Hippocampus: Molecular, Cellular, and Circuit Features in Anxiety / 神经科学通报·英文版

Anxiety disorders are currently a major psychiatric and social problem, the mechanisms of which have been only partially elucidated. The hippocampus serves as a major target of stress mediators and is closely related to anxiety modulation. Yet so far, its complex anatomy has been a challenge for research on the mechanisms of anxiety regulation. Recent advances in imaging, virus tracking, and optogenetics/chemogenetics have permitted elucidation of the activity, connectivity, and function of specific cell types within the hippocampus and its connected brain regions, providing mechanistic insights into the elaborate organization of the hippocampal circuitry underlying anxiety. Studies of hippocampal neurotransmitter systems, including glutamatergic, GABAergic, cholinergic, dopaminergic, and serotonergic systems, have contributed to the interpretation of the underlying neural mechanisms of anxiety. Neuropeptides and neuroinflammatory factors are also involved in anxiety modulation. This review comprehensively summarizes the hippocampal mechanisms associated with anxiety modulation, based on molecular, cellular, and circuit properties, to provide tailored targets for future anxiety treatment.

Regulatory Mechanisms of Environmental Molecular Signaling in the Tangential Migration of Cortical Interneurons / 中国生物化学与分子生物学报

Brain activity requires the regulation of excitatory and inhibitory neurons. GABAergic interneurons are considered to prevent hyperexcitability in brain. Severe GABAergic deficits have been proved to cause pathological hyperexcitability. Most cortical interneurons originate from the ventral telencephalon and then undergo a long tangential migration to the cortex, followed by radial migration into developing cortical plate. Among them, tangential migration is considered to be the main migration manner of interneurons. The process is rather complex but also precise. With the deepening research on the tangential migration of cortical neurons, many molecules have been proved to play important roles in the process of migration. In this review, we mainly describe the migration path and migration manner of interneurons, and its underlying mechanism in two aspects. On the one hand, neurotrophins such as BDNF, NT-4, GDNF, HGF and neurotransmitters such as GABA, Glu, DA can enhance the motility of interneurons. On the other hand, several protein families as well as proteoglycans, such as Ephrin, Sema and Nrg, can bind to membrane-bound or secreted guidance cues of interneurons, providing direction clues for neuronal migration. In this review, we discussed the tangential migration of interneurons in mice, in order to provide novel insights into the regulatory molecular mechanisms of cerebral cortical development and help to develop new targets against defects in neural developments.

The effect of µ-opioid receptor activation on GABAergic neurons in the spinal dorsal horn

The superficial dorsal horn of the spinal cord plays an important role in pain transmission and opioid activity. Several studies have demonstrated that opioids modulate pain transmission, and the activation of µ-opioid receptors (MORs) by opioids contributes to analgesic effects in the spinal cord. However, the effect of the activation of MORs on GABAergic interneurons and the contribution to the analgesic effect are much less clear. In this study, using transgenic mice, which allow the identification of GABAergic interneurons, we investigated how the activation of MORs affects the excitability of GABAergic interneurons and synaptic transmission between primary nociceptive afferent and GABAergic interneurons. We found that a selective µ-opioid agonist, [D-Ala², NMe-Phe⁴, Gly-ol]-enkephanlin (DAMGO), induced an outward current mediated by K⁺ channels in GABAergic interneurons. In addition, DAMGO reduced the amplitude of evoked excitatory postsynaptic currents (EPSCs) of GABAergic interneurons which receive monosynaptic inputs from primary nociceptive C fibers. Taken together, we found that DAMGO reduced the excitability of GABAergic interneurons and synaptic transmission between primary nociceptive C fibers and GABAergic interneurons. These results suggest one possibility that suppression of GABAergic interneurons by DMAGO may reduce the inhibition on secondary GABAergic interneurons, which increase the inhibition of the secondary GABAergic interneurons to excitatory neurons in the spinal dorsal horn. In this circumstance, the sum of excitation of the entire spinal network will control the pain transmission.

