Gamma-aminobutyric Acid Release Research Articles

Fully flexible implantable neural probes for electrophysiology recording and controlled neurochemical modulation

Targeted delivery of neurochemicals and biomolecules for neuromodulation of brain activity is a powerful technique that, in addition to electrical recording and stimulation, enables a more thorough investigation of neural circuit dynamics. We have designed a novel, flexible, implantable neural probe capable of controlled, localized chemical stimulation and electrophysiology recording. The neural probe was implemented using planar micromachining processes on Parylene C, a mechanically flexible, biocompatible substrate. The probe shank features two large microelectrodes (chemical sites) for drug loading and sixteen small microelectrodes for electrophysiology recording to monitor neuronal response to drug release. To reduce the impedance while keeping the size of the microelectrodes small, poly(3,4-ethylenedioxythiophene) (PEDOT) was electrochemically coated on recording microelectrodes. In addition, PEDOT doped with mesoporous sulfonated silica nanoparticles (SNPs) was used on chemical sites to achieve controlled, electrically-actuated drug loading and releasing. Different neurotransmitters, including glutamate (Glu) and gamma-aminobutyric acid (GABA), were incorporated into the SNPs and electrically triggered to release repeatedly. An in vitro experiment was conducted to quantify the stimulated release profile by applying a sinusoidal voltage (0.5 V, 2 Hz). The flexible neural probe was implanted in the barrel cortex of the wild-type Sprague Dawley rats. As expected, due to their excitatory and inhibitory effects, Glu and GABA release caused a significant increase and decrease in neural activity, respectively, which was recorded by the recording microelectrodes. This novel flexible neural probe technology, combining on-demand chemical release and high-resolution electrophysiology recording, is an important addition to the neuroscience toolset used to dissect neural circuitry and investigate neural network connectivity.

HISTOSTRUCTURAL ALTERATIONS IN THE CEREBRAL ARCHITECTURE ASSOCIATED WITH THE PROGRESSION OF ALCOHOL INTOXICATION: AN EXPERIMENTAL ANALYSIS

The aim of this study is to evaluate the histological changes in the cerebellum of rat brains following chronic alcohol intoxication. Materials and Methods. We employed a classical approach for modeling chronic alcohol intoxication by administering 40% ethanol to rats (n=55) in a dosage of 2 ml per 100 g of body weight daily for three months. The cerebellar structure was then analyzed. Results. This study investigates the impact of chronic alcohol intoxication on the histological structures of the cerebellar cortex. The cerebellum, like the nervous system overall, possesses a significant cellular and functional reserve. However, teratogenic factors, including ethanol, notably influence the activity of cerebellar neurons, increasing it. Ethanol exposure during early pregnancy can lead to prenatal growth retardation, stillbirth, cleft palate, hydrocephaly, and reductions in fetal body size. There is evidence suggesting a correlation between blood ethanol levels and a reduction in the number of Purkinje cells. Chronic alcohol consumption results in cerebellar ataxia, alterations in upper limb movements, decreased reaction speeds, reduced attention concentration, impaired coordination accuracy, and disturbances in postural stability and balance. Conclusion. The cerebellum, especially during development, is particularly vulnerable to the toxic effects of alcohol. Recent research suggests that changes in the neurotransmission of gamma-aminobutyric acid (GABA)-dependent receptors may contribute to cerebellar dysfunction induced by ethanol. Ethanol exposure increases the release of GABA not only in Purkinje cells but also in the interneurons of the molecular layer and granule cells.

Calcium-permeable AMPA and kainate receptors of GABAergic neurons.

