Projection-defined median raphe Pet+ subpopulations are diversely implicated in seizure.

The raphe nuclei, the primary resource of forebrain 5-HT, play an important but heterogeneous role in regulating subcortical excitabilities. Fundamental circuit organizations of different median raphe (MR) subsystems are far from completely understood. In the present study, using cell-specific viral tracing, Ca2+ fiber photometry and epilepsy model, we map out the forebrain efferent and afferent of different MR Pet+ subpopulations and their divergent roles in epilepsy. We found that PetMR neurons send both collateral and parallel innervations to different downstream regions through different subpopulations. Notably, CA3-projecting PetMR subpopulations are largely distinct from habenula (Hb)-projecting PetMR subpopulations in anatomical distribution and topological organization, while majority of the CA3-projecting PetMR subpopulations are overlapped with the medial septum (MS)-projecting PetMR subpopulations. Further, using Ca2+ fiber photometry, we monitor activities of PetMR neurons in hippocampal-kindling seizure, a classical epilepsy model with pathological mechanisms caused by excitation-inhibition imbalance. We found that soma activities of PetMR neurons are heterogeneous during different periods of generalized seizures. These divergent activities are contributed by different projection-defined PetMR subpopulations, manifesting as increased activities in CA3 but decreased activity in Hb resulting from their upstream differences. Together, our findings provide a novel framework of MR subsystems showing that projection-defined MR Pet+ subpopulations are topologically heterogenous with divergent circuit connections and are diversely implicated in seizures. This may help in the understanding of heterogeneous nature of MR 5-HTergic subsystems and the paradox roles of 5-HTergic systems in epilepsy.

Adult-born neurons in critical period maintain hippocampal seizures via local aberrant excitatory circuits.

Temporal lobe epilepsy (TLE), one common type of medically refractory epilepsy, is accompanied with altered adult-born dentate granule cells (abDGCs). However, the causal role of abDGCs in recurrent seizures of TLE is not fully understood. Here, taking advantage of optogenetic and chemogenetic tools to selectively manipulate abDGCs in a reversible manner, combined with Ca2+ fiber photometry, trans-synaptic viral tracing, in vivo/vitro electrophysiology approaches, we aimed to test the role of abDGCs born at different period of epileptogenic insult in later recurrent seizures in mouse TLE models. We found that abDGCs were functionally inhibited during recurrent seizures. Optogenetic activation of abDGCs significantly extended, while inhibition curtailed, the seizure duration. This seizure-modulating effect was attributed to specific abDGCs born at a critical early phase after kindled status, which experienced specific type of circuit re-organization. Further, abDGCs extended seizure duration via local excitatory circuit with early-born granule cells (ebDGCs). Repeated modulation of "abDGC-ebDGC" circuit may easily induce a change of synaptic plasticity, and achieve long-term anti-seizure effects in both kindling and kainic acid-induced TLE models. Together, we demonstrate that abDGCs born at a critical period of epileptogenic insult maintain seizure duration via local aberrant excitatory circuits, and inactivation of these aberrant circuits can long-termly alleviate severity of seizures. This provides a deeper and more comprehensive understanding of the potential pathological changes of abDGCs circuit and may be helpful for the precise treatment in TLE.

Interictal-period-activated neuronal ensemble in piriform cortex retards further seizure development.

Epileptic networks are characterized as having two states, seizures or more prolonged interictal periods. However, cellular mechanisms underlying the contribution of interictal periods to ictal events remain unclear. Here, we use an activity-dependent labeling technique combined with genetically encoded effectors to characterize and manipulate neuronal ensembles recruited by focal seizures (FS-Ens) and interictal periods (IP-Ens) in piriform cortex, a region that plays a key role in seizure generation. Ca2+ activities and histological evidence reveal a disjointed correlation between the two ensembles during FS dynamics. Optogenetic activation of FS-Ens promotes further seizure development, while IP-Ens protects against it. Interestingly, both ensembles are functionally involved in generalized seizures (GS) due to circuit rearrangement. IP-Ens bidirectionally modulates FS but not GS by controlling coherence with hippocampus. This study indicates that the interictal state may represent a seizure-preventing environment, and the interictal-activated ensemble may serve as a potential therapeutic target for epilepsy.

