Forebrain excitatory neuron-specific SENP2 knockout mouse displays hyperactivity, impaired learning and memory, and anxiolytic-like behavior.

Sentrin/SUMO-specific protease 2 (SENP2) is a member of SENPs family involved in maturation of SUMO precursors and deSUMOylation of specific target, and is highly expressed in the central nervous system (CNS). Although SENP2 has been shown to modulate embryonic development, fatty acid metabolism, atherosclerosis and epilepsy, the function of SENP2 in the CNS remains poorly understood. To address the role of SENP2 in the CNS and its potential involvement in neuropathology, we generated SENP2 conditional knockout mice by crossing floxed SENP2 mice with CaMKIIα-Cre transgenic mice. Behavioral tests revealed that SENP2 ablation induced hyper-locomotor activity, anxiolytic-like behaviors, spatial working memory impairment and fear-associated learning defect. In line with these observations, our RNA sequencing (RNA-seq) data identified a variety of differential expression genes that are particularly enriched in locomotion, learning and memory related biologic process. Taken together, our results indicated that SENP2 plays a critical role in emotional and cognitive regulation. This SENP2 conditional knockout mice model may help reveal novel mechanisms that underlie a variety of neuropsychiatric disorders associated with anxiety and cognition.

Proteoglycan (Keratan Sulfate) Barrier in Developing Human Forebrain Isolates Cortical Epileptic Networks From Deep Heterotopia, Insulates Axonal Fascicles, and Explains Why Axosomatic Synapses Are Inhibitory.

Axons from deep heterotopia do not extend through U-fibers, except transmantle dysplasias. Keratan sulfate (KS) in fetal spinal cord/brainstem median septum selectively repels glutamatergic axons while enabling GABAergic commissural axons. Immunocytochemical demonstration of KS in neocortical resections and forebrain at autopsy was studied in 12 fetuses and neonates 9-41 weeks gestational age (GA), 9 infants, children, and adolescents and 5 patients with focal cortical dysplasias (FCD1a). From 9 to 15 weeks GA, no KS is seen in the cortical plate; 19-week GA reactivity is detected in the molecular zone. By 28 weeks GA, patchy granulofilamentous reactivity appears in extracellular matrix and adheres to neuronal somata with increasing intensity in deep cortex and U-fibers at term. Perifascicular KS surrounds axonal bundles of both limbs of the internal capsule and within basal ganglia from 9 weeks GA. Thalamus and globus pallidus exhibit intense astrocytic reactivity from 9 weeks GA. In FCD1a, U-fiber reactivity is normal, discontinuous or radial. Ultrastructural correlates were not demonstrated; KS is not electron-dense. Proteoglycan barrier of the U-fiber layer impedes participation of deep heterotopia in cortical epileptic networks. Perifascicular KS prevents aberrant axonal exit from or entry into long and short tracts. KS adhesion to neuronal somatic membranes may explain inhibitory axosomatic synapses.

Postinjury Inhibition of miR-181a Promotes Restoration of Hippocampal CA1 Neurons after Transient Forebrain Ischemia in Rats.

The cellular and molecular mechanisms regulating postinjury neurogenesis in the adult hippocampus remain undefined. We have previously demonstrated that preinjury treatment with anti-microRNA (miR)-181a preserved neurons and prevented astrocyte dysfunction in the hippocampal cornu ammonis-1 (CA1) following transient forebrain ischemia. In the present study, we assessed postinjury treatment with anti-miR-181a on recovery of CA1 neurons following transient forebrain ischemia in rats. Stereotactic CA1 injection of miR-181a antagomir at either 2 h or 7 d postinjury resulted in improved restoration of CA1 measured at 28 d postinjury. Treatment with antagomir was associated with overexpression of the mir-181a target cell adhesion-associated, oncogene-related protein and enhanced expression of the neuroprogenitor cell marker doublecortin (DCX) in the CA1. Assessment of GFAP+ cell fate by Cre/Lox-mediated deletion demonstrated that some GFAP+ cells in CA1 exhibited de novo DCX expression in response to injury. In vitro experiments using primary neuronal stem cells confirmed that miR-181a inhibition augmented the expression of DCX and directed cellular differentiation toward a neuronal fate. These results suggest that miR-181a inhibition plays a central role in the restoration of CA1 neurons via augmentation of early latent neurogenic gene activation in neural progenitor cells, including some reactive astrocytes. Therapeutic interventions targeting this restorative process may represent a novel postinjury approach to improve clinical outcomes in survivors of forebrain ischemia.

