Critical involvement of the orbitofrontal cortex in hyperlocomotion induced by NMDA receptor blockade in mice

Altered Functional Connectivity of the Orbital Cortex and Striatum Associated with Catalepsy Induced by Dopamine D1 and D2 Antagonists

The dopamine system plays an important role in regulating many brain functions, including the motor function. The blockade of dopamine receptors results in a serious motor dysfunction, such as catalepsy and Parkinsonism. However, the neuronal mechanism underlying the drug-induced motor dysfunction is not well understood. Here, we examine brain-wide activation patterns in Fos-enhanced green fluorescent protein reporter mice that exhibit cataleptic behavior induced by SCH39166, a dopamine D1-like receptor antagonist, and raclopride, a dopamine D2-like receptor antagonist. Support vector classifications showed that the orbital cortex (ORB) and striatum including the caudoputamen (CP) and nucleus accumbens (ACB), prominently contribute to the discrimination between brains of the vehicle-treated and both SCH39166- and raclopride-treated mice. Interregional correlations indicated that the increased functional connectivity of functional networks, including the ORB, CP, and ACB, is the common mechanism underlying SCH39166- and raclopride-induced cataleptic behavior. Moreover, the distinct mechanisms in the SCH39166- and raclopride-induced cataleptic behaviors are the decreased functional connectivity between three areas above and the cortical amygdala, and between three areas above and the anterior cingulate cortex, respectively. Thus, the alterations of functional connectivity in diverse brain regions, including the ORB, provide new insights on the mechanism underlying drug-induced movement disorders.

Sequential habituation to space, object and stranger is differentially modulated by glutamatergic, cholinergic and dopaminergic transmission

Novel object and social interaction tasks allow assessments of rodent cognition and social behavior. Here, we combined these tasks and defined unequivocal locations of interest. Our procedure, termed OF-NO-SI, comprised habituation to the open field (OF), novel object (NO) and social interaction (SI) stages. Habituation was measured within- and between-trials (10 minutes each, two per stage). Ambulation emerged as the appropriate proxy during the OF stage, but NO and SI trials were best quantified via direct exploration measures. We pharmacologically validated the paradigm using 5-month old C57BL/6J male mice, treated intraperitoneally with (1) 0.5 mg/kg scopolamine, (2) 0.05 mg/kg MK-801 and (3) 0.05 mg/kg SCH-23390 to block muscarinic (M1), NMDA, and D1 receptors, respectively, or (4) vehicle (distilled water). Activity and gross exploratory behavior were affected by all compounds cf. vehicle: scopolamine and MK-801 cohorts were hyperactive, while SCH-23390 caused hypo-locomotion throughout. Vehicle treated mice showed reliable habituation to all stages for time in interaction zone, directed exploration and number of visits. Exploration was severely impaired by scopolamine. MK-801 mostly affected within-session exploration but also increased exploration of the conspecific compared to the object. Interestingly, even though within-trial habituation was lacking in the SCH-23390 cohort, between-trial habituation was largely intact, despite reduced locomotion. Our data suggest that the OF-NO-SI task is a convenient and robust paradigm to measure habituation to different experimental settings and stimuli. It allows the dissociation of proxies related to activity and non-associative learning/memory, as revealed by distinct pharmacological treatment effects within- vs. between-trials.

Potential antipsychotic action of the selective agonist of adenosine A1 receptors, 5'-Cl-5'-deoxy-ENBA, in amphetamine and MK-801 rat models

Background

Disturbances of dopaminergic and glutamatergic transmissions have been suggested to be involved in the pathomechanisms underlying psychotic symptoms of schizophrenia. In line with this concept, hyperlocomotion induced by the dopaminomimetic amphetamine and the uncompetitive antagonist of NMDA receptors MK-801 (dizocilpine) in rodents is a generally established model for screening of new potential antipsychotic drugs. Since recent studies have indicated that receptors for adenosine may be targets for antipsychotic therapy, the aim of the present study was to investigate an influence of 5′-Cl-5′-deoxy-ENBA, a potent and selective adenosine A₁ receptor agonist, on hyperlocomotion induced by amphetamine and MK-801.

