RESUMEN
Information is transmitted between brain regions through the release of neurotransmitters from long-range projecting axons. Understanding how the activity of such long-range connections contributes to behavior requires efficient methods for reversibly manipulating their function. Chemogenetic and optogenetic tools, acting through endogenous G-protein-coupled receptor pathways, can be used to modulate synaptic transmission, but existing tools are limited in sensitivity, spatiotemporal precision or spectral multiplexing capabilities. Here we systematically evaluated multiple bistable opsins for optogenetic applications and found that the Platynereis dumerilii ciliary opsin (PdCO) is an efficient, versatile, light-activated bistable G-protein-coupled receptor that can suppress synaptic transmission in mammalian neurons with high temporal precision in vivo. PdCO has useful biophysical properties that enable spectral multiplexing with other optogenetic actuators and reporters. We demonstrate that PdCO can be used to conduct reversible loss-of-function experiments in long-range projections of behaving animals, thereby enabling detailed synapse-specific functional circuit mapping.
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Neuronas , Optogenética , Optogenética/métodos , Animales , Neuronas/fisiología , Neuronas/metabolismo , Transmisión Sináptica , Opsinas/genética , Opsinas/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Receptores Acoplados a Proteínas G/genética , Ratones , Humanos , Sinapsis/fisiología , Sinapsis/metabolismoRESUMEN
In humans and numerous other mammalian species, individuals considerably vary in their level of trait anxiety. This well known phenomenon is closely related to the etiology of several psychiatric disorders, but its neurophysiological basis remains poorly understood. Here, we applied voltage-sensitive dye imaging to brain slices from animals of the high (HAB), normal (NAB), and low (LAB) trait anxiety mouse model and investigated whether evoked neuronal activity propagations from the lateral (LA) to the central (CeA) amygdala differ in their relative strength among HAB, NAB, and LAB mice. For this purpose, we divided a real-time measure of neuronal population activity in the CeA by a respective measure obtained for the LA. This calculation yielded the metric "CeA/LA activity." Our data clearly demonstrate a positive correlation between trait anxiety levels evaluated by the elevated plus-maze test and CeA/LA activity. Moreover, we found reduced CeA/LA activity in HAB mice, which responded with decreased anxiety levels to an environmental enrichment and, inversely, detected increased anxiety levels and CeA/LA activity in LAB mice that experienced chronic mild stress. We did not observe differences in the spread of neuronal activity in the motor and visual cortex among HAB, NAB, and LAB animals. Collectively, these findings provide evidence that, in mammals, interindividual variability in trait anxiety is causally linked to individual variations in the physiological constitution of the LA-to-CeA circuitry that give rise to a differential regulation of neuronal signal flow through this fundamental input-output network of the amygdala.
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Amígdala del Cerebelo/fisiopatología , Ansiedad/fisiopatología , Conducta Animal , Animales , Conducta Animal/fisiología , Modelos Animales de Enfermedad , Aprendizaje por Laberinto/fisiología , Ratones , Imagen de Colorante Sensible al VoltajeRESUMEN
Vasopressin secretion from the magnocellular neurosecretory cells (MNCs) is crucial for body fluid homeostasis. Osmotic regulation of MNC activity involves the concerted modulation of intrinsic mechanosensitive ion channels, taurine release from local astrocytes as well as excitatory inputs derived from osmosensitive forebrain regions. Extracellular signal-regulated protein kinases (ERK) are mitogen-activated protein kinases that transduce extracellular stimuli into intracellular post-translational and transcriptional responses, leading to changes in intrinsic neuronal properties and synaptic function. Here, we investigated whether ERK activation (i.e. phosphorylation) plays a role in the functioning of forebrain osmoregulatory networks. We found that within 10 min after intraperitoneal injections of hypertonic saline (3 m, 6 m) in rats, many phosphoERK-immunopositive neurones were observed in osmosensitive forebrain regions, including the MNC containing supraoptic nuclei. The intensity of ERK labelling was dose-dependent. Reciprocally, slow intragastric infusions of water that lower osmolality reduced basal ERK phosphorylation. In the supraoptic nucleus, ERK phosphorylation predominated in vasopressin neurones vs. oxytocin neurones and was absent from astrocytes. Western blot experiments confirmed that phosphoERK expression in the supraoptic nucleus was dose dependent. Intracerebroventricular administration of the ERK phosphorylation inhibitor U 0126 before a hyperosmotic challenge reduced the number of both phosphoERK-immunopositive neurones and Fos expressing neurones in osmosensitive forebrain regions. Blockade of ERK phosphorylation also reduced hypertonically induced depolarization and an increase in firing of the supraoptic MNCs recorded in vitro. It finally reduced hypertonically induced vasopressin release in the bloodstream. Altogether, these findings identify ERK phosphorylation as a new element contributing to the osmoregulatory mechanisms of vasopressin release.