This Commentary presents a brief discussion of the action of glutamate calcium permeable receptors present with neurons on the release of the neurotransmitter gamma-aminobutyric acid (GABA). In particular, Glutamate sensitive Kainic Acid Receptors (KARs) and α-Amino-3-hydroxy-5-Methyl-4-isoxazole Propionic Acid Receptor (AMPARs) are Na+ channels that typically cause neuronal cells to depolarize and release GABA. Some of these receptors are also permeable to Ca2+ and are hence involved in the calcium-dependent release of GABA neurotransmitters. Calcium-permeable kainate and AMPA receptors (CP-KARs and CP-AMPARs) are predominantly located in GABAergic neurons in the mature brain and their primary role is to regulate GABA release. AMPARs which do not contain the GluA2 subunit are mainly localized in the postsynaptic membrane. CP-KAR receptors are located mainly in the presynapse. GABAergic neurons expressing CP-KARs and CP-AMPARs respond to excitation earlier and faster, suppressing hyperexcitation of other neurons by the advanced GABA release due to an early rapid [Ca2+]i increase. CP-AMPARs have demonstrated a more pronounced impact on plasticity compared to NMDARs because of their capacity to elevate intracellular Ca2+ levels independently of voltage. GABAergic neurons that express CP-AMPARs contribute to the disinhibition of glutamatergic neurons by suppressing GABAergic neurons that express CP-KARs. Hence, the presence of glutamate CP-KARs and CP-AMPARs is crucial in governing hyperexcitation and synaptic plasticity in GABAergic neurons.

Long-term inhibition of ODC1 in APP/PS1 mice rescues amyloid pathology and switches astrocytes from a reactive to active state

Alzheimer’s disease (AD) is characterized by the loss of memory due to aggregation of misphosphorylated tau and amyloid beta (Aβ) plaques in the brain, elevated release of inhibitory neurotransmitter gamma-aminobutyric acid (GABA) and reactive oxygen species from astrocytes, and subsequent neurodegeneration. Recently, it was found that enzyme Ornithine Decarboxylase 1 (ODC1) acts as a bridge between the astrocytic urea cycle and the putrescine-to-GABA conversion pathway in the brain of AD mouse models as well as human patients. In this study, we show that the long-term knockdown of astrocytic Odc1 in APP/PS1 animals was sufficient to completely clear Aβ plaques in the hippocampus while simultaneously switching the astrocytes from a detrimental reactive state to a regenerative active state, characterized by proBDNF expression. Our experiments also reveal an effect of astrocytic ODC1 inhibition on the expression of genes involved in synapse pruning and organization, histone modification, apoptotic signaling and protein processing. These genes are previously known to be associated with astrocytic activation and together create a neuroregeneration-supportive environment in the brain. By inhibiting ODC1 for a long period of 3 months in AD mice, we demonstrate that the beneficial amyloid-clearing process of astrocytes can be completely segregated from the systemically harmful astrocytic response to insult. Our study reports an almost complete clearance of Aβ plaques by controlling an endogenous degradation process, which also modifies the astrocytic state to create a regeneration-supportive environment in the brain. These findings present the potential of modulating astrocytic clearance of Aβ as a powerful therapeutic strategy against AD.

Dopamine D3 receptor modulates D2 receptor effects on cAMP and GABA release at striatopallidal terminals-Modulation by the Ca2+-Calmodulin-CaMKII system.

Dopamine D2 receptor (D2R) is expressed in striatopallidal neurons and decreases forskolin-stimulated cyclic adenine monophosphate (cAMP) accumulation and gamma-aminobutyric acid (GABA) release. Dopamine D3 receptor (D3R) mRNA is expressed in a population of striatal D2R-expressing neurons. Also, D3R protein and binding have been reported in the neuropil of globus pallidus. We explore whether D2R and D3R colocalize in striatopallidal terminals and whether D3R modulates the D2R effect on forskolin-stimulated [3H]cAMP accumulation in pallidal synaptosomes and high K+ stimulated-[3H]GABA release in pallidal slices. Previous reports in heterologous systems indicate that calmodulin (CaM) and CaMKII modulate D2R and D3R functions; thus, we study whether this system regulates its functional interaction. D2R immunoprecipitates with CaM, and pretreatment with ophiobolin A or depolarization of synaptosomes with 15 mM of K+ decreases it. Both treatments increase the D2R inhibition of forskolin-stimulated [3H]cAMP accumulation when activated with quinpirole, indicating a negative modulation of CaM on D2R function. Quinpirole also activates D3R, potentiating D2R inhibition of cAMP accumulation in the ophiobolin A-treated synaptosomes. D2R and D3R immunoprecipitate in pallidal synaptosomes and decrease after the kainic acid striatal lesion, indicating the striatal origin of the presynaptic receptors. CaM-kinase II alfa (CaMKIIα) immunoprecipitates with D3R and increases after high K+ depolarization. In the presence of KN62, a CaMKIIα blocker, D3R potentiates D2R effects on cAMP accumulation in depolarized synaptosomes and GABA release in pallidal slices, indicating D3R function regulation by CaMKIIα. Our data indicate that D3R potentiates the D2R effect on cAMP accumulation and GABA release at pallidal terminals, an interaction regulated by the CaM-CaMKIIα system.