Comparison of the detrimental features of microglia and infiltrated macrophages in traumatic brain injury: A study using a hypnotic bromovalerylurea.

Microglia and blood-borne macrophages in injured or diseased brains are difficult to distinguish because they share many common characteristics. However, the identification of microglia-specific markers and the use of flow cytometry have recently made it easy to discriminate these types of cells. In this study, we analyzed the features of blood-borne macrophages, and activated and resting microglia in a rat traumatic brain injury (TBI) model. Oxidative injury was indicated in macrophages and neurons in TBI lesions by the presence of 8-hydroxy-2'-deoxyguanosine (8-OHdG). Generation of mitochondrial reactive oxygen species (ROS) was markedly observed in granulocytes and macrophages, but not in activated or resting microglia. Dihydroethidium staining supported microglia not being the major source of ROS in TBI lesions. Furthermore, macrophages expressed NADPH oxidase 2, interleukin-1ß (IL-1ß), and CD68 at higher levels than microglia. In contrast, microglia expressed transforming growth factor ß1 (TGFß1), interleukin-6 (IL-6), and tumor necrosis factor α at higher levels than macrophages. A hypnotic, bromovalerylurea (BU), which has anti-inflammatory effects, reduced both glycolysis and mitochondrial oxygen consumption. BU administration inhibited chemokine CCL2 expression, accumulation of monocytes/macrophages, 8-OHdG generation, mitochondrial ROS generation, and proinflammatory cytokine expression, and markedly ameliorated the outcome of the TBI model. Yet, BU did not inhibit microglial activation or expression of TGFß1 and insulin-like growth factor 1 (IGF-1). These results indicate that macrophages are the major aggravating cell type in TBI lesions, in particular during the acute phase. Activated microglia may even play favorable roles. Reduction of cellular energy metabolism in macrophages and suppression of CCL2 expression in injured tissue may lead to amelioration of TBI.

Forebrain cellular bioenergetics in neonatal mice.

BACKGROUND: Hypoglycemia occurs frequently in the neonate and may result in neurologic dysfunction. Its impact on the kinetics of cellular respiration and bioenergetics in the neonatal brain remains to be explored. AIMS: Develop murine model to investigate the effects of hypoglycemia on neonatal brain bioenergetics. STUDY DESIGN: Forebrain fragments were excised from euthanized BALB/c pups aged <24 hours to 14 days. We measured cellular respiration (µM O2 min-1.mg-1) in phosphate-buffered saline with and without glucose, using phosphorescence oxygen analyzer, as well as cellular adenosine triphosphate (ATP, nmol.mg-1) using the luciferin-luciferase system. RESULTS: In the presence of glucose, although cellular respiration was 11% lower in pups ≤3 days compared to those 3- 14 days old (0.48 vs. 0.54), that difference was not statistically significant (p = 0.14). Respiration driven by endogenous metabolic fuels (without added glucose) was 16% lower in pups ≤3 days compared to those 3- 14 days (0.35 vs. 0.42, p = 0.03), confirming their increased dependency on exogenous glucose. Although cellular ATP was similar between the two age groups (14.9 vs. 11.2, p = 0.32), the ATP content was more severely depleted without added glucose in the younger pups, especially in the presence of the cytochrome c oxidase inhibitor cyanide. The first-order rate constant of cellular ATP decay (hydrolysis) was 44% lower in 2-day-old pups compared to 14-day-old mice (0.43 vs. 0.77 min-1, p = 0.03). CONCLUSIONS: Forebrain cellular respiration and ATP consumption are lower in young pups than older mice. In the absence of glucose, the support for these processes is reduced in young pups, explaining their brain hypersensitivity to hypoglycemia.

A new mouse model of ARX dup24 recapitulates the patients' behavioral and fine motor alterations.

