Spatial Distribution of Parvalbumin-Positive Fibers in the Mouse Brain and Their Alterations in Mouse Models of Temporal Lobe Epilepsy and Parkinson's Disease / 神经科学通报·英文版

Parvalbumin interneurons belong to the major types of GABAergic interneurons. Although the distribution and pathological alterations of parvalbumin interneuron somata have been widely studied, the distribution and vulnerability of the neurites and fibers extending from parvalbumin interneurons have not been detailly interrogated. Through the Cre recombinase-reporter system, we visualized parvalbumin-positive fibers and thoroughly investigated their spatial distribution in the mouse brain. We found that parvalbumin fibers are widely distributed in the brain with specific morphological characteristics in different regions, among which the cortex and thalamus exhibited the most intense parvalbumin signals. In regions such as the striatum and optic tract, even long-range thick parvalbumin projections were detected. Furthermore, in mouse models of temporal lobe epilepsy and Parkinson's disease, parvalbumin fibers suffered both massive and subtle morphological alterations. Our study provides an overview of parvalbumin fibers in the brain and emphasizes the potential pathological implications of parvalbumin fiber alterations.

Functional Autapses Form in Striatal Parvalbumin Interneurons but not Medium Spiny Projection Neurons / 神经科学通报·英文版

Autapses selectively form in specific cell types in many brain regions. Previous studies have also found putative autapses in principal spiny projection neurons (SPNs) in the striatum. However, it remains unclear whether these neurons indeed form physiologically functional autapses. We applied whole-cell recording in striatal slices and identified autaptic cells by the occurrence of prolonged asynchronous release (AR) of neurotransmitters after bursts of high-frequency action potentials (APs). Surprisingly, we found no autaptic AR in SPNs, even in the presence of Sr2+. However, robust autaptic AR was recorded in parvalbumin (PV)-expressing neurons. The autaptic responses were mediated by GABAA receptors and their strength was dependent on AP frequency and number. Further computer simulations suggest that autapses regulate spiking activity in PV cells by providing self-inhibition and thus shape network oscillations. Together, our results indicate that PV neurons, but not SPNs, form functional autapses, which may play important roles in striatal functions.

Correlation Analysis of Molecularly-Defined Cortical Interneuron Populations with Morpho-Electric Properties in Layer V of Mouse Neocortex / 神经科学通报·英文版

Cortical interneurons can be categorized into distinct populations based on multiple modalities, including molecular signatures and morpho-electrical (M/E) properties. Recently, many transcriptomic signatures based on single-cell RNA-seq have been identified in cortical interneurons. However, whether different interneuron populations defined by transcriptomic signature expressions correspond to distinct M/E subtypes is still unknown. Here, we applied the Patch-PCR approach to simultaneously obtain the M/E properties and messenger RNA (mRNA) expression of >600 interneurons in layer V of the mouse somatosensory cortex (S1). Subsequently, we identified 11 M/E subtypes, 9 neurochemical cell populations (NCs), and 20 transcriptomic cell populations (TCs) in this cortical lamina. Further analysis revealed that cells in many NCs and TCs comprised several M/E types and were difficult to clearly distinguish morpho-electrically. A similar analysis of layer V interneurons of mouse primary visual cortex (V1) and motor cortex (M1) gave results largely comparable to S1. Comparison between S1, V1, and M1 suggested that, compared to V1, S1 interneurons were morpho-electrically more similar to M1. Our study reveals the presence of substantial M/E variations in cortical interneuron populations defined by molecular expression.

Developmental Origins of Human Cortical Oligodendrocytes and Astrocytes / 神经科学通报·英文版

Human cortical radial glial cells are primary neural stem cells that give rise to cortical glutaminergic projection pyramidal neurons, glial cells (oligodendrocytes and astrocytes) and olfactory bulb GABAergic interneurons. One of prominent features of the human cortex is enriched with glial cells, but there are major gaps in understanding how these glial cells are generated. Herein, by integrating analysis of published human cortical single-cell RNA-Seq datasets with our immunohistochemistical analyses, we show that around gestational week 18, EGFR-expressing human cortical truncated radial glial cells (tRGs) give rise to basal multipotent intermediate progenitors (bMIPCs) that express EGFR, ASCL1, OLIG2 and OLIG1. These bMIPCs undergo several rounds of mitosis and generate cortical oligodendrocytes, astrocytes and olfactory bulb interneurons. We also characterized molecular features of the cortical tRG. Integration of our findings suggests a general picture of the lineage progression of cortical radial glial cells, a fundamental process of the developing human cerebral cortex.

