GABA Agonist Research Articles

Baclofen and the risk of fall and fracture in older adults: A real-world cohort study.

The growth of oral muscle relaxant prescriptions among older adults in the United States is concerning due to the drugs' adverse sedative effects. Baclofen is a gamma-aminobutyric acid agonist muscle relaxant that is associated with encephalopathy. We characterized the risk of fall and fracture associated with oral baclofen against other muscle relaxants (tizanidine or cyclobenzaprine) in older adults. We designed a new-user, active-comparator study using tertiary health system data from Geisinger Health, Pennsylvania (January 2005 through December 2018). Older adults (aged ≥65 years) newly treated with baclofen, tizanidine, or cyclobenzaprine were included. Propensity score-based inverse probability of treatment weighting (IPTW) was used to balance the treatment groups on 58 baseline characteristics. Fine-Gray competing risk regression was used to estimate the risk of fall and fracture. The study cohort comprised of 2205 new baclofen users, 1103 new tizanidine users, and 9708 new cyclobenzaprine users. During a median follow-up of 100 days, baclofen was associated with a higher risk of fall compared to tizanidine (IPTW incidence rate, 108.4 vs. 61.9 per 1000 person-years; subdistribution hazard ratio [SHR], 1.68 [95% CI, 1.20-2.36]). The risk of fall associated with baclofen was comparable to cyclobenzaprine (SHR, 1.17 [95% CI, 0.93-1.47]) with a median follow-up of 106 days. The risk of fracture was similar among patients treated with baclofen versus tizanidine (SHR, 0.85 [95% CI, 0.63-1.14]) or cyclobenzaprine (SHR, 0.85 [95% CI, 0.67-1.07]). The risk of fall associated with baclofen was greater than tizanidine, but not compared to cyclobenzaprine in older adults. The risk of fracture was comparable among the older users of baclofen, tizanidine, and cyclobenzaprine. Our findings may inform risk-benefit considerations in the increasingly common clinical encounters where oral muscle relaxants are prescribed.

A hypothalamus-habenula circuit regulates psychomotor responses induced by cocaine.

Administration of cocaine increases synaptic dopamine levels by blocking dopamine reuptake and leads to increased locomotor activity and compulsive drug-seeking behaviour. It has been suggested that the lateral hypothalamus (LH) or lateral habenula (LHb) is involved in drug-seeking behaviours. To explore the role of the LH and the LHb in cocaine-induced psychomotor responses, we tested whether modulation of the LH or the LH-LHb circuit affects cocaine-induced locomotion. Cocaine-induced locomotor activity and dopamine release were suppressed by the activation of the LH with 2-[2,6-difluoro-4-[[2-[(phenylsulfonyl)amino]ethyl]thio]phenoxy]acetamide (PEPA), an AMPA receptor agonist. When the LH was inhibited by microinjection of a GABA receptor agonists mixture prior to cocaine injection, the cocaine's effects were enhanced. Furthermore, optogenetic activation of the LH-LHb circuit attenuated the cocaine-induced locomotion, while optogenetic inhibition of the LH-LHb circuit increased it. In vivo extracellular recording found that the LH sent a glutamatergic projection to the LHb. These findings suggest that the LH glutamatergic projection to the LHb plays an active role in the modulation of cocaine-induced psychomotor responses.

Inactivation of the paraventricular nucleus attenuates the cardiogenic sympathetic afferent reflex in the spontaneously hypertensive rat.

Myocardial ischemia causes the release of bradykinin, which stimulates cardiac afferents, causing sympathetic excitation and chest pain. Glutamatergic activation of the paraventricular hypothalamic nucleus (PVN) in the spontaneously hypertensive rat (SHR) drives elevated basal sympathetic activity. Thus, we tested the hypothesis that inactivation of the PVN attenuates the elevated reflex response to epicardial bradykinin in the SHR and that ionotropic PVN glutamate receptors mediate the elevated reflex. We recorded the arterial pressure and renal sympathetic nerve activity (RSNA) response to epicardial bradykinin application in anesthetized SHR and Wistar Kyoto (WKY) rats before and after PVN microinjection of GABA A agonist muscimol or ionotropic glutamate receptor antagonist kynurenic acid. Muscimol significantly decreased the arterial pressure response to bradykinin from 180.4 ± 5.8 to 119.5 ± 6.9 mmHg in the SHR and from 111.8 ± 7.0 to 84.2 ± 8.3 mmHg in the WKY and the RSNA response from 186.2 ± 7.1 to 142.7 ± 7.3% of baseline in the SHR and from 201.0 ± 11.5 to 160.2 ± 9.3% of baseline in the WKY. Kynurenic acid significantly decreased the arterial pressure response in the SHR from 164.5 ± 5.0 to 126.2 ± 7.7 mmHg and the RSNA response from 189.9 ± 13.7to 168.5 ± 12.7% of baseline but had no effect in the WKY. These results suggest that tonic PVN activity is critical for the full manifestation of the CSAR in both the WKY and SHR. Glutamatergic PVN activity contributes to the augmented CSAR observed in the SHR.

