Gamma-aminobutyric Acid Transmission Research Articles

Effects of psoralidin on the expression of glutamate decarboxylases and inhibitory synapse development

Gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter required for excitation/inhibition balance is synthesized by the glutamic acid decarboxylases (GADs) in GABAergic neurons. The levels and activity of GADs are strongly correlated with GABA and neural transmission. Dysregulation of GADs and GABA is associated with various neurological disorders. The study used psoralidin, found in the seeds of Psoralea corylifolia, to investigate its effect on GAD levels and regulatory mechanisms in primary cortical neurons. Psoralidin reduced GAD67 through transcriptional regulation. The reduction was not mediated by the N-methyl-D-aspartate receptor. Additionally, psoralidin attenuated the formation of inhibitory synapses in primary hippocampal neurons.

Abstract SS02-02: Hormone Replacement and Alternatives for Relief of Vasomotor Symptoms in Women at Increased Risk for Breast Cancer

Abstract 70% of women will experience vasomotor symptoms sufficient to impact their quality of life during menopause transition and the early menopause. These symptoms are thought result from neurotransmitter imbalances resulting from ovarian hormone reductions and hypersecretion of gonadotropins. Increases in gonadotropins result in neurotransmitter triggered stimulation of the neurokinin 3 (NK3) receptor and thermoregulatory imbalance. Estrogen deficiency also reduces serotonin which can also trigger increases in hot flashes, and sleep disturbances. Vasomotor symptoms last on the average for 7 years until acclimation to persistent low estrogen levels occurs. Estrogen +/- progestin replacement therapy is associated with the greatest likelihood of vasomotor symptom relief as it reduces gonadotropin and NK3 receptor signaling and increases serotonin. Progestins also increase the neuroinhibitory transmitter gamma-aminobutyric acid (GABA) which improves sleep quality. There continues to be confusion on the part of providers and patients regarding the excess risk of breast cancer and thromboembolic events as these risks are affected by type of agent, route of delivery, age, duration of treatment, and presence of obesity. The majority of placebo controlled randomized clinical trial data on hormone replacement with estrogen or estrogen + a progestin comes from the Women’s Health Initiative (WHI) for women 50-79 in which oral conjugated estrogen (CE) 0.625 mg was used as the estrogen for women without a uterus and medroxyprogesterone acetate (MPA) was added to CE for women with a uterus to protect against endometrial hyperplasia and cancer. The median age at entry to WHI that trial was 63 and a substantial proportion had previously taken hormones. Large longitudinal cohort studies have been helpful in assessing risks in women starting hormones at a more clinically relevant age (45-55) and with hormonal preparations other than oral CE and MPA. Five to seven years of estrogen alone results in minimal if any increased risk for breast cancer. However, combined estrogen+ progestin replacement for women over 50, necessary for women with a uterus, results in an ~ 30 % relative increased risk for breast cancer if taken for up to 5 years and a doubling of risk with 10 years of treatment. So called bioidentical hormones often compounded as oral troches of estradiol, progesterone, and testosterone, are also associated with increased breast cancer risk. Vaginal hormones have not been found to increase risk for breast cancer. Increased risk of thromboembolism is predominately observed in women over 50 using oral as opposed to transdermal preparations. Increased risk for stroke and dementia was observed in the WHI again with oral hormones in women over 65. In the WHI there was no increase in cancer related, cardiovascular or overall mortality with estrogen or estrogen and progestin. For high-risk peri and post-menopausal women with who would like to reduce/alleviate their vasomotor symptoms with no increase in risk for breast cancer there are several options: 1) the tissue selective estrogen complex bazedoxifene (BZA) combined with conjugated estrogen (CE) 2) the non-hormonal option of NK3 receptor antagonists such as fezolinetant ( 3) non-hormonal options of gabapentin, selective serotonin reuptake inhibitors (SSRI) and serotonin and norepinephrine uptake inhibitors (SNRI). BZA and CE and fezolinetant are reported to reduce hot flashes in 70% or more of individuals with paroxetine effectiveness reported as 50%. All three are FDA approved for reduction of vasomotor symptoms. The combination of BZA and CE is also being investigated for breast cancer risk reduction. These agents differ with respect to side effects with increased risk of blood clots for bazedoxifene and conjugated estrogen, increased risk of nausea, diarrhea, and liver dysfunction for fezolinetant and drowsiness and dry mouth for SSRIs. Drug costs may also dramatically affect insurance coverage and patient uptake of a particular strategy. A recent online perusal of a popular site for finding the lowest drug price suggested substantial differences in the cost of drugs for relief of vasomotor symptoms. The approximate cost for a 30- day supply of oral estradiol was $30, estradiol transdermal patches $35, oral progesterone $15, combined estradiol and levonorgestrel transdermal patches $240, oral CE $200, oral CE + medoxyprogesterone acetate $240, and for BZA+ CE $200. For non-hormonal therapies the cost of 30 days of gabapentin was $11, paroxetine $30 and fezolinetant $550. Crandall, Mehta, and Manson JAMA 2023 329:405-420 Collaborative Group on Hormonal Factors in Breast Cancer Lancet 2019 394: 1159-1168 Fabian et al Ca Prev Res 2019 10:711-720 Modi and Dhillo Neuroendocrinology 2019 109:242–248 Citation Format: C. Fabian. Hormone Replacement and Alternatives for Relief of Vasomotor Symptoms in Women at Increased Risk for Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr SS02-02.

