Knockout of NPFFR2 Prevents LPS-Induced Depressive-Like Responses in Mice

Mouse Model of Parkinson's Disease with Bilateral Dorsal Striatum Lesion with 6-Hydroxydopamine Exhibits Cognitive Apathy-like Behavior

Among the symptoms of Parkinson's disease (PD), apathy comprises a set of behavioral, affective, and cognitive features that can be classified into several subtypes. However, the pathophysiology and brain regions that are involved in these different apathy subtypes are still poorly characterized. We examined which subtype of apathy is elicited in a mouse model of PD with 6-hydroxydopamine (6-OHDA) lesions and the behavioral symptoms that are exhibited. Male C57/BL6J mice were allocated to sham (n = 8) and 6-OHDA (n = 13) groups and locally injected with saline or 4 µg 6-OHDA bilaterally in the dorsal striatum. We then conducted motor performance tests and apathy-related behavioral experiments. We then pathologically evaluated tyrosine hydroxylase (TH) immunostaining. The 6-OHDA group exhibited significant impairments in motor function. In the behavioral tests of apathy, significant differences were observed between the sham and 6-OHDA groups in the hole-board test and novelty-suppressed feeding test. The 6-OHDA group exhibited impairments in inanimate novel object preference, whereas social preference was maintained in the three-chamber test. The number of TH+ pixels in the caudate putamen and substantia nigra compacta was significantly reduced in the 6-OHDA group. The present mouse model of PD predominantly showed dorsal striatum dopaminergic neuronal loss and a decrease in novelty seeking as a symptom that is related to the cognitive apathy component.

Short-term memory impairment following recovery from systemic inflammation induced by lipopolysaccharide in mice

The relationship between neuroinflammation and mental disorders has been recognized and investigated for over 30 years. Diseases of systemic or peripheral inflammation, such as sepsis, peritonitis, and infection, are associated with increased risk of mental disorders with neuroinflammation. To elucidate the pathogenesis, systemic administration of lipopolysaccharide (LPS) in mice is often used. LPS-injected mice exhibit behavioral abnormalities with glial activation. However, these studies are unlikely to recapitulate the clinical pathophysiology of human patients, as most studies focus on the acute inflammatory response with systemic symptoms occurring within 24 h of LPS injection. In this study, we focus on the effects of LPS on behavioral abnormalities following recovery from systemic symptoms and investigate the mechanisms of pathogenesis. Several behavioral tests were performed in LPS-injected mice, and to assess neuroinflammation, the time course of the morphological change and expression of inflammatory factors in neurons, astrocytes, and microglia were investigated. At 7 days post-LPS injection, mice exhibited short-term memory impairment accompanied by the suppression of neuronal activity and increases in morphologically immature spines. Glial cells were transiently activated in the hippocampus concomitant with upregulation of the microglial phagocytosis marker CD68 3 days after injection. Here we show that transient glial cell activation in the acute response phase affects neuronal activity and behavior following recovery from systemic symptoms. These findings provide novel insights for studies using the LPS-induced inflammation model and that will contribute to the development of treatments for mental disorders of this etiology.

Role of the GRP/GRPR System in Regulating Brain Functions

Re-examining the relationship between neuropeptide systems and neural circuits will help us to understand more intensively the critical role of neuropeptides in brain function as the neural circuits responsible for specific brain functions are gradually revealed. Gastrin-releasing peptide receptors (GRPRs) are Gαq-coupling neuropeptide receptors and widely distributed in the brain, including hippocampus, amygdala, hypothalamus, nucleus tractus solitarius (NTS), suprachiasmatic nucleus (SCN), paraventricular nucleus of the hypothalamus (PVN), preoptic area of the hypothalamus (POA), preBötzinger complex (preBötC), etc., implying the GRP/GRPR system is involved in modulating multiple brain functions. In this review, we focus on the functionality of GRPR neurons and the regulatory role of the GRP/GRPR system in memory and cognition, fear, depression and anxiety, circadian rhythms, contagious itch, gastric acid secretion, food intake, body temperature, and sighing behavior. It can be found that GRPR is usually centered on a certain brain nucleus or anatomical structure and modulates richer or more specific behaviors by connecting with additional different nuclei. In order to explain the regulatory mechanism of the GRP/GRPR system, more precise intervention methods are needed.