DEVELOPMENT AND EVALUATION OF FLOATING BEADS OF BACLOFEN AS A GASTRORETENTIVE DOSAGE FORM

Gastro retentive delivery systems are designed to be retained in the stomach for a prolonged time and release their active ingredients and thereby enable sustained and prolonged input of the drug to the upper part of the gastrointestinal (GI) tract. The goal of any drug delivery system is to provide a therapeutic amount of drug to proper site in the body to achieve promptly and then maintain a desired drug concentration. Baclofen is a gamma-aminobutyric acid (GABA) agonist used as a skeletal muscle relaxant used for the relief of painful and uncomfortable muscle spasms caused by a variety of conditions. Twelve different formulation of Baclofen floating beads were successfully developed using emulsion solvent diffusion method. The beads had good yield and showed high, drug entrapment efficiency. The flow properties of beads were within the acceptable range and therefore would be easily filled into capsules. Study concludes successfully delivery of Baclofen by the means of floating beads.

Muscimol inhibits plasma membrane rupture and ninjurin-1(NINJ1) oligomerization during pyroptosis

Pyroptosis is a cell death process that causes inflammation and contributes to numerous diseases. Pyroptosis is mediated by caspase-1 family proteases that cleave the pore-forming protein gasdermin D, causing plasma membrane rupture and release of pathogenic cellular contents. We previously identified muscimol as a small molecule that prevents plasma membrane rupture during pyroptosis via an unidentified mechanism. Here, we show that muscimol has reversible activity to prevent cellular lysis without affecting earlier pyroptotic events. Although muscimol is a well-characterized agonist for neuronal GABAA receptors, muscimol protection is not altered by GABAA receptor antagonists or recapitulated by other GABAA agonists, suggesting that muscimol acts via a novel mechanism. We find that muscimol blocks oligomerization of ninjurin-1, which is required for plasma membrane rupture downstream of gasdermin D pore formation. Our structure-activity relationship studies reveal distinct molecular determinants defining inhibition of pyroptotic lysis compared to GABAA binding. In addition, we demonstrate that muscimol reduces lethality during LPS-induced septic shock. Together, these findings demonstrate that ninjurin-1-mediated plasma membrane rupture can be pharmacologically modulated and pave the way toward identification of therapeutic strategies for pathologic conditions associated with pyroptosis.

