Synthesis and impact of neuroestradiol on hippocampal neuronal networks

The production of estradiol within the brain, that is, neuroestradiol (nE2), is widely documented. nE2 deeply impacts adult brain physiology and synaptic plasticity. In the hippocampus, a region of the brain essential for cognitive function, multiple cellular sources, and targets of nE2 have been identified. The impact of estradiol in excitatory and inhibitory neurotransmission suggests a role for regulated nE2 synthesis in the coordination of the activity of different cellular elements of hippocampal network. Here, we review the role of nE2 in the physiology of the hippocampal circuits taking into account the cellular heterogeneity of the hippocampus. We aspire at expanding the consideration of neuron-derived estradiol as a neuromodulator of hippocampal network activities underlying cognition

GSK-3β orchestrates the inhibitory innervation of adult-born dentate granule cells in vivo

Adult hippocampal neurogenesis enhances brain plasticity and contributes to the cognitive reserve during aging. Adult hippocampal neurogenesis is impaired in neurological disorders, yet the molecular mechanisms regulating the maturation and synaptic integration of new neurons have not been fully elucidated. GABA is a master regulator of adult and developmental neurogenesis. Here we engineered a novel retrovirus encoding the fusion protein Gephyrin:GFP to longitudinally study the formation and maturation of inhibitory synapses during adult hippocampal neurogenesis in vivo. Our data reveal the early assembly of inhibitory postsynaptic densities at 1 week of cell age. Glycogen synthase kinase 3 Beta (GSK-3β) emerges as a key regulator of inhibitory synapse formation and maturation during adult hippocampal neurogenesis. GSK-3β-overexpressing newborn neurons show an increased number and altered size of Gephyrin+ postsynaptic clusters, enhanced miniature inhibitory postsynaptic currents, shorter and distanced axon initial segments, reduced synaptic output at the CA3 and CA2 hippocampal regions, and impaired pattern separation. Moreover, GSK-3β overexpression triggers a depletion of Parvalbumin+ interneuron perineuronal nets. These alterations might be relevant in the context of neurological diseases in which the activity of GSK-3β is dysregulatedPID2020-113007RB-I00, SAF-2017-82185-R, PID2020-112824GB-10

Selectivity of action of pregabalin on Ca2+ channels but not on fusion pore, exocytotic machinery, or mitochondria in chromaffin cells of the adrenal gland

et al.The present study was planned to investigate the action of pregabalin on voltage-dependent Ca2+ channels (VDCCs) and novel targets (fusion pore formed between the secretory vesicle and the plasma membrane, exocytotic machinery, and mitochondria) that would further explain its inhibitory action on neurotransmitter release. Electrophysiological recordings in the perforated-patch configuration of the patch-clamp technique revealed that pregabalin inhibits by 33.4 ± 2.4 and 39 ± 4%, respectively, the Ca2+ current charge density and exocytosis evoked by depolarizing pulses in mouse chromaffin cells. Approximately half of the inhibitory action of pregabalin was rescued by L-isoleucine, showing the involvement of α2δ-dependent and -independent mechanisms. Ca2+ channel blockers were used to inhibit Cav1, Cav2.1, and Cav2.2 channels in mouse chromaffin cells, which were unselectively blocked by the drug. Similar values of Ca2+ current charge blockade were obtained when pregabalin was tested in human or bovine chromaffin cells, which express very different percentages of VDCC types with respect to mouse chromaffin cells. These results demonstrate that the inhibitory action of pregabalin on VDCCs and exocytosis does not depend on α1 Ca2+ channel subunit types. Carbon fiber amperometric recordings of digitonin-permeabilized cells showed that neither the fusion pore nor the exocytotic machinery were targeted by pregabalin. Mitochondrial Ca2+ measurements performed with mitochondrial ratiometric pericam demonstrated that Ca2+ uptake or release from mitochondria were not affected by the drug. The selectivity of action of pregabalin might explain its safety, good tolerability, and reduced adverse effects. In addition, the inhibition of the exocytotic process in chromaffin cells might have relevant clinical consequences. Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics.This work was supported by the Ministerio de Ciencia e Innovación [Grants BFU2008-01382, BFU2011-27690 (to A.A.), BFU2010-17379 (to M.T.A.)]; and Pfizer S.L.U. (to A.A.). A.H.-V. holds a fellowship from the Universidad Autónoma de Madrid, and A.J.M.-O. holds a fellowship from the Ministerio de Educación.Peer Reviewe