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.

More than just immaturity: evidence supporting the hypothesis that sleep spindle characteristics reflect GABAergic depolarization in infancy.

Sleep spindles are thalamocortical oscillations with waxing-waning morphology, which comprise the key electroencephalographic (EEG) hallmark of stage 2 non-rapid eye movement sleep. The functional role of sleep spindles is not sufficiently clear, but there is a large body of literature that indicates the relationship between spindle activity and neural plasticity. Many of the spindle parameters (frequency, configuration, duration, density, and topography) vary significantly throughout life. However, the long duration, asynchrony and sharp morphology are the most distinctive characteristics of sleep spindles in infants. This unique infantile phenotype of sleep spindles typically changes after approximately one year of postnatal life in humans. Considering that EEG reflects brain electrochemical activity, there is evidence to suggest that substantial neurochemical events underlie these changes. In this paper, we hypothesize that the GABA (gamma-aminobutyric acid) shift is a key event influencing the sleep spindle phenotype during infancy. We briefly review evidence for the relation between infantile sleep spindles and depolarizing GABA transmission occurring in the developing brain.

The cortical silent period in schizophrenia: A systematic review and meta-analysis focusing on disease stage and antipsychotic medication.

Although numerous studies reported some changes of cortical silent period (CSP), an indicator of gamma-aminobutyric acid (GABA) function in central nervous system, in schizophrenia patients, it has been unknown how the disease stage and antipsychotic medication affect CSP values. The present study conducted a systematic review of previous literature comparing CSP between schizophrenia patients and healthy subjects, and then performed meta-analysis on the effects of (1) the disease stage and (2) antipsychotics on CSP. (1) In the comparison of the disease stage comprising a total of 17 reports, there was no significant difference in CSP between patients under drug-naïve first-episode psychoses and healthy controls, or between patients with antipsychotic medication and healthy controls. (2) In the comparison of the antipsychotic class, patients treated with clozapine were longer in CSP compared to healthy controls. Patients treated with olanzapine/quetiapine or with other type of antipsychotics were not different from healthy controls. Regarding other type of antipsychotics, the iteration analysis after leaving out one literature showed that patients were shorter in CSP than healthy controls. The results showed that clozapine seems to surely prolong CSP, indicating the enhancement of GABA transmission via GABAB receptors, suggesting the possible relationship between the CSP prolongation by clozapine and its high efficacy in psychopathology. The finding of shorter CSP in patients with other type of antipsychotics was distinct from clozapine/olanzapine/quetiapine, but was difficult to interpret since this group included a variety of transcranial magnetic stimulation (TMS) methodologies and patients' background.

GABAergic System Dysfunction in Autism Spectrum Disorders.