The aristaless-related homeobox (ARX) transcription factor is involved in the development of GABAergic and cholinergic neurons in the forebrain. ARX mutations have been associated with a wide spectrum of neurodevelopmental disorders in humans, among which the most frequent, a 24 bp duplication in the polyalanine tract 2 (c.428_451dup24), gives rise to intellectual disability, fine motor defects with or without epilepsy. To understand the functional consequences of this mutation, we generated a partially humanized mouse model carrying the c.428_451dup24 duplication (Arxdup24/0) that we characterized at the behavior, neurological and molecular level. Arxdup24/0 males presented with hyperactivity, enhanced stereotypies and altered contextual fear memory. In addition, Arxdup24/0 males had fine motor defects with alteration of reaching and grasping abilities. Transcriptome analysis of Arxdup24/0 forebrains at E15.5 showed a down-regulation of genes specific to interneurons and an up-regulation of genes normally not expressed in this cell type, suggesting abnormal interneuron development. Accordingly, interneuron migration was altered in the cortex and striatum between E15.5 and P0 with consequences in adults, illustrated by the defect in the inhibitory/excitatory balance in Arxdup24/0 basolateral amygdala. Altogether, we showed that the c.428_451dup24 mutation disrupts Arx function with a direct consequence on interneuron development, leading to hyperactivity and defects in precise motor movement control and associative memory. Interestingly, we highlighted striking similarities between the mouse phenotype and a cohort of 33 male patients with ARX c.428_451dup24, suggesting that this new mutant mouse line is a good model for understanding the pathophysiology and evaluation of treatment.

Genetic disruption of ankyrin-G in adult mouse forebrain causes cortical synapse alteration and behavior reminiscent of bipolar disorder.

Genome-wide association studies have implicated the ANK3 locus in bipolar disorder, a major human psychotic illness. ANK3 encodes ankyrin-G, which organizes the neuronal axon initial segment (AIS). We generated a mouse model with conditional disruption of ANK3 in pyramidal neurons of the adult forebrain (Ank-G cKO). This resulted in the expected loss of pyramidal neuron AIS voltage-gated sodium and potassium channels. There was also dramatic loss of markers of afferent GABAergic cartridge synapses, resembling the cortical microcircuitry changes in brains from psychotic patients, and suggesting disinhibition. Expression of c-fos was increased in cortical pyramidal neurons, consistent with increased neuronal activity due to disinhibition. The mice showed robust behavioral phenotypes reminiscent of aspects of human mania, ameliorated by antimania drugs lithium and valproate. Repeated social defeat stress resulted in repeated episodes of dramatic behavioral changes from hyperactivity to "depression-like" behavior, suggestive of some aspects of human bipolar disorder. Overall, we suggest that this Ank-G cKO mouse model recapitulates some of the core features of human bipolar disorder and indicates that cortical microcircuitry alterations during adulthood may be involved in pathogenesis. The model may be useful for studying disease pathophysiology and for developing experimental therapeutics.

Subchronic metformin pretreatment enhances novel object recognition memory task in forebrain ischemia: behavioural, molecular, and electrophysiological studies.

Metformin exerts its effect via AMP-activated protein kinase (AMPK), which is a key sensor for energy homeostasis that regulates different intracellular pathways. Metformin attenuates oxidative stress and cognitive impairment. In our experiment, rats were divided into 8 groups; some were pretreated with metformin (Met, 200 mg/kg) and (or) the AMPK inhibitor Compound C (CC) for 14 days. On day 14, rats underwent transient forebrain global ischemia. Data indicated that pretreatment of ischemic rats with metformin reduced working memory deficits in a novel object recognition test compared to group with ischemia-reperfusion (I-R) (P < 0.01). Pretreatment of the I-R animals with metformin increased phosphorylated cyclic-AMP response element-binding protein (pCREB) and c-fos levels compared to the I-R group (P < 0.001 for both). The level of CREB and c-fos was significantly lower in ischemic rats pretreated with Met + CC compared to the Met + I-R group. Field excitatory postsynaptic potential (fEPSP) amplitude and slope was significantly lower in the I-R group compared to the sham operation group (P < 0.001). Data showed that fEPSP amplitude and slope was significantly higher in the Met + I-R group compared to the I-R group (P < 0.001). Treatment of ischemic animals with Met + CC increased fEPSP amplitude and slope compared to the Met + I-R group (P < 0.01). We unravelled new aspects of the protective role of AMPK activation by metformin, further emphasizing the potency of metformin pretreatment against cerebral ischemia.

Deep brain stimulation of the dorsal raphe inhibits avoidance and escape reactions and activates forebrain regions related to the modulation of anxiety/panic.

