Activation of the dopamine D1 receptor can extend long-term spatial memory persistence via PKA signaling in mice

The effect of lansoprazole on MK-801-induced schizophrenia-like behaviors in mice

As a heterogeneous disorder, schizophrenia is known to be associated with neuroinflammation. A recent study showed that several cytokines are higher in the plasma and cerebrospinal fluid of schizophrenia patients. Lansoprazole, a proton pump inhibitor used for treating erosive esophagitis, has been reported to reduce INF-γ-induced neurotoxicity and decrease inflammatory cytokines including IL-1β, IL-6, and TNF-α. These findings persuaded us to examine whether lansoprazole ameliorates schizophrenia-like symptoms. The schizophrenia mouse model was induced by the acute administration of MK-801, an NMDA receptor antagonist. Sensorimotor gating, Barnes maze, and social novelty preference tests were conducted to evaluate schizophrenia-like behaviors. We found that lansoprazole (0.3, 1, or 3 mg/kg) ameliorated sensorimotor gating deficits, spatial learning, and social deficits caused by MK-801 treatment (0.2 mg/kg). The catalepsy test, balance beam test, and rotarod test were performed to reveal the adverse effects of lansoprazole on motor coordination. The behavioral results indicated that lansoprazole did not result in any motor function deficits. Moreover, lansoprazole decreased inflammatory cytokines including IL-6 and TNF-α only in the cortex, but not in the hippocampus. Collectively, these results suggest that lansoprazole could be a potential candidate for treating schizophrenia patients who suffer from sensorimotor gating deficits or social disability without any motor-related adverse effects.

Agmatine relieves behavioral impairments in Fragile X mice model

BACKGROUND

Fragile X syndrome (FXS) is the most common heritable form of neurodevelopmental disorder, which is caused by the loss of fragile X mental retardation protein (FMRP) expression. Despite the unceasing efforts to develop therapeutic agents against FXS based on the pathophysiological changes observed in animal models of FXS and human patients, therapeutic candidates including mGluR signaling modulators have failed to provide sufficient effects. Based on the recent successful demonstration of an endogenous polyamine, agmatine, to improve the autism-like symptoms in the valproic acid animal model of autism, we investigated the effects of agmatine against FXS symptoms using Fmr1 knockout (KO) mice.

METHODS

We used male Fmr1 KO mice for behavioral tests such as marble burying, open-field test, memory tasks, social interaction tests and startle response to confirm the symptoms of FXS. We also checked the electrophysiological profile of neural activity in agmatine-treated Fmr1 KO mice.

RESULTS

Agmatine reversed the compulsion, learning and memory deficits, hyperactivity, aberrant social interaction, and communication deficit in Fmr1 KO mice while it normalized the aberrant LTP and LTD in the hippocampus.

CONCLUSIONS

The results highlight the potential of agmatine's novel disease-ameliorating effects in FXS, which warrants further studies to ascertain whether these findings translate into clinical effects in FXS patients.

Per2 Expression Regulates the Spatial Working Memory of Mice through DRD1-PKA-CREB Signaling

Several individuals worldwide show cognitive impairment due to various reasons, including a prolonged lifespan and an altered lifestyle. Various causes, such as broken circadian rhythms and dopamine-related factors, have been proposed to be involved in the development of cognitive impairment. However, the underlying pathways remain elusive. Humans with circadian misalignment often face cognitive impairments, and animals with mutations in circadian rhythm-related genes display impaired cognitive functions. To analyze this in detail, this study aimed to investigate the pathways potentially involved in cognitive impairment using Period2 (Per2) transgenic animals. Spatial working memory performance in Per2 knockout (KO) and wild-type mice was assessed using the Barnes maze and Y-maze. The dopamine-related protein expression levels in the hippocampus were measured by Western blotting and enzyme-linked immunosorbent assay (ELISA). Per2 KO mice exhibited impaired spatial working memory, and the expression levels of dopamine receptor D1 (DRD1), protein kinase A (PKA), and cAMP response element-binding protein (CREB) were higher in Per2 KO mice than in control mice. Additionally, DRD1 expression levels were inversely proportional to those of PER2. Thus, memory tests were again conducted after administration of the DRD1 antagonist SCH-23390. Per2 KO mice recovered from memory impairment, and the levels of PKA and CREB decreased after treatment. The effects of Aβ on memory in Per2 mice were also investigated, and we found the increased Aβ levels did not influence the memory performance of Per2 mice after SCH-23390 treatment. These results indicate that Per2 expression levels might influence spatial working memory performance via DRD1-PKA-CREB-dependent signaling.