A fluid-structure interaction model accounting arterial vessels as a key part of the blood-flow engine for the analysis of cardiovascular diseases.

According to the classical Windkessel model, the heart is the only power source for blood flow, while the arterial system is assumed to be an elastic chamber that acts as a channel and buffer for blood circulation. In this paper we show that in addition to the power provided by the heart for blood circulation, strain energy stored in deformed arterial vessels in vivo can be transformed into mechanical work to propel blood flow. A quantitative relationship between the strain energy increment and functional (systolic, diastolic, mean and pulse blood pressure) and structural (stiffness, diameter and wall thickness) parameters of the aorta is described. In addition, details of blood flow across the aorta remain unclear due to changes in functional and other physiological parameters. Based on the arterial strain energy and fluid-structure interaction theory, the relationship between physiological parameters and blood supply to organs was studied, and a corresponding mathematical model was developed. The findings provided a new understanding about blood-flow circulation, that is, cardiac output allows blood to enter the aorta at an initial rate, and then strain energy stored in the elastic arteries pushes blood toward distal organs and tissues. Organ blood supply is a key factor in cardio-cerebrovascular diseases (CCVD), which are caused by changes in blood supply in combination with multiple physiological parameters. Also, some physiological parameters are affected by changes in blood supply, and vice versa. The model can explain the pathophysiological mechanisms of chronic diseases such as CCVD and hypertension among others, and the results are in good agreement with epidemiological studies of CCVD.

Discrete subicular circuits control generalization of hippocampal seizures.

Epilepsy is considered a circuit-level dysfunction associated with imbalanced excitation-inhibition, it is therapeutically necessary to identify key brain regions and related circuits in epilepsy. The subiculum is an essential participant in epileptic seizures, but the circuit mechanism underlying its role remains largely elusive. Here we deconstruct the diversity of subicular circuits in a mouse model of epilepsy. We find that excitatory subicular pyramidal neurons heterogeneously control the generalization of hippocampal seizures by projecting to different downstream regions. Notably, anterior thalamus-projecting subicular neurons bidirectionally mediate seizures, while entorhinal cortex-projecting subicular neurons act oppositely in seizure modulation. These two subpopulations are structurally and functionally dissociable. An intrinsically enhanced hyperpolarization-activated current and robust bursting intensity in anterior thalamus-projecting neurons facilitate synaptic transmission, thus contributing to the generalization of hippocampal seizures. These results demonstrate that subicular circuits have diverse roles in epilepsy, suggesting the necessity to precisely target specific subicular circuits for effective treatment of epilepsy.

The diverse role of the raphe 5-HTergic systems in epilepsy.

The raphe nuclei comprise nearly all of 5-hydroxytryptaminergic (5-HTergic) neurons in the brain and are widely acknowledged to participate in the modulation of neural excitability. "Excitability-inhibition imbalance" results in a variety of brain disorders, including epilepsy. Epilepsy is a common neurological disorder characterized by hypersynchronous epileptic seizures accompanied by many psychological, social, cognitive consequences. Current antiepileptic drugs and other therapeutics are not ideal to control epilepsy and its comorbidities. Cumulative evidence suggests that the raphe nuclei and 5-HTergic system play an important role in epilepsy and epilepsy-associated comorbidities. Seizure activities propagate to the raphe nuclei and induce various alterations in different subregions of the raphe nuclei at the cellular and molecular levels. Intervention of the activity of raphe nuclei and raphe 5-HTergic system with pharmacological or genetic approaches, deep brain stimulation or optogenetics produces indeed diverse and even contradictory effects on seizure and epilepsy-associated comorbidities in different epilepsy models. Nevertheless, there are still many open questions left, especially regarding to the relationship between 5-HTergic neural circuit and epilepsy. Understanding of 5-HTergic network in a circuit- and molecule-specific way may not only be therapeutically relevant for increasing the drug specificity and precise treatment in epilepsy, but also provide critical hints for other brain disorders with abnormal neural excitability. In this review we focus on the roles of the raphe 5-HTergic system in epilepsy and epilepsy-associated comorbidities. Besides, further perspectives about the complexity and diversity of the raphe nuclei in epilepsy are also addressed.

