Investigating the role of Prefrontal Neurons in cognitive tasks through Fiber Photometry and Adapted Barnes Maze Protocols

The medial prefrontal cortex (mPFC) is essential in the execution of cognitive tasks, however very little is known on how these neurons are modulated during specific tasks and which subtype of neurons are responsible for so. Therego, with the intention of addressing this issue, we recorded mPFC gabaergic and glutamatergic activation patterns through fiber photometry (FIP) in mice, while simultaneously performing the Barnes Maze (BM) cognitive task (4 day behavioral trial). In addition, an altered structural and procedural protocol for BM was validated in this study due to necessary modifications allowing FIP and BM to happen simultaneously. A successful protocol validation was followed by our preliminary results, which showed that both glutamatergic and gabaergic neurons presented significant change in activation intensity and number of events in specific contexts throughout the task days. In addition, when stratified and crossed with BM performance parameters, such as latency to complete tasks and adopted strategy, glutamatergic and gabaergic neurons presented a significant decline in both activation patterns and number of activation events throughout the days. This data suggest not only an important role of glutamatergic and gabaergic mPFC neurons in learning, memory and decision making, but also that activation patterns of each of these groups may serve as markers for cognitive progression and/or dysfunction. KEY-WORDS: Memory, Learning, Decision Making, Medial Prefrontal Cortex (mPFC), Fiber Photometry (FIP), Barnes Maze (BM), Glutamatergic, Gabaergic, Neuronal Activity, Neuronal Activation Patterns, Neuronal Dynamics.

O córtex pré-frontal medial (mPFC) é essencial na execução de tarefas cognitivas, no entanto, pouco se sabe sobre como esses neurônios são modulados durante tarefas específicas e qual subtipo de neurônios é responsável por isso. Portanto, com a intenção de abordar essa questão, registramos os padrões de ativação de neurônios gabaérgicos e glutamatérgicos do mPFC por meio de fotometria de fibra (FIP) em camundongos, enquanto realizávamos simultaneamente a tarefa cognitiva do Labirinto de Barnes (BM) (ensaio comportamental de 4 dias). Além disso, um protocolo estrutural e procedimental alterado para o BM foi validado neste estudo devido a modificações necessárias que permitiram a realização simultânea de FIP e BM. Uma validação bem-sucedida do protocolo foi seguida pelos nossos resultados preliminares, que mostraram que tanto os neurônios glutamatérgicos quanto os gabaérgicos apresentaram mudanças significativas na intensidade de ativação e no número de eventos em contextos específicos ao longo dos dias da tarefa. Além disso, quando estratificados e cruzados com parâmetros de desempenho do BM, como latência para completar as tarefas e estratégia adotada, os neurônios glutamatérgicos e gabaérgicos apresentaram uma diminuição significativa nos padrões de ativação e no número de eventos de ativação ao longo dos dias. Esses dados sugerem não apenas um papel importante dos neurônios glutamatérgicos e gabaérgicos do mPFC na aprendizagem, memória e tomada de decisões, mas também que os padrões de ativação de cada um desses grupos podem servir como marcadores de progressão e/ou disfunção cognitiva. PALAVRAS-CHAVE: Memória, Aprendizagem, Tomada de Decisões, Córtex Pré-Frontal Medial (mPFC), Fotometria de Fibra (FIP), Labirinto de Barnes (BM), Glutamatérgico, Gabaérgico, Atividade Neuronal, Padrões de Ativação Neuronal, Dinâmica Neuronal.

Advances in new fast-acting antidepressants / 中国临床药理学与治疗学

Antidepressants are mainly used to treat mental illnesses. Traditional antidepressants mainly target monoamine neurotransmitters, but these drugs are slow to be effective and cannot meet clinical needs. Recently, therapeutics have been developed that depart from the traditional monoamine hypothesis and focus on the glutamatergic, GABAergic, opioidergic, and inflammatory systems. In recent years, great progress has been made in the development of new antidepressants, some of which have been applied in clinical practice. This article mainly summarizes the research mechanisms and treatment programs of new antidepressants, and briefly reviews common rapid-acting antidepressants.