Decoding Cortical Glial Cell Development / 神经科学通报·英文版

Mouse cortical radial glial cells (RGCs) are primary neural stem cells that give rise to cortical oligodendrocytes, astrocytes, and olfactory bulb (OB) GABAergic interneurons in late embryogenesis. There are fundamental gaps in understanding how these diverse cell subtypes are generated. Here, by combining single-cell RNA-Seq with intersectional lineage analyses, we show that beginning at around E16.5, neocortical RGCs start to generate ASCL1

Hippocampal Interneurons are Required for Trace Eyeblink Conditioning in Mice / 神经科学通报·英文版

While the hippocampus has been implicated in supporting the association among time-separated events, the underlying cellular mechanisms have not been fully clarified. Here, we combined in vivo multi-channel recording and optogenetics to investigate the activity of hippocampal interneurons in freely-moving mice performing a trace eyeblink conditioning (tEBC) task. We found that the hippocampal interneurons exhibited conditioned stimulus (CS)-evoked sustained activity, which predicted the performance of conditioned eyeblink responses (CRs) in the early acquisition of the tEBC. Consistent with this, greater proportions of hippocampal pyramidal cells showed CS-evoked decreased activity in the early acquisition of the tEBC. Moreover, optogenetic suppression of the sustained activity in hippocampal interneurons severely impaired acquisition of the tEBC. In contrast, suppression of the sustained activity of hippocampal interneurons had no effect on the performance of well-learned CRs. Our findings highlight the role of hippocampal interneurons in the tEBC, and point to a potential cellular mechanism subserving associative learning.

A Whole-brain Map of Long-range Inputs to GABAergic Interneurons in the Mouse Caudal Forelimb Area / 神经科学通报·英文版

The caudal forelimb area (CFA) of the mouse cortex is essential in many forelimb movements, and diverse types of GABAergic interneuron in the CFA are distinct in the mediation of cortical inhibition in motor information processing. However, their long-range inputs remain unclear. In the present study, we combined the monosynaptic rabies virus system with Cre driver mouse lines to generate a whole-brain map of the inputs to three major inhibitory interneuron types in the CFA. We discovered that each type was innervated by the same upstream areas, but there were quantitative differences in the inputs from the cortex, thalamus, and pallidum. Comparing the locations of the interneurons in two sub-regions of the CFA, we discovered that their long-range inputs were remarkably different in distribution and proportion. This whole-brain mapping indicates the existence of parallel pathway organization in the forelimb subnetwork and provides insight into the inhibitory processes in forelimb movement to reveal the structural architecture underlying the functions of the CFA.

Adolescent stress increases depression-like behaviors and alters the excitatory-inhibitory balance in aged mice / 中华医学杂志(英文版)

Background@#Depression affects approximately 5% of elderly people and its etiology might be related to chronic stress exposure during neurodevelopmental periods. In this study, we examined the effects of adolescent chronic social stress in aged mice on depressive behaviors and the excitatory-inhibitory (E/I) balance in stress-sensitive regions of the brain.@*Methods@#Sixty-four adolescent, male C57BL/6 mice were randomly assigned to either the 7-week (from post-natal days 29 to 77) social instability stress (stress group, n = 32) or normal housing conditions (control group, n = 32). At 15 months of age, 16 mice were randomly selected from each group for a series of behavioral tests, including two depression-related tasks (the sucrose preference test and the tail suspension test). Three days following the last behavioral test, eight mice were randomly selected from each group for immunohistochemical analyses to measure the cell density of parvalbumin (PV+)- and calretinin (CR+)-positive gamma-aminobutyric-acid (GABA)ergic inhibitory inter-neurons, and the expression levels of vesicular transporters of glutamate-1 (VGluT1) and vesicular GABA transporter (VGAT) in three stress-sensitive regions of the brain (the medial pre-frontal cortex [mPFC], hippocampus, and amygdala).@*Results@#Behaviorally, compared with the control group, adolescent chronic stress increased depression-like behaviors as shown in decreased sucrose preference (54.96 ± 1.97% vs. 43.11 ± 2.85%, t(22) = 3.417, P = 0.003) and reduced latency to immobility in the tail suspension test (92.77 ± 25.08 s vs. 33.14 ± 5.95 s, t(25) = 2.394, P = 0.025), but did not affect anxiety-like behaviors and pre-pulse inhibition. At the neurobiologic level, adolescent stress down-regulated PV+, not CR+, inter-neuron density in the mPFC (F(1, 39) = 19.30, P < 0.001), and hippocampus (F(1, 42) = 5.823, P = 0.020) and altered the CR+, not PV+, inter-neuron density in the amygdala (F(1, 28) = 23.16, P < 0.001). The VGluT1/VGAT ratio was decreased in all three regions (all F > 10.09, all P < 0.004), which suggests stress-induced hypoexcitability in these regions.@*Conclusions@#Chronic stress during adolescence increased depression-like behaviors in aged mice, which may be associated with the E/I imbalance in stress-sensitive brain regions.