Autism spectrum disorder (ASD) refers to a series of neurodevelopmental diseases characterized by two hallmark symptoms, social communication deficits and repetitive behaviors. Gamma-aminobutyric acid (GABA) is one of the most important inhibitory neurotransmitters in the central nervous system (CNS). GABAergic inhibitory neurotransmission is critical for the regulation of brain rhythm and spontaneous neuronal activities during neurodevelopment. Genetic evidence has identified some variations of genes associated with the GABA system, indicating an abnormal excitatory/inhibitory (E/I) neurotransmission ratio implicated in the pathogenesis of ASD. However, the specific molecular mechanism by which GABA and GABAergic synaptic transmission affect ASD remains unclear. Transgenic technology enables translating genetic variations into rodent models to further investigate the structural and functional synaptic dysregulation related to ASD. In this review, we summarized evidence from human neuroimaging, postmortem, and genetic and pharmacological studies, and put emphasis on the GABAergic synaptic dysregulation and consequent E/I imbalance. We attempt to illuminate the pathophysiological role of structural and functional synaptic dysregulation in ASD and provide insights for future investigation.

Is essential tremor a disorder of primary GABA dysfunction? Yes.

Dysfunction in gamma-aminobutyric acid (GABA) neurotransmission has emerged as a prime suspect for the underlying neurochemical dysfunction in essential tremor (ET). This dysfunction has been termed the GABA hypothesis. We review findings to date supporting the 4 steps in this hypothesis in studies of cerebrospinal fluid, pathology, genetics, animal models, imaging, computational models, and human drugs, while not overlooking the evidence of negative studies and controversies. It remains to be elucidated whether reduced GABAergic tone is a primary contributing factor to ET pathophysiology, a consequence of altered Purkinje cell function, or even a result of Purkinje cell death. More studies are clearly needed to confirm both the neurodegenerative nature of ET and the reduction in GABA activity in the cerebellum. Also necessary is to test further therapies to enhance GABA transmission specifically focused on the cerebellar area.

Self-Administration of Entactogen Psychostimulants Dysregulates Gamma-Aminobutyric Acid (GABA) and Kappa Opioid Receptor Signaling in the Central Nucleus of the Amygdala of Female Wistar Rats.

Male rats escalate intravenous self-administration of entactogen psychostimulants, 3,4-methylenedioxymethcathinone (methylone) and 3,4-methylenedioxymethamphetamine (MDMA) under extended access conditions, as with typical psychostimulants. Here, we investigated whether female rats escalate self-administration of methylone, 3,4-methylenedioxypentedrone (pentylone), and MDMA and then studied consequences of MDMA and pentylone self-administration on GABAA receptor and kappa opioid receptor (KOR) signaling in the central nucleus of the amygdala (CeA), a brain area critically dysregulated by extended access self-administration of alcohol or cocaine. Adult female Wistar rats were trained to self-administer methylone, pentylone, MDMA (0.5 mg/kg/infusion), or saline-vehicle using a fixed-ratio 1 response contingency in 6-h sessions (long-access: LgA) followed by progressive ratio (PR) dose-response testing. The effects of pentylone-LgA, MDMA-LgA and saline on basal GABAergic transmission (miniature post-synaptic inhibitory currents, mIPSCs) and the modulatory role of KOR at CeA GABAergic synapses were determined in acute brain slices using whole-cell patch-clamp. Methylone-LgA and pentylone-LgA rats similarly escalated their drug intake (both obtained more infusions compared to MDMA-LgA rats), however, pentylone-LgA rats reached higher breakpoints in PR tests. At the cellular level, baseline CeA GABA transmission was markedly elevated in pentylone-LgA and MDMA-LgA rats compared to saline-vehicle. Specifically, pentylone-LgA was associated with increased CeA mIPSC frequency (GABA release) and amplitude (post-synaptic GABAA receptor function), while mIPSC amplitudes (but not frequency) was larger in MDMA-LgA rats compared to saline rats. In addition, pentylone-LgA and MDMA-LgA profoundly disrupted CeA KOR signaling such as both KOR agonism (1 mM U50488) and KOR antagonism (200 nM nor-binaltorphimine) decreased mIPSC frequency suggesting recruitment of non-canonical KOR signaling pathways. This study confirms escalated self-administration of entactogen psychostimulants under LgA conditions in female rats which is accompanied by increased CeA GABAergic inhibition and altered KOR signaling. Collectively, our study suggests that CeA GABA and KOR mechanisms play a critical role in entactogen self-administration like those observed with escalation of alcohol or cocaine self-administration.