Expression of the vesicular GABA transporter within neuromedin S+ neurons sustains behavioral circadian rhythms.

The suprachiasmatic nucleus (SCN) of the hypothalamus is the site of a central circadian clock that orchestrates overt rhythms of physiology and behavior. Circadian timekeeping requires intercellular communication among SCN neurons, and multiple signaling pathways contribute to SCN network coupling. Gamma-aminobutyric acid (GABA) is produced by virtually all SCN neurons, and previous work demonstrates that this transmitter regulates coupling in the adult SCN but is not essential for the nucleus to sustain overt circadian rhythms. Here, we show that the deletion of the gene that codes for the GABA vesicular transporter Vgat from neuromedin-S (NMS)+ neurons-a subset of neurons critical for SCN function-causes arrhythmia of locomotor activity and sleep. Further, NMS-Vgat deletion impairs intrinsic clock gene rhythms in SCN explants cultured ex vivo. Although vasoactive intestinal polypeptide (VIP) is critical for SCN function, Vgat deletion from VIP-expressing neurons did not lead to circadian arrhythmia in locomotor activity rhythms. Likewise, adult SCN-specific deletion of Vgat led to mild impairment of behavioral rhythms. Our results suggest that while the removal of GABA release from the adult SCN does not affect the pacemaker's ability to sustain overt circadian rhythms, its removal from a critical subset of neurons within the SCN throughout development removes the nucleus ability to sustain circadian rhythms. Our findings support a model in which SCN GABA release is critical for the developmental establishment of intercellular network properties that define the SCN as a central pacemaker.

Different mechanisms of synapsin-induced vesicle clustering at inhibitory and excitatory synapses

Synapsins cluster synaptic vesicles (SVs) to provide a reserve pool (RP) of SVs that maintains synaptic transmission during sustained activity. However, it is unclear how synapsins cluster SVs. Here we show that either liquid-liquid phase separation (LLPS) or tetramerization-dependent cross-linking can cluster SVs, depending on whether a synapse is excitatory or inhibitory. Cell-free reconstitution reveals that both mechanisms can cluster SVs, with tetramerization being more effective. At inhibitory synapses, perturbing synapsin-dependent LLPS impairs SV clustering and synchronization of gamma-aminobutyric acid (GABA) release, while preventing synapsin tetramerization does not. At glutamatergic synapses, the opposite is true: synapsin tetramerization enhances clustering of glutamatergic SVs and mobilization of these SVs from the RP, while synapsin LLPS does not. Comparison of inhibitory and excitatory transmission during prolonged synaptic activity reveals that synapsin LLPS serves as a brake to limit GABA release, while synapsin tetramerization enables rapid mobilization of SVs from the RP to sustain glutamate release.

Lipopolysaccharide augments microglial GABA uptake by increasing GABA transporter-1 trafficking and bestrophin-1 expression.