Effect of sevoflurane on the electric activities of inhibitory interneurons in basal forebrain area / 临床麻醉学杂志

Objective To provide new experimental evidences associated with the mechanisms of inhaled anesthetics, the effects of sevoflurane on the electric activities of inhibitory interneurons in basal forebrain area (BF) were observed.Methods C57BL/6 mice, aged 2-3 weeks, were used and BF sections were cut for whole patch-clamp recording.Artificial cerebrospinal fluid containing sevoflurane was given and action potential, inhibitory postsynaptic potential were recorded.Results Sevoflurane could increase the frequency of firing rate of inhibitory interneurons in basal forebrain area (P<0.001), which could increase the frequency of action potential caused by depolarization current (P<0.05), and increase the frequency of spontaneous inhibitory postsynaptic currents of pyramidal neurons (P<0.05), while AP-depended miniature inhibitory postsynaptic currents were not significantly changed.Conclusion The basal forebrain inhibitory interneurons are involved in the anesthetic effect of sevoflurane.

New use of old drug:introductiono f the antidepressant effects of ketamine and the underlying mechanisms / 医学研究生学报

Ketamine, a nons-elective N -methyl-D-aspartate (NMDA ) receptor antagonist , is widely used as a general anesthetic in clinical practice. Recent studies have shown that ketamine can produce rapid , effective, and long-lasting antidepressant effects , and the strength of synaptic plasticity induced by inhibitory interneurons , excitatory transmitters , AMPA receptors , and postsynaptic signal pathways may be involved in this procedure .The antidepressant effects of ketamine and the underlying mechanisms are concisely intro -duced in this paper .

Gamma Oscillation in Schizophrenia

Dysfunctional neural circuitry has been found to be involved in abnormalities of perception and cognition in patients with schizophrenia. Gamma oscillations are essential for integrating information within neural circuits and have therefore been associated with many perceptual and cognitive processes in healthy human subjects and animals. This review presents an overview of the neural basis of gamma oscillations and the abnormalities in the GABAergic interneuronal system thought to be responsible for gamma-range deficits in schizophrenia. We also review studies of gamma activity in sensory and cognitive processes, including auditory steady state response, attention, object representation, and working memory, in animals, healthy humans and patients with schizophrenia.

Immunolocalization of estrogen receptor alpha in adult female rat hippocampus / Inmunolocalización del receptor de estrógeno alfa en el hipocampo de rata hembra adulta

The present study was planned to demonstrate the detailed immunoreactive (IR) distribution pattern of estrogen receptors (ER) in hippocampus of 15 female rats, adult, female Wistar rats in estrous phase. 30 µm thick setions of hippocampal region fixed (4 percent buffered paraformaldehyde) were obtained with cryostat. The sections were processed free- floating for immunolocalization of ER using, mouse monoclonal anti-ER-a antibody with PAP technique. The results showed presence of ER immunoreactive neurons in all the subfields of hippocampus with some variations. In cornua ammonis (CA) maximum ER positive (+ve) neurons were localized in CA3 region. Layer analysis showed maximum localization in the stratum oriens (SO) region. In other subfields and layers of CA the IR neurons were comparatively less in number. The morphological characters of all ER +ve neurons showed them to be interneurons both in CA as well as in Dentate gyrus (DG).

El estudio fue diseñado para demostrar el patrón de distribución inmunorreactivo (IR) detallado de los receptores estrogénicos (RE) en el hipocampo de 15 ratas Wistar, hembras, adultas, en fase de estro. Fueron obtenidas secciones 30 µm de grosor con un crióstato, de la región del hipocampo fijadas por perfusión (4 por ciento de paraformaldehído tamponado). Las secciones fueron procesadas, por libre flotación, para la inmunolocalización de RE utilizando anticuerpo monoclonal de ratón anti-ER-a con la técnica de PAP. Los resultados mostraron la presencia de neuronas inmunorreactivas ER en todos los subcampos del hipocampo con algunas variaciones. En el cuerno ventral (CA) la mayor zona RE positiva (+ ve) de las neuronas se localizaron en la región CA3. El análisis de las capas mostró la localización máxima en la región del estrato oriens (SO). En otros subcampos y capas de la CA las neuronas IR fueron comparativamente menores en número. Las características morfológicas de todas las neuronas RE + ve resultaron ser interneuronas tanto en el CA como en el giro dentado (DG).