Paradoxical effects of posterior intralaminar thalamic calretinin neurons on hippocampal seizure via distinct downstream circuits.

Epilepsy is a circuit-level brain disorder characterized by hyperexcitatory seizures with unclear mechanisms. Here, we investigated the causal roles of calretinin (CR) neurons in the posterior intralaminar thalamic nucleus (PIL) in hippocampal seizures. Using c-fos mapping and calcium fiber photometry, we found that PIL CR neurons were activated during hippocampal seizures in a kindling model. Optogenetic activation of PIL CR neurons accelerated seizure development, whereas inhibition retarded seizure development. Further, viral-based circuit tracing verified that PIL CR neurons were long-range glutamatergic neurons, projecting toward various downstream regions. Interestingly, selective inhibition of PIL-lateral amygdala CR circuit attenuated seizure progression, whereas inhibition of PIL-zona incerta CR circuit presented an opposite effect. These results indicated that CR neurons in the PIL play separate roles in hippocampal seizures via distinct downstream circuits, which complements the pathogenic mechanisms of epilepsy and provides new insight for the precise medicine of epilepsy.

Revealing the Precise Role of Calretinin Neurons in Epilepsy: We Are on the Way.

Epilepsy is a common neurological disorder characterized by hyperexcitability in the brain. Its pathogenesis is classically associated with an imbalance of excitatory and inhibitory neurons. Calretinin (CR) is one of the three major types of calcium-binding proteins present in inhibitory GABAergic neurons. The functions of CR and its role in neural excitability are still unknown. Recent data suggest that CR neurons have diverse neurotransmitters, morphologies, distributions, and functions in different brain regions across various species. Notably, CR neurons in the hippocampus, amygdala, neocortex, and thalamus are extremely susceptible to excitotoxicity in the epileptic brain, but the causal relationship is unknown. In this review, we focus on the heterogeneous functions of CR neurons in different brain regions and their relationship with neural excitability and epilepsy. Importantly, we provide perspectives on future investigations of the role of CR neurons in epilepsy.

Inhibition of hyperactivity of the dorsal raphe 5-HTergic neurons ameliorates hippocampal seizure.

AIMS: Epilepsy, frequently comorbid with depression, easily develops drug resistance. Here, we investigated how dorsal raphe (DR) and its 5-HTergic neurons are implicated in epilepsy. METHODS: In mouse hippocampal kindling model, using immunochemistry, calcium fiber photometry, and optogenetics, we investigated the causal role of DR 5-HTergic neurons in seizure of temporal lobe epilepsy (TLE). Further, deep brain stimulation (DBS) of the DR with different frequencies was applied to test its effect on hippocampal seizure and depressive-like behavior. RESULTS: Number of c-fos+ neurons in the DR and calcium activities of DR 5-HTergic neurons were both increased during kindling-induced hippocampal seizures. Optogenetic inhibition, but not activation, of DR 5-HTergic neurons conspicuously retarded seizure acquisition specially during the late period. For clinical translation, 1-Hz-specific, but not 20-Hz or 100-Hz, DBS of the DR retarded the acquisition of hippocampal seizure. This therapeutic effect may be mediated by the inhibition of DR 5-HTergic neurons, as optogenetic activation of DR 5-HTergic neurons reversed the anti-seizure effects of 1-Hz DR DBS. However, DBS treatment had no effect on depressive-like behavior. CONCLUSION: Inhibition of hyperactivity of DR 5-HTergic neuron may present promising anti-seizure effect and the DR may be a potential DBS target for the therapy of TLE.

Deep brain stimulation in the medial septum attenuates temporal lobe epilepsy via entrainment of hippocampal theta rhythm.

