Anxiolytic-like Effects and Quantitative EEG Profile of Palmitone Induces Responses Like Buspirone Rather Than Diazepam as Clinical Drugs.

Anxiety is a mental disorder with a growing worldwide incidence due to the SARS-CoV-2 virus pandemic. Pharmacological therapy includes drugs such as benzodiazepines (BDZs) or azapirones like buspirone (BUSP) or analogs, which unfortunately produce severe adverse effects or no immediate response, respectively. Medicinal plants or their bioactive metabolites are a shared global alternative to treat anxiety. Palmitone is one active compound isolated from Annona species due to its tranquilizing activity. However, its influence on neural activity and possible mechanism of action are unknown. In this study, an electroencephalographic (EEG) spectral power analysis was used to corroborate its depressant activity in comparison with the anxiolytic-like effects of reference drugs such as diazepam (DZP, 1 mg/kg) and BUSP (4 mg/kg) or 8-OH-DPAT (1 mg/kg), alone or in the presence of the GABAA (picrotoxin, PTX, 1 mg/kg) or serotonin 5-HT1A receptor antagonists (WAY100634, WAY, 1 mg/kg). The anxiolytic-like activity was assayed using the behavioral response of mice employing open-field, hole-board, and plus-maze tests. EEG activity was registered in both the frontal and parietal cortex, performing a 10 min baseline and 30 min recording after the treatments. As a result, anxiety-like behavior was significantly decreased in mice administered with palmitone, DZP, BUSP, or 8-OH-DPAT. The effect of palmitone was equivalent to that produced by 5-HT1A receptor agonists but 50% less effective than DZP. The presence of PTX and WAY prevented the anxiolytic-like response of DZP and 8-OH-DPAT, respectively. Whereas only the antagonist of the 5-HT1A receptor (WAY) inhibited the palmitone effects. Palmitone and BUSP exhibited similar changes in the relative power bands after the spectral power analysis. This response was different to the changes induced by DZP. In conclusion, brain electrical activity was associated with the anxiolytic-like effects of palmitone implying a serotoninergic rather than a GABAergic mechanism of action.

Neuroinflammation microenvironment sharpens seizure circuit.

A large set of inflammatory molecules and their receptors are induced in epileptogenic foci of patients with pharmacoresistant epilepsies of structural etiologies or with refractory status epilepticus. Studies in animal models mimicking these clinical conditions have shown that the activation of specific inflammatory signallings in forebrain neurons or glial cells may modify seizure thresholds, thus contributing to both ictogenesis and epileptogenesis. The search for mechanisms underlying these effects has highlighted that inflammatory mediators have CNS-specific neuromodulatory functions, in addition to their canonical activation of immune responses for pathogen recognition and clearance. This review reports the neuromodulatory effects of inflammatory mediators and how they contribute to alter the inhibitory/excitatory balance in neural networks that underlie seizures. In particular, we describe key findings related to the ictogenic role of prototypical inflammatory cytokines (IL-1ß and TNF) and danger signals (HMGB1), their modulatory effects of neuronal excitability, and the mechanisms underlying these effects. It will be discussed how harnessing these neuromodulatory properties of immune mediators may lead to novel therapies to control drug-resistant seizures.

Gut microbiome in neuropsychiatric disorders.

BACKGROUND: Neuropsychiatric disorders are a significant cause of death and disability worldwide. The mechanisms underlying these disorders include a constellation of structural, infectious, immunological, metabolic, and genetic etiologies. Advances in next-generation sequencing techniques have demonstrated that the composition of the enteric microbiome is dynamic and plays a pivotal role in host homeostasis and several diseases. The enteric microbiome acts as a key mediator in neuronal signaling via metabolic, neuroimmune, and neuroendocrine pathways. OBJECTIVE: In this review, we aim to present and discuss the most current knowledge regarding the putative influence of the gut microbiome in neuropsychiatric disorders. METHODS: We examined some of the preclinical and clinical evidence and therapeutic strategies associated with the manipulation of the gut microbiome. RESULTS: targeted taxa were described and grouped from major studies to each disease. CONCLUSIONS: Understanding the complexity of these ecological interactions and their association with susceptibility and progression of acute and chronic disorders could lead to novel diagnostic biomarkers based on molecular targets. Moreover, research on the microbiome can also improve some emerging treatment choices, such as fecal transplantation, personalized probiotics, and dietary interventions, which could be used to reduce the impact of specific neuropsychiatric disorders. We expect that this knowledge will help physicians caring for patients with neuropsychiatric disorders.