Nitrous oxide as an adjunctive therapy in major depressive disorder: a randomized controlled double-blind pilot trial

Objective: Major depressive disorder (MDD) is related to glutamatergic dysfunction. Antagonists of glutamatergic N-methyl-D-aspartate receptor (NMDAR), such as ketamine, have antidepressant properties. Nitrous oxide (N2O) is also a NMDAR antagonist. Thus, this study aimed to evaluate the effects of augmenting antidepressant treatment with N2O. Methods: This double blind, placebo-controlled randomized parallel pilot trial was conducted from June 2016 to June 2018 at the Hospital das Clínicas, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo. Twenty-three subjects with MDD (aged 18 to 65, on antidepressants, with a score > 17 on the 17-item-Hamilton Depression Rating Scale [HAM-D17]) received 50% N2O (n=12; 37.17±13.59 years) or placebo (100% oxygen) (n=11; 37.18±12.77 years) for 60 minutes twice a week for 4 weeks. The primary outcome was changes in HAM-D17 from baseline to week 4. Results: Depressive symptoms improved significantly in the N2O group (N2O: from 22.58±3.83 to 5.92±4.08; placebo: from 22.44±3.54 to 12.89±5.39, p < 0.005). A total of 91.7% and 75% of the N2O group subjects achieved response (≥ 50% reduction in HAM-D17 score) and remission (HAM-D17 < 7), respectively. The predominant adverse effects of N2O treatment were nausea, vomiting, and headache. Conclusion: N2O treatment led to a statistically significant reduction in HAM-D17 scores compared to placebo. Clinical trial registration: Brazilian Register of Clinical Trials, RBR-5rz5ch

Optogenetic study of glutamatergic neuron in parasubiculum in visuospatial memory / 中华行为医学与脑科学杂志

Objective:To investigate the function of glutamatergic neuron of the parasubiculum in spatial memory.Methods:Sixteen adult male C57BL/6 mice aged 6-8 weeks were divided into two groups randomly, 0.4 μl AAV5-CaMKⅡα-eNpHR3.0-eYFP was injected into the bilateral parasubiculum respectively in experimental group, equal dose AAV5-CaMKⅡα-eYFP for control group.The optic fiber was implanted 6 weeks after virus injection.The novel object place recognition test was performed one week after optic fiber implantation, continuous yellow light was delivered during the behavioral test to inhibit the function of glutamatergic neuron in the parasubiculum.The standard memory index (D2) was used to evaluate the spatial memory function.SPSS 20.0 software was used to process the data, and the independent-samples t-test and paired-samples t-test were used for data analysis. Results:In the novel object place recognition experiment, the mice showed no preference for either object in both control group(new object: 0.51±0.06, familiar object: 0.49±0.04, t=1.21, P>0.05) and experimental group(new object: 0.49±0.05, familiar object: 0.50±0.04, t=-0.78, P>0.05). Compared with the control group (0.55±0.06), the D2 score of the experimental group (0.26±0.07) was significantly lower ( t=-2.96, P<0.05), and the number of c-fos positive neuron in experimental group (96.33±7.13) was also significantly less than that in control group (127.67±5.24, t=-3.54, P<0.05). Conclusion:Inhibiting glutamatergic neuronal activity in the parasubiculum impairs spatial memory in mice, suggesting that glutamatergic neurons of the parasubiculum play an important role in spatial memory.

Lateral Hypothalamic Area Glutamatergic Neurons and Their Projections to the Lateral Habenula Modulate the Anesthetic Potency of Isoflurane in Mice / 神经科学通报·英文版

The lateral hypothalamic area (LHA) plays a pivotal role in regulating consciousness transition, in which orexinergic neurons, GABAergic neurons, and melanin-concentrating hormone neurons are involved. Glutamatergic neurons have a large population in the LHA, but their anesthesia-related effect has not been explored. Here, we found that genetic ablation of LHA glutamatergic neurons shortened the induction time and prolonged the recovery time of isoflurane anesthesia in mice. In contrast, chemogenetic activation of LHA glutamatergic neurons increased the time to anesthesia and decreased the time to recovery. Optogenetic activation of LHA glutamatergic neurons during the maintenance of anesthesia reduced the burst suppression pattern of the electroencephalogram (EEG) and shifted EEG features to an arousal pattern. Photostimulation of LHA glutamatergic projections to the lateral habenula (LHb) also facilitated the emergence from anesthesia and the transition of anesthesia depth to a lighter level. Collectively, LHA glutamatergic neurons and their projections to the LHb regulate anesthetic potency and EEG features.