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Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Sistema de Señalización de MAP Quinasas , Neuronas/enzimología , Osmorregulación , Prosencéfalo/enzimología , Animales , Ingestión de Líquidos , Activación Enzimática , Potenciales Evocados , Quinasas MAP Reguladas por Señal Extracelular/antagonistas & inhibidores , Femenino , Inyecciones Intraperitoneales , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Masculino , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Concentración Osmolar , Osmorregulación/efectos de los fármacos , Fosforilación , Prosencéfalo/efectos de los fármacos , Prosencéfalo/metabolismo , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Proto-Oncogénicas c-fos/metabolismo , Ratas Wistar , Solución Salina Hipertónica/administración & dosificación , Núcleo Supraóptico/enzimología , Núcleo Supraóptico/metabolismo , Factores de Tiempo , Vasopresinas/metabolismoRESUMEN
Pharmacological approaches to induce N-methyl-d-aspartate receptor (NMDAR) hypofunction have been intensively used to understand the aetiology and pathophysiology of schizophrenia. Yet, the precise cellular and molecular mechanisms that relate to brain network dysfunction remain largely unknown. Here, we used a set of complementary approaches to assess the functional network abnormalities present in male mice that underwent a 7-day subchronic phencyclidine (PCP 10 mg/kg, subcutaneously, once daily) treatment. Our data revealed that pharmacological intervention with PCP affected cognitive performance and auditory evoked gamma oscillations in the prefrontal cortex (PFC) mimicking endophenotypes of some schizophrenia patients. We further assessed PFC cellular function and identified altered neuronal intrinsic membrane properties, reduced parvalbumin (PV) immunostaining and diminished inhibition onto L5 PFC pyramidal cells. A decrease in the strength of optogenetically-evoked glutamatergic current at the ventral hippocampus to PFC synapse was also demonstrated, along with a weaker shunt of excitatory transmission by local PFC interneurons. On a macrocircuit level, functional ultrasound measurements indicated compromised functional connectivity within several brain regions particularly involving PFC and frontostriatal circuits. Herein, we reproduced a panel of schizophrenia endophenotypes induced by subchronic PCP application in mice. We further recapitulated electrophysiological signatures associated with schizophrenia and provided an anatomical reference to critical elements in the brain circuitry. Together, our findings contribute to a better understanding of the physiological underpinnings of deficits induced by subchronic NMDAR antagonist regimes and provide a test system for characterization of pharmacological compounds.
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Modelos Animales de Enfermedad , Fenciclidina , Corteza Prefrontal , Receptores de N-Metil-D-Aspartato , Animales , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/metabolismo , Masculino , Fenciclidina/farmacología , Receptores de N-Metil-D-Aspartato/metabolismo , Ratones , Esquizofrenia/inducido químicamente , Esquizofrenia/fisiopatología , Esquizofrenia/metabolismo , Ratones Endogámicos C57BL , Parvalbúminas/metabolismo , Adaptación Fisiológica/efectos de los fármacos , Adaptación Fisiológica/fisiología , Células Piramidales/efectos de los fármacos , Células Piramidales/fisiología , Ritmo Gamma/efectos de los fármacos , Ritmo Gamma/fisiología , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Antagonistas de Aminoácidos Excitadores/farmacologíaRESUMEN
Information is transmitted between brain regions through the release of neurotransmitters from long-range projecting axons. Understanding how the activity of such long-range connections contributes to behavior requires efficient methods for reversibly manipulating their function. Chemogenetic and optogenetic tools, acting through endogenous G-protein coupled receptor (GPCRs) pathways, can be used to modulate synaptic transmission, but existing tools are limited in sensitivity, spatiotemporal precision, or spectral multiplexing capabilities. Here we systematically evaluated multiple bistable opsins for optogenetic applications and found that the Platynereis dumerilii ciliary opsin (PdCO) is an efficient, versatile, light-activated bistable GPCR that can suppress synaptic transmission in mammalian neurons with high temporal precision in-vivo. PdCO has superior biophysical properties that enable spectral multiplexing with other optogenetic actuators and reporters. We demonstrate that PdCO can be used to conduct reversible loss-of-function experiments in long-range projections of behaving animals, thereby enabling detailed synapse-specific functional circuit mapping.