Apoptosis of the GABAergic interneuron in the dorsal horn of the chronic post-ischemic pain model / 대한마취과학회지

BACKGROUND: It is well known that the GABAergic inhibitory interneuronal system plays an important role in modulation of the noxious stimulation transmitted from the primary afferent input. Some studies have revealed the role that the GABA inhibitory interneuronal system plays in the modulation of pain transmission and the changes in the GABAergic interneurons that occur during the neuropathic pain. This study was conducted to evaluate the apoptosis of the GABAergic interneuron, which is assumed to contribute to neuropathic pain. METHODS: Male Sprague-Dawley rats weighing 290-310 g were used to create a CPIP (chronic post-ischemic pain) model, which was made by placing a tourniquet on the left hindpaw of the rats. The tourniquet was maintained for 3 hours, after which it was released to allow reperfusion. Thirty minutes prior to reperfusion, N-acetyl-L-cysteine (NAC group) or normal saline (control group) was injected. After reperfusion, mechanical allodynia and cold allodynia were measured. In addition, the release of cytochrome c into the cytosol was evaluated through western blot or immunohistochemistry of the spinal cord. RESULTS: Mechanical and cold allodynia developed and the number of GABA interneurons was reduced in the control group. Additionally, The cytochrome c from the GABA interneuron was released into the cytosol in the control group, but the amount released was reduced in response to treatment with NAC. CONCLUSIONS: The results of this study showed that the GABA interneuron in the Rexed laminae I, II released cytochrome c into the cytosol in CPIP neuropathic pain model, which is known to lead to apoptosis. However, treatment with N-acetyl-L-cysteine prevented this process.

Number changes and axonal sprouting of somatostatin positive interneurons in the hippocampus of pilocarpine-induced epileptic rats / 中华神经科杂志

Objective To investigate the roles of somatostatin(SS)positive intemeurons in the development and compensation of temporal lobe epilepsy.Methods Piloearpine-induced epilepsy rat model was established.Immunohistochemistry method was used to detect number changes and axonal sprouting of SS positive intemeurons in different domains of the hippocampus at difierent time points.Degeneration of SS positive interneurons and their neurophils were detected by the double immunofluorescence staining with SS and Fluoro-Jade B(FJB)at 7 and 60 days after status epilepticus (SE).Results In the exoerimental rat group,the number of SS positive neurons decreased in each hippocampal domain,and it reached the lowest at 7 days post-SE(There were 11.1±3.3 in hilus,2.8±0.9 in CA1region and 1.8±0.7 in CA1region,t=13.519,9.644 and 8.808,all P<0.01).In chronic phase,the number of SS neurons gradually recovered,and exceeded the control group in CA1 area at 60 days post-SE(12.8±1.5 vs 8.8±1.3,t=-4.506,P<0.01),however,the number of SS neurons in the hilus(25.5±4.6)and CA1 area(4.8±0.8)remained significantly less than normal levels(t value were 4.691 and 3.953.both P<0.01).Increased SS positive fibers were found in the lacunosum-molecular (1m)layer and outer molecular layer of dentate gyrus after 30 days post-SE,and numerous SS positive fibers were seen threnghout the layers of area CA1 at 60 days post-SE.Double immunofluuorescence revealed that a few SS positive interneurons and fibers were also labeled by FJB in area CA1 at 7 days post-SE and in CA domain/hilus at 60 days post-SE.Conclusions SS intemeurons loss plays an important role in the development of temporal lobe epilepsy.The loss is partially caIlsed by the degeneration and death of neurons;SS positive neurophils increase within area CA1 in chronic phase may play a significant role in the generation and compensation of temporal lobe epilepsy.