Sinoatrial node pacemaker cells share dominant biological properties with glutamatergic neurons

Activation of the heart normally begins in the sinoatrial node (SAN). Electrical impulses spontaneously released by SAN pacemaker cells (SANPCs) trigger the contraction of the heart. However, the cellular nature of SANPCs remains controversial. Here, we report that SANPCs exhibit glutamatergic neuron-like properties. By comparing the single-cell transcriptome of SANPCs with that of cells from primary visual cortex in mouse, we found that SANPCs co-clustered with cortical neurons. Tissue and cellular imaging confirmed that SANPCs contained key elements of glutamatergic neurotransmitter system, expressing genes encoding glutamate synthesis pathway (Gls), ionotropic and metabotropic glutamate receptors (Grina, Gria3, Grm1 and Grm5), and glutamate transporters (Slc17a7). SANPCs highly expressed cell markers of glutamatergic neurons (Snap25 and Slc17a7), whereas Gad1, a marker of GABAergic neurons, was negative. Functional studies revealed that inhibition of glutamate receptors or transporters reduced spontaneous pacing frequency of isolated SAN tissues and spontaneous Ca

Preventive effects of Topiramate on methylphenidate induced behavioral disorders / Efectos preventivos de topiramato en los trastornos del comportamiento inducidos por metilfenidato

Neuronal cell damage is often caused by prolonged misuse of Methylphenidate (MPH). Topiramate (TPM) carries neuroprotective properties but its assumed mechanism remains unclear. The present study evaluates in vivo role of various doses of TPM and its mechanism against MPH-induced motor activity and related behavior disorder. Thus, we used domoic acid (DOM), bicuculline (BIC), Ketamine (KET), Yohimibine (YOH) and Haloperidole (HAL) as AMPA/kainite, GABAA, NMDA, ɑ2 adrenergic and D2 of dopamine receptor antagonists respectively. Open Field Test (OFT), Elevated Plus Maze (EPM) and Forced Swim Test (FST) were used to study motor activity, anxiety and depression level. TPM (100 and 120 mg/kg) reduced MPH-induced rise and inhibited MPH-induced promotion in motor activity disturbance, anxiety and depression. Pretreatment of animals with KET, HAL, YOH and BIC inhibited TPM- improves anxiety and depression through the interacting with Dopaminergic, GABAA, NMDA and ɑ2-adrenergic receptors.

El daño a las células neuronales a menudo es causado por el uso prolongado de metilfenidato (MPH). El topiramato (TPM) tiene propiedades neuroprotectoras, pero su mecanismo de acción no es claro. El presente estudio evalúa el papel in vivo de varias dosis de TPM y su mecanismo contra la actividad motora inducida por MPH y el trastorno de comportamiento relacionado. Utilizamos ácido domoico (DOM), bicuculina (BIC), ketamina (KET), yohimbina (YOH) y haloperidol (HAL), así como antagonistas AMPA/kainato, GABAA, NMDA, ɑ2-adrenérgico y D2 dopaminérgicos, respectivamente. Se utilizaron las pruebas de campo abierto (OFT), elevación de laberinto (EPM) y natación forzada (FST) para estudiar la actividad motora, la ansiedad y el nivel de depresión. El TPM (100 y 120 mg/kg) redujo el aumento inducido por MPH e inhibió la promoción inducida por MPH en la alteración de la actividad motora, la ansiedad y la depresión. El tratamiento previo de animales con KET, HAL, YOH y BIC inhibió el TPM, mejora la ansiedad y la depresión a través de la interacción con los receptores dopaminérgicos, GABAA, NMDA y ɑ2-adrenérgico.