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Adverse events in early life can modulate the response to additional stressors later in life and increase the risk of developing psychiatric disorders. The underlying molecular mechanisms responsible for these effects remain unclear. Here, we uncover that early life adversity (ELA) in mice leads to social subordination. Using single-cell RNA sequencing (scRNA-seq), we identified cell type-specific changes in the transcriptional state of glutamatergic and GABAergic neurons in the ventral hippocampus of ELA mice after exposure to acute social stress in adulthood. These findings were reflected by an alteration in excitatory and inhibitory synaptic transmission induced by ELA in response to acute social stress. Finally, enhancing the inhibitory network function through transient diazepam treatment during an early developmental sensitive period reversed the ELA-induced social subordination. Collectively, this study significantly advances our understanding of the molecular, physiological, and behavioral alterations induced by ELA, uncovering a previously unknown cell type-specific vulnerability to ELA.
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Experiencias Adversas de la Infancia , Trastornos Mentales , Humanos , Ratones , Animales , Transcriptoma , Estrés Psicológico/genética , Estrés Psicológico/psicología , HipocampoRESUMEN
Pharmacotherapies for the treatment of major depressive disorder were serendipitously discovered almost seven decades ago. From this discovery, scientists pinpointed the monoaminergic system as the primary target associated with symptom alleviation. As a result, most antidepressants have been engineered to act on the monoaminergic system more selectively, primarily on serotonin, in an effort to increase treatment response and reduce unfavorable side effects. However, slow and inconsistent clinical responses continue to be observed with these available treatments. Recent findings point to the glutamatergic system as a target for rapid acting antidepressants. Investigating different cohorts of depressed individuals treated with serotonergic and other monoaminergic antidepressants, we found that the expression of a small nucleolar RNA, SNORD90, was elevated following treatment response. When we increased Snord90 levels in the mouse anterior cingulate cortex (ACC), a brain region regulating mood responses, we observed antidepressive-like behaviors. We identified neuregulin 3 (NRG3) as one of the targets of SNORD90, which we show is regulated through the accumulation of N6-methyladenosine modifications leading to YTHDF2-mediated RNA decay. We further demonstrate that a decrease in NRG3 expression resulted in increased glutamatergic release in the mouse ACC. These findings support a molecular link between monoaminergic antidepressant treatment and glutamatergic neurotransmission.
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Trastorno Depresivo Mayor , Animales , Ratones , Afecto , Antidepresivos/farmacología , Trastorno Depresivo Mayor/tratamiento farmacológico , Transducción de Señal , Transmisión SinápticaRESUMEN
A single sub-anesthetic dose of ketamine produces a rapid and sustained antidepressant response, yet the molecular mechanisms responsible for this remain unclear. Here, we identified cell-type-specific transcriptional signatures associated with a sustained ketamine response in mice. Most interestingly, we identified the Kcnq2 gene as an important downstream regulator of ketamine action in glutamatergic neurons of the ventral hippocampus. We validated these findings through a series of complementary molecular, electrophysiological, cellular, pharmacological, behavioral, and functional experiments. We demonstrated that adjunctive treatment with retigabine, a KCNQ activator, augments ketamine's antidepressant-like effects in mice. Intriguingly, these effects are ketamine specific, as they do not modulate a response to classical antidepressants, such as escitalopram. These findings significantly advance our understanding of the mechanisms underlying the sustained antidepressant effects of ketamine, with important clinical implications.