AIMS: Temporal lobe epilepsy (TLE), often associated with cognitive impairment, is one of the most common types of medically refractory epilepsy. Deep brain stimulation (DBS) shows considerable promise for the treatment of TLE. However, the optimal stimulation targets and parameters of DBS to control seizures and related cognitive impairment are still not fully illustrated. METHODS: In the present study, we evaluated the therapeutic potential of DBS in the medial septum (MS) on seizures and cognitive function in mouse acute and chronic epilepsy models. RESULTS: We found that DBS in the MS alleviated the severity of seizure activities in both kainic acid-induced acute seizure model and hippocampal-kindled epilepsy model. DBS showed antiseizure effects with a wide window of effective stimulation frequencies. The antiseizure effects of DBS were mediated by the hippocampal theta rhythm, as atropine, which reversed the DBS-induced augmentation of the hippocampal theta oscillation, abolished the antiseizure effects of DBS. Further, in the kainic acid-induced chronic TLE model, DBS in the MS not only reduced spontaneous seizures, but also improved behavioral performance in novel object recognition. CONCLUSION: DBS in the MS is a promising approach to attenuate TLE probably through entrainment of the hippocampal theta rhythm, which may be therapeutically significant for refractory TLE treatment.

Pharmaco-genetic inhibition of pyramidal neurons retards hippocampal kindling-induced epileptogenesis.

AIMS: Pharmaco-genetics emerges as a new promising approach for epileptic seizures. Whether it can modulate epileptogenesis is still unknown. METHODS: Here, parvalbumin neurons and pyramidal neurons of the seizure focus were transfected with engineered excitatory Gq-coupled human muscarinic receptor hM3Dq and engineered inhibitory Gi-coupled human muscarinic receptor hM4Di, respectively. And their therapeutic value in mouse hippocampal kindling-induced epileptogenesis was tested. RESULTS: Pharmaco-genetic activating parvalbumin neurons limitedly retarded the progression of behavioral seizure stage and afterdischarge duration (ADD) during epileptogenesis induced by kindling. Activating parvalbumin neurons delayed seizure development only in the early stage, but accelerated it in late stages. On the contrary, pharmaco-genetic inhibiting pyramidal neurons robustly retarded the progression of seizure stages and ADDs, which greatly delayed seizure development in both early and late stages. Although both pharmaco-genetic therapeutics efficiently alleviated the severity of acute kindling-induced seizures, pharmaco-genetic inhibiting pyramidal neurons were able to reverse the enhanced synaptic plasticity during epileptogenesis, compared with that of pharmaco-genetic activating parvalbumin neurons. CONCLUSION: Our results demonstrated that pharmaco-genetic inhibiting pyramidal neurons retard hippocampal kindling-induced epileptogenesis and reverse the enhanced synaptic plasticity during epileptogenesis, compared with that of pharmaco-genetic activating parvalbumin neurons. It suggests that pharmaco-genetics targeting pyramidal neurons may be a promising treatment for epileptogenesis.

A disinhibitory nigra-parafascicular pathway amplifies seizure in temporal lobe epilepsy.

The precise circuit of the substantia nigra pars reticulata (SNr) involved in temporal lobe epilepsy (TLE) is still unclear. Here we found that optogenetic or chemogenetic activation of SNr parvalbumin+ (PV) GABAergic neurons amplifies seizure activities in kindling- and kainic acid-induced TLE models, whereas selective inhibition of these neurons alleviates seizure activities. The severity of seizures is bidirectionally regulated by optogenetic manipulation of SNr PV fibers projecting to the parafascicular nucleus (PF). Electrophysiology combined with rabies virus-assisted circuit mapping shows that SNr PV neurons directly project to and functionally inhibit posterior PF GABAergic neurons. Activity of these neurons also regulates seizure activity. Collectively, our results reveal that a long-range SNr-PF disinhibitory circuit participates in regulating seizure in TLE and inactivation of this circuit can alleviate severity of epileptic seizures. These findings provide a better understanding of pathological changes from a circuit perspective and suggest a possibility to precisely control epilepsy.