Vesicular Glutamate Transporter 1 (VGLUT1)- and VGLUT2-containing Terminals on the Rat Jaw-closing γ-Motoneurons

Currently, compared to jaw-closing (JC) α-motoneurons, the information on the distribution and morphology of glutamatergic synapses on the jaw-closing (JC) γ-motoneurons, which may help elucidate the mechanism of isometric contraction of the JC muscle, is very limited. This study investigated the distribution and ultrastructural features of vesicular glutamate transporter 1 (VGLUT1)- and VGLUT2-immunopositive (+) axon terminals (boutons) on JC γ-motoneurons by retrograde tracing with horseradish peroxidase, electron microscopic immunocytochemistry, and quantitative analysis. About 35% of the boutons on identified JC γ-motoneurons were VGLUT+, and of those, 99% were VGLUT2+. The fraction of VGLUT1+ boutons of all boutons and the percentage of membrane of JC γ-motoneurons covered by these boutons were significantly lower than those for the JC α-motoneurons, revealed in our previous work. The bouton volume, mitochondrial volume, and active zone area of the VGLUT2+ boutons on the JC γ-motoneurons were uniformly small. These findings suggest that the JC γ-motoneurons, in contrast to the JC α-motoneurons, receive generally weak glutamatergic synaptic input almost exclusively from VGLUT2+ premotoneurons that form direct synapse with motoneurons.

Develop a 3D neurological disease model of human cortical glutamatergic neurons using micropillar-based scaffolds

Establishing an effective three-dimensional (3D) culture system to better model human neurological diseases is desirable, since the human brain is a 3D structure. Here, we demonstrated the development of a polydimethylsiloxane (PDMS) pillar-based 3D scaffold that mimicked the 3D microenvironment of the brain. We utilized this scaffold for the growth of human cortical glutamatergic neurons that were differentiated from human pluripotent stem cells. In comparison with the 2D culture, we demonstrated that the developed 3D culture promoted the maturation of human cortical glutamatergic neurons by showing significantly more MAP2 and less Ki67 expression. Based on this 3D culture system, we further developed an disease-like model of traumatic brain injury (TBI), which showed a robust increase of glutamate-release from the neurons, in response to mechanical impacts, recapitulating the critical pathology of TBI. The increased glutamate-release from our 3D culture model was attenuated by the treatment of neural protective drugs, memantine or nimodipine. The established 3D human neural culture system and TBI-like model may be used to facilitate mechanistic studies and drug screening for neurotrauma or other neurological diseases.

Aucubin Promotes Differentiation of Neural Precursor Cells into GABAergic Neurons

Aucubin is a small compound naturally found in traditional medicinal herbs with primarily anti-inflammatory and protective effects. In the nervous system, aucubin is reported to be neuroprotective by enhancing neuronal survival and inhibiting apoptotic cell death in cultures and disease models. Our previous data, however, suggest that aucubin facilitates neurite elongation in cultured hippocampal neurons and axonal regrowth in regenerating sciatic nerves. Here, we investigated whether aucubin facilitates the differentiation of neural precursor cells (NPCs) into specific types of neurons. In NPCs cultured primarily from the rat embryonic hippocampus, aucubin significantly elevated the number of GAD65/67 immunoreactive cells and the expression of GAD65/67 proteins was upregulated dramatically by more than three-fold at relatively low concentrations of aucubin (0.01 µM to 10 µM). The expression of both NeuN and vGluT1 of NPCs, the markers for neurons and glutamatergic cells, respectively, and the number of vGluT1 immunoreactive cells also increased with higher concentrations of aucubin (1 µM and 10 µM), but the ratio of the increases was largely lower than GAD expression and GAD immunoreactive cells. The GABAergic differentiation of pax6-expressing late NPCs into GABA-producing cells was further supported in cortical NPCs primarily cultured from transgenic mouse brains, which express recombinant GFP under the control of pax6 promoter. The results suggest that aucubin can be developed as a therapeutic candidate for neurodegenerative disorders caused by the loss of inhibitory GABAergic neurons.