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Ketamina , Animales , Antidepresivos/farmacología , Hipocampo , Canal de Potasio KCNQ2/genética , Ketamina/farmacología , Ketamina/uso terapéutico , Ratones , Proteínas del Tejido Nervioso , NeuronasRESUMEN
Many organisms sense light using rhodopsins, photoreceptive proteins containing a retinal chromophore. Here we report the discovery, structure and biophysical characterization of bestrhodopsins, a microbial rhodopsin subfamily from marine unicellular algae, in which one rhodopsin domain of eight transmembrane helices or, more often, two such domains in tandem, are C-terminally fused to a bestrophin channel. Cryo-EM analysis of a rhodopsin-rhodopsin-bestrophin fusion revealed that it forms a pentameric megacomplex (~700 kDa) with five rhodopsin pseudodimers surrounding the channel in the center. Bestrhodopsins are metastable and undergo photoconversion between red- and green-absorbing or green- and UVA-absorbing forms in the different variants. The retinal chromophore, in a unique binding pocket, photoisomerizes from all-trans to 11-cis form. Heterologously expressed bestrhodopsin behaves as a light-modulated anion channel.
Asunto(s)
Canales Iónicos , Rodopsina , Bestrofinas , Rodopsina/químicaRESUMEN
Information is carried between brain regions through neurotransmitter release from axonal presynaptic terminals. Understanding the functional roles of defined neuronal projection pathways requires temporally precise manipulation of their activity. However, existing inhibitory optogenetic tools have low efficacy and off-target effects when applied to presynaptic terminals, while chemogenetic tools are difficult to control in space and time. Here, we show that a targeting-enhanced mosquito homolog of the vertebrate encephalopsin (eOPN3) can effectively suppress synaptic transmission through the Gi/o signaling pathway. Brief illumination of presynaptic terminals expressing eOPN3 triggers a lasting suppression of synaptic output that recovers spontaneously within minutes in vitro and in vivo. In freely moving mice, eOPN3-mediated suppression of dopaminergic nigrostriatal afferents induces a reversible ipsiversive rotational bias. We conclude that eOPN3 can be used to selectively suppress neurotransmitter release at presynaptic terminals with high spatiotemporal precision, opening new avenues for functional interrogation of long-range neuronal circuits in vivo.
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Dopamina/metabolismo , Proteínas de Insectos/genética , Optogenética/métodos , Rodopsina/genética , Potenciales Sinápticos , Animales , Células Cultivadas , Culicidae , Neuronas Dopaminérgicas/metabolismo , Neuronas Dopaminérgicas/fisiología , Células HEK293 , Humanos , Proteínas de Insectos/metabolismo , Locomoción , Ratones , Ratones Endogámicos C57BL , Ratas , Ratas Sprague-Dawley , Ratas Wistar , Rodopsina/metabolismo , Sustancia Negra/citología , Sustancia Negra/fisiologíaRESUMEN
Complex behavioral phenotyping techniques are becoming more prevalent in the field of behavioral neuroscience, and thus methods for manipulating neuronal activity must be adapted to fit into such paradigms. Here, we present a head-mounted, magnetically activated device for wireless optogenetic manipulation that is compact, simple to construct, and suitable for use in group-living mice in an enriched semi-natural arena over several days. Using this device, we demonstrate that repeated activation of oxytocin neurons in male mice can have different effects on pro-social and agonistic behaviors, depending on the social context. Our findings support the social salience hypothesis of oxytocin and emphasize the importance of the environment in the study of social neuromodulators. Our wireless optogenetic device can be easily adapted for use in a variety of behavioral paradigms, which are normally hindered by tethered light delivery or a limited environment.