Нейроэндокринные нарушения при COVID-19 и постковидном синдроме и особенности их лечения препаратами гамма-аминомасляной кислоты (обзор литературы и собственные данные)

В статье освещены основные патогенетические механизмы развития нейроэндокринных нарушений при COVID-19 и постковидном синдроме. К проявлениям поражения центральной нервной системы относятся жалобы на головную боль, часто очень сильную, повышенную утомляемость, «мозговой туман» и периодическое кратковременное головокружение, изменения психического состояния и когнитивных функций. Поражение периферической нервной системы проявляется аносмией и гипогевзией, болями в мышцах и суставах, миофасциальными болями, болями, похожими на невропатии, гиперестезией кожи. Наблюдаются нарушения эндокринного статуса в виде аутоиммунного тиреоидита с дисфункцией щитовидной железы, нарушения толерантности к углеводам или инсулиннезависимого сахарного диабета (2-го типа), дисменореи у женщин и эректильной дисфункции у мужчин. Патогенетические изменения персистенции вируса SARS-CoV-2 вызывают состояние хронического стресса с гипоталамической дисфункцией. Также выявлены гистологические изменения в виде нарушений нейроглиальных взаимодействий: с учетом тесной связи астроцитов и нейронов изменения метаболизма в астроцитах нарушают функцию нейронов, влияют на синаптическую функцию трансмиссии гамма-аминомасляной кислоты. Актуальна оптимизация терапии у пациентов с COVID-19, постковидным синдромом с нейроэндокринной симптоматикой. Гамалате В6 — препарат гамма-аминомасляной кислоты, имеющий лучшие характеристики для таких пациентов.

Cell-type-specific imaging of neurotransmission reveals a disrupted excitatory-inhibitory cortical network in isoflurane anaesthesia.

BackgroundDespite the fundamental clinical significance of general anaesthesia, the cortical mechanism underlying anaesthetic-induced loss of consciousness (aLOC) remains elusive.MethodsHere, we measured the dynamics of two major cortical neurotransmitters, gamma-aminobutyric acid (GABA) and glutamate, through in vivo two-photon imaging and genetically encoded neurotransmitter sensors in a cell type-specific manner in the primary visual (V1) cortex.FindingsWe found a general decrease in cortical GABA transmission during aLOC. However, the glutamate transmission varies among different cortical cell types, where in it is almost preserved on pyramidal cells and is significantly reduced on inhibitory interneurons. Cortical interneurons expressing vasoactive intestinal peptide (VIP) and parvalbumin (PV) specialize in disinhibitory and inhibitory effects, respectively. During aLOC, VIP neuronal activity was delayed, and PV neuronal activity was dramatically inhibited and highly synchronized.InterpretationThese data reveal that aLOC resembles a cortical state with a disrupted excitatory-inhibitory network and suggest that a functional inhibitory network is indispensable in the maintenance of consciousness.FundingThis work was supported by the grants of the National Natural Science Foundation of China (grant nos. 81620108012 and 82030038 to H.D. and grant nos. 31922029, 61890951, and 61890950 to J.H.).

Neurobiological Mechanisms of Transcranial Direct Current Stimulation for Psychiatric Disorders; Neurophysiological, Chemical, and Anatomical Considerations

Backgrounds: Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique for the treatment of several psychiatric disorders, e.g., mood disorders and schizophrenia. Therapeutic effects of tDCS are suggested to be produced by bi-directional changes in cortical activities, i.e., increased/decreased cortical excitability via anodal/cathodal stimulation. Although tDCS provides a promising approach for the treatment of psychiatric disorders, its neurobiological mechanisms remain to be explored.Objectives: To review recent findings from neurophysiological, chemical, and brain-network studies, and consider how tDCS ameliorates psychiatric conditions.Findings: Enhancement of excitatory synaptic transmissions through anodal tDCS stimulation is likely to facilitate glutamate transmission and suppress gamma-aminobutyric acid transmission in the cortex. On the other hand, it positively or negatively modulates the activities of dopamine, serotonin, and acetylcholine transmissions in the central nervous system. These neural events by tDCS may change the balance between excitatory and inhibitory inputs. Specifically, multi-session tDCS is thought to promote/regulate information processing efficiency in the cerebral cortical circuit, which induces long-term potentiation (LTP) by synthesizing various proteins.Conclusions: This review will help understand putative mechanisms underlying the clinical benefits of tDCS from the perspective of neurotransmitters, network dynamics, intracellular events, and related modalities of the brain function.