Neurotransmisores del sistema límbico. Hipocampo. GABA y memoria. Segunda parte

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Summary: Action of GABA agonists and antagonists on memory. The θ rhythm. Muscimol may directly alter memory. Recently, a modified matching to position (MTP) paradigm was employed aimed at influencing the type of associations a rat may use to solve the task. The main behavioral manipulation was the application of a differential outcomes procedure (DOP). DOP implies correlating each event to be remembered with a different reward condition. This procedure will result in the development of specific reward expectations which will in turn increase and guide choice behavior. Such different reward expectations will not be present when the reward assignation used is either common or random (non-differential outcomes procedure, NOP). Intraventricular infusion of muscimol or CSF in rats carrying out a delayed MTP using either a MOP or an NOP protocol will affect both groups of rats, but the nature of the deficit will differ depending on the reinforcement contingencies. Rats trained in DOP will show general non-mnemonic damage independent of delay, i.e., performance will be affected at all delay intervals employed. On the contrary, rats trained in NOP will show delay-dependent damage. This appears to demonstrate that muscimol may also have untoward memory effects, which further indicates that activation of GABA receptors will affect a set of memory associations and functions. Difficulties experienced in the past regarding LTP induction at the level of the CA3-CA1 synapse using time-based spike presentation protocols have been disconcerting given the preeminence of these synapses as a model system for the study of synaptic plasticity. Results previously discussed in experiments using picrotoxin as a GABA inhibitor have suggested that such difficulties arise from the requirement that, for LTP to be induced, CA1 dendrites must be persistently and totally activated. Doublets used in this case represent a minimal burst, or level of post-synaptic stimulation for LTP induction that subsumes greater depolarizations. In vitro, synaptically induced bursts would correspond to regenerative electrical events in apical dendrites of pyramidal neurons. The same requirements for dendritic activation would be satisfied in vivo during the θ rhythm, which is present during active exploration. Therefore, GABA might serve as an engram modulator through the activation of the hippocampal θ rhythm. Effect of μ-opioid receptors on hippocampal memory activity. Hippocampal μ-opioid receptors (MOR) have been involved in the formation of memory associated with the abuse of opioid drugs. When chronically activated, and during programmed drug abstinence, MORs acutely modulate hippocampal synaptic plasticity At the level of neuronal networks, MORs increase excitability of area CA1 by means of a disinhibition of pyramidal cells. The specific inhibitory interneuronal subtypes which become affected by activation of MORs are not known. Nevertheless, not all subtypes are inhibited and some subtypes preferentially express these receptors. In one study, the effect of activation of MORs on inhibitory patterns and propagation of excitatory activity in CA1 of rat hippocampus was investigated through cortical images created using voltage-sensitive dyes. MOR activation increased excitatory activity originated by the increased stimulating input to stratum oriens (i.e., Schäffer collateral and commissural [SCC] fibers, as well as the retrograde pathway), to stratum radiatum (i.e., SCC fibers) and to stratum lacunosum-moleculare (i.e., the perforant pathway and the thalamus). Increased excitatory activity was additionally facilitated by propagation through the neural network of area CA1. This was observed as a proportionally greater increment of amplitudes of excitatory activity in sites distant from the originally evoked activity. Such facilitation was noted in excitatory activity propagating from three sites of stimulation. The increment and facilitation were prevented with GABAA receptor antagonists (bicuculline, 30 μM), but not with GABAB receptor antagonists (CGP, 10 μM). Besides, MOR activation inhibited inhibitory post-synaptic potentials (IPSPs) in every layer of area CA1. These findings suggest that MOR-originated suppression of GABA release to GABAA receptors increases every type of input to pyramidal CA1 neurons and facilitates propagation of excitatory activity through the neural network of area CA1. Cannabis indica and memory. Cannabinoids (derived from Cannabis indica, or marihuana) disturb memory processes in mammalians. In spite of the fact that the neuronal cannabinoid CB1 receptor was identified several years ago, the neuronal network mechanisms mediating these effects are still controversial. Tritium-labeled GABA-releasing experiments have been used to test for the localization of this receptor at a cellular and subcellular level in the human hippocampus. CB1 expression detected with this technique is limited to hippocampal interneurons, most of which, it could be determined, are cholecystokinin-containing basket neurons. The CB1-positive neuronal somata show immune staining of their cytoplasm, but not of their somatodendritic plasma membrane. CB1-immunoreactive axonic terminals densely cover the entire hippocampus and form symmetrical synapses, characteristic of GABAergic neuronal boutons. It could thus be observed that WIN 55,212-2, a CB1-receptor agonist, considerably reduces the release of tritium-labeled GABA, and that this effect is preventable using the receptor antagonist, SR 141716A. This single pattern of expression and pre-synaptic modulation of GABA release suggests the existence of a preserved role of CB1 receptors in the control of inhibitory hippocampal networks responsible for the generation and maintenance of fast and slow oscillation patterns. Therefore, a probable mechanism whereby cannabinoids could affect associational processes in memory might be a disturbance of synchrony of rhythmical events in distinct neuronal populations. GABA effects against aging. Certain components which stimulate GABAergic neurotransmission might prevent the hippocampal and striatal degeneration which typically appears with old age and causes memory deterioration. On using a 4-vessel occlusion model in animals to study the effect of ischemia on expression of GABAA receptor subunits, which are vulnerable in region CA1 and resistant in region CA3 of Amnion's horn, an increment in expression of GABAA2, GABA B2, GABA G2 units and a decrement in expression of GABA A1 and GABA A3 subunits in region CA3 were obtained. On the contrary, there was no change in region CA1 or the dentate gyrus under the same conditions. These data speak in favor of the stimulation of type 2 receptor GABAergic subunits which might protect certain hippocampal areas against a harmful neurodegenerative effect, for example, of memory activities during old age.