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Conducta Agonística/fisiología , Conducta Animal/fisiología , Neuronas/fisiología , Optogenética/métodos , Oxitocina/metabolismo , Conducta Social , Tecnología Inalámbrica , Animales , Ratones , Neuronas/metabolismoRESUMEN
A series of nipecotic acid derivatives with new azo benzene based photoswitchable N-substituents was synthesized and characterized in their ( E)- and ( Z)-form for their functional inhibitory activity at γ-aminobutyric acid transporters subtype 1 (GAT1), the most common γ-aminobutyric acid (GABA) transporter subtype in the central nervous system (CNS). This led to the identification of the first photoswitchable ligands exhibiting a moderate uptake inhibition of GABA in their ( E)- but distinctive higher inhibitory potency in their ( Z)-form resulting from photoirradiation. For the most efficient photoactivatable nipecotic acid derivative displaying an N-but-3-yn-1-yl linker with a terminal diphenyldiazene unit, an inhibitory potency of 4.65 ± 0.05 (pIC50) was found for its ( E)-form. which increased by almost two log units up to 6.38 ± 0.04 when irradiated. The effect of this photoswitchable mGAT1 inhibitor has also been evaluated and confirmed in patch-clamp recordings in acute hippocampal slices from mice.
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Compuestos Azo/química , Compuestos Azo/farmacología , Procesos Fotoquímicos , Ácido gamma-Aminobutírico/metabolismo , Transporte Biológico/efectos de los fármacos , Células HEK293 , Humanos , Simulación del Acoplamiento Molecular , N-Acetilglucosaminiltransferasas/antagonistas & inhibidores , N-Acetilglucosaminiltransferasas/química , N-Acetilglucosaminiltransferasas/metabolismo , Ácidos Nipecóticos/química , Conformación Proteica , Relación Estructura-ActividadRESUMEN
The interplay between corticotropin-releasing hormone (CRH) and the dopaminergic system has predominantly been studied in addiction and reward, while CRH-dopamine interactions in anxiety are scarcely understood. We describe a new population of CRH-expressing, GABAergic, long-range-projecting neurons in the extended amygdala that innervate the ventral tegmental area and alter anxiety following chronic CRH depletion. These neurons are part of a distinct CRH circuit that acts anxiolytically by positively modulating dopamine release.
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Amígdala del Cerebelo/fisiología , Ansiedad/psicología , Hormona Liberadora de Corticotropina/deficiencia , Dopamina/metabolismo , Neuronas GABAérgicas/fisiología , Amígdala del Cerebelo/citología , Animales , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/fisiología , Hormona Liberadora de Corticotropina/farmacología , Espinas Dendríticas/ultraestructura , Inyecciones , Masculino , Ratones , Ratones Noqueados , Actividad Motora , Optogenética , Percepción del Dolor , Receptores de Hormona Liberadora de Corticotropina/metabolismo , Área Tegmental Ventral/citología , Área Tegmental Ventral/fisiologíaRESUMEN
The neurophysiological processes that can cause theta-to-gamma frequency range (4-80 Hz) network oscillations in the rhinal cortical-hippocampal system and the potential connectivity-based interactions of such forebrain rhythms are a topic of intensive investigation. Here, using selective Channelrhodopsin-2 (ChR2) expression in mouse forebrain glutamatergic cells, we were able to locally, temporally precisely, and reliably induce fast (20-40 Hz) field potential oscillations in hippocampal area CA1 in vitro (at 25°C) and in vivo (i.e., slightly anesthetized NEX-Cre-ChR2 mice). As revealed by pharmacological analyses and patch-clamp recordings from pyramidal cells and GABAergic interneurons in vitro, these light-triggered oscillations can exclusively arise from sustained suprathreshold depolarization (~200 ms or longer) and feedback inhibition of CA1 pyramidal neurons, as being mandatory for prototypic pyramidal-interneuron network (P-I) oscillations. Consistently, the oscillations comprised rhythmically occurring population spikes (generated by pyramidal cells) and their frequency increased with increasing spectral power. We further demonstrate that the optogenetically driven CA1 oscillations, which remain stable over repeated evocations, are impaired by the stress hormone corticotropin-releasing factor (CRF, 125 nM) in vitro and, even more remarkably, found that they are accompanied by concurrent states of enforced theta activity in the memory-associated perirhinal cortex (PrC) in vivo. The latter phenomenon most likely derives from neurotransmission via a known, but poorly studied excitatory CA1âPrC pathway. Collectively, our data provide evidence for the existence of a prototypic (CRF-sensitive) P-I gamma rhythm generator in area CA1 and suggest that CA1 P-I oscillations can rapidly up-regulate theta activity strength in hippocampus-innervated rhinal networks, at least in the PrC.