THU356 Muscle Pain In A Diabetic: Think Outside The Box

Abstract Disclosure: R. Ellangovan: None. M. Rizk: None. V. Singh MD: None. C. Sherpa: None. Introduction: Stiff person syndrome (SPS) is a rare immunological disorder associated with GAD antibody-spectrum disorders and characterized by rigidity and painful muscle spasms. SPS has a prevalence of 1-2 cases per million and affects females more than men. We present a case of SPS who was admitted for progressive muscle pain and rigidity causing impaired ambulation. Case Presentation: A 60-year-old female with a two-year history of type 2 diabetes, Graves' disease was diagnosed with acral lentiginous melanoma of the left foot. One month after Nivolumab immunotherapy, she converted to type 1 diabetes with low C-peptide and positive GAD antibody. She was admitted with severe muscle pain and spasms in her lower extremities and trunk, debilitating enough to make her bedbound. Her muscle strength and sensory function were intact. MRI of thigh was concerning for myositis versus diabetic myonecrosis. She was initiated on NSAIDs with no improvement. Core muscle biopsy revealed necrosis and granulation tissue with no evidence of malignancy. Extensive work up including myositis panel and myasthenia gravis panel were negative. The presence of GAD antibodies and no improvement to NSAIDs, prompted suspicion for SPS. The patient declined lumbar puncture (LP) for further evaluation. Diazepam showed mild improvement. Due to persistent severe symptoms, she was treated with IVIG for 5 days that resulted in marked improvement. Discussion: There is no gold standard test for definitive diagnosis of SPS. Classic features of SPS include muscle spasms, pain, and rigidity typically involving the trunk and lower extremities. There are GAD antibodies in serum and CSF and glycine receptor or amphiphysin antibodies. EMG study will show continuous motor unit activity in affected muscles. A robust response to muscle relaxants like GABA agonists and exclusion of alternative neurological disorder favors SPS. LP or EMG was not performed on this patient, yet she met other criteria including the presence of other GAD disorders like type 1 diabetes. Current recommended therapy for symptomatic relief includes GABA agonists or baclofen. If no improvement is noted, IVIG can be considered. Plasmapheresis and rituximab have been used with variable efficacy. Prognosis is variable and many patients experience disability despite combining multiple therapies. Hence it is crucial to have a high index of suspicion in GAD spectrum disorders for early recognition and prompt treatment. Presentation: Thursday, June 15, 2023

Single-nucleus genomics in outbred rats with divergent cocaine addiction-like behaviors reveals changes in amygdala GABAergic inhibition.

The amygdala processes positive and negative valence and contributes to addiction, but the cell-type-specific gene regulatory programs involved are unknown. We generated an atlas of single-nucleus gene expression and chromatin accessibility in the amygdala of outbred rats with high and low cocaine addiction-like behaviors following prolonged abstinence. Differentially expressed genes between the high and low groups were enriched for energy metabolism across cell types. Rats with high addiction index (AI) showed increased relapse-like behaviors and GABAergic transmission in the amygdala. Both phenotypes were reversed by pharmacological inhibition of the glyoxalase 1 enzyme, which metabolizes methylglyoxal-a GABAA receptor agonist produced by glycolysis. Differences in chromatin accessibility between high and low AI rats implicated pioneer transcription factors in the basic helix-loop-helix, FOX, SOX and activator protein 1 families. We observed opposite regulation of chromatin accessibility across many cell types. Most notably, excitatory neurons had greater accessibility in high AI rats and inhibitory neurons had greater accessibility in low AI rats.

Activation of Beta-adrenergic Receptors Upregulates the Signal-to-Noise Ratio of Auditory Input in the Medial Prefrontal Cortex and Mediates Auditory Fear Conditioning.

Norepinephrine (NE) is involved in auditory fear conditioning (AFC) in posttraumatic stress disorder (PTSD). However, it is still unclear how it acts on neurons. We aimed to investigate whether the activation of the β-adrenergic receptor (β-AR) improves AFC by sensitization of the prelimbic (PL) cortex at the animal, cellular, and molecular levels. In vivo single-cell electrophysiological recording was used to characterize the changes in neurons in the PL cortex after AFC. Then, PL neurons were locally administrated by the β-AR agonist isoproterenol (ISO), the GABAaR agonist muscimol, or intervened by optogenetic method, respectively. Western blotting and immunohistochemistry were finally used to assess molecular changes. Noise and low-frequency tones induced similar AFC. The expression of β-ARs in PL cortex neurons was upregulated after fear conditioning. Microinjection of muscimol into the PL cortex blocked the conformation of AFC, whereas ISO injection facilitated AFC. Moreover, PL neurons can be distinguished into two types, with type I but not type II neurons responding to conditioned sound and being regulated by β-ARs. Our results showed that β-ARs in the PL cortex regulate conditional fear learning by activating type I PL neurons.