Gamma-aminobutyric acid (GABA), the principal inhibitory neurotransmitter in the brain, affects numerous immune cell functions. Microglia, the brain's resident innate immune cells, regulate GABA signaling through GABA receptors and express the complete GABAergic machinery for GABA synthesis, uptake, and release. Here, the use of primary microglial cell cultures and ex vivo brain tissue sections allowed for demonstrating that treatment with lipopolysaccharide (LPS) increased microglial GABA uptake as well as GABA transporter (GAT)-1 trafficking. This effect was not entirely abolished by treatment with GAT inhibitors (GAT-Is). Notably, LPS also induced microglial upregulation of bestrophin-1 (BEST-1), a Ca2+ -activated Cl- channel permeable to GABA. Combined administration of GAT-Is and a BEST-1 inhibitor completely abolished LPS-induced microglial GABA uptake. Interestingly, increased microglial GAT-1 membrane turnover via syntaxin 1A was detected in LPS-treated cultures after BEST-1 blockade. Altogether, these findings provided evidence for a novel mechanism through which LPS may trigger the inflammatory response by directly altering microglial GABA clearance and identified the GAT-1/BEST-1 interplay as a potential novel mechanism involved in brain inflammation.

Axon terminal hypertrophy of striatal projection neurons with levodopa-induced dyskinesia priming.

A rat model of levodopa-induced dyskinesia (LID) showed enlarged axon terminals of striatal direct pathway neurons in the internal segment of the globus pallidus (GPi) with excessive gamma-aminobutyric acid (GABA) storage in them. Massive GABA release to GPi upon levodopa administration determines the emergence of LID. We examined whether LID and axon terminal hypertrophy gradually develop with repeated levodopa treatment in Parkinsonian rats to examine if the hypertrophy reflects dyskinesia priming. 6-hydroxydopamine-lesioned hemiparkinsonian rats were randomly allocated to receive saline injections (placebo group, 14 days; n = 4), injections of 6 mg/kg levodopa methyl ester combined with 12.5 mg/kg benserazide (levodopa-treated groups, 3-day-treatment; n = 4, 7-day-treatment; n = 4, 14-day-treatment; n = 4), or injections of 6 mg/kg levodopa methyl ester with 12.5 mg/kg benserazide and 1 mg/kg 8-hydroxy-2-(di-n-propylamino)tetralin for 14 days (8-OH-DPAT-treated group; n = 4). We evaluated abnormal involuntary movement (AIM) scores and axon terminals in the GPi. The AIM score increased with levodopa treatment, as did the hypertrophy of axon terminals in the GPi, showing an increased number of synaptic vesicles in hypertrophied terminals. Increased GABA storage in axon terminals of the direct pathway neurons represents the priming process of LID.

Immune-Mediated Cerebellar Ataxias

Autoimmune mechanisms affect the cerebellum leading to the development of cerebellar ataxias (CAs), which are termed immune-mediated cerebellar ataxias (IMCAs). IMCAs have diverse etiologies. Gluten ataxia (GA), post-infectious cerebellitis (PIC), paraneoplastic cerebellar degeneration (PCD), opsoclonus myoclonus syndrome (OMS), anti-glutamate decarboxylase 65 antibody-associated CA (anti-GAD ataxia), and primary autoimmune cerebellar ataxia (PACA). In addition to these well-established entities, CAs are associated with autoimmunity against ion channels and their related proteins, synaptic adhesion proteins, transmitter receptors, glial cells, and brainstem antigens. Cell-mediated mechanisms are assumed to be involved in PCD, whereas accumulating evidence shows that anti-GAD antibodies decrease gamma-aminobutyric acid (GABA) release to elicit functional synaptic deficits. The therapeutic benefits of immunotherapies vary depending on the etiology. Early intervention is recommended when the cerebellar reserve, abilities for compensation and restoration of pathologies are preserved.