Corticotropin-releasing Factor (CRF) and Urocortin Promote the Survival of Cultured Cerebellar GABAergic Neurons Through the Type 1 CRF Receptor

Corticotropin releasing factor (CRF) is known to be involved in the stress response and in some degenerative brain disorders. In addition, CRF has a role as a neuromodulator in adult cerebellar circuits. Data from developmental studies suggest a putative role for CRF as a trophic factor during cerebellar development. In this study, we investigated the trophic role for CRF family of peptides by culturing cerebellar neurons in the presence of CRF, urocortin or urocortin II. Primary cell cultures of cerebella from embryonic day 18 mice were established, and cells were treated for either 1, 5 or 9 days with Basal Medium Eagles complete medium alone or complete medium with 1 micrometer CRF, urocortin, or urocortin II. The number of GABA-positive neurons in each treatment condition was counted at each culture age for monitoring the changes in neuronal survival. Treatment with 1 micrometer CRF or 1 micrometer urocortin increased the survival of GABAergic neurons at 6 days in vitro and 10 days in vitro, and this survival promoting effect was abolished by treatment with astressin in the presence of those peptides. Based on these data, we suggest that CRF or urocortin has a trophic role promoting the survival of cerebellar GABAergic neurons in cultures.

Neuronal Nicotinic Acetylcholine Receptor Expression, Aging and Mouse Strain-Specific Hippocampal Cytoarchitecture

The differing response by individuals to nicotine reflects the biological outcome of a combination of genetic and environmental factors. Because nicotine imparts its effects through interacting with neuronal nicotinic acetylcholine receptors (nAChR), and mice of different inbred strains differ in their responses to nicotine; mice afford an excellent model for experimentally dissecting the biology of these varied responses. To begin this investigation, we compared the expression of nAChR subunits α3, α4, α5, α7, β2 and β4 in the dorsal hippocampus between 8 mouse strains that differ in their response to nicotine in defined ways. In terms of neuronal distribution, all nAChR subunits co-localized with glutamic acid decarboxylase (GAD) positive interneurons, and heterogeneity in nAChR subunit expression defines four interneuron subgroups. An unexpected finding was that nAChRs are also expressed by astrocytes in a mouse strain¬specific manner and their occurrence varies inversely with nAChR+ interneurons. This relationship is dynamic during the animal’s life span where aged animals exhibit increased nAChR+ astrocyte/interneuron ratios. These findings reveal a complex interplay between genetic and developmental factors that individualize the expression of this modulatory neurotransmitter system in the mammalian nervous system, and would likely customize the response to nicotine.