Rapid eye movements associated with REM sleep is involved in consolidation of visuospatial learning in rats

Rapid eye movement (REM) sleep plays a significant role in visuospatial learning and memory consolidation; however, its mechanism of action is unknown. Rapid eye movements (REMs), a characteristic active feature of REM sleep, is a potential correlate of neural processing for visual memory consolidation. The superior colliculus (SC) plays a central role in oculomotor control and spatial localization of objects in the visual field. We proposed that local reversible inactivation of the SC during post-learning sessions might interfere with REMs and negatively impact REM sleep associated consolidation of the visuospatial learnt task. Under gaseous anesthesia, bilateral cannulae aiming SC and electrodes for recording electrophysiological signals to classify sleep-waking were implanted. Following standard protocol, all rats were subjected to Morris water maze (MWM) training for 5 consecutive days followed by probe trial. After MWM training, on all except the probe test days, the rat SC were bilaterally infused with either vehicle (control, Group 1), Lidocaine hydrochloride a local anesthetic (Lox 2%, Group 2), or muscimol (Mus, GABA agonist, Group 3) and sleep-wakefulness recorded after day 1, 4, and post-probe learning sessions. Post-learning, compared to vehicle, Mus treated group significantly decreased REMs, phasic REM sleep, percent time spent in REM sleep and REM sleep frequency/hr. Also, during probe test, the escape latency was significantly increased, and the percentage time spent in the platform quadrant were significantly decreased in both, Mus and Lox 2% treated rats, while the number of platform location crossings was decreased in Mus treated group. The results showed that Lox 2% and Mus into SC reduced consolidation of visuospatial learning. The findings support our contention that SC mediated activation of REMs exerts a positive influence in processing and consolidation of visual learning during REM sleep. The findings explain the role of REMs during REM sleep in visual memory consolidation.

Sex-dependent neuronal effects of α-synuclein reveal that GABAergic transmission is neuroprotective of sleep-controlling neurons

BackgroundSleep disorders (SDs) are a symptom of the prodromal phase of neurodegenerative disorders that are mechanistically linked to the protein α-synuclein (α-syn) including Parkinson’s disease (PD). SDs during the prodromal phase could result from neurodegeneration induced in state-controlling neurons by accumulation of α-syn predominant early in the disease, and consistent with this, we reported the monomeric form of α-syn (monomeric α-syn; α-synM) caused cell death in the laterodorsal tegmental nucleus (LDT), which controls arousal as well as the sleep and wakefulness state. However, we only examined the male LDT, and since sex is considered a risk factor for the development of α-syn-related diseases including prodromal SDs, the possibility exists of sex-based differences in α-synM effects. Accordingly, we examined the hypothesis that α-synM exerts differential effects on membrane excitability, intracellular calcium, and cell viability in the LDT of females compared to males.MethodsPatch clamp electrophysiology, bulk load calcium imaging, and cell death histochemistry were used in LDT brain slices to monitor responses to α-synM and effects of GABA receptor acting agents.ResultsConsistent with our hypothesis, we found differing effects of α-synM on female LDT neurons when compared to male. In females, α-synM induced a decrease in membrane excitability and heightened reductions in intracellular calcium, which were reliant on functional inhibitory acid transmission, as well as decreased the amplitude and frequency of spontaneous excitatory postsynaptic currents (sEPSCs) with a concurrent reduction in action potential firing rate. Cell viability studies showed higher α-synM-mediated neurodegeneration in males compared to females that depended on inhibitory amino acid transmission. Further, presence of GABA receptor agonists was associated with reduced cell death in males.ConclusionsWhen taken together, we conclude that α-synM induces a sex-dependent effect on LDT neurons involving a GABA receptor-mediated mechanism that is neuroprotective. Understanding the potential sex differences in neurodegenerative processes, especially those occurring early in the disease, could enable implementation of sex-based strategies to identify prodromal PD cases, and promote efforts to illuminate new directions for tailored treatment and management of PD.

Potential strategies to optimize the efficacy of antidepressants: Beyond the monoamine theory

Depression is characterized by a feeling of sadness and a lack of pleasure, with impaired daily functioning and poor quality of life. The neurobiology and the pathogenesis of depression are not fully understood yet. Several hypotheses have been discussed including, monoamine theory, neurotransmission, oxidation, inflammation, glutamatergic transmission, neurotrophic factors, and others. Reviewing three decades of randomized controlled trials of antidepressants revealed that the antidepressants response rate is about 54% compared to a placebo response rate of 37%. Treatment-resistant depression (TRD) could be defined as an inadequate response to two different of antidepressants. In TRD, a combination strategy of using two FDA-approved antidepressants is used, which may predispose patients to adverse effects. Therefore, there is a compelling need to explore the potential “out of the box” adjuvants to antidepressants to provide higher and consistent response rates with high tolerability. These adjuvants could be medications available for other indications, food supplements, or even experimental drugs. This review will highlight potentially beneficial adjuvants to antidepressants such as nitric oxide modulators, NMDA antagonists, anti-inflammatory, antioxidants, mitochondrial modulators, insulin sensitizers, opioids, probiotics, and GABA agonists.