A capital role for the brain’s insula in the diverse fibromyalgia-associated symptoms

Unexplained yet persisting general and widespread non-articular musculoskeletal pain and the associated complaints, known as fibromyalgia (FM), is a common disorder with major social and economic impact. We postulate that in FM disturbance of neurotransmitter balances at the brain’s insula not only leads to aberrant pain processing but could also govern other associated symptoms. Symptoms might arise from central nervous system dysregulation mediated through an imbalance between the excitatory neurotransmitter glutamate and the inhibitory transmitter gamma-amino butyric acid. The insula could also have a leading role in the dysregulation of heart rate and blood pressure, bladder and bowel symptoms, and anxiety and sleep disturbances which are experienced by many FM patients. The presented hypothesis explains how the diverse FM-associated symptoms could be linked, and puts the brain’s insula forward as a possible therapeutic target to be further explored for FM.

Cefixime induce non convulsive status epileptics: a neurotoxic effect

Nonconvulsive status epileptics comprises a group of syndromes that display a great diversity regarding response to anticonvulsants ranging from virtually self-limiting variants to entirely refractory forms cephalosporins are thought to provoke seizure through inhibitory effects on gamma-aminobutyric acid (GABA) transmission and GABA receptors. Interference with GABA transmission result in pre-disposition towards excitatory neurotransmission, which can leads to seizures. Antibiotics can alter the serum concentration of anti-epileptic, resulting in seizures and anti-epileptic drugs toxicity.

Cannabinoid Exposure via Lactation in Rats Disrupts Perinatal Programming of the Gamma-Aminobutyric Acid Trajectory and Select Early-Life Behaviors

BackgroundCannabis usage is increasing with its widespread legalization. Cannabis use by mothers during lactation transfers active cannabinoids to the developing offspring during this critical period and alters postnatal neurodevelopment. A key neurodevelopmental landmark is the excitatory to inhibitory gamma-aminobutyric acid (GABA) switch caused by reciprocal changes in expression ratios of the K+/Cl− transporters potassium-chloride cotransporter 2 (KCC2) and sodium-potassium-chloride transporter (NKCC1). MethodsRat dams were treated with Δ9-tetrahydrocannabinol or a synthetic cannabinoid during the first 10 days of postnatal development, and experiments were then conducted in the offspring exposed to these drugs via lactation. The network influence of GABA transmission was analyzed using cell-attached recordings. KCC2 and NKCC1 levels were determined using Western blot and quantitative polymerase chain reaction analyses. Ultrasonic vocalization and homing behavioral experiments were carried out at relevant time points. ResultsTreating rat dams with cannabinoids during early lactation retards transcriptional upregulation and expression of KCC2, thereby delaying the GABA switch in pups of both sexes. This perturbed trajectory was corrected by the NKCC1 antagonist bumetanide and accompanied by alterations in ultrasonic vocalization without changes in homing behavior. Neurobehavioral deficits were prevented by CB1 receptor antagonism during maternal exposure, showing that the CB1 receptor underlies the cannabinoid-induced alterations. ConclusionsThese results reveal how perinatal cannabinoid exposure retards an early milestone of development, delaying the trajectory of GABA’s polarity transition and altering early-life communication.

EA at PC6 Promotes Gastric Motility: Role of Brainstem Vagovagal Neurocircuits.