Progress in Research on CNTN5, a Member of the Immunoglobulin Superfamily / 中国医科大学学报

Contactin 5 (CNTN5) belongs to a subgroup of the immunoglobulin superfamily.It is highly expressed in the amygdala and occipital lobe of the human brain as well as in the presynaptic terminal of glutamatergic neurons in the auditory system.In recent years,researchers have used animal experiments to identify the biological functions of CNTN5.They have also investigated the relationship between CNTN5 and menial disorders including autism,Alzheimer's disease,and anorexia nervosa among others.Furthermore,immunofluorescence assays have shown that CNTN5 is expressed in glutamatergic neurons in the hypothalamus.A reduction in the number of glutamatergic neurons can cause the long-term potentiation of synapses.Long-term potentiation is an important mechanism in post-traumatic stress disorder (PTSD).It suggests that mutation of CNTN5 may be one of the mechanisms underlying PTSD.We reviewed the research concerning CNTN5 to identify future research directions.

Valproic Acid Induces Telomerase Reverse Transcriptase Expression during Cortical Development

The valproic acid (VPA)-induced animal model is one of the most widely utilized environmental risk factor models of autism. Autism spectrum disorder (ASD) remains an insurmountable challenge among neurodevelopmental disorders due to its heterogeneity, unresolved pathological pathways and lack of treatment. We previously reported that VPA-exposed rats and cultured rat primary neurons have increased Pax6 expression during post-midterm embryonic development which led to the sequential upregulation of glutamatergic neuronal markers. In this study, we provide experimental evidence that telomerase reverse transcriptase (TERT), a protein component of ribonucleoproteins complex of telomerase, is involved in the abnormal components caused by VPA in addition to Pax6 and its downstream signals. In embryonic rat brains and cultured rat primary neural progenitor cells (NPCs), VPA induced the increased expression of TERT as revealed by Western blot, RT-PCR, and immunostainings. The HDAC inhibitor property of VPA is responsible for the TERT upregulation. Chromatin immunoprecipitation revealed that VPA increased the histone acetylation but blocked the HDAC1 binding to both Pax6 and Tert genes. Interestingly, the VPA-induced TERT overexpression resulted to sequential upregulations of glutamatergic markers such as Ngn2 and NeuroD1, and inter-synaptic markers such as PSD-95, α-CaMKII, vGluT1 and synaptophysin. Transfection of Tert siRNA reversed the effects of VPA in cultured NPCs confirming the direct involvement of TERT in the expression of those markers. This study suggests the involvement of TERT in the VPA-induced autistic phenotypes and has important implications for the role of TERT as a modulator of balanced neuronal development and transmission in the brain.

Regulatory effects of PB on sleep and wakefulness / 中国药理学通报

The parabrachial nucleus (PB)is made up of gray matter around the Pons combination(BC),mainly consisting of glutamatergic,GABAergic and enkephalinergic neurons.PB is connected to hypothalamus and basal forebrain through a network of nerve fibers.Specific lesion of the entire parabrachial complex in animals leads to a deep coma.PB also projects to the non-rapid eye movement(NREM)-related regions including the ven-trolateral preoptic,and receives the projections from the parafa-cial zone.Activation of the GABAergic neurons in parafacial zone can promote NREM sleep,which indicates that PB partici-pates in NREM sleep.Furthermore,the lateral PB is actived when rapid eye movement(REM)sleep is deprived.In conclu-sion,PB participates in regulating wakefulness, NREM and REM sleep.This review summarizes the advances in the roles of PB in sleep-wake regulation.

Advances in the study of the effect of basal forebrain on sleep-wake regulation / 药学学报

The basal forebrain (BF) is known to participate in the control of motion, attention, learning and memory, and it also plays a key role in sleep-wake regulation. Although there is a strong heterogeneity among neurons in the BF, the main types are cholinergic, gamma-aminobutyric acid (GABAergic) and glutamatergic neurons. This review provided the research progress in the regulation of sleep-wakefulness behavior by the 3 neurons in the BF. The cholinergic neurons play roles in activation of cortex and promote phase transition between sleep and wakefulness. The cortical projecting GABAergic neurons, which accept the projections from the adjacent cholinergic and glutamatergic neurons, contribute to awakening and the maintenance of normal wakefulness. The GABAergic interneurons may promote sleepiness by inhibiting the wake-active neurons which excite the cortical neurons. The glutamatergic neurons regulate sleep and wakefulness by interacting with neighbor cholinergic and cortical projecting GABAergic neurons or through the direct projection to the cortex as well.