Efficacy and safety of ciprofol for long-term sedation in patients receiving mechanical ventilation in ICUs: a prospective, single-center, double-blind, randomized controlled protocol.

Introduction: Critically ill patients who receive mechanical ventilation after endotracheal intubation commonly experience discomfort and pressure. The major sedative drugs that are currently used in clinical practice present with many complications, such as hypotension, bradycardia, and respiratory depression. Ciprofol (HSK3486), which is a newly developed structural analog of propofol, is a short-acting gamma-aminobutyric acid (GABA) receptor agonist, and its mechanism of action is sedation or anesthesia by enhancing GABA-mediated chloride influx. The high efficacy of ciprofol for short-term sedation is comparable to that of propofol, and it has a relatively low incidence of adverse effects and high level of safety, which has been confirmed by multiple clinical studies. However, few studies have examined its safety and efficacy for long-term sedation. The purpose of the study is to evaluate the efficacy and safety of ciprofol for long-term sedation in mechanically ventilated patients. Methods: A prospective, single-center, double-blind, randomized, propofol-controlled, non-inferiority trial is proposed. The study will enroll 112 mechanically ventilated patients hospitalized in the intensive care unit (ICU) of the Shanghai Fourth People's Hospital affiliated with Tongji University based on the inclusion and exclusion criteria of the study, and randomly assign them to a group sedated with either ciprofol or propofol. The primary outcome is the percentage of time spent under target sedation, and secondary outcomes include drug dose, number of cases requiring additional dextrometropine, incidence of systolic blood pressure <80 or >180mmHg, incidence of diastolic blood pressure <50 or >100mmHg, incidence of heart rate <50 beats per minute (bpm) or >120bpm, inflammatory indicators, blood lipid levels, liver and kidney functions, nutritional indicators, ventilator-free days within the 7-day period after enrollment, 28-day mortality, ICU stay duration, and hospitalization costs. Discussion: We hypothesize that the efficacy and safety of ciprofol for long-term sedation in mechanically ventilated ICU patients will not be inferior to that of propofol. Trial registration: Chinese Clinical Trials Registry identifier ChiCTR2200066951.

Activation of GABA receptor attenuates intestinal inflammation by modulating enteric glial cells function through inhibiting NF-κB pathway

AimsEmerging research indicates that γ-aminobutyric acid (GABA) provides substantial benefits during enteritis. Nevertheless, GABA signaling roles on enteric glial cells (EGCs) remain unknown. The study's objective was to evaluate the underlying mechanisms of GABA signaling on EGCs in vitro and in vivo. Main methodsWe established LPS-induced mouse models and stimulated EGCs with LPS to mimic intestinal inflammation, and combined GABA, GABAA receptor (GABAAR) or GABAB receptor (GABABR) agonists to explore the exact mechanisms of GABA signaling. Key findingsEGCs were immunopositive for GAD65, GAD67, GAT1, GABAARα1, GABAARα3, and GABABR1, indicating GABAergic and GABAceptive properties. GABA receptor activation significantly inhibited the high secretions of proinflammatory factors in EGCs upon LPS stimulation. Interestingly, we found that EGCs express immune-related molecules such as CD16, CD32, CD80, CD86, MHC II, iNOS, Arg1, and CD206, thus establishing their characterization of E1 and E2 phenotype. EGCs exposed to LPS mainly acted as E1 phenotype, whereas GABABR activation strongly promoted EGCs polarization into E2 phenotype. Transcriptome analysis of EGCs indicated that GABA, GABAAR or GABABR agonists treatment participated in various biological processes, however all of these treatments exhibit inhibitory effects on NF-κB pathway. Notably, in LPS-induced mice, activation of GABABR mitigated intestinal damage through modulating inflammatory factors expressions, strengthening sIgA and IgG levels, inhibiting NF-κB pathway and facilitating EGCs to transform into E2 phenotype. SignificanceThese data demonstrate that the anti-inflammatory actions of GABA signaling system offer in enteritis via regulating EGCs-polarized function through impeding NF-κB pathway, thus providing potential targets for intestinal inflammatory diseases.