Gut microbiome in neuropsychiatric disorders / O microbioma intestinal nas doenças neuropsiquiátricas

ABSTRACT Background: Neuropsychiatric disorders are a significant cause of death and disability worldwide. The mechanisms underlying these disorders include a constellation of structural, infectious, immunological, metabolic, and genetic etiologies. Advances in next-generation sequencing techniques have demonstrated that the composition of the enteric microbiome is dynamic and plays a pivotal role in host homeostasis and several diseases. The enteric microbiome acts as a key mediator in neuronal signaling via metabolic, neuroimmune, and neuroendocrine pathways. Objective: In this review, we aim to present and discuss the most current knowledge regarding the putative influence of the gut microbiome in neuropsychiatric disorders. Methods: We examined some of the preclinical and clinical evidence and therapeutic strategies associated with the manipulation of the gut microbiome. Results: targeted taxa were described and grouped from major studies to each disease. Conclusions: Understanding the complexity of these ecological interactions and their association with susceptibility and progression of acute and chronic disorders could lead to novel diagnostic biomarkers based on molecular targets. Moreover, research on the microbiome can also improve some emerging treatment choices, such as fecal transplantation, personalized probiotics, and dietary interventions, which could be used to reduce the impact of specific neuropsychiatric disorders. We expect that this knowledge will help physicians caring for patients with neuropsychiatric disorders.

RESUMO Antecedentes: Os transtornos neuropsiquiátricos são uma importante causa de morte e invalidez no mundo. Os mecanismos subjacentes a esses transtornos incluem uma constelação de etiologias estruturais, infecciosas, imunológicas, metabólicas e genéticas. Avanços nas técnicas de sequenciamento do DNA têm demonstrado que a composição do microbioma entérico é dinâmica e desempenha um papel fundamental não apenas na homeostase do hospedeiro, mas também em várias doenças. O microbioma entérico atua como mediador na sinalização das vias metabólica, neuroimune e neuroendócrina. Objetivo: Apresentar os estudos mais recentes sobre a possível influência do microbioma intestinal nas diversas doenças neuropsiquiátricas e discutir tanto os resultados quanto a eficácia dos tratamentos que envolvem a manipulação do microbioma intestinal. Métodos: foram examinadas algumas das evidências pré-clínicas e clínicas e estratégias terapêuticas associadas à manipulação do microbioma intestinal. Resultados: os táxons-alvo foram descritos e agrupados a partir dos principais estudos para cada doença. Conclusões: Entender a fundo a complexidade das interações ecológicas no intestino e sua associação com a suscetibilidade a certas doenças agudas e crônicas pode levar ao desenvolvimento de novos biomarcadores diagnósticos com base em alvos moleculares. Além disso, o estudo do microbioma intestinal pode auxiliar na otimização de tratamentos não farmacológicos emergentes, tais como o transplante de microbiota fecal, o uso de probióticos e intervenções nutricionais personalizadas. Dessa forma, terapias alternativas poderiam ser usadas para reduzir o impacto dos transtornos neuropsiquiátricos na saúde pública. Esperamos que esse conhecimento seja útil para médicos que cuidam de pacientes com diversos transtornos neuropsiquiátricos.

Tabernaemontana arborea and ibogaine induce paroxysmal EEG activity in freely moving mice: Involvement of serotonin 5-HT1A receptors.