One of the main neurochemical systems associated with anxiety/panic is the serotonergic system originating from the dorsal raphe nucleus (DR). Previous evidence suggests that the DR is composed of distinct subpopulations of neurons, both morphologically and functionally distinct. It seems that mainly the dorsal region of the DR (DRD) regulates anxiety-related reactions, while lateral wings DR (lwDR) serotonin (5-HT) neurons inhibit panic-related responses. In this study we used the technique of deep brain stimulation (DBS) to investigate the role played by the DRD and lwDR in defense. Male Wistar rats were submitted to high-frequency stimulation (100µA, 100Hz) in one of the two DR regions for 1h and immediately after tested in the avoidance or escape tasks of the elevated T-maze (ETM). In clinical terms, these responses have been related to generalized anxiety and panic disorder, respectively. After being submitted to the ETM, animals were placed in an open field for locomotor activity assessment. An additional group of rats was submitted to DBS of the DRD or the lwDR and used for quantification of c-Fos immunoreactive (Fos-ir) neurons in brain regions related to the modulation of defense. Results showed that stimulation of the DRD decreased avoidance latencies, an anxiolytic-like effect. DRD stimulation also led to increases in Fos-ir in the medial amygdala, lateral septum and cingulate cortex. DBS applied to the lwDR increased escape latencies, a panicolytic-like effect. This data highlights the importance of raphe topography and the potential benefit of the DBS technique for the treatment of anxiety-related disorders.

Effect of electrolytic lesions of the dorsal diencephalic conduction system on the distribution of Fos-like immunoreactivity induced by rewarding electrical stimulation.

The dorsal diencephalic conduction system (DDC) is an important pathway of the brain reward circuitry, linking together forebrain and midbrain structures. The present work was aimed at describing the effect of a DDC lesion on the distribution of Fos-like immunoreactivity (FLIR) following intracranial self-stimulation (ICSS) of the lateral hypothalamus (LH). Rats were implanted with monopolar electrodes and divided into three groups; the first two groups were trained to self-stimulate at the LH, whereas the third group received no stimulation and served as a control. Among the two groups that were trained for ICSS, one of them received a lesion at the DDC and was tested for ICSS on the subsequent 5days. On the last day of testing, control rats were placed in operant chambers without receiving any stimulation, and the remaining rats were allowed to receive the stimulation for 1h. All rats were then processed for FLIR. As previously shown, a lesion at the DDC resulted in significant attenuations of the rewarding effectiveness of LH stimulation. Results also show a higher FLIR in several reward-related areas following LH stimulation, especially in the hemisphere ipsilateral to the stimulation electrode. Compared to non-lesioned rats, lesioned animals had lower FLIR in certain brain regions, suggesting that those regions that were activated by the rewarding stimulation may be functionally interconnected with the DDC.

Hyperbaric oxygen and hyperbaric air preconditioning induces ischemic tolerance to transient forebrain ischemia in the gerbil.

Ischemic preconditioning with sublethal stress triggers defensive mechanisms against ischemic brain damage; however, such manipulations are potentially dangerous and, therefore, safe stimuli have been sought. Hyperoxia preconditioning by administration of hyperbaric (HBO) or normobaric oxygen (NBO) may have neuroprotective potential. The aim of this study was to determine whether preconditioning with HBO and air (HBA) applied at 2.5 absolute pressure (ATA) or NBO preconditioning induces ischemic tolerance in the brain of gerbils subjected to 3min transient cerebral ischemia. Neuronal cell survival, changes in brain temperature, the generation of factors involved in neurodegeneration and basic behavior in nest building were all tested. Hyperoxic preconditioning prevented ischemia-induced neuronal cell loss, reduced the number of TUNEL positive cells in the CA1 region of the hippocampus and improved the nest building process compared to untreated ischemic animals. Preconditioning also suppressed the production of reactive oxygen species and increased Bax expression normally observed after an ischemic episode. Only HBO preconditioning inhibited ischemia-evoked increases in brain temperature. Our results show that hyperoxic preconditioning results in induction of ischemic tolerance and prevents ischemia-induced neuronal damage in the gerbil brain. Pressurized air preconditioning was as effective as HBO or NBO preconditioning in providing neuroprotection. The observed neuroprotection probably results from mild oxidative stress evoked by increased brain tissue oxidation and activation of antioxidant and antiapoptotic defenses.