Age and asymmetry of corticospinal excitability, but not cardiorespiratory fitness, predict cognitive impairments in multiple sclerosis

BackgroundCognitive impairment is a disabling and underestimated consequence of multiple sclerosis (MS), with multiple determinants that are poorly understood. ObjectivesWe explored predictors of MS-related processing speed impairment (PSI) and age-related mild cognitive impairment (MCI) and hypothesized that cardiorespiratory fitness and corticospinal excitability would predict these impairments. MethodsWe screened 73 adults with MS (53 females; median [range]: Age 48 [21–70] years, EDSS 2.0 [0.0–6.5]) for PSI and MCI using the Symbol Digit Modalities Test and Montréal Cognitive Assessment, respectively. We identified six persons with PSI (No PSI, n = 67) and 13 with MCI (No MCI, n = 60). We obtained clinical data from medical records and self-reports; used transcranial magnetic stimulation to test corticospinal excitability; and assessed cardiorespiratory fitness using a graded maximal exercise test. We used receiver operator characteristic (ROC) curves to discern predictors of PSI and MCI. ResultsInterhemispheric asymmetry of corticospinal excitability was specific for PSI, while age was both sensitive and specific for MCI. MS-related PSI was also associated with statin prescriptions, while age-related MCI was related to progressive MS and GABA agonist prescriptions. Cardiorespiratory fitness was associated with neither PSI nor MCI. DiscussionCorticospinal excitability is a potential marker of neurodegeneration in MS-related PSI, independent of age-related effects on global cognitive function. Age is a key predictor of mild global cognitive impairment. Cardiorespiratory fitness did not predict cognitive impairments in this clinic-based sample of persons with MS.

Development and validation of an LC-MS/MS method for simultaneous determination of EVT201 and its five metabolites in human plasma: Application to a clinical study in Chinese healthy subjects

EVT201 is a partial GABAA receptor agonist, which inhibits nervous system to treat insomnia. EVT201 can form a variety of metabolites in vivo including Ro46–1927, Ro18–5528, Ro40–9970, Ro66–9196 and Ro66–5448. This study developed a simple method to realize the simultaneous determination of EVT201 and its five metabolites by HPLC-MS/MS with an electrospray ion source (ESI). The deuterium substitute of EVT201 was chosen as the internal standard and the multiple reaction monitoring (MRM) was used for the quantification. The separation of the six compounds was accomplished with an ACE Excel 3 AQ column (50 × 2.1 mm, 3 µm, ACE). The process of protein precipitating-transferring-nitrogen blowing-reconstituting was adopted for the sample pretreatment. This method was successfully validated according to the FDA guidance. Calibration curves were linear over the concentration range of 0.100–100 ng/mL for EVT201, 0.0300–30.0 ng/mL for Ro46–1927, 0.0600–6.00 ng/mL for Ro18–5528, 0.0200–4.00 ng/mL for Ro40–9970, 0.100–20.0 ng/mL for Ro66–9196 and 0.100–20.0 ng/mL for Ro66–5448. The intra-run and inter-run precisions and accuracies were all within 14.5%. This fully validated method was successfully applied to a clinical pharmacokinetic study of EVT201 and its five metabolites in Chinese healthy subjects after the single (2.5 mg and 5 mg, N = 12) and multiple dose (2.5 mg, N = 13) administration of EVT201 capsules. The test results of 2.5 mg dose group showed that for EVT201, Ro46–1927, Ro18–5528, Ro40–9970, Ro66–9196 and Ro66–5448, the Cmax values (ng/mL) were 39.2 ± 9.2, 10.3 ± 1.4, 0.218 ± 0.044, 0.128 ± 0.051, 7.01 ± 1.51, 8.73 ± 3.69, respectively; the AUC0−t values (h·ng/mL) were 231 ± 79, 143 ± 72, 10.9 ± 2.1, 1.84 ± 0.78, 55.9 ± 18.7, 135 ± 40 respectively. For EVT201, Ro46–1927, Ro66–5528, Ro66–9196 and Ro40–5448, the results of Cmax and AUC0−t proved that the five compounds showed linear pharmacokinetic profile over the dose ranges of 2.5 mg to 5 mg. Meanwhile, it is the first report to evaluate the pharmacokinetic characteristics of Ro40–9970, Ro66–9196 and Ro66–5448 in human plasma. It provided meaningful parameters for the safety and tolerability evaluation of EVT201 capsules in human.