The effects of aging and dopaminergic inhibition on large scale maze learning in rhesus monkeys

Studies have shown that both aging and dopaminergic dysfunction affected spatial learning and memory. Systematic dopaminergic inhibition, by dopamine receptor (DR) antagonist treatment, impaired spatial delayed-response (SDR) performance, which mostly requires self/body centered egocentric reference frame, in rhesus monkeys. However, the influence of DR blocking on large scale maze learning, which mainly involves world centered allocentric reference frame, remains unclear. Moreover, the effects of aging on the process also remain unknown. Present study investigated the issues, using large scale mazes composed of 8 maze units. Maze No. 1 was used for adaptation and training. Mazes No. 2-4 were used to investigate influence of aging, by comparing learning performance between young and aged rhesus monkeys. Mazes No. 5-8 were used to investigate the effects of DR antagonist treatment, SKF-83566 (0.02, 0.2 mg/kg) and haloperidol (0.001, 0.01 mg/kg). The result showed similar learning performance between young and aged monkeys in mazes No. 2-4. In mazes No. 5-8, we also found similar learning performance after acute DR antagonist injection, compared with pre-treatment baseline performance in mazes No. 2-4, in both young and aged groups. The result showed similar maze learning performance between young and aged monkeys in mazes (No. 2-4), suggesting no significant influence of aging on allocentric spatial learning. We also found similar maze performance in both groups, after dopamine receptor antagonist treatment in mazes (No. 5-8) compared with pre-treatment baseline performance in mazes (No. 2-4), suggesting no significant influence of dopaminergic inhibition on allocentric spatial learning. Together, the present study potentially suggested insensitivity of allocentric spatial learning to cognitive aging and acute systematic dopaminergic inhibition.

A-Kinase Anchoring Protein 150 and Protein Kinase A Complex in the Basolateral Amygdala Contributes to Depressive-like Behaviors Induced by Chronic Restraint Stress

BACKGROUND

The basolateral amygdala (BLA) has been widely implicated in the pathophysiology of major depressive disorder. A-kinase anchoring protein 150 (AKAP150) directs kinases and phosphatases to synaptic glutamate receptors, controlling synaptic transmission and plasticity. However, the role of the AKAP150 in the BLA in major depressive disorder remains poorly understood.

METHODS

Depressive-like behaviors in C57BL/6J mice were developed by chronic restraint stress (CRS). Mice received either intra-BLA injection of lentivirus-expressing Akap5 short hairpin RNA or Ht-31, a peptide to disrupt the interaction of AKAP150 and protein kinase A (PKA), followed by depressive-like behavioral tests. Alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid glutamate receptor (AMPAR)-mediated miniature excitatory postsynaptic currents were recorded by whole-cell patch-clamp techniques.

RESULTS

Chronic stress exposure induced depressive-like behaviors, which were accompanied by an increase in total and synaptic AKAP150 expression in the BLA. Accordingly, CRS facilitated the association of AKAP150 with PKA, but not of calcineurin in the BLA. Intra-BLA infusion of lentivirus-expressing Akap5 short hairpin RNA or Ht-31 prevented depressive-like behaviors and normalized phosphorylation of serine 845 and surface expression of AMPAR subunit 1 (GluA1) in the BLA of CRS mice. Finally, blockage of AKAP150-PKA complex signaling rescued the changes in AMPAR-mediated miniature excitatory postsynaptic currents in depressive-like mice.

CONCLUSIONS

These results suggest that AKAP150-PKA directly modulates BLA neuronal synaptic strength, and that AKAP150-PKA-GluA1 streamline signaling complex is responsible for CRS-induced disruption of synaptic AMPAR-mediated transmission and depressive-like behaviors in mice.

Anxiety-like features and spatial memory problems as a consequence of hippocampal SV2A expression

The Synaptic Vesicle Protein 2A (SV2A) is a transmembrane protein whose presence is reduced both in animal models and in patients with chronic epilepsy. Besides its implication in the epileptic process, the behavioural consequences of the changes in its expression remain unclear. The purpose of our research is to better understand the possible role(s) of this protein through the phenotype of cKO (Grik4 Cre+/-, SV2A lox/lox) mice, male and female, which present a specific decrease of SV2A expression levels in the hippocampal glutamatergic neurons but without any epileptic seizures. In this study, we compare the cKO mice with cHZ (Grik4 Cre+/-, SV2A lox/+) and WT (Grik4 Cre+/+, SV2A lox/lox) mice through a battery of tests, used to evaluate different features: the anxiety-related features (Elevated Plus Maze), the locomotor activity (Activity Chambers), the contextual fear-related memory (Contextual Fear Conditioning), and the spatial memory (Barnes Maze). Our results showed statistically significant differences in the habituation to a new environment, an increase in the anxiety levels and spatial memory deficit in the cHZ and cKO groups, compared to the WT group. No statistically significant differences due to the genotype appeared in the spontaneous locomotor activity or the fear-linked memory. However, sexual differences were observed in this last feature. These results highlight not only an important role of the SV2A protein in the cognitive and anxiety problems typically encountered in epileptic patients, but also a possible role in the symptomatology of other neurodegenerative diseases, such as the Alzheimer’s disease.