Neuroligins Differentially Mediate Subtype-Specific Synapse Formation in Pyramidal Neurons and Interneurons / 神经科学通报·英文版

Neuroligins (NLs) are postsynaptic cell-adhesion proteins that play important roles in synapse formation and the excitatory-inhibitory balance. They have been associated with autism in both human genetic and animal model studies, and affect synaptic connections and synaptic plasticity in several brain regions. Yet current research mainly focuses on pyramidal neurons, while the function of NLs in interneurons remains to be understood. To explore the functional difference among NLs in the subtype-specific synapse formation of both pyramidal neurons and interneurons, we performed viral-mediated shRNA knockdown of NLs in cultured rat cortical neurons and examined the synapses in the two major types of neurons. Our results showed that in both types of neurons, NL1 and NL3 were involved in excitatory synapse formation, and NL2 in GABAergic synapse formation. Interestingly, NL1 affected GABAergic synapse formation more specifically than NL3, and NL2 affected excitatory synapse density preferentially in pyramidal neurons. In summary, our results demonstrated that different NLs play distinct roles in regulating the development and balance of excitatory and inhibitory synapses in pyramidal neurons and interneurons.

Perineuronal nets-a double-edged sword regulating neuropsychiatric disorders / 中国药理学通报

Perineuronal nets (PNNs) are unique extracellular matrix (ECM) structures surrounding parvalbumin (PV) positive intemeurons in the central nervous system (CNS). The intact structure of PNNs is critical to the function of CNS. PNNs regulate the function of GABA neurons, inhibit the damage of neurons induced by reactive oxygen species, and also participate in the regulation of neuroplasticity and the development of central nervous system. They will change in quantity and quality after mental disorders, aging, memory and drug abuse. Here the focus is on how the PNNs protect interneuron and control plasticity , and on the role of PNNs in memory in normal aging, Alzheimer's disease and drug addiction, and the association with altered PNNs formation. Understanding the molecular mechanism on PNNs would offer insights into new treatments of relevant diseases.

Laminar Distribution of Neurochemically-Identified Interneurons and Cellular Co-expression of Molecular Markers in Epileptic Human Cortex / 神经科学通报·英文版

Inhibitory GABAergic interneurons are fundamental elements of cortical circuits and play critical roles in shaping network activity. Dysfunction of interneurons can lead to various brain disorders, including epilepsy, schizophrenia, and anxiety. Based on the electrophysiological properties, cell morphology, and molecular identity, interneurons could be classified into various subgroups. In this study, we investigated the density and laminar distribution of different interneuron types and the co-expression of molecular markers in epileptic human cortex. We found that parvalbumin (PV) and somatostatin (SST) neurons were distributed in all cortical layers except layer I, while tyrosine hydroxylase (TH) and neuropeptide Y (NPY) were abundant in the deep layers and white matter. Cholecystokinin (CCK) neurons showed a high density in layers IV and VI. Neurons with these markers constituted ~7.2% (PV), 2.6% (SST), 0.5% (TH), 0.5% (NPY), and 4.4% (CCK) of the gray-matter neuron population. Double- and triple-labeling revealed that NPY neurons were also SST-immunoreactive (97.7%), and TH neurons were more likely to express SST (34.2%) than PV (14.6%). A subpopulation of CCK neurons (28.0%) also expressed PV, but none contained SST. Together, these results revealed the density and distribution patterns of different interneuron populations and the overlap between molecular markers in epileptic human cortex.