Maternal hyperhomocysteinemia increases seizures susceptibility of neonatal rats

AimsNeonatal seizures are severe pathologies which may result in long-term neurological consequences. High plasma concentrations of homocysteine – hyperhomocysteinemia (hHCy) - are associated with epilepsy. In the present study, we evaluated susceptibility to seizure of neonatal rats with prenatal hHCy. Main methodsPrenatal hHCy was induced by feeding females with a high-methionine diet. Experiments were performed on pups during the first three postnatal weeks. Flurothyl-induced epileptic behavior was assessed according to Racine's scale. Epileptiform activity in the hippocampus was recorded using electrophysiological methods. The balance of excitation/inhibition, functional GABAergic inhibition and GABA reversal potential in hippocampal neurons were analyzed. Key findingsRats with hHCy developed more severe stages of behavioral patterns during flurothyl-induced epilepsy with shorter latency. Electrophysiological recordings demonstrated higher background neuronal activity in rats with hHCy. Seizure-like events triggered by flurothyl (in vivo) or 4-aminopyridine (in vitro) showed shorter latency, higher power and amplitude. An increased glutamate/GABA synaptic ratio was shown in the pyramidal neurons of rats with hHCy and more slices demonstrated excitation by isoguvacine, a selective GABA(A) receptor agonist, during the first and second postnatal weeks. The GABA driving force and the reversal potential of GABA(A) currents were more positive during the second postnatal week for hHCy rats. SignificanceThe higher susceptibility to seizures in rats with prenatal hHCy due to a shift in the balance of excitation/inhibition toward excitation may underlie the clinical evidence about the association of hHCy with an increased risk of epilepsy.

The indirect corticopontine pathway relays perioral sensory signals to the cerebellum via the mesodiencephalic junction

In the cerebro-cerebellar loop, outputs from the cerebral cortex are thought to be transmitted via monosynaptic corticopontine gray (PG) pathways and subsequently relayed to the cerebellum. However, it is unclear whether this pathway is used constitutively for cerebro-cerebellar transduction. We examined perioral sensory pathways by unit recording from Purkinje cells in ketamine/xylazine-anesthetized mice. Infraorbital nerve stimulations enhanced simple spikes (SSs) with short and long latencies (first and second peaks), followed by SS inhibition. The second peak and SS inhibition were suppressed by muscimol (a GABAA agonist) injections into not only the PG but also the mesodiencephalic junction (MDJ). The pathway from the secondary somatosensory area (SII) to the MDJ, but not the cortico-PG pathway, transmitted the second peak signals. SS inhibition was processed in the SII and primary motor area. Thus, the indirect cortico-PG pathway, via the MDJ, is recruited for perioral sensory transduction.

Protective Effect of Baclofen on Ovarian Cystogenesis and Morphine-Induced Lipid Profile Change in Female Rats.

Morphine induces ovarian cysts that cause obesity and disrupt sex hormone secretion. Baclofen, a gamma-aminobutyric acid receptor agonist, can help regulate sex hormones and reduce harmful blood lipids by protecting against morphine-induced gamma-aminobutyric acid inhibition. We investigated the prophylactic effect of baclofen in rats receiving morphine by comparing with the untreated groups. Forty eight female Wistar rats were randomly divided into several groups, including control (saline 1 mL/kg, i.p.), morphine (5 mg/kg, i.p.), baclofen (10, 20, and 30 mg/kg, i.p.), and baclofen (10, 20, and 30 mg/kg) before morphine (5 mg/kg). Twenty four hours after the treatment, blood and serum samples were taken to check the levels of gonadotropins (LH & FSH) and lipid profile. The ovaries and uterus were also studied, and a proinflammatory nitric oxide (NO) diagnostic test was completed. The results were analyzed using analysis of variance (α = 0.05). In comparison with the control group, the levels of LH and not FSH decreased in the morphine group and the number of ovarian cysts was more in the morphine group. These problems were not observed in the group of baclofen alone and baclofen + morphine. However, the triglyceride level increased slightly in the baclofen 30 mg/kg + morphine group. But the LDL level somewhat decreased. The proinflammatory NO system did not show significant activation in the ovary and uterus, except for the baclofen 10 mg/kg + baclofen group. Morphine can cause ovarian cysts by lowering LH but baclofen prophylaxis can protect reproductive properties by adapting major metabolic changes.