Background We aimed to assess whether electroacupuncture (EA) at PC6 affects gastric motility via the vagovagal reflex and if so whether brainstem vagovagal neurocircuits and related transmitters are involved. Methods Gastric motility was measured in male Sprague-Dawley (SD) rats by placing a small manometric balloon in the gastric antrum. The rats were subjected to control, sham surgery, vagotomy, sympathectomy, and microinjection group, including artificial cerebrospinal fluid, gamma-aminobutyric acid (GABA), and glutamic acid (L-Glu). The effect of EA at PC6 on gastric motility was measured. Moreover, electrophysiological testing was used to measure the effect of EA at PC6 on the parasympathetic and sympathetic nerves. In addition, artificial cerebrospinal fluid, L-Glu, and GABA have been microinjected into the dorsal motor nucleus of the vagus (DMV) to measure the changes in gastric motility and parasympathetic nerve discharge induced by EA at PC6. Key Results EA facilitated the gastric motility in control group. In the vagotomy group, gastric motility was not affected by EA at PC6. However, in the sympathectomy group, gastric motility was similar to control group. Acupuncture at PC6 increased parasympathetic nerve discharge but not sympathetic nerve discharge. Furthermore, the microinjection of L-Glu into the DMV increased gastric motility, although EA at PC6 showed no remarkable change in this group. The injection of GABA reduced gastric motility and parasympathetic nerve discharge, but EA at PC6 significantly increased gastric motility and the parasympathetic nerve discharge in this group. Conclusions and Inferences EA at PC6—primarily by inhibiting GABA transmission to DMV—reduced the inhibition of efferent vagal motor fibers and thus promoted efferent vagus nerve activity and increased gastric motility.

Effect of intracerebroventricular injection of GABA receptors antagonists on morphine-induced changes in GABA and GLU transmission within the mPFC: an in vivo microdialysis study.

Objective(s):Many studies have focused on ventral tegmental area than of other mesocorticolimbic areas, and implicated a key role for the medial prefrontal cortex (mPFC) in the development of addictive behaviors. So far, the role of gamma-aminobutyric acid (GABA) receptors in the discriminative properties of morphine has received little attention and few studies evaluated the role of these receptors in drug dependence. Hence, we investigated the role of this receptor on morphine- induced GABA/ glutamate (GLU) changes in the mPFC following morphine administration using in vivo microdialysis.Materials and Methods:In this study, 60 rats weighing 270-300 g were divided into six groups. First, microdialysis probe was inserted into the mPFC and was perfused with artificial cerebrospinal fluid and collected the baseline samples in all groups. In saline and morphine groups, the saline, in phaclophen and (phaclofen+morphine) groups, phaclofen (100 nmol), and in bicuculline and (bicuculline+morphine) groups, bicuculline (20 nmol) was injected intracerebroventricular. In saline, phaclofen and bicuculline groups 20 min later, animals received saline (0.2 ml, IP) and others groups received morphine (20 mg/kg, IP).Results:Our results showed that morphine increased the average concentration of GABA and decreased the concentration of GLU within mPFC. Pretreatment with phaclofen and bicuculline 20 min before morphine administration had no effect on GABA and GLU release for 100 min.Conclusion:The present study indicated that morphine influence the GABA and GLU transmission in mPFC. Therefore evaluation of neurochemistry changes of this neural circuitry may provide further insight into the mechanisms underlying drug dependence.

Loren Parsons' contribution to addiction neurobiology.

Loren (Larry) H. Parsons passed away at the age of 51. In spite of his premature departure, Larry much contributed to the drug abuse field. Since his graduate studies for the Ph.D. in Chemistry in J.B. Justice lab, microdialysis is the tread that links Larry's research topics, namely, the role of dopamine (DA), serotonin (5-HT), gamma-aminobutyric acid (GABA), glutamate and endocannabinoids (eCBs) in drug reinforcement and dependence. Larry was the first to show that abstinence from chronic cocaine reduces extracellular DA in the NAc, consistent with the so called 'dopamine depletion hypothesis' of cocaine addiction. Another Larry's major contributions are the studies on 5-HT and 5-HT receptors' role in cocaine stimulant actions, which resulted in the identification of 5-HT1B receptors as a critical substrate of cocaine reinforcement. By applying mass spectrometry to eCBs analysis in brain dialysates, Larry's lab showed that ethanol, heroin, nicotine and cocaine differentially affect anandamide and 2-arachidonoylglicerol overflow in the NAc shell, a critical site of drugs of abuse DA stimulant actions. Larry also applied microdialysis to study GABA and glutamate's role in ethanol dependence and heroin reinforcement, providing in vivo evidence for a sensitization of corticotropin-releasing factor-dependent release of GABA in the central amygdala in withdrawal from chronic ethanol and for a reduction of GABA transmission in the ventral pallidum in heroin but not cocaine intravenous self-administration. Larry showed the wide possibilities of microdialysis as a general purpose methodology for monitoring neurotransmitters and neuromodulators in the brain extracellular compartment. From this viewpoint, he stands as the best advocate for microdialysis.