The Puzzling Case of Hyperexcitability in Amyotrophic Lateral Sclerosis

The development of hyperexcitability in amyotrophic lateral sclerosis (ALS) is a well-known phenomenon. Despite controversy as to the underlying mechanisms, cortical hyperexcitability appears to be closely related to the interplay between excitatory corticomotoneurons and inhibitory interneurons. Hyperexcitability is not a static phenomenon but rather shows a pattern of progression in a spatiotemporal aspect. Cortical hyperexcitability may serve as a trigger to the development of anterior horn cell degeneration through a 'dying forward' process. Hyperexcitability appears to develop during the early disease stages and gradually disappears in the advanced stages of the disease, linked to the destruction of corticomotorneuronal pathways. As such, a more precise interpretation of these unique processes may provide new insight regarding the pathophysiology of ALS and its clinical features. Recently developed technologies such as threshold tracking transcranial magnetic stimulation and automated nerve excitability tests have provided some clues about underlying pathophysiological processes linked to hyperexcitability. Additionally, these novel techniques have enabled clinicians to use the specific finding of hyperexcitability as a useful diagnostic biomarker, enabling clarification of various ALS-mimic syndromes, and the prediction of disease development in pre-symptomatic carriers of familial ALS. In terms of nerve excitability tests for peripheral nerves, an increase in persistent Na+ conductances has been identified as a major determinant of peripheral hyperexcitability in ALS, inversely correlated with the survival in ALS. As such, the present Review will focus primarily on the puzzling theory of hyperexcitability in ALS and summarize clinical and pathophysiological implications for current and future ALS research.

Alterations of the Cerebellar Inhibitory Interneurons and Inhibitory Synapse Following KA-induced Seizures / 대한해부학회지

Most epileptic patients have commonly suffered from recurrent seizures for many years. These seizures are usually associated with inhibitory synaptic reorganization of the hippocampal region, but it is not known whether cerebellar inhibitory synaptic changes can be induced by seizure activity. We sought to determine the pattern of cerebellar alterations in the cerebellar inhibitory interneurons (basket and stellate cells) and then tested if the alterations are associated with their synaptic transmission at the cerebellar GABAergic synapses between inhibitory interneurons and Purkinje cells after systemic kainic acid administration by immunohistochemistry, western blot analysis, dot blot analysis and confocal microscopy. A dramatic increase of the intensity of GAP-43 immunostaining was obvious in the pinceau structures following KA-induced seizures and the intense GAP-43 immunoreaction involved in high expression of PKC-sigma. The activation of the presynaptic terminal at the cerebellar inhibitory synapse is accompanied with strong GABA immunoreactivity in pinceau region (especially 48 h) after KA-seizures. These results suggest a possibility that KA-seizures increase the release of GABA at the cerebellar inhibitory presynaptic terminal and it would be contribute to the depression of Purkinje cell activity, disinhibition, during the epileptogenesis.

PARVALBUMIN-IMMUNOREACTIVE INTERNEURONS ARE CONTROLLED BY AN INHIBITORY NEURONAL NETWORK IN BASOLATERAL NUCLEUS OF THE RAT AMYGDALA / 神经解剖学杂志

As the elements of local neuronal circuits, parvalbumin (PV)-containing interneurons in the basolateral nucleus (BL) of the amygdala play an important role in the amygdaloid functions of emotion, learning and memory. In order to investigate how the PV-containing interneurons in the BL are controlled, the synapses established on PV- containing interneurons in the BL of the rat amygdala were examined under immunoelectron microscopy using the double labeling methods with anti-PV and anti-dopamine (DA) antibodies for a reference of dopaminergic axon terminals. The results show that the PV immunoreactive (IR) neurons formed the synapses mainly on the dendritic structures from shafts of the dendrites to median and small dendritic branches. 68% of the synapses on the PV-IR profiles were formed by unlabeled axon terminals, and 32 % of them were formed by DA- (21 % ) and PV- (11 % )IR axon terminals. Majority of the synapses on the PV-IR neurons formed by unlabeled axon terminals were symmetric type, and only a small a mount of them were asymmetric that were observed between the PV-IR spines and unlabeled axon terminals and in the serial synapses in which an unlabeled axon terminal symmetrically contacted to another unlabeled axon terminal that, in turn, synapsed asymmetrically to the PV-IR dendritic profiles. The synapses formed between the PV-IR profiles and DA- or PV-IR axon terminals were exclusively symmetric. The present results suggest that the PV-containing interneurons in the BL of the rat amygdala were controlled by an inhibitory network formed by the symmetric synapses around them, among which the DA system was included.