Direct Septum-Hippocampus Cholinergic Circuit Attenuates Seizure Through Driving Somatostatin Inhibition.

BACKGROUND: Previous studies indicated the involvement of cholinergic neurons in seizure; however, the specific role of the medial septum (MS)-hippocampus cholinergic circuit in temporal lobe epilepsy (TLE) has not yet been completely elucidated. METHODS: In the current study, we used magnetic resonance imaging and diffusion tensor imaging to characterize the pathological change of the MS-hippocampus circuit in 42 patients with TLE compared with 22 healthy volunteers. Using optogenetics and chemogenetics, combined with in vivo or in vitro electrophysiology and retrograde rabies virus tracing, we revealed a direct MS-hippocampus cholinergic circuit that potently attenuates seizure through driving somatostatin inhibition in animal TLE models. RESULTS: We found that patients with TLE with hippocampal sclerosis showed a decrease of neuronal fiber connectivity of the MS-hippocampus compared with healthy people. In the mouse TLE model, MS cholinergic neurons ceased firing during hippocampal seizures. Optogenetic and chemogenetic activation of MS cholinergic neurons (but not glutamatergic or GABAergic [gamma-aminobutyric acidergic] neurons) significantly attenuated hippocampal seizures, while specific inhibition promoted hippocampal seizures. Electrophysiology combined with modified rabies virus tracing studies showed that direct (but not indirect) MS-hippocampal cholinergic projections mediated the antiseizure effect by preferentially targeting hippocampal GABAergic neurons. Furthermore, chemogenetic inhibition of hippocampal somatostatin-positive (rather than parvalbumin-positive) subtype of GABAergic neurons reversed the antiseizure effect of the MS-hippocampus cholinergic circuit, which was mimicked by activating somatostatin-positive neurons. CONCLUSIONS: These findings underscore the notable antiseizure role of the direct cholinergic MS-hippocampus circuit in TLE through driving the downstream somatostatin effector. This may provide a better understanding of the changes of the seizure circuit and the precise spatiotemporal control of epilepsy.

Indoor air formaldehyde (HCHO) pollution of urban coach cabins.

Urban coach cabin is an important indoor environment for long journey, formaldehyde (HCHO) is a carcinogenic gas and damages indoor air quality of cabins. In order to control the HCHO pollution, the air samples inside cabins were analysed with a thermally desorbed gas chromatograph, and the HCHO diffusion was simulated with a methodology of computational fluid dynamics (CFD). Results show that through the experimental monitoring, the HCHO pollution level range from 33.6 to 142.3 µg/m3, decrease quickly with time, and the attenuation trendline is univariate cubic equation. Through the CFD simulation, the indoor temperature and HCHO level of cabin front and rear ends are higher than ones of other areas for the insufficient air supply and the unreasonable arrangement of air exhaust outlet. Moreover, through the CFD simulation, the HCHO level decreases with height growth of breathing zone and increasing air supply speed, and fresh air lead to diffusion of HCHO pollution from cabin seat area to the surrounding area. Through the CFD simulation, the HCHO pollution under the wind speeds of 3~5 m/s is higher than the HCHO limit level from indoor air standard of China vehicles, which shows that the HCHO emission of cabin seat has an important impact on airborne HCHO pollution inside vehicle cabins.

The piriform cortex in epilepsy: What we learn from the kindling model.

Epilepsy is a circuit-level brain disorder characterized by excessive or hypersynchronous epileptic seizures involving a complex epileptogenic network. Cumulative evidence suggests that the piriform cortex (PC) is a crucial site in seizure initiation, propagation, and generalization in epilepsy. The kindling model is a classic animal model of complex partial seizures with secondarily generalized tonic seizures, which is usually used for the study of epilepsy pathogenesis and preclinical anti-epilepsy drug evaluation. Various essential functions of the PC in epilepsy were discovered in the kindling model, therefore, this review focuses on discussing the role of the PC in the kindling model. We review what pathological changes happen in the PC in the kindling model, how the PC is involved in the kindling model through different interventions, and finally we also provide perspectives on some possible research directions for future studies.