Abnormal mitochondrial transport and morphology as early pathological changes in human models of spinal muscular atrophy.

Spinal muscular atrophy (SMA), characterized by specific degeneration of spinal motor neurons, is caused by mutations in the survival of motor neuron 1, telomeric (SMN1) gene and subsequent decreased levels of functional SMN. How the deficiency of SMN, a ubiquitously expressed protein, leads to spinal motor neuron-specific degeneration in individuals affected by SMA remains unknown. In this study, we examined the role of SMN in mitochondrial axonal transport and morphology in human motor neurons by generating SMA type 1 patient-specific induced pluripotent stem cells (iPSCs) and differentiating these cells into spinal motor neurons. The initial specification of spinal motor neurons was not affected, but these SMA spinal motor neurons specifically degenerated following long-term culture. Moreover, at an early stage in SMA spinal motor neurons, but not in SMA forebrain neurons, the number of mitochondria, mitochondrial area and mitochondrial transport were significantly reduced in axons. Knocking down of SMN expression led to similar mitochondrial defects in spinal motor neurons derived from human embryonic stem cells, confirming that SMN deficiency results in impaired mitochondrial dynamics. Finally, the application of N-acetylcysteine (NAC) mitigated the impairment in mitochondrial transport and morphology and rescued motor neuron degeneration in SMA long-term cultures. Furthermore, NAC ameliorated the reduction in mitochondrial membrane potential in SMA spinal motor neurons, suggesting that NAC might rescue apoptosis and motor neuron degeneration by improving mitochondrial health. Overall, our data demonstrate that SMN deficiency results in abnormal mitochondrial transport and morphology and a subsequent reduction in mitochondrial health, which are implicated in the specific degeneration of spinal motor neurons in SMA.

Combined MSC-Secreted Factors and Neural Stem Cell Transplantation Promote Functional Recovery of PD Rats.

Stem cell transplantation has enormous potential for the treatment of neurodegenerative disorders like Parkinson's disease (PD). Mesenchymal stem cells (MSCs) have attracted much attention because they can secrete a wide variety of cellular factors that promote cell growth. In this study, we prepared a conditioned medium (CM) using lyophilized MSC culture medium that contained the secretome of MSCs and applied this CM to the culture of neural stem cells (CM-NSCs) for the transplantation of PD model rats. Quantitative real-time PCR, Western blot, and immunocytochemistry were used to identify cell differentiation and expression of dopaminergic neuron-specific genes in vitro. Behavioral tests including rotational behavior and MWM training tests were also performed to assess the recovery. Our results indicated that combined treatment of CM and neural stem cell transplantation can significantly reduce apomorphine-induced rotational asymmetry and improve spatial learning ability. The CM-NSCs were able to differentiate into dopaminergic neurons in the ventral tegmental area (VTA) and medial forebrain bundle (MFB), and migrated around the lesion site. They showed a higher activity than untreated NSCs in cell survival, migration, and behavior improvement in the dopa-deficit rat model. These findings suggest that the neural stem cells treated with conditioned medium possess a great potential as a graft candidate for the treatment of Parkinson's disease.

Neuronal activity and amyloid plaque pathology: an update.

A breakthrough in Alzheimer's disease (AD) research came with the discovery of the link between activity-dependent release of amyloid-ß (Aß) from neurons and formation of amyloid plaques. Along with elucidating the cellular basis of behavioral-dependent fluctuations in Aß levels in the brain, insights have been gained toward understanding the mechanisms that warrant selective vulnerability of various forebrain circuits to amyloid pathology. The notion of elevated activity as a source of excessive Aß production and plaque formation is, however, in conflict with ample electrophysiological data, which demonstrate exceedingly intense activity (both intrinsic and synaptic) of neurons in several brain regions that are spared or marginally affected by amyloid plaques of AD. Thus, the link between the functional load of brain circuits and their vulnerability to amyloidosis, while evident, is also complex and remains poorly understood. Here, we discuss emerging data suggestive of a major role for super-intense synchronous activity of cortical and limbic networks in excessive Aß production and plaque formation. It is proposed that dense recurrent wiring of associative areas prone to epileptic seizures might be of critical relevance to their higher susceptibility to plaque pathology and related functional impairments.

Blocking miRNA Biogenesis in Adult Forebrain Neurons Enhances Seizure Susceptibility, Fear Memory, and Food Intake by Increasing Neuronal Responsiveness.