EVALUATION OF ANTIDEPRESSANT AND ANXIOLYTIC ACTIVITY OF OXAPROZIN IN SWISS ALBINO MICE

Depression is a prevalent mental illness. According to estimates, 5 percent of adults worldwide experience depression. Depression affects more women than males. Oxaprozin is a non-narcotic, non-steroidal anti-inflammatory medication (NSAID) used to treat osteoarthritis and rheumatoid arthritis-related inflammation, edoema, stiffness, and joint discomfort. The present study is based on the evaluation of antidepressant and anxiolytic activity of oxaprozin in Swiss albino (either sex) weight 20-25 gm were procured from ICAR-Indian Veterinary Research Institute (ICAR-IVRI), Izzat nagar, Bareilly, Uttar Pradesh. All the mice were divided into 4 groups (n=6) i.e., normal control which was given normal saline, positive control given Imipramine (10mg/kg, i.p.) and diazepam (10mg/kg, subcutaneously), test 1given oxaprozin(10mg/kg, p.o.) and test 2 given Oxaprozin (20mg/kg, p.o.) up to 7 days. The anxiolytic and antidepressant activity were evaluated by parameters i.e., elevated plus maze, FST, rota-rod test and biochemical parameters. It resulted that oxaprozin demonstrates anxiolytic and antidepressant activity. It exhibits antidepressant action probably by facilitating the release of neurotransmitters i. e., serotonin, dopamine. It also increases the release of GABA (Gamma Amino Butyric Acid) and chloride ions influx that leads to hyperpolarization .In conclusion, Oxaprozin is a predominant anxiolytic & anti-depressant drug. It can be effectively used in the treatment of depression, mental agitation and other neurological disorders after successfully evaluating mechanism of action against the same.This study refers, that it might be used in the treatment of depression among human beings after clinical trials.

Metabolic Role of GABA in the Secretory Function of Pancreatic β-Cells: Its Hypothetical Implication in β-Cell Degradation in Type 2 Diabetes.

The stimulus-secretion coupling of a glucose-induced release is generally attributed to the metabolism of the hexose in the β-cells in the glycolytic pathway and the citric acid cycle. Glucose metabolism generates an increased cytosolic concentration of ATP and of the ATP/ADP ratio that closes the ATP-dependent K+-channel at the plasma membrane. The resultant depolarization of the β-cells opens voltage-dependent Ca2+-channels at the plasma membrane that triggers the exocytosis of insulin secretory granules. The secretory response is biphasic with a first and transient peak followed by a sustained phase. The first phase is reproduced by a depolarization of the β-cells with high extracellular KCl maintaining the KATP-channels open with diazoxide (triggering phase); the sustained phase (amplifying phase) depends on the participation of metabolic signals that remain to be determined. Our group has been investigating for several years the participation of the β-cell GABA metabolism in the stimulation of insulin secretion by three different secretagogues (glucose, a mixture of L-leucine plus L-glutamine, and some branched chain alpha-ketoacids, BCKAs). They stimulate a biphasic secretion of insulin accompanied by a strong suppression of the intracellular islet content of gamma-aminobutyric acid (GABA). As the islet GABA release simultaneously decreased, it was concluded that this resulted from an increased GABA shunt metabolism. The entrance of GABA into the shunt is catalyzed by GABA transaminase (GABAT) that transfers an amino group between GABA and alpha-ketoglutarate, resulting in succinic acid semialdehyde (SSA) and L-glutamate. SSA is oxidized to succinic acid that is further oxidized in the citric acid cycle. Inhibitors of GABAT (gamma-vinyl GABA, gabaculine) or glutamic acid decarboxylating activity (GAD), allylglycine, partially suppress the secretory response as well as GABA metabolism and islet ATP content and the ATP/ADP ratio. It is concluded that the GABA shunt metabolism contributes together with the own metabolism of metabolic secretagogues to increase islet mitochondrial oxidative phosphorylation. These experimental findings emphasize that the GABA shunt metabolism is a previously unrecognized anaplerotic mitochondrial pathway feeding the citric acid cycle with a β-cell endogenous substrate. It is therefore a postulated alternative to the proposed mitochondrial cataplerotic pathway(s) responsible for the amplification phase of insulin secretion. It is concluded the new postulated alternative suggests a possible new mechanism of β-cell degradation in type 2 (perhaps also in type 1) diabetes.