A new perspective on hippocampal synaptic plasticity and post-stroke depression

Post-stroke depression, a common complication after stroke, severely affects the recovery and quality of life of patients with stroke. Owing to its complex mechanisms, post-stroke depression treatment remains highly challenging. Hippocampal synaptic plasticity is one of the key factors leading to post-stroke depression; however, the precise molecular mechanisms remain unclear. Numerous studies have found that neurotrophic factors, protein kinases and neurotransmitters influence depressive behaviour by modulating hippocampal synaptic plasticity. This review further elaborates on the role of hippocampal synaptic plasticity in post-stroke depression by summarizing recent research and analysing possible molecular mechanisms. Evidence for the correlation between hippocampal mechanisms and post-stroke depression helps to better understand the pathological process of post-stroke depression and improve its treatment.

Protective Role and Functional Engineering of Neuropeptides in Depression and Anxiety: An Overview

Behavioral disorders, such as anxiety and depression, are prevalent globally and touch children and adults on a regular basis. Therefore, it is critical to comprehend how these disorders are affected. It has been demonstrated that neuropeptides can influence behavior, emotional reactions, and behavioral disorders. This review highlights the majority of the findings demonstrating neuropeptides' behavioral role and functional engineering in depression and anxiety. Gut-brain peptides, hypothalamic releasing hormone peptides, opioid peptides, and pituitary hormone peptides are the four major groups of neuropeptides discussed. Some neuropeptides appear to promote depression and anxiety-like symptoms, whereas others seem to reduce it, all depending on the receptors they are acting on and on the brain region they are localized in. The data supplied here are an excellent starting point for future therapy interventions aimed at treating anxiety and depression.

Anxiety and Depression: What Do We Know of Neuropeptides?

In modern society, there has been a rising trend of depression and anxiety. This trend heavily impacts the population’s mental health and thus contributes significantly to morbidity and, in the worst case, to suicides. Modern medicine, with many antidepressants and anxiolytics at hand, is still unable to achieve remission in many patients. The pathophysiology of depression and anxiety is still only marginally understood, which encouraged researchers to focus on neuropeptides, as they are a vast group of signaling molecules in the nervous system. Neuropeptides are involved in the regulation of many physiological functions. Some act as neuromodulators and are often co-released with neurotransmitters that allow for reciprocal communication between the brain and the body. Most studied in the past were the antidepressant and anxiolytic effects of oxytocin, vasopressin or neuropeptide Y and S, or Substance P. However, in recent years, more and more novel neuropeptides have been added to the list, with implications for the research and development of new targets, diagnostic elements, and even therapies to treat anxiety and depressive disorders. In this review, we take a close look at all currently studied neuropeptides, their related pathways, their roles in stress adaptation, and the etiology of anxiety and depression in humans and animal models. We will focus on the latest research and information regarding these associated neuropeptides and thus picture their potential uses in the future.

Elevated Serum Neuropeptide FF Levels Are Associated with Cognitive Decline in Patients with Spinal Cord Injury

BACKGROUND

Spinal cord injury (SCI) has high incidence globally and is frequently accompanied by subsequent cognitive decline. Accurate early risk-categorization of SCI patients for cognitive decline using biomarkers can enable the timely application of appropriate neuroprotective measures and the development of new agents for the management of SCI-associated cognitive decline. Neuropeptide FF is an endogenous neuropeptide with a multitude of functions and is associated with neuroinflammatory processes. This prospective study investigated the predictive value of serum neuropeptide FF levels measured after acute SCI for subsequent cognitive decline.

METHODS

88 patients presenting with acute SCI without preexisting neurological injury, brain trauma, or severe systemic illness and 60 healthy controls were recruited. Serum neuropeptide FF levels, clinical, and routine laboratory variables including low-density lipoprotein, high-density lipoprotein, fasting blood glucose, total triiodothyronine (TT3), total thyroxine (TT4), and thyroid-stimulating hormone (TSH) levels collected from all subjects were assessed. Montreal cognitive assessment (MoCA) was performed 3 months after enrollment. SCI patients were grouped according to quartile of serum neuropeptide FF level and MoCA scores were compared using ANOVA. Additionally, multivariate linear regression with clinical and laboratory variables was performed to predict MoCA scores.

RESULTS

SCI patients displayed significantly higher baseline serum neuropeptide FF levels than healthy controls (38.5 ± 4.1 versus 23.4 ± 2.0 pg/ml, p < 0.001∗∗). SCI patients in higher quartiles of baseline serum neuropeptide FF displayed significantly lower MoCA scores at 3 months. Linear regression analysis indicated serum neuropeptide FF levels as a significant independent predictor of worse MoCA scores after SCI (r = 0.331, p = 0.034∗).

CONCLUSION

Early serum neuropeptide FF levels significantly and independently predicted cognitive decline after acute SCI among patients without preexisting neurological disorders.