The RNase Dicer is essential for the maturation of most microRNAs, a molecular system that plays an essential role in fine-tuning gene expression. To gain molecular insight into the role of Dicer and the microRNA system in brain function, we conducted 2 complementary RNA-seq screens in the hippocampus of inducible forebrain-restricted Dicer1 mutants aimed at identifying the microRNAs primarily affected by Dicer loss and their targets, respectively. Functional genomics analyses predicted the main biological processes and phenotypes associated with impaired microRNA maturation, including categories related to microRNA biology, signal transduction, seizures, and synaptic transmission and plasticity. Consistent with these predictions, we found that, soon after recombination, Dicer-deficient mice exhibited an exaggerated seizure response, enhanced induction of immediate early genes in response to different stimuli, stronger and more stable fear memory, hyperphagia, and increased excitability of CA1 pyramidal neurons. In the long term, we also observed slow and progressive excitotoxic neurodegeneration. Overall, our results indicate that interfering with microRNA biogenesis causes an increase in neuronal responsiveness and disrupts homeostatic mechanisms that protect the neuron against overactivation, which may explain both the initial and late phenotypes associated with the loss of Dicer in excitatory neurons.

Forebrain glucocorticoid receptor gene deletion attenuates behavioral changes and antidepressant responsiveness during chronic stress.

Stress is an important risk factor for mood disorders. Stress also stimulates the secretion of glucocorticoids, which have been found to influence mood. To determine the role of forebrain glucocorticoid receptors (GR) in behavioral responses to chronic stress, the present experiments compared behavioral effects of repeated social defeat in mice with forebrain GR deletion and in floxed GR littermate controls. Repeated defeat produced alterations in forced swim and tail suspension immobility in floxed GR mice that did not occur in mice with forebrain GR deletion. Defeat-induced changes in immobility in floxed GR mice were prevented by chronic antidepressant treatment, indicating that these behaviors were dysphoria-related. In contrast, although mice with forebrain GR deletion exhibited antidepressant-induced decreases in tail suspension immobility in the absence of stress, this response did not occur in mice with forebrain GR deletion after defeat. There were no marked differences in plasma corticosterone between genotypes, suggesting that behavioral differences depended on forebrain GR rather than on abnormal glucocorticoid secretion. Defeat-induced gene expression of the neuronal activity marker c-fos in the ventral hippocampus, paraventricular thalamus and lateral septum correlated with genotype-related differences in behavioral effects of defeat, whereas c-fos induction in the nucleus accumbens and central and basolateral amygdala correlated with genotype-related differences in behavioral responses to antidepressant treatment. The dependence of both negative (dysphoria-related) and positive (antidepressant-induced) behaviors on forebrain GR is consistent with the contradictory effects of glucocorticoids on mood, and implicates these or other forebrain regions in these effects.

Long-term inhibition of Rho-kinase restores the LTP impaired in chronic forebrain ischemia rats by regulating GABAA and GABAB receptors.

We previously demonstrated that inactivation of Rho-kinase by hydroxyfasudil could impact N-methyl-d-aspartate (NMDA) excitatory interneurons in the hippocampus and attenuate the spatial learning and memory dysfunction of rats caused by chronic forebrain hypoperfusion ischemia. Complementary interactions between the excitatory neurotransmitter glutamate and the inhibitory neurotransmitter GABA form the molecular basis of synaptic plasticity and cognitive performance. However, whether the GABAergic inhibitory interneurons are involved in the mechanisms underlying these processes remains unclear. Here, we further examined the role of GABAergic interneurons in the neuroprotective effect of the Rho-kinase inhibitor. Chronic forebrain ischemia was induced in Wistar rats by bilateral common carotid artery occlusion (BCAO). The general synaptic transmission and long-term potentiation (LTP) of hippocampal CA3 neurons were evaluated at 30 days after sham surgery or BCAO. Real-time PCR and Western blot analyses were conducted to determine the effect of the Rho-kinase inhibitor hydroxyfasudil on GABAergic inhibitory interneuron expression and function after ischemia. Hydroxyfasudil showed no significant effect on general synaptic transmission, but it could abolish the inhibition of LTP induced by chronic forebrain ischemia. Moreover, the mRNA and protein levels of GABAA and GABAB in three brain regions after ischemia were markedly decreased, and hydroxyfasudil could up-regulate all mRNA and protein expression levels in these areas except for GABAA mRNA in the cerebral cortex and striatum. Using phosphorylation antibodies against specific sites on the GABAA and GABAB receptors, we further demonstrated that hydroxyfasudil could inhibit GABAergic interneuron phosphorylation triggered by the theta burst stimulation. In summary, our results indicated that the inactivation of Rho-kinase could enhance GABAA and GABAB expressions by different mechanisms to guarantee the induction of hippocampal LTP, and it could decrease the phosphorylation level of GABAergic inhibitory interneurons to promote the LTP induction rate and magnitude, hence improving the cognitive deficit suffered after chronic forebrain ischemia.