Modulation of H Reflex and Reciprocal Inhibition of Soleus Muscle via Electrical and Transcranial Magnetic Stimulation of Antagonist Muscle

OBJECTIVE: To evaluate the effect of a transcranial magnetic stimulation on reciprocal inhibition of the human leg. METHOD: Twenty healthy human subjects who showed significant inhibition of soleus H reflex after conditioning electrical stimulation of tibialis anterior at a conditioning-test interval of 2 ms were included in this study. Changes in the amount of reciprocal inhibition by conditioning electrical stimulus were compared after transcranial magnetic stimulation of tibialis anterior. RESULTS: Approximately 12% inhibition of H reflex was produced by motor threshold stimulation, and 14% inhibition by maximum stimulation of common peroneal nerve. When a submotor threshold cortical shock was given with test-conditioning interval 0 ms, this inhibition was not significantly changed. There was no significant change of H reflex amplitude ratio by conditioning electrical stimulation after delivering supramotor threshold cortical shock. Amplitude of H reflex was enhanced by transcranial magnetic stimulation at each same conditioning electrical stimulation. CONCLUSION: We conclude that TMS can produce excitatory effects on spinal motor neurons rather than Ia inhibitory interneuron and there is no evidence for convergence onto Ia inhibitory interneurons from the fiber systems excited by magnetic stimulation over the cortex.

The Morphologic Changes of Parvalbumin- Immunoreactive Interneurons of the Dentate Gyrus in Kainate-Treated Mouse Hippocampal Slice Culture Epilepsy Model

PURPOSE: Loss of hippocampal interneurons in dentate gyrus has been reported in patients with severe temporal lobe epilepsy and in animals treated with kainic acid(KA). Interneurons contain Ca2+- binding protein parvalbumin(PV). The effects of kainic acid on parvalbumin-immunoreactive (PV-IR) interneurons in dentate gyrus were investigated in organotypic hippocampal slice cultures. METHODS: Cultured hippocampal slices from postnatal day nine C57/BL6 mice were exposed to 10 muM KA, and were observed at 0, 8, 24, 48, 72 hours after a one hour KA exposure. Neuronal injury was determined by morphologic changes of PV-IR interneuron in dentate gyrus. RESULTS: Transient(1 hour) exposure of hippocampal explant cultures to KA produced marked varicosities in dendrites of PV-IR interneuron in dentate gyrus and the shaft of interbeaded dendrite is often much thinner than those in control. The presence of varicosities in dendrites was reversible with KA washout. The dendrites of KA treated explants were no longer beaded at 8, 24, 48 and 72 hours after KA exposure. The number of cells in PV-IR interneurons in dentate gyrus was decreased at 0, 8 hours after exposure. But there was no significant difference in 24, 48 and 72 hours recovery group compared with control group. CONCLUSIONS: The results suggested that loss of PV-IR interneurons in dentate gyrus is transient, and is not accompanied by PV-IR interneuronal cell death.

Loss of Parvalbumin Reactive Interneuron in Area CA3 of the Kainate-Treated Mouse Hippocampal Slice Culture / 대한소아신경학회지