Sex differences in VTA GABA transmission and plasticity during opioid withdrawal

The effectiveness of current treatments for opioid use disorder (OUD) varies by sex. Our understanding of the neurobiological mechanisms mediating negative states during withdrawal is lacking, particularly with regard to sex differences. Based on preclinical research in male subjects, opioid withdrawal is accompanied by increased gamma-aminobutyric acid (GABA) release probability at synapses onto dopamine neurons in the ventral tegmental area (VTA). It is unclear, however, if the physiological consequences of morphine that were originally elucidated in male rodents extend to females. The effects of morphine on the induction of future synaptic plasticity are also unknown. Here, we show that inhibitory synaptic long-term potentiation (LTPGABA) is occluded in the VTA in male mice after repeated morphine injections and 1 day of withdrawal, while morphine-treated female mice maintain the ability to evoke LTPGABA and have basal GABA activity similar to controls. Our observation of this physiological difference between male and female mice connects previous reports of sex differences in areas upstream and downstream of the GABA-dopamine synapse in the VTA during opioid withdrawal. The sex differences highlight the mechanistic distinctions between males and females that can be targeted when designing and implementing treatments for OUD.

Cubosome-based thermosensitive in situ gelling system for intranasal administration of lamotrigine with enhanced antiepileptic efficacy

Lamotrigine (LTG) is a second-generation antiepileptic drug that belongs to Biopharmaceutics Classification System (BCS) class II. LTG has a low probability of crossing the BBB if administered orally. This study was designed to fabricate LTG cubosomal dispersion that is further loaded in a thermosensitive in situ gel to increase nasal residence time and enhance drug absorption across the nasal mucosal membrane. LTG-loaded cubosomes exhibited an entrapment efficiency ranging from 24.83% to 60.13%, a particle size ranging from 116.2 to 197.6 nm, and a zeta potential ≤ −25.5 mV. The selected LTG-loaded cubosomal formulation was loaded in a thermosensitive in situ gel (cubogel) employing different concentrations of poloxamer 407. In vitro release study revealed sustained drug release from cubosomal and cubogel compared with free drug suspension. In vivo studies revealed enhanced antiepileptic efficacy of LTG cubogel and LTG cubosomes compared with free drug in rats with pilocarpine-induced epilepsy by stimulating the release of gamma-aminobutyric acid (GABA), total antioxidant capacity (TAC), and serotonin and by inhibiting the release of Ca2+, dopamine, acetylcholine (Ach), C-reactive protein (CRP), and glial fibrillary acidic protein (GFAP). LTG cubogel exhibited superior activity over LTG cubosomes. These findings reveal that the developed cubosomal thermosensitive in situ gel can enhance the antiepileptic efficacy of LTG via the intranasal route.

The Effects of Alcohol Intoxication and Withdrawal on Hypothalamic Neurohormones and Extrahypothalamic Neurotransmitters.

The aim of the present study was to determine the effects of alcohol intoxication and withdrawal on hypothalamic neurohormones such as corticotropin-releasing factor (CRF) and arginine vasopressin (AVP), and extrahypothalamic neurotransmitters such as striatal dopamine (DA), amygdalar gamma aminobutyric acid (GABA), and hippocampal glutamate (GLU). In addition, the participation of the two CRF receptors, CRF1 and CRF2, was investigated. For this purpose, male Wistar rats were exposed to repeated intraperitoneal (ip) administration of alcohol every 12 h, for 4 days and then for 1 day of alcohol abstinence. On the fifth or sixth day, intracerebroventricular (icv) administration of selective CRF1 antagonist antalarmin or selective CRF2 antagonist astressin2B was performed. After 30 min, the expression and concentration of hypothalamic CRF and AVP, the concentration of plasma adrenocorticotropic hormone (ACTH) and corticosterone (CORT), and the release of striatal DA, amygdalar GABA, and hippocampal GLU were measured. Our results indicate that the neuroendocrine changes induced by alcohol intoxication and withdrawal are mediated by CRF1, not CRF2, except for the changes in hypothalamic AVP, which are not mediated by CRF receptors.

Two decades of research on anoxia tolerance - mitochondria, -omics and physiological diversity.