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[This corrects the article on p. 108 in vol. 10, PMID: 27199662.].
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Signaling by the corticotropin-releasing factor receptor type 1 (CRFR1) plays an important role in mediating the autonomic response to stressful challenges. Multiple hypothalamic nuclei regulate sympathetic outflow. Although CRFR1 is highly expressed in the arcuate nucleus (Arc) of the hypothalamus, the identity of these neurons and the role of CRFR1 here are presently unknown. Our studies show that nearly half of Arc-CRFR1 neurons coexpress agouti-related peptide (AgRP), half of which originate from POMC precursors. Arc-CRFR1 neurons are innervated by CRF neurons in the hypothalamic paraventricular nucleus, and CRF application decreases AgRP(+)CRFR1(+) neurons' excitability. Despite similar anatomy in both sexes, only female mice selectively lacking CRFR1 in AgRP neurons showed a maladaptive thermogenic response to cold and reduced hepatic glucose production during fasting. Thus, CRFR1, in a subset of AgRP neurons, plays a regulatory role that enables appropriate sympathetic nervous system activation and consequently protects the organism from hypothermia and hypoglycemia.
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Adaptación Fisiológica , Proteína Relacionada con Agouti/metabolismo , Frío , Neuronas/metabolismo , Receptores de Hormona Liberadora de Corticotropina/metabolismo , Estrés Fisiológico , Sistema Nervioso Simpático/metabolismo , Adaptación Fisiológica/efectos de los fármacos , Animales , Hormona Liberadora de Corticotropina/metabolismo , Ayuno/fisiología , Conducta Alimentaria/efectos de los fármacos , Femenino , Glucosa/metabolismo , Calor , Leptina/administración & dosificación , Leptina/farmacología , Hígado/efectos de los fármacos , Hígado/metabolismo , Ratones , Neuronas/efectos de los fármacos , Núcleo Hipotalámico Paraventricular/efectos de los fármacos , Núcleo Hipotalámico Paraventricular/metabolismo , Fosforilación/efectos de los fármacos , Proopiomelanocortina/metabolismo , Factor de Transcripción STAT3/metabolismo , Transducción de Señal/efectos de los fármacos , Estrés Fisiológico/efectos de los fármacos , Sistema Nervioso Simpático/efectos de los fármacos , Termogénesis/efectos de los fármacosRESUMEN
Social encounters are associated with varying degrees of emotional arousal and stress. The mechanisms underlying adequate socioemotional balance are unknown. The medial amygdala (MeA) is a brain region associated with social behavior in mice. Corticotropin-releasing factor receptor type-2 (CRF-R2) and its specific ligand urocortin-3 (Ucn3), known components of the behavioral stress response system, are highly expressed in the MeA. Here we show that mice deficient in CRF-R2 or Ucn3 exhibit abnormally low preference for novel conspecifics. MeA-specific knockdown of Crfr2 (Crhr2) in adulthood recapitulated this phenotype. In contrast, pharmacological activation of MeA CRF-R2 or optogenetic activation of MeA Ucn3 neurons increased preference for novel mice. Furthermore, chemogenetic inhibition of MeA Ucn3 neurons elicited pro-social behavior in freely behaving groups of mice without affecting their hierarchal structure. These findings collectively suggest that the MeA Ucn3-CRF-R2 system modulates the ability of mice to cope with social challenges.