Bipolar Disorder Associated microRNA, miR-1908-5p, Regulates the Expression of Genes Functioning in Neuronal Glutamatergic Synapses

Bipolar disorder (BD), characterized by recurrent mood swings between depression and mania, is a highly heritable and devastating mental illness with poorly defined pathophysiology. Recent genome-wide molecular genetic studies have identified several protein-coding genes and microRNAs (miRNAs) significantly associated with BD. Notably, some of the proteins expressed from BD-associated genes function in neuronal synapses, suggesting that abnormalities in synaptic function could be one of the key pathogenic mechanisms of BD. In contrast, however, the role of BD-associated miRNAs in disease pathogenesis remains largely unknown, mainly because of a lack of understanding about their target mRNAs and pathways in neurons. To address this problem, in this study, we focused on a recently identified BD-associated but uncharacterized miRNA, miR-1908-5p. We identified and validated its novel target genes including DLGAP4, GRIN1, STX1A, CLSTN1 and GRM4, which all function in neuronal glutamatergic synapses. Moreover, bioinformatic analyses of human brain expression profiles revealed that the expression levels of miR-1908-5p and its synaptic target genes show an inverse-correlation in many brain regions. In our preliminary experiments, the expression of miR-1908-5p was increased after chronic treatment with valproate but not lithium in control human neural progenitor cells. In contrast, it was decreased by valproate in neural progenitor cells derived from dermal fibroblasts of a BD subject. Together, our results provide new insights into the potential role of miR-1908-5p in the pathogenesis of BD and also propose a hypothesis that neuronal synapses could be a key converging pathway of some BD-associated protein-coding genes and miRNAs.

Early postnatal exposure to lithium in vitro induces changes in AMPAR mEPSCs and vesicular recycling at hippocampal glutamatergic synapses.

Lithium is an effective mood stabilizer but its use is associated with many side effects. Electrophysiological recordings of miniature excitatory postsynaptic currents (mEPSCs) mediated by glutamate receptor AMPA-subtype (AMPARs) in hippocampal pyramidal neurons revealed that CLi (therapeutic concentration of 1 mM lithium, from days in vitro 4–10) decreased the mean amplitude and mean rectification index (RI) of AMPAR mEPSCs. Lowered mean RI indicate that contribution of Ca2+-permeable AMPARs in synaptic events is higher in CLi neurons (supported by experiments sensitive to Ca2+-permeable AMPAR modulation). Co-inhibiting PKA, GSK-3β and glutamate reuptake was necessary to bring about changes in AMPAR mEPSCs similar to that seen in CLi neurons. FM1-43 experiments revealed that recycling pool size was affected in CLi cultures. Results from minimum loading, chlorpromazine treatment and hyperosmotic treatment experiments indicate that endocytosis in CLi is affected while not much difference is seen in modes of exocytosis. CLi cultures did not show the high KCl associated presynaptic potentiation observed in control cultures. This study, by calling attention to long-term lithium-exposure-induced synaptic changes, might have implications in understanding the side effects such as CNS complications occurring in perinatally exposed babies and cognitive dulling seen in patients on lithium treatment.