Mature Hippocampal Neurons Require LIS1 for Synaptic Integrity: Implications for Cognition

BackgroundPlatelet-activating factor acetylhydrolase 1B1 (LIS1), a critical mediator of neuronal migration in developing brain, is expressed throughout life. However, relatively little is known about LIS1 function in the mature brain. We previously demonstrated that LIS1 involvement in the formation and turnover of synaptic protrusions and synapses of young brain after neuronal migration is complete. Here we examine the requirement for LIS1 to maintain hippocampal circuit function in adulthood. MethodsEffects of conditional Lis1 inactivation in excitatory pyramidal neurons, starting in juvenile mouse brain, were probed using high-resolution approaches combining mouse genetics, designer receptor exclusively activated by designer drug technology to specifically manipulate CA1 pyramidal neuron excitatory activity, electrophysiology, hippocampus-selective behavioral testing, and magnetic resonance imaging tractography to examine the connectivity of LIS1-deficient neurons. ResultsWe found progressive excitatory and inhibitory postsynaptic dysfunction as soon as 10 days after conditional inactivation of Lis1 targeting CA1 pyramidal neurons. Surprisingly, by postnatal day 60 it also caused CA1 histological disorganization, with a selective decline in parvalbumin-expressing interneurons and further reduction in inhibitory neurotransmission. Accompanying these changes were behavioral and cognitive deficits that could be rescued by either designer receptor exclusively activated by designer drug–directed specific increases in CA1 excitatory transmission or pharmacological enhancement of gamma-aminobutyric acid transmission. Lagging behind electrophysiological changes was a progressive, selective decline in neural connectivity, affecting hippocampal efferent pathways documented by magnetic resonance imaging tractography. ConclusionsLIS1 supports synaptic function and plasticity of mature CA1 neurons. Postjuvenile loss of LIS1 disrupts the structure and cellular composition of the hippocampus, its connectivity with other brain regions, and cognition dependent on hippocampal circuits.

Rogdi Defines GABAergic Control of a Wake-promoting Dopaminergic Pathway to Sustain Sleep in Drosophila

Kohlschutter-Tönz syndrome (KTS) is a rare genetic disorder with neurological dysfunctions including seizure and intellectual impairment. Mutations at the Rogdi locus have been linked to development of KTS, yet the underlying mechanisms remain elusive. Here we demonstrate that a Drosophila homolog of Rogdi acts as a novel sleep-promoting factor by supporting a specific subset of gamma-aminobutyric acid (GABA) transmission. Rogdi mutant flies displayed insomnia-like behaviors accompanied by sleep fragmentation and delay in sleep initiation. The sleep suppression phenotypes were rescued by sustaining GABAergic transmission primarily via metabotropic GABA receptors or by blocking wake-promoting dopaminergic pathways. Transgenic rescue further mapped GABAergic neurons as a cell-autonomous locus important for Rogdi-dependent sleep, implying metabotropic GABA transmission upstream of the dopaminergic inhibition of sleep. Consistently, an agonist specific to metabotropic but not ionotropic GABA receptors titrated the wake-promoting effects of dopaminergic neuron excitation. Taken together, these data provide the first genetic evidence that implicates Rogdi in sleep regulation via GABAergic control of dopaminergic signaling. Given the strong relevance of GABA to epilepsy, we propose that similar mechanisms might underlie the neural pathogenesis of Rogdi-associated KTS.

Amoxicillin, a potential epileptogenic drug

Beta-lactams are known to cause a wide spectrum of neurotoxic manifestations including epileptic seizures. The neurotoxicity of penicillin was first reported in 1945 by Johnson and Walker and is believed to exert an inhibitory effect on gamma-aminobutyric acid transmission of cortical pyramidal cells, due to its beta-lactam ring structure. Epileptogenicity is also a feature of the semisynthetic beta-lactams including aminopenicillins. In this report, we present a patient with a recurrent history of discrete body twitching/jerks of epileptic nature in the context of amoxicillin exposure. The EEG revealed intermittent generalized short bursts of beta-frequency polyspikes. This electro-clinical picture was reversed by amoxicillin discontinuation.