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Amígdala del Cerebelo/metabolismo , Receptores de Hormona Liberadora de Corticotropina/metabolismo , Conducta Social , Urocortinas/metabolismo , Animales , Conducta Animal/fisiología , Hormona Liberadora de Corticotropina/metabolismo , Inhibición Psicológica , Ratones , Ratones Noqueados , Neuronas/metabolismo , Receptores de Hormona Liberadora de Corticotropina/genética , Urocortinas/genéticaRESUMEN
Decades of brain research have identified various parallel loops linking the hippocampus with neocortical areas, enabling the acquisition of spatial and episodic memories. Especially the hippocampal trisynaptic circuit [entorhinal cortex layer II â dentate gyrus (DG) â cornu ammonis (CA)-3 â CA1] was studied in great detail because of its seemingly simple connectivity and characteristic structures that are experimentally well accessible. While numerous researchers focused on functional aspects, obtained from a limited number of cells in distinct hippocampal subregions, little is known about the neuronal network dynamics which drive information across multiple synapses for subsequent long-term storage. Fast voltage-sensitive dye imaging in vitro allows real-time recording of activity patterns in large/meso-scale neuronal networks with high spatial resolution. In this way, we recently found that entorhinal theta-frequency input to the DG most effectively passes filter mechanisms of the trisynaptic circuit network, generating activity waves which propagate across the entire DG-CA axis. These "trisynaptic circuit waves" involve high-frequency firing of CA3 pyramidal neurons, leading to a rapid induction of classical NMDA receptor-dependent long-term potentiation (LTP) at CA3-CA1 synapses (CA1 LTP). CA1 LTP has been substantially evidenced to be essential for some forms of explicit learning in mammals. Here, we review data with particular reference to whole network-level approaches, illustrating how activity propagation can take place within the trisynaptic circuit to drive formation of CA1 LTP.
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The neurobiological basis of pathological anxiety and the improvement of its pharmacological treatment are a matter of intensive investigation. Here, using electrophysiological techniques in brain slices from animals of the high anxiety-related behavior (HAB) and normal anxiety-related behavior (NAB) mouse model, we show that basal neurotransmission at ventral hippocampal CA3-CA1 synapses is weaker in HAB compared to NAB mice. We further demonstrate that paired-pulse facilitation (PPF) and long-term potentiation (LTP) at these synapses are more pronounced in slices from HAB animals. Based on previous findings, we also examined whether intranasal delivery of neuropeptide S (NPS), which increasingly emerges as a potential novel treatment option for anxiety symptoms occurring in a variety of diseases like anxiety disorders, posttraumatic stress disorder, and major depression, impacts on the high-anxiety electrophysiological endophenotype in HAB mice. Strikingly, we detected enhanced basal neurotransmission and reduced PPF and LTP in slices from NPS-treated HAB animals. Collectively, our study uncovers a multifaceted high-anxiety neurophysiological endophenotype in the murine ventral hippocampus and provides the first evidence that an intranasally applied neuropeptide can shift such an endophenotype in an anxiety-regulating brain structure towards a "normal"-anxiety one.
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Ansiedad/fisiopatología , Fenómenos Electrofisiológicos/efectos de los fármacos , Endofenotipos , Hipocampo/efectos de los fármacos , Hipocampo/fisiopatología , Neuropéptidos/administración & dosificación , Neuropéptidos/farmacología , Administración Intranasal , Animales , Conducta Animal/efectos de los fármacos , Potenciación a Largo Plazo/efectos de los fármacos , Masculino , Ratones , Sinapsis/efectos de los fármacos , Sinapsis/fisiología , Transmisión Sináptica/efectos de los fármacosRESUMEN
The GABAergic system is the main source of inhibition in the mammalian brain. Consequently, much effort is still made to develop new modulators of GABAergic synaptic transmission. In contrast to glutamatergic postsynaptic potentials (PSPs), accurate monitoring of GABA receptor-mediated PSPs (GABAR-PSPs) and their pharmacological modulation in brain tissue invariably requires the use of intracellular recording techniques. However, these techniques are expensive, time- and labor-consuming, and, in case of the frequently employed whole-cell patch-clamp configuration, impact on intracellular ion concentrations, signaling cascades, and pH buffering systems. Here, we describe a novel approach to circumvent these drawbacks. In particular, we demonstrate in mouse hippocampal slices that selective optogenetic activation of interneurons leads to prominent field inhibitory GABAAR- and GABABR-PSPs in area CA1 which are easily and reliably detectable by a single extracellular recording electrode. The field PSPs exhibit typical temporal and pharmacological characteristics, display pronounced paired-pulse depression, and remain stable over many consecutive evocations. Additionally validating the methodological value of this approach, we further show that the neuroactive steroid 5α-THDOC (5 µM) shifts the inhibitory GABAAR-PSPs towards excitatory ones.