Several Apocynaceae species, most notably Tabernanthe iboga, Voacanga africana and many Tabernaemontana species, produce ibogan-type alkaloids. Although a large amount of information exists about the Tabernaemontana genus, knowledge concerning chemistry and biological activity remains lacking for several species, especially related to their effects on the central nervous system (CNS). The aim of this study was to evaluate the effect of Tabernaemontana arborea Rose ex J.D.Sm. (T. arborea) hydroalcoholic extract (30, 56.2 and 100 mg/kg, i.p.) and two of its main alkaloids (ibogaine and voacangine, 30 mg/kg, i.p.) on electroencephalographic (EEG) activity alone and in the presence of the chemical convulsant agent pentylenetetrazole (PTZ, 85 mg/kg, i.p.) in mice. EEG spectral power analysis showed that T. arborea extract (56.2 and 100 mg/kg) and ibogaine (30 mg/kg, i.p.) promoted a significant increase in the relative power of the delta band and a significant reduction in alpha band values, denoting a CNS depressant effect. Voacangine (30 mg/kg, i.p.) provoked an EEG flattening pattern. The PTZ-induced seizures were not modified in the presence of T. arborea, ibogaine, or voacangine. However, sudden death was observed in mice treated with T. arborea extract at 100 mg/kg, i.p., combined with PTZ. Because T. arborea extract (100 mg/kg, i.p.) and ibogaine (30 mg/kg, i.p.), but not voacangine (30 mg/kg, i.p.), induced paroxysmal activity in the EEG, both were explored in the presence of a serotonin 5-HT1A receptor antagonist (WAY100635, 1 mg/kg, i.p.). The antagonist abolished the paroxysmal activity provoked by T. arborea (100 mg/kg, i.p.) but not that observed with ibogaine, corroborating the participation of serotonin neurotransmission in the T. arborea effects. In conclusion, high doses of the T. arborea extract induced abnormal EEG activity due in part to the presence of ibogaine and involving serotonin 5-HT1A receptor participation. Nevertheless, other possible constituents and mechanisms might participate in this complex excitatory activity that would be interesting to explore in future studies.

Gut-microbiota-directed strategies to treat epilepsy: clinical and experimental evidence.

A growing appreciation that the intestinal microbiota might exert changes on the central nervous system via the gut-brain has emerged as a new research frontier in neurological disorders. Moreover, new approaches for studying and manipulating the gut microbiome, including metabolomics and faecal microbiota transplantation, have highlighted the tremendous potential that microbes have on neuroinflammation, metabolic, and neuroendocrine signaling pathways. Despite the large proliferation of studies in animal models examining the linkage between microbial disequilibrium and epilepsy, intestinal profiles at a functional level in humans have remained scarce. We reviewed the scientific evidence on gut microbiota's role in epilepsy, both in clinical and experimental studies, to better understand how targeting the gut microbiota could serve as a diagnostic or prognostic research tool. Likewise, translating microbial molecular mechanisms to medical settings could fill the gaps related to alternative therapies for patients with epilepsy, mainly in cases with refractory phenotypes.

Chronic intermittent hypoxia alters main olfactory bulb activity and olfaction.

Olfactory dysfunction is commonly observed in patients with obstructive sleep apnea (OSA), which is related to chronic intermittent hypoxia (CIH). OSA patients exhibit alterations in discrimination, identification and odor detection threshold. These olfactory functions strongly rely on neuronal processing within the main olfactory bulb (MOB). However, a direct evaluation of the effects of controlled CIH on olfaction and MOB network activity has not been performed. Here, we used electrophysiological field recordings in vivo to evaluate the effects of 21-day-long CIH on MOB network activity and its response to odors. In addition, we assessed animals´ olfaction with the buried food and habituation/dishabituation tests. We found that mice exposed to CIH show alterations in MOB spontaneous activity in vivo, consisting of a reduction in beta and gamma frequency bands power along with an increase in the theta band power. Likewise, the MOB was less responsive to odor stimulation, since the proportional increase of the power of its population activity in response to four different odorants was smaller than the one observed in control animals. These CIH-induced MOB functional alterations correlate with a reduction in the ability to detect, habituate and discriminate olfactory stimuli. Our findings indicate that CIH generates alterations in the MOB neural network, which could be involved in the olfactory deterioration in patients with OSA.

Alterations in Piriform and Bulbar Activity/Excitability/Coupling Upon Amyloid-ß Administration in vivo Related to Olfactory Dysfunction.