Roles of Stem Cell Factor and c-kit Receptor in the Development of Cerebellar GABAergic Neurons / 대한해부학회지

Evidence that Stem cell factor (SCF) and c-Kit receptor tyrosine kinase are expressed in the cerebellum during postnatal development, suggests a possible contribution of the SCF/Kit signaling pathway in the cerebellar development. In the present study, we prepared cerebellar cultures from C57Bl/6J mouse at postnatal day 1and 7 to investigate the role of c-kit receptor and SCF in regulation of growth and differentiation in the postnatal cerebellar GABAergic cells. SCF increased the number of survival cerebellar cells and density of glutamic acid decarboxylase 65/67 (GAD65/67) and calbindin D-28K expression in the immunoblot analysis. SCF also improved the neurite extension of the interneuron neuritis and dendritogenesis of Purkinje cells. Treatment with c-Kit antibody accelerated cellular loss in serum-free media and decreased the growth ability and dendritogenesis of Purkinje cells and cerebellar inhibitory interneurons. Our data suggest that SCF and c-kit receptor are required for the normal growth of postnatal cerebellum and a possible involvement of functional regulation through the SCF/c-kit receptor pathways in the postnatal cerebellar development.

Effect of exogenous orexinA on different neurons in mouse prefrontal cortex prelimbic area / 第三军医大学学报

Objective To investigate the effect of exogenous orexinA on the pyramid neurons and interneurons in the prefrontal cortex prelimbic(PL)area.Methods The pyramid neurons and interneurons in PL area of Kunming mice were selected from prefrontal cortex slices by infrared visual patch clamp technique.The morphology and electrophysiological features of the pyramid neurons and interneurons were observed.The effect of exogenous orexinA at a concentration of 400 nmol/L on these cells was studied using the whole cell configuration.Results The pyramid neurons were large,pyramidal in cell body with clear apical dendrites extending vertically and several basal dendrites radiating.The interneurons were comparatively smaller and had several processes from cell body.In current clamp mode,all 54 pyramid neurons having been recorded showed frequency adaption,and the 15 recorded interneurons discharged rapidly and had no frequency adaption.While in vol-tage clamp mode,36 pyramid neurons were regarded as Ih(+)pyramid neurons for recorded hyperpolariztion-activated cation current,and the left 18 and 15 interneurons were Ih(-).Exogenous orexinA had a total reaction rate of 51.9% on 54 recorded pyramid neurons under current clamp,and a rate of 66.7% on 36 Ih(+)pyramid neurons and of 22.2% on the Ih(-)pyramid neurons under voltage clamp.All 15 recorded interneurons had no reaction to exogenous orexinA under either mode.Conclusion OrexinA plays excitatory effect on pyramid neurons in the prefrontal cortex PL area,and this effect is much more noticeable in pyramid neurons with Ih currents.

Electrophysiological and Morphological Classification of Inhibitory Interneurons in Layer II/III of the Rat Visual Cortex

Interneuron diversity is one of the key factors to hinder understanding the mechanism of cortical neural network functions even with their important roles. We characterized inhibitory interneurons in layer II/III of the rat primary visual cortex, using patch-clamp recording and confocal reconstruction, and classified inhibitory interneurons into fast spiking (FS), late spiking (LS), burst spiking (BS), and regular spiking non-pyramidal (RSNP) neurons according to their electrophysiological characteristics. Global parameters to identify inhibitory interneurons were resting membrane potential (> -70 mV) and action potential (AP) width ( 200 M omega) and the shorter P-T time (< 20 msec) than those of regular spiking pyramidal neurons. Confocal reconstruction of recorded cells revealed characteristic morphology of each subtype of inhibitory interneurons. Thus, our results provide at least four subtypes of inhibitory interneurons in layer II/III of the rat primary visual cortex and a classification scheme of inhibitory interneurons.

Experimental study of the relationship between the changes of GABAergic interneurons and temporal lobe epilepsy / 临床神经病学杂志

Objective To systemically discuss the role of Parvalbumin (PV), Calretinin (CR) and Calbindin-D28k (CB)-containing GABAergic interneurons in the acute onset and development of temporal lobe epilepsy.Methods Immunohistochemistry method was used to detect the changes of PV, CR and CB-containing interneuron numbers in hippocampus of temporal lobe epileptic rats induced by lithium-pilocarpine at different time points (6 h, 24 h, 7 d, 15 d, 30 d and 60 d).Results Compared with control group, no loss of PV-positive cells was observed in CA3 region at any time point in epileptic model groups, while dramatic reduction of PV-positive cells was seen in CA1 region ( P0.05). In CA1 region, the number of CB positive interneurons decreased dramatically at 6 h ( P