Pharmaco-genetic therapeutics targeting parvalbumin neurons attenuate temporal lobe epilepsy.

Temporal lobe epilepsy (TLE) is the most common type of epilepsy and is often medically refractory. Previous studies suggest that selective pharmaco-genetic inhibition of pyramidal neurons has therapeutic value for the treatment of epilepsy, however there is a risk of disrupting normal physical functions. Here, we test whether pharmaco-genetic activation of parvalbumin neurons, which are transgenetically transduced with the modified muscarinic receptor hM3Dq can attenuate TLE. We found that pharmaco-genetic activation of hippocampal parvalbumin neurons in epileptogenic zone not only significantly extends the latency to different seizure stages and attenuates seizure activities in acute seizure model, but also greatly alleviates the severity of seizure onsets in two chronic epilepsy models. This manipulation did not affect the normal physical function evaluated in various cognitive tasks. Further, the activation of parvalbumin neurons produced an inhibition on parts of surrounding pyramidal neurons, and the direct inactivation of pyramidal neurons via the viral expression of a modified muscarinic receptor hM4Di produced a similar anti-ictogenic effect. Interestingly, pharmaco-genetic inactivation of pyramidal neurons was more sensitive to impair cognitive function. Those data demonstrated that pharmaco-genetic seizure attenuation through targeting parvalbumin neurons rather than pyramidal neurons may be a novel and relatively safe approach for treating refractory TLE.

Phase calibration unwrapping algorithm for phase data corrupted by strong decorrelation speckle noise.

Robust phase unwrapping in the presence of high noise remains an open issue. Especially, when both noise and fringe densities are high, pre-filtering may lead to phase dislocations and smoothing that complicate even more unwrapping. In this paper an approach to deal with high noise and to unwrap successfully phase data is proposed. Taking into account influence of noise in wrapped data, a calibration method of the 1st order spatial phase derivative is proposed and an iterative approach is presented. We demonstrate that the proposed method is able to process holographic phase data corrupted by non-Gaussian speckle decorrelation noise. The algorithm is validated by realistic numerical simulations in which the fringe density and noise standard deviation is progressively increased. Comparison with other established algorithms shows that the proposed algorithm exhibits better accuracy and shorter computation time, whereas others may fail to unwrap. The proposed algorithm is applied to phase data from digital holographic metrology and the unwrapped results demonstrate its practical effectiveness. The realistic simulations and experiments demonstrate that the proposed unwrapping algorithm is robust and fast in the presence of strong speckle decorrelation noise.

Health risk equations and risk assessment of airborne benzene homologues exposure to drivers and passengers in taxi cabins.

Interior air environment and health problems of vehicles have attracted increasing attention, and benzene homologues (BHs) including benzene, toluene, ethylbenzene, xylenes, and styrene are primary hazardous gases in vehicular cabins. The BHs impact on the health of passengers and drivers in 38 taxis is assessed, and health risk equations of in-car BHs to different drivers and passengers are induced. The health risk of in-car BHs for male drivers is the highest among all different receptors and is 1.04, 6.67, and 6.94 times more than ones for female drivers, male passengers, and female passengers, respectively. In-car BHs could not lead to the non-cancer health risk to all passengers and drivers as for the maximal value of non-cancer indices is 0.41 and is less than the unacceptable value (1.00) of non-cancer health risk from USEPA. However, in-car BHs lead to cancer health risk to drivers as for the average value of cancer indices is 1.21E-04 which is 1.21 times more than the unacceptable value (1.00E-04) of cancer health risk from USEPA. Finally, for in-car airborne benzene concentration (X, µg/m(3)) to male drivers, female drivers, male passengers, and female passengers, the cancer health risk equations are Y = 1.48E-06X, Y = 1.42E-06X, Y = 2.22E-07X, and Y = 2.13E-07X, respectively, and the non-cancer health risk equations are Y = 1.70E-03X, Y = 1.63E-03X, Y = 2.55E-04X, and Y = 2.45E-04X, respectively.