Methods

Locomotor activity was measured by Force Plate Actimeters where four force transducers located below the corners of the floor of the cage tracked the animal position on a Cartesian plane at each time point.

Results

Hyperlocomotion induced by either amphetamine (1 mg/kg sc) or MK-801 (0.3 mg/kg ip) was inhibited by 5′-Cl-5′-deoxy-ENBA (0.1 mg/kg ip). The effect of 5′-Cl-5′-deoxy-ENBA on the amphetamine- and MK-801-induced hyperlocomotion was antagonized by the selective antagonist of adenosine A₁ receptor DPCPX at doses of 1 and 2 mg/kg ip, respectively.

Conclusion

The present study suggests that stimulation of adenosine A₁ receptors may produce antipsychotic effects.

Different FDG-PET metabolic patterns of anti-AMPAR and anti-NMDAR encephalitis: Case report and literature review

INTRODUCTION

¹⁸ F-fluorodeoxyglucose (FDG)-PET metabolic patterns of brain differ among autoimmune encephalitis with different neuronal surface antigens. In this case report, we compared the topographical relationship of cerebral glucose metabolism and antigen distribution in the patients with anti-NMDAR and anti-AMPAR encephalitis. Literature review summarized the common features of brain metabolism of autoimmune encephalitis.

METHODS

The cerebral glucose metabolism was evaluated by FDG-PET/CT during acute-to-subacute stage of autoimmune encephalitis and after treatment. The stereo and quantitative analysis of cerebral metabolism used standardized z-score and visualized on three-dimensional stereotactic surface projection. To map NMDAR and AMPAR in human brain, we adopted genetic atlases from the Allen Institute and protein atlases from Zilles's receptor densities.

RESULTS

The three-dimensional stereotactic surface projection displayed frontal-dominant hypometabolism in a 66-year-old female patient with anti-AMPAR encephalitis and occipital-dominant hypometabolism in a 29-year-old female patient with anti-NMDAR encephalitis. Receptor density maps revealed opposite frontal-occipital gradients of AMPAR and NMDAR, which reflect reduced metabolism in the correspondent encephalitis. FDG-PET hypometabolic areas possibly represent receptor hypofunction with spatial correspondence to receptor distributions of the autoimmune encephalitis. The reversibility of hypometabolism was in line with patients' cognitive improvement. The literature review summarized six features of metabolic anomalies of autoimmune encephalitis: (a) temporal hypermetabolism, (b) frontal hypermetabolism and (c) occipital hypometabolism in anti-NMDAR encephalitis, (d) hypometabolism in association cortices, (e) sparing of unimodal primary motor cortex, and (e) reversibility in recovery.

CONCLUSIONS

The distinct cerebral hypometabolic patterns of autoimmune encephalitis were representative for receptor hypofunction and topographical distribution of antigenic receptors. The reversibility of hypometabolism marked the clinical recovery of autoimmune encephalitis and made FDG-PET of brain a valuable diagnostic tool.

Hyperactive and anxiolytic-like behaviors result from loss of COUP-TFI/Nr2f1 in the mouse cortex

