not rely solely on processes used in NMDA-dependent LTP or LTD (although it might be independently supported by components of each type of process with one substituting for the other)

The role of GluN2A and GluN2B subunits on the effects of NMDA receptor antagonists in modeling schizophrenia and treating refractory depression

Paradoxically, N-methyl-D-aspartate (NMDA) receptor antagonists are used to model certain aspects of schizophrenia as well as to treat refractory depression. However, the role of different subunits of the NMDA receptor in both conditions is poorly understood. Here we used biochemical and behavioral readouts to examine the in vivo prefrontal efflux of serotonin and glutamate as well as the stereotypical behavior and the antidepressant-like activity in the forced swim test elicited by antagonists selective for the GluN2A (NVP-AAM077) and GluN2B (Ro 25-6981) subunits. The effects of the non-subunit selective antagonist, MK-801; were also studied for comparison. The administration of MK-801 dose dependently increased the prefrontal efflux of serotonin and glutamate and markedly increased the stereotypy scores. NVP-AAM077 also increased the efflux of serotonin and glutamate, but without the induction of stereotypies. In contrast, Ro 25-6981 did not change any of the biochemical and behavioral parameters tested. Interestingly, the administration of NVP-AAM077 and Ro 25-6981 alone elicited antidepressant-like activity in the forced swim test, in contrast to the combination of both compounds that evoked marked stereotypies. Our interpretation of the results is that both GluN2A and GluN2B subunits are needed to induce stereotypies, which might be suggestive of potential psychotomimetic effects in humans, but the antagonism of only one of these subunits is sufficient to evoke an antidepressant response. We also propose that GluN2A receptor antagonists could have potential antidepressant activity in the absence of potential psychotomimetic effects.This work was supported by the Instituto de Salud Carlos III, Subdirección General del Evaluación y Fomento de la Investigación (FIS Grants PI10-01103 and PI13-00038) that were co-funded by the European Regional Development Fund (“A way to build Europe”). Funding from the Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), and the Generalitat de Catalunya (2009SGR220) is also acknowledgedPeer Reviewe