BACKGROUND: Deficits in odor detection and discrimination are premature symptoms of Alzheimer's disease (AD) that correlate with pathological signs in the olfactory bulb (OB) and piriform cortex (PCx). Similar olfactory dysfunction has been characterized in AD transgenic mice that overproduce amyloid-ß peptide (Aß), which can be prevented by reducing Aß levels by immunological and pharmacological means, suggesting that olfactory dysfunction depends on Aß accumulation and Aß-driven alterations in the OB and/or PCx, as well as on their activation. However, this possibility needs further exploration. OBJECTIVE: To characterize the effects of Aß on OB and PCx excitability/coupling and on olfaction. METHODS: Aß oligomerized solution (containing oligomers, monomers, and protofibrils) or its vehicle were intracerebroventricularlly injected two weeks before OB and PCx excitability and synchrony were evaluated through field recordings in vivo and in brain slices. Synaptic transmission from the OB to the PCx was also evaluated in slices. Olfaction was assessed through the habituation/dishabituation test. RESULTS: Aß did not affect lateral olfactory tract transmission into the PCx but reduced odor habituation and cross-habituation. This olfactory dysfunction was related to a reduction of PCx and OB network activity power in vivo. Moreover, the coherence between PCx-OB activities was also reduced by Aß. Finally, Aß treatment exacerbated the 4-aminopyridine-induced excitation in the PCx in slices. CONCLUSION: Our results show that Aß-induced olfactory dysfunction involves a complex set of pathological changes at different levels of the olfactory pathway including alterations in PCx excitability and its coupling with the OB. These pathological changes might contribute to hyposmia in AD.

Chronic intermittent hypoxia transiently increases hippocampal network activity in the gamma frequency band and 4-Aminopyridine-induced hyperexcitability in vitro.

Chronic intermittent hypoxia (CIH) is the most distinct feature of obstructive sleep apnea (OSA), a common breathing and sleep disorder that leads to several neuropathological consequences, including alterations in the hippocampal network and in seizure susceptibility. However, it is currently unknown whether these alterations are permanent or remit upon normal oxygenation. Here, we investigated the effects of CIH on hippocampal spontaneous network activity and hyperexcitability in vitro and explored whether these alterations endure or fade after normal oxygenation. Results showed that applying CIH for 21 days to adult rats increases gamma-band hippocampal network activity and aggravates 4-Aminopyridine-induced epileptiform activity in vitro. Interestingly, these CIH-induced alterations remit after 30 days of normal oxygenation. Our findings indicate that hippocampal network alterations and increased seizure susceptibility induced by CIH are not permanent and can be spontaneously reverted, suggesting that therapeutic interventions against OSA in patients with epilepsy, such as surgery or continuous positive airway pressure (CPAP), could be favorable for seizure control.

Single amyloid-beta injection exacerbates 4-aminopyridine-induced seizures and changes synaptic coupling in the hippocampus.

Accumulation of amyloid-beta (Aß) in temporal lobe structures, including the hippocampus, is related to a variety of Alzheimer's disease symptoms and seems to be involved in the induction of neural network hyperexcitability and even seizures. Still, a direct evaluation of the pro-epileptogenic effects of Aß in vivo, and of the underlying mechanisms, is missing. Thus, we tested whether the intracisternal injection of Aß modulates 4-aminopyridine (4AP)-induced epileptiform activity, hippocampal network function, and its synaptic coupling. When tested 3 weeks after its administration, Aß (but not its vehicle) reduces the latency for 4AP-induced seizures, increases the number of generalized seizures, exacerbates the time to fully recover from seizures, and favors seizure-induced death. These pro-epileptogenic effects of Aß correlate with a reduction in the power of the spontaneous hippocampal network activity, involving all frequency bands in vivo and only the theta band (4-10 Hz) in vitro. The pro-epileptogenic effects of Aß also correlate with a reduction of the Schaffer-collateral CA1 synaptic coupling in vitro, which is exacerbated by the sequential bath application of 4-AP and Aß. In summary, Aß produces long-lasting pro-epileptic effects that can be due to alterations in the hippocampal circuit, impacting its coordinated network activity and its synaptic efficiency. It is likely that normalizing synaptic coupling and/or coordinated neural network activity (i.e., theta activity) may contribute not only to improve cognitive function in Alzheimer's disease but also to avoid hyperexcitation in conditions of amyloidosis.

Transcranial focal electrical stimulation via concentric ring electrodes in freely moving cats: Antiepileptogenic and postictal effects.