Just over two decades ago, Bob Boutilier published a much-cited Review in this journal on the mechanisms of cell survival in hypoxia and hypothermia. Here, we celebrate this important Review by describing how our knowledge of the mechanisms behind anoxia tolerance have progressed since 2001, including new key roles of mitochondria, something Boutilier had started exploring. Evidence now suggests that, in anoxia-tolerant brains, mitochondria initiate responses aimed at suppressing electrical activity and energy use. These responses are largely dependent on gamma-aminobutyric acid (GABA) release. Animals that survive anoxia must also tolerate reoxygenation - a major challenge that could cause a massive production of damaging reactive oxygen species (ROS). Here, the handling of succinate, which builds up during anoxia, is critical. Interestingly, there are clear species differences in succinate handling among anoxia-tolerant vertebrates (Trachemys and Chrysemys turtles and crucian carp, Carassius carassius). Trachemys turtles suppress succinate build-up during anoxia, presumably to limit ROS production during reoxygenation. By contrast, in crucian carp, reduction of fumarate to succinate during anoxia appears to be essential for keeping their mitochondria charged and viable. Consequently, during anoxia, crucian carp accumulate much more succinate than Trachemys turtles. Moreover, during anoxia, succinate is apparently transported from crucian carp brain and heart to the liver, which handles succinate upon reoxygenation. This is one example of the striking physiological diversity among vertebrates that survive long-term anoxia. More examples are given, and we argue that -omics approaches are, and will be, helpful in providing new insight and moving the field forward.

5-HT7 Receptors Regulate Excitatory-Inhibitory Balance in Mouse Spinal Cord Dorsal Horn.

Serotonergic receptors of the 5-HT7 type (5-HT7Rs) are widely expressed in the central nervous system (CNS), where they modulate several functions, such as pain. Behavioral experiments in vivo have shown both anti- and pro-nociceptive actions of 5-HT7Rs, although an analgesic effect seems to be prevalent. In the spinal cord dorsal horn, the mechanisms involved in 5-HT7R-mediated synaptic modulation are still poorly understood, especially those regarding the control of synaptic inhibition. The present study investigated the modulation exerted by 5-HT7Rs on dorsal horn excitatory and inhibitory synaptic circuits, by performing patch-clamp recordings from lamina II neurons in mouse spinal cord slices. Our results show that applying the selective 5-HT7 agonist LP-211 facilitates glutamatergic release by enhancing the frequency of spontaneous postsynaptic currents (sEPSCs) and increasing the peak amplitude of excitatory postsynaptic currents (EPSCs) evoked by dorsal root stimulation. The effects on sEPSCs were still observed in the presence of the 5-HT1A antagonist WAY-100635, while the 5-HT7 antagonist SB-269970 blocked them. LP-211 was also able to increase the release of gamma-aminobutyric acid (GABA) and glycine, as shown by the increase of spontaneous inhibitory currents (sIPSC) frequency and evoked inhibitory postsynaptic currents (IPSC) amplitude. LP-211 was proved to be more effective in potentiating synaptic inhibition as compared to excitation: consistently, 5-HT7R activation significantly enhanced the excitability of tonic firing neurons, mainly corresponding to inhibitory interneurons. Our data bring new insights into the mechanisms of synaptic modulation mediated by 5-HT7Rs in the dorsal horn. Stronger impact on synaptic inhibition supports the hypothesis that these receptors may play an anti-nociceptive role in the spinal cord of naïve animals.

Effects of Chronic Inhalation of Electronic Cigarette Vapor Containing Nicotine on Neurobehaviors and Pre/Postsynaptic Neuron Markers.