PURPOSE: Loss of hippocampal interneurons in area CA3 has been reported in patients with severe temporal lobe epilepsy and in animals treated with kainic acid(KA). The effects of kainic acid on the survival of parvalbumin-immunoreactive(PARV-IR) interneurons in area CA3 were investigated in organotypic hippocampal slice cultures. METHODS: Cultured hippocampal slices from postnatal day 8-10 FVB mouse were exposed to 5 microM KA, and were analyzed at 0, 8, 24, 48, 72 hours after 1 hour KA exposure. Neuronal injury was determined by morphologic changes of PARV-IR interneuron in area CA3. RESULTS: Untreated cultures displayed an organotypic organization and morphology of PARV-IR interneurons in the hippocampus which paralelled those reported to occur in vivo. The reduction in numbers of PARV-IR interneurons in CA3 after transient(1 hour) exposure to 5 microM KA were similar to those reported to occur in CA1 after transient exposure to 10 microM. Parvalbumin-immunoreactivity transiently was reduced from the soma and dendrites of PARV-IR interneuron within 24 hours. Transient exposure of hippocampal slice cultures to KA produced marked focal swellings of the dendrites of PARV-IR interneurons. At 5 microM KA, more than 30% of the PARV-IR interneuron dendrites in area CA3 had a beaded appearance. The presence of focal swellings was reversible with KA washout and was not accompanied by interneuronal cell death. CONCLUSION: The results suggest that KA-induced cell death is delayed, therefore acute edema is insufficient to kill PARV-IR interneurons in area CA3.

The DiI Staining of Interneuron Dendrites in Kainate-Treated Hippocampal Slice Culture / 대한소아신경학회지

PURPOSE: Excitotoxic injury of the dendrites of inhibitory interneurons could lead to decrease in their synaptic activation, and explain subsequent local circuit hyperexcitability and epilepsy. A hallmark of dendrotoxicity at least in principal neurons of the hippocampus and cortex are focal or varicose swellings of dendritic abors. This research was designed to study morphologic changes of interneuron dendrite in kainate-treated hippocampal slice culture overtime. METHODS: Cultures aged 15-16 Equivalent Postnatal Days (EPD) were exposed to 10 microM kainic acid (KA), and analyzed at 0, 8, 24, 48, 72 hours after transient (1 hour) KA exposure. Neuronal injury was determined by morphologic changes of interneuron dendrites in area CA1 of DiI stained sections. RESULTS: 1) Transient (1 hour) exposure of hippocampal explant cultures to KA produced marked focal swellings of the dendrites of DiI stained interneurons in a highly reproducible manner. 2) The presence of focal swellings was reversible with kainate washout. The dendrites of KA treated explants were no longer beaded at 8, 24, 48, 72 hours after KA exposure. 3) There was no significant difference in the thickness of dendrites in DiI stained interneuron among 8hr, 24hr, 48hr and 72hr recovery group, compared with control group. CONCLUSION: The presence of focal swellings was reversible with kainate washout, and was not accompanied by interneuronal cell death.

The Morphologic Changes of Interneuron Dendrites in Kainate-treated Hippocampal Slice Culture / 대한소아신경학회지

PURPOSE: Excitotoxic injury of the dendrites of inhibitory interneurons could lead to decrease in their synaptic activation, and explain subsequent local circuit hyperexcitability and epilepsy. A hallmark of dendrotoxicity at least in principal neurons of the hippocampus and cortex are focal or varicose swellings of dendritic abors. This research was designed to study morphologic changes of interneuron dendrite in kainate-treated hippocampal slice culture overtime. METHODS: Cultures aged to 15-16 Equivalent Postnatal Day (EPD) were exposed to 10microM kainic acid (KA), and were analyzed at 0, 8, 24, 48, 72 hours after transient (1 hour) KA exposure. Neuronal injury was determined by morphologic changes of parvalbumin (PV) positive interneuron dendrites in area CA1 of PV-immunohistochemically stained sections. RESULTS: 1) Transient (1 hour) exposure of hippocampal explant cultures to KA produced marked focal swellings of the dendrites of PV-immunoreactive interneurons in a highly reproducible manner. 2) The presence of focal swellings was reversible with kainate washout. The dendrites of KA treated explants were no longer beaded at 8, 24, 48, 72hours after KA exposure.3) The number of cells in PV-immunoreactive interneuron was decreased at 0, 8, 24 hours after exposure. But there was no significant difference among 48hr and 72hr recovery group compare with control group.4) The total length of dendrites was decreased between 0 and 8hours after exposure. But there was no significant difference among 24, 48, and 72hr recovery group compare with control group.5) The branches of dendrites were decreased just after exposure. But there was no significant difference among 8hr, 24hr, 48hr, and 72hr recovery group compare with control group. CONCLUSION: The presence of focal swellings was reversible with kainate washout, and was not accompanied by interneuronal cell death.