The nuclear receptor COUP TFI (also known as Nr2f1) plays major roles in specifying distinct neuronal subtypes during patterning of the neocortical motor and somatosensory cortex, as well as in regulating the longitudinal growth of the hippocampus during development. In humans, mutations in the NR2F1 gene lead to a global developmental delay and intellectual disabilities. While more than 30% of patients show behavioral features of autism spectrum disorder, 16% of haploinsufficient children show signs of hyperactivity and impulsivity. Loss of COUP-TFI in the cortical mouse primordium results in altered area organization and serotonin distribution, abnormal coordination of voluntary movements and learning and memory deficits. Here, we asked whether absence of COUP-TFI affects locomotor activity, anxiety, as well as depression. Mice mutant for COUP-TFI have normal motor coordination, but significant traits of hyperactivity, which does not seem to respond to N-Methyl-D-aspartate (NMDA) antagonists. However, no changes in anxiety, despite increased locomotor performances, were observed in the open field task. On the contrary, elevated plus maze and dark-light test explorations indicate a decreased anxiety-like behavior in COUP-TFI mutant mice. Finally, significantly reduced immobility in the forced swim test and no changes in anhedonia in the sucrose preference task suggest no particular depressive behaviors in mutant mice. Taken together, our study shows that loss of COUP-TFI leads to increased locomotor activity but less anxiety and contributes in further deciphering the pathophysiology of patients haploinsufficient for NR2F1.

Early life esophageal acid exposure reduces expression of NMDAR1 in the adult rat dorsal hippocampus and medial prefrontal cortex: Potential relationship with hyperlocomotion

OBJECTIVE

Early life esophageal acid exposure causes long-term molecular alterations in the rostral cingulate cortex; however, whether it induces behavioral changes remains unverified. Little is known about the molecular changes resulting from this event in the developing hippocampus and medial prefrontal cortex (mPFC). This study aimed to investigate the influence of early life esophageal acid exposure on spontaneous locomotor behavior and N-methyl-D-aspartate receptor (NMDAR), expression in these brain regions of adult rats.

METHODS

Male Sprague-Dawley rats were administered with an esophageal acid or saline infusion once per day (postnatal days 7-14). Some of these rats were given acute esophageal acid rechallenge in adulthood (postnatal day 60). The spontaneous locomotor behavior and expressions of esophageal epithelial caludin-1 and NMDAR subunits in the dorsal hippocampus (DH), ventral hippocampus (VH) and mPFC of the adult rats were recorded.

RESULTS

Neonatal esophageal acid stimulation caused long-term impairment of the tight junctions in the adult esophagus. Simultaneously, hyperlocomotion and reduced expression of NMDAR1 subunits in both the DH and mPFC were observed, but not in the VH regions. Adult acute acid rechallenge reversed the decreased NMDAR1 expression in the DH and mPFC. The glycine ligand to NMDAR1 subunits was also changed.

CONCLUSIONS

Peripheral visceral stimulation such as esophageal acid exposure during cerebral development induces increased locomotor activity, which may be related to the alteration of central sensitivity via NMDAR1 subunit reduction in the DH and mPFC. The impairment of tight junctions in the esophageal epithelium may contribute to the formation of central neuroplasticity.

Knockdown of the mitochondria-localized protein p13 protects against experimental parkinsonism

Mitochondrial dysfunction in the nigrostriatal dopaminergic system is a critical hallmark of Parkinson's disease (PD). Mitochondrial toxins produce cellular and behavioural dysfunctions resembling those in patients with PD Causative gene products for familial PD play important roles in mitochondrial function. Therefore, targeting proteins that regulate mitochondrial integrity could provide convincing strategies for PD therapeutics. We have recently identified a novel 13-kDa protein (p13) that may be involved in mitochondrial oxidative phosphorylation. In the current study, we examine the mitochondrial function of p13 and its involvement in PD pathogenesis using mitochondrial toxin-induced PD models. We show that p13 overexpression induces mitochondrial dysfunction and apoptosis. p13 knockdown attenuates toxin-induced mitochondrial dysfunction and apoptosis in dopaminergic SH-SY5Y cells via the regulation of complex I. Importantly, we generate p13-deficient mice using the CRISPR/Cas9 system and observe that heterozygous p13 knockout prevents toxin-induced motor deficits and the loss of dopaminergic neurons in the substantia nigra. Taken together, our results suggest that manipulating p13 expression may be a promising avenue for therapeutic intervention in PD.