Nicotine-exposed animal models exhibit neurobehavioral changes linked to impaired synaptic plasticity. Previous studies highlighted alterations in neurotransmitter levels following nicotine exposure. Vesicular glutamate transporter (VGLUT1) and vesicular gamma-aminobutyric acid (GABA) transporter (VGAT) are essential for the transport and release of glutamate and GABA, respectively, from presynaptic neurons into synapses. In our work, an e-cigarette device was used to deliver vapor containing nicotine to C57BL/6J mice for four weeks. Novel object recognition, locomotion, and Y-maze tests were performed to investigate the behavioral parameters. Protein studies were conducted to study the hippocampal expression of VGLUT1, VGAT, and postsynaptic density protein 95 (PSD95) as well as brain cytokine markers. Long-term memory and locomotion tests revealed that e-cigarette aerosols containing nicotine modulated recognition memory and motor behaviors. We found that vapor exposure increased VGLUT1 expression and decreased VGAT expression in the hippocampus. No alterations were found in PSD95 expression. We observed that vapor-containing nicotine exposure altered certain brain cytokines such as IFNβ-1 and MCP-5. Our work provides evidence of an association between neurobehavioral changes and altered hippocampal VGLUT1 and VGAT expression in mice exposed to e-cigarette vapors containing nicotine. Such exposure was also associated with altered neurobehaviors, which might affect neurodegenerative diseases.

Central amygdala corticotropin-releasing factor neurons promote hyponeophagia but do not control alcohol drinking in mice.

Corticotropin-releasing factor (CRF) signaling in the central nucleus of the amygdala (CeA) plays a critical role in rodent models of excessive alcohol drinking. However, the source of CRF acting in the CeA during alcohol withdrawal remains to be identified. In the present study, we hypothesized that CeA CRF interneurons may represent a behaviorally relevant source of CRF to the CeA increasing motivation for alcohol via negative reinforcement. We first observed that Crh mRNA expression in the anterior part of the mouse CeA correlates positively with alcohol intake in C57BL/6J males with a history of chronic binge drinking followed by abstinence and increases upon exposure to chronic intermittent ethanol (CIE) vapor inhalation. We then found that chemogenetic activation of CeA CRF neurons in Crh-IRES-Cre mouse brain slices increases gamma-aminobutyric acid (GABA) release in the medial CeA, in part via CRF1 receptor activation. While chemogenetic stimulation exacerbated novelty-induced feeding suppression (NSF) in alcohol-naïve mice, thereby mimicking the effect of withdrawal from CIE, it had no effect on voluntary alcohol consumption, following either acute or chronic manipulation. Furthermore, chemogenetic inhibition of CeA CRF neurons did not affect alcohol consumption or NSF in chronic alcohol drinkers exposed to air or CIE. Altogether, these findings indicate that CeA CRF neurons produce local release of GABA and CRF and promote hyponeophagia in naïve mice, but do not drive alcohol intake escalation or negative affect in CIE-withdrawn mice. The latter result contrasts with previous findings in rats and demonstrates species specificity of CRF circuit engagement in alcohol dependence.

Ivermectin: Evaluation of Efficacy and Safety in COVID-19

The search for an effective and safe COVID-19 therapy involves, among other things, assessment of efficacy of medicines already used for the treatment of other diseases, and having potential antiviral activity against SARS-CoV-2. The relevance of the presented study stems from ambiguous data on the off-label use of the antiparasitic medicine ivermectin for the treatment of COVID-19 patients. The aim of the study was to analyse ivermectin efficacy and safety for COVID-19 treatment, as reflected in the scientific literature. Ivermectin, an antiparasitic medicine from the group of macrocyclic lactones produced byStreptomyces avermitilis, stimulates release of the inhibitory neurotransmitter gamma-aminobutyric acid, which leads to impaired transmission of nerve impulses, paralysis and death of parasites. The results of preclinical studies show ivermectin’s inhibitory activity against a number of RNA and DNA viruses, including SARS-CoV-2. The results of ivermectin clinical studies are ambiguous: a number of studies demonstrated a positive effect on the condition of COVID-19 patients, however, there is currently no convincing evidence of the validity and efficacy of ivermectin use for the prevention and treatment of COVID-19 patients. The safety profile of ivermectin is relatively favourable. Large randomised controlled trials are needed to fully assess the feasibility of using ivermectin in COVID-19.