Systematic review of N-acetylcysteine in the treatment of addictions

Objective: To conduct the first systematic literature review of clinical trials of N-acetylcysteine (NAC) for the treatment of substance abuse disorders and addictive behaviors. Methods: A search of the MEDLINE, Embase and PsycINFO databases was conducted. The inclusion criteria for the review were clinical trials that used NAC in the treatment of a disorder related to substance use and/or addictive behaviors, limited to texts in English, Spanish, or French. The selected studies were evaluated with respect to type of trial, sample size, diagnostic input, intervention, length of follow-up, outcome variables, and results. Results: Nine studies analyzing a total of 165 patients met the eligibility criteria and were included in qualitative analysis. These studies evaluated the role of NAC in cocaine dependence (three studies), cannabis dependence (two studies), nicotine dependence (two studies), methamphetamine addiction (one study), and pathological gambling (one study). Five of these trials were double-blind, randomized, and placebo-controlled. Conclusions: The studies analyzed suggest a potential role for NAC in the treatment of addiction, especially of cocaine and cannabis dependence. These results are concordant with the hypothesis of the involvement of glutamatergic pathways in the pathophysiology of addiction. .

Research progress of the antidepressants targeting the glutamate receptors / 中国药理学通报

Depression is a worldwide neuropsychiatric disorder. Currently most preclinical and clinical studies of depression focus on monoaminergic system. However, there is growing evidence which suggests that glutamatergic system plays a critical role in the pathophysiology of depression. This review focuses on the de-velopment of new antidepressants that target glutamatergic sys-tem, summarizes the current mechanisms of antidepressants, and also highlights new insights to the pathophysiology of depression.

The Amygdala's Neurochemical Ratios after 12 Weeks Administration of 20 mg Long-acting Methylphenidate in Children with Attention Deficit and Hyperactivity Disorder: A Pilot Study Using 1H Magnetic Resonance Spectroscopy

OBJECTIVE: Recent pediatric studies have suggested a correlation between decreased amygdala volume and attention deficit and hyperactivity disorder (ADHD) symptoms, including the emotional dysregulation. To investigate the hypothesis that medication treatment of ADHD specifically improves amygdala function, we used 1H magnetic resonance spectroscopy (MRS) to study the effect of 12 weeks of treatment with daily 20 mg long-acting methylphenidate on the Glu/Cr, NAA/Cr, Cho/Cr, and mI/Cr ratios in the amygdala of medication-naive children with ADHD. METHODS: This was a prospective study, using a pre- and post-test design, on a single group of 21 children (average age 8.52 years, 17 males and 4 females) diagnosed with ADHD. Low Time Echo MRS scans sampled voxels of interest (1.5x1.5x2.0) from both the right and left amygdala. RESULTS: There was significant clinical improvement after 12 weeks of treatment with 20 mg long-acting methylphenidate. On 1H MRS, there were no statistical significant differences of NAA/Cr ratio, Cho/Cr ratio, mI/Cr ratio before and after 12 weeks administration of 20 mg long-acting methylphenidate both in the right and left amygdala. In addition, Glu/Cr ratio decreased 14.1% in the right amygdala (p=0.029) and 11.4% in the left amygdala (p=0.008). Standardized mean effect sizes ranged from 0.14-0.32. CONCLUSION: The findings are consistent with the possibility that hyperglutamatergic processes in the amygdale are related to the hyperactive-impulsive symptoms of ADHD.

Activation of group II metabotropic glutamate receptors blocks zinc release from hippocampal mossy fibers

BACKGROUND: The hippocampal CA3 area contains large amounts of vesicular zinc in the mossy fiber terminals which is released during synaptic activity, depending on presynaptic calcium. Another characteristic of these synapses is the presynaptic localization of high concentrations of group II metabotropic glutamate receptors, specifically activated by DCG-IV. Previous work has shown that DCG-IV affects only mossy fiber-evoked responses but not the signals from associational-commissural afferents, blocking mossy fiber synaptic transmission. Since zinc is released from mossy fibers even for single stimuli and it is generally assumed to be co-released with glutamate, the aim of the work was to investigate the effect of DCG-IV on mossy fiber zinc signals. RESULTS: Studies were performed using the membrane-permeant fluorescent zinc probe TSQ, and indicate that DCG-IV almost completely abolishes mossy fiber zinc changes as it does with synaptic transmission. CONCLUSIONS: Zinc signaling is regulated by the activation of type II metabotropic receptors, as it has been previously shown for glutamate, further supporting the corelease of glutamate and zinc from mossy fibers.