The α1 and γ2 subunit-containing GABAA receptor-mediated inhibitory transmission in the anteroventral bed nucleus of stria terminalis is involved in the regulation of anxiety in rats with substantia nigra lesions

The anteroventral bed nucleus of the stria terminalis (avBNST) is widely acknowledged as a key brain structure that regulates negative emotional states, such as anxiety. At present, it is still unclear whether GABAA receptor-mediated inhibitory transmission in the avBNST is involved in Parkinson's disease (PD)-related anxiety. In this study, unilateral 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra pars compacta (SNc) in rats induced anxiety-like behaviors, increased GABA synthesis and release, and upregulated expression of GABAA receptor subunits in the avBNST, as well as decreased level of dopamine (DA) in the basolateral amygdala (BLA). In both sham and 6-OHDA rats, intra-avBNST injection of GABAA receptor agonist muscimol induced the following changes: (i) anxiolytic-like responses, (ii) inhibition of the firing activity of GABAergic neurons in the avBNST, (iii) excitation of dopaminergic neurons in the ventral tegmental area (VTA) and serotonergic neurons in the dorsal raphe nucleus (DRN), and (iv) increase of DA and 5-HT release in the BLA, whereas antagonist bicuculline induced the opposite effects. Collectively, these findings suggest that degeneration of the nigrostriatal pathway enhances GABAA receptor-mediated inhibitory transmission in the avBNST, which is involved in PD-related anxiety. Further, activation and blockade of avBNST GABAA receptors affect the firing activity of VTA dopaminergic and DRN serotonergic neurons, and then change release of BLA DA and 5-HT, thereby regulating anxiety-like behaviors.

A Human Microglial Cell Line Expresses γ-Aminobutyric Acid (GABA) Receptors and Responds to GABA and Muscimol by Increasing Production of IL-8

Gamma-aminobutyric acid (GABA) is an essential neurotransmitter and an important regulator of neuroinflammation and disease. Microglia are important immune cells in the brain that express GABA receptors (GABAR) and respond to both GABA and GABAR agonists, yet the effect of GABA on microglial inflammatory responses is unclear. We hypothesized that GABA and GABAR agonists might modify the activation of a human microglial cell line (HMC3). We further hypothesized that Amanita muscaria extract (AME-1), which contained GABAR agonists (GABA and muscimol), would similarly stimulate HMC3. Ligand-gated GABAR (GABAAR) and G protein-coupled GABAR (GABABR) subunit expression was analyzed by qRT-PCR, metabolic activity was determined by nicotinamide adenine dinucleotide (NADH)-dependent oxidoreductase assay (XTT), reactive oxygen species (ROS) generation was analyzed by 2′,7′-dichlorodihydrofluorescein diacetate (DCFDA), and interleukin-8 (IL-8) production was analyzed by an enzyme-linked immunosorbent assay (ELISA). HMC3 expressed several neuroreceptors such as subunits of the GABAA receptor (GABAAR). HMC3 constitutively produce IL-8 and ROS. Both muscimol and GABA stimulated HMC3 to produce more IL-8 but had no effect on constitutive ROS production. GABA and muscimol altered the morphology and Iba1 localization of HMC3. GABA, but not muscimol, increased HMC3 metabolic activity. Similarly, AME-1 induced HMC3 to produce more IL-8 but not ROS and altered cell morphology and Iba1 localization. GABA induction of IL-8 was blocked by bicuculline, an antagonist of GABAAR. AME-1-induced production of IL-8 was not blocked by bicuculline, suggesting that AME-1’s effect on HMC3 was independent of GABAAR. In conclusion, these data show that GABA and GABA agonists stimulate HMC3 to increase their production of IL-8. Mixtures that contain GABA and muscimol, such as AME-1, have similar effects on HMC3 that are independent of GABAAR.