Melanopsin for precise optogenetic activation of astrocyte-neuron networks

Optogenetics has been widely expanded to enhance or suppress neuronal activity and it has been recently applied to glial cells. Here, we have used a new approach based on selective expression of melanopsin, a G-protein-coupled photopigment, in astrocytes to trigger Ca2+ signaling. Using the genetically encoded Ca2+ indicator GCaMP6f and two-photon imaging, we show that melanopsin is both competent to stimulate robust IP3-dependent Ca2+ signals in astrocyte fine processes, and to evoke an ATP/Adenosine-dependent transient boost of hippocampal excitatory synaptic transmission. Additionally, under low-frequency light stimulation conditions, melanopsin-transfected astrocytes can trigger long-term synaptic changes. In vivo, melanopsin-astrocyte activation enhances episodic-like memory, suggesting melanopsin as an optical tool that could recapitulate the wide range of regulatory actions of astrocytes on neuronal networks in behaving animals. These results describe a novel approach using melanopsin as a precise trigger for astrocytes that mimics their endogenous G-protein signaling pathways, and present melanopsin as a valuable optical tool for neuron-glia studies.The authors thank Dr. J. Chen (UCSD, CA, USA) for providing IP3R2−/− mice; Dr. W. Buño, Dr. E. Martin and Dr. Araque for helpful comments; Dr. JA Esteban, C. Sánchez and M.A. Muñoz for helpful assistance with the two‐photon technical assistance; Dr. M. Valero for MATLAB advice. This work was supported by PhD fellowship program (MINECO, BES‐2014‐067594) to S.M; and MINECO grants (BFU2013‐47265R; Intramural 201620I017; BFU2016‐75107‐P) to G.P

Monkey Adrenal Chromaffin Cells Express α6β4* Nicotinic Acetylcholine Receptors

<div><p>Nicotinic acetylcholine receptors (nAChRs) that contain α6 and β4 subunits have been demonstrated functionally in human adrenal chromaffin cells, rat dorsal root ganglion neurons, and on noradrenergic terminals in the hippocampus of adolescent mice. In human adrenal chromaffin cells, α6β4* nAChRs (the asterisk denotes the possible presence of additional subunits) are the predominant subtype whereas in rodents, the predominant nAChR is the α3β4* subtype. Here we present molecular and pharmacological evidence that chromaffin cells from monkey (<i>Macaca mulatta</i>) also express α6β4* receptors. PCR was used to show the presence of transcripts for α6 and β4 subunits and pharmacological characterization was performed using patch-clamp electrophysiology in combination with α-conotoxins that target the α6β4* subtype. Acetylcholine-evoked currents were sensitive to inhibition by BuIA[T5A,P6O] and MII[H9A,L15A]; α-conotoxins that inhibit α6-containing nAChRs. Two additional agonists were used to probe for the expression of α7 and β2-containing nAChRs. Cells with currents evoked by acetylcholine were relatively unresponsive to the α7-selctive agonist choline but responded to the agonist 5-I-A-85380. These studies provide further insights into the properties of natively expressed α6β4* nAChRs.</p></div

Sex-specific regulation of inhibition and network activity by local aromatase in the mouse hippocampus

Cognitive function relies on a balanced interplay between excitatory and inhibitory neurons (INs), but the impact of estradiol on IN function is not fully understood. Here, we characterize the regulation of hippocampal INs by aromatase, the enzyme responsible for estradiol synthesis, using a combination of molecular, genetic, functional and behavioral tools. The results show that CA1 parvalbumin-expressing INs (PV-INs) contribute to brain estradiol synthesis. Brain aromatase regulates synaptic inhibition through a mechanism that involves modification of perineuronal nets enwrapping PV-INs. In the female brain, aromatase modulates PV-INs activity, the dynamics of network oscillations and hippocampal-dependent memory. Aromatase regulation of PV-INs and inhibitory synapses is determined by the gonads and independent of sex chromosomes. These results suggest PV-INs are mediators of estrogenic regulation of behaviorally-relevant activity.We thank E. Jiménez, A. Arroyo, and C. Sanmartín Segovia for help with image analysis; C. Sánchez for Python data processing scripts, J.G. Yagüe and M.A. Arévalo for production and validation of aromatase antibody; A.P. Arnold (UCLA, USA) for the kind gift of the FCG mice and A. Bacci (ICM, Paris, France) and L.M. García-Segura (Cajal Institute, Madrid, Spain) for helpful discussions on the manuscript. This work was supported by grants: RYC-2015-18545 (to P.M.), funded by MCIN/AEI/ 10.13039/501100011033 by “ESF Investing in your future”, BFU2017-84490-P (to P.M.) and RTI2018-098581-B-I00 (to L.M.P.) funded by MCIN/AEI/ 10.13039/501100011033 by “ERDF A way of making Europe” and PID2020-112824GB-100 (to P.M.) funded by MCIN/AEI/ 10.13039/501100011033. N.C.-A. is supported by the Ph.D. fellowship PRE2018-084857 funded by MCIN/AEI/10.13039/501100011033 by “ESF Investing in your future”. A.S.-A. is supported by the Juan de la Cierva program FJCI-2017-32719 funded by MCIN/AEI/10.13039/501100011033

Sequence alignment of monkey and human α6 nAChR subunits.

<p>A, Sequence alignment of monkey and human α6 subunits identified a single residue in the extracellular ligand-binding domain at position 100 that differed between the two species. The asterisks identify residues that have previously shown to be important for α-Ctx binding <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094142#pone.0094142-Hone3" target="_blank">[47]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094142#pone.0094142-Azam5" target="_blank">[48]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094142#pone.0094142-Kim1" target="_blank">[49]</a>. Note that these residues are strictly conserved between the two species. TM indicates the transmembrane domains.</p