Transcranial focal electrical stimulation (TFS) via tripolar concentric ring electrodes (TCRE), tripolar TFS, is proposed to treat pharmacoresistant epilepsy. We determined the effect of tripolar TFS on electrical amygdaloid kindling (AK) in freely moving cats. Fifteen cats were bilaterally implanted with electrodes in the amygdala (AM) and prefrontal cortex and assigned to three groups: the control group, which only received AK; the tripolar TFS before AK group, in which TCREs were placed over the vertex and tripolar TFS (300 Hz, 200 µs biphasic equal charge, square pulses) was delivered for 40 min just prior to AK; and the tripolar TFS after AK group, in which the TCREs were placed over the temporal bone ipsilateral to the kindled AM, while tripolar TFS was administered for 2 min just after AK onset for 40 days, and, thereafter, only AK was applied. AK was applied daily until all animals reached kindling stage VI. A three concentric spheres finite element cat head model was developed to analyze the electric fields caused by tripolar TFS. Tripolar TFS after AK inhibited kindling development. Animals with tripolar TFS after AK remained at the focal seizure stages for 20 days after tripolar TFS cessation and required 80.0 ±â€¯15.42 AK stimulations to reach stage VI, significantly higher than TFS before AK, and control (P < .001). Tripolar TFS before AK did not show signs of protection against epileptogenesis. The finite modeling of tripolar TFS showed that the electric field is >0.3 mV/mm at depths less than approximately 12.6 mm in the cat brain, which should be strong enough to alter brain activity. In conclusion, tripolar TFS applied via a TCRE over the ipsilateral temporal area significantly delayed AK. This taken together with other reports of tripolar TFS aborting seizures in acute seizure models suggests that tripolar TFS is a promising new modality that should be considered for further testing.

Effects of High- and Low-Frequency Stimulation of the Thalamic Reticular Nucleus on Pentylentetrazole-Induced Seizures in Rats.

RATIONALE: The use of electrical stimulation therapy to treat epilepsy is currently being studied in experimental animals and patients. Our study was designed to evaluate the effects of electrical stimulation applied in the thalamic reticular nucleus (TRN) on the development of pentylentetrazole-induced seizures. MATERIALS AND METHODS: Experiments were performed using male Wistar rats with electrodes stereotaxically implanted in the left TRN. Epidural EEG recording screws were implanted in the motor cortex for EEG recording. The rats were classified in seven groups: one sham group, four groups receiving either high- or low-frequency preemptive stimulation for either 10 or 60 minutes, and two groups receiving either high- or low-frequency responsive stimulation for ten minutes. All animals received a single dose of pentylentetrazole throughout five days. EEG recordings were obtained from the cortex and were evaluated to assess ictal behavior more than 45 to 90 minutes. RESULTS: Ten minutes of preemptive high-frequency stimulation in the TRN induced a significant decrease in seizure severity compared to 60 minutes of preemptive stimulation and ten minutes of responsive stimulation. Additionally, ten minutes of preemptive high-frequency stimulation protected against death as aftereffect of status epilepticus. The spike-wave complex frequency was not modified. CONCLUSIONS: These data could contribute to the characterization of the TRN in mediating the initiation and spreading of seizure activity and provide preclinical support for optimal parameters to use to obtain beneficial effects against convulsive activity.

Hydrogen peroxide extracellular concentration in the ventrolateral medulla and its increase in response to hypoxia in vitro: Possible role of microglia.

Hydrogen peroxide (H2O2) is a messenger involved in both damaging neuroinflammatory responses and physiological cell communication. The ventrolateral medulla, which regulates several vital functions including breathing and blood pressure, is highly influenced by hydrogen peroxide, whose extracellular levels could be determined by hypoxia and microglial activity, both of which modulate ventrolateral medulla function. Therefore, in this study we aimed to test whether different patterns of hypoxia and/or putative microglial modulators change extracellular hydrogen peroxide in the ventrolateral medulla by using an enzymatic reactor online sensing procedure specifically designed for this purpose. With this new technique, we detected extracellular levels of hydrogen peroxide in the ventrolateral medulla in vitro, which spontaneously fluctuated. These fluctuations are reduced by minocycline, a putative microglial inhibitor, and by the microglial toxin liposomal clodronate. Suitably, lipopolysaccharide increases extracellular hydrogen peroxide, while minocycline and liposomal clodronate reduce this increase. Application of blue light to slices with microglia expressing channelrhodopsin-2 also increases extracellular hydrogen peroxide. Moreover, long-lasting and intermittent hypoxia (as well as subsequent reoxygenation) increase extracellular hydrogen peroxide to similar levels, which is partially prevented by minocycline. The effect of long-lasting hypoxia was reproduced in vivo. Overall, our data show that changes in oxygen concentration, and possibly microglial function, modulate extracellular H2O2 levels in the ventrolateral medulla, which could influence the function of this neural circuit under normal and pathological conditions related to inflammation and/or hypoxia.