Ropinirole regulates emotionality and neuronal activity markers in the limbic forebrain.

Restless legs syndrome (RLS) and Parkinson's disease (PD) are movement disorders usually accompanied by emotional and cognitive deficits. Although D3/D2 receptor agonists are effective against motor and non-motor deficits in RLS and PD, the exact behavioral and neurochemical effects of these drugs are not clearly defined. This study aimed to evaluate the effects of acute ropinirole (0, 0.1, 1 or 10 mg/kg, i.p.), a preferential D3/D2 receptor agonist, on intracranial self-stimulation (ICSS), spontaneous motor activity, anxiety- and depression-like behaviors, spatial reference and working memory in rats as well as on certain markers of neuronal activity, i.e. induction of immediate early genes, such as c-fos and arc, and crucial phosphorylations on GluA1 subunit of α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and NA1, NA2A and NA2B subunits of N-methyl-D-aspartate (NMDA) receptors. Ropinirole decreased ICSS thresholds and induced anxiolytic- and antidepressive-like effects without affecting motor activity or spatial memory. The effects on emotionality were associated with a decrease in p-Ser897-NA1 and an increase in p-Tyr1472-NA2B in the ventral striatum as well as an increased induction of c-fos messenger RNA (mRNA) in the prefrontal cortex (PFC) and decreased expression of arc mRNA in the striatum and the shell of the nucleus accumbens. Our data indicate that ropinirole significantly affects emotionality at doses (1-10 mg/kg, i.p.) that exert no robust effects on locomotion or cognition. The data reinforce the use of D3/D2 receptor agonists in the treatment of RLS and PD patients characterized by emotional deficits and suggest that altered NMDA-mediated neurotransmission in the limbic forebrain may underlie some of ropinirole's therapeutic actions.

Ultrasound-microbubble transplantation of bone marrow stromal cells improves neurological function after forebrain ischemia in adult mice.

In this study, bone marrow stromal cells (MSCs) were transplanted into the brain of adult rats after forebrain ischemia induced by 4VO. SD rats (n = 60) were randomly divided into three groups: (I) rats (n = 20) were subjected to 4VO and transplanted with MSCs into the ischemic region using ultrasound-microbubble method, (2) rats (n = 20) were subjected to 4VO and transplanted with MSCs into the ischemic region (n = 20), and (3) 4VO alone (n = 20). Rats were sacrificed 28 days after treatment. Neurological functions of rats were evaluated by Morris Water Maze. The current findings suggest that the ultrasound microbubble transplanted MSCs survived in the ischemic brain and significantly improved functional recovery of adult rats compared to regular transplantation.

DCC expression by neurons regulates synaptic plasticity in the adult brain.

The transmembrane protein deleted in colorectal cancer (DCC) and its ligand, netrin-1, regulate synaptogenesis during development, but their function in the mature central nervous system is unknown. Given that DCC promotes cell-cell adhesion, is expressed by neurons, and activates proteins that signal at synapses, we hypothesized that DCC expression by neurons regulates synaptic function and plasticity in the adult brain. We report that DCC is enriched in dendritic spines of pyramidal neurons in wild-type mice, and we demonstrate that selective deletion of DCC from neurons in the adult forebrain results in the loss of long-term potentiation (LTP), intact long-term depression, shorter dendritic spines, and impaired spatial and recognition memory. LTP induction requires Src activation of NMDA receptor (NMDAR) function. DCC deletion severely reduced Src activation. We demonstrate that enhancing NMDAR function or activating Src rescues LTP in the absence of DCC. We conclude that DCC activation of Src is required for NMDAR-dependent LTP and certain forms of learning and memory.