Short- and Long-Term Social Recognition Memory Are Differentially Modulated by Neuronal Histamine

Enhanced Recognition Memory through Dual Modulation of Brain Carbonic Anhydrases and Cholinesterases

This study introduces a novel multitargeting strategy that combines carbonic anhydrase (CA) activators and cholinesterase (ChE) inhibitors to enhance cognitive functions. A series of tacrine-based derivatives with amine/amino acid moieties were synthesized and evaluated for their dual activity on brain CA isoforms and ChEs (AChE and BChE). Several derivatives, notably compounds 26, 30, 34, and 40, demonstrated potent CA activation, particularly of hCA II and VII, and strong ChE inhibition with subnanomolar to low nanomolar IC50 values. In vivo studies using a mouse model of social recognition memory showed that these derivatives significantly improved memory consolidation at doses 10-100 times lower than the reference compounds (either alone or in combination). Molecular modeling and ADMET predictions elucidated the compound binding modes and confirmed favorable pharmacokinetic and safety profiles. The findings suggest that dual modulation of CA and ChE activities is a promising strategy for treating cognitive deficits associated with neurodegenerative and psychiatric disorders.

Potential role of oxytocin in the regulation of memories and treatment of memory disorders

Oxytocin (OXT) is an "affiliative" hormone or neurohormone or neuropeptide consists of nine amino acids, synthesized in magnocellular neurons of paraventricular (PVN) and supraoptic nuclei (SON) of hypothalamus. OXT receptors are widely distributed in various region of brain and OXT has been shown to regulate various social and nonsocial behavior. Hippocampus is the main region which regulates the learning and memory. Hippocampus particularly regulates the acquisition of new memories and retention of acquired memories. OXT has been shown to regulate the synaptic plasticity, neurogenesis, and consolidation of memories. Further, findings from both preclinical and clinical studies have suggested that the OXT treatment improves performance in memory related task. Various trials have suggested the positive impact of intranasal OXT in the dementia patients. However, these studies are limited in number. In the present study authors have highlighted the role of OXT in the formation and retrieval of memories. Further, the study demonstrated the outcome of OXT treatment in various memory and related disorders.

Targeting Microglia in Neuroinflammation: H3 Receptor Antagonists as a Novel Therapeutic Approach for Alzheimer's Disease, Parkinson's Disease, and Autism Spectrum Disorder

Histamine performs dual roles as an immune regulator and a neurotransmitter in the mammalian brain. The histaminergic system plays a vital role in the regulation of wakefulness, cognition, neuroinflammation, and neurogenesis that are substantially disrupted in various neurodegenerative and neurodevelopmental disorders. Histamine H3 receptor (H3R) antagonists and inverse agonists potentiate the endogenous release of brain histamine and have been shown to enhance cognitive abilities in animal models of several brain disorders. Microglial activation and subsequent neuroinflammation are implicated in impacting embryonic and adult neurogenesis, contributing to the development of Alzheimer's disease (AD), Parkinson's disease (PD), and autism spectrum disorder (ASD). Acknowledging the importance of microglia in both neuroinflammation and neurodevelopment, as well as their regulation by histamine, offers an intriguing therapeutic target for these disorders. The inhibition of brain H3Rs has been found to facilitate a shift from a proinflammatory M1 state to an anti-inflammatory M2 state, leading to a reduction in the activity of microglial cells. Also, pharmacological studies have demonstrated that H3R antagonists showed positive effects by reducing the proinflammatory biomarkers, suggesting their potential role in simultaneously modulating crucial brain neurotransmissions and signaling cascades such as the PI3K/AKT/GSK-3β pathway. In this review, we highlight the potential therapeutic role of the H3R antagonists in addressing the pathology and cognitive decline in brain disorders, e.g., AD, PD, and ASD, with an inflammatory component.

Chemogenetic activation or inhibition of histaminergic neurons bidirectionally modulates recognition memory formation and retrieval in male and female mice

Several lines of evidence demonstrate that the brain histaminergic system is fundamental for cognitive processes and the expression of memories. Here, we investigated the effect of acute silencing or activation of histaminergic neurons in the hypothalamic tuberomamillary nucleus (TMNHA neurons) in vivo in both sexes in an attempt to provide direct and causal evidence of the necessary role of these neurons in recognition memory formation and retrieval. To this end, we compared the performance of mice in two non-aversive and non-rewarded memory tests, the social and object recognition memory tasks, which are known to recruit different brain circuitries. To directly establish the impact of inactivation or activation of TMNHA neurons, we examined the effect of specific chemogenetic manipulations during the formation (acquisition/consolidation) or retrieval of recognition memories. We consistently found that acute chemogenetic silencing of TMNHA neurons disrupts the formation or retrieval of both social and object recognition memory in males and females. Conversely, acute chemogenetic activation of TMNHA neurons during training or retrieval extended social memory in both sexes and object memory in a sex-specific fashion. These results suggest that the formation or retrieval of recognition memory requires the tonic activity of histaminergic neurons and strengthen the concept that boosting the brain histaminergic system can promote the retrieval of apparently lost memories.

Mechanism of Microwave Radiation-Induced Learning and Memory Impairment Based on Hippocampal Metabolomics

The brain is complex and metabolically active, and the detection of metabolites plays an important role in brain development and diseases. Currently, there is a lack of research on the metabolic spectrum changes in learning and memory impairment, and hippocampal damage induced by microwave radiation from the metabolic perspective. Aiming to provide sensitive indicators for microwave radiation-induced brain damage and establish a foundation for understanding its injury mechanisms, this study employed non-targeted metabolomics to investigate metabolic fluctuations and key metabolic pathway alterations in rats' hippocampal tissue after microwave radiation. The memory and spatial exploration abilities of rats decreased after radiation. The postsynaptic densities were thickened in the MW group. The cholesterol sulfate, SM(d16:1/24:1(15Z)), and linoelaidylcarnitine were significantly increased after radiation, whereas etrahydrocorticosterone, L-phenylalanine, and histamine were significantly decreased after radiation. These metabolites were enriched in signaling pathways related to the inflammatory mediator regulation of transient receptor potential (TRP) channels, neuroactive ligand-receptor interaction, steroid hormone biosynthesis, and phenylalanine, tyrosine, and tryptophan biosynthesis. These findings indicate that microwave radiation causes spatial learning and memory dysfunction in rats and structural damage to hippocampal tissue.

From rodents to humans: Rodent behavioral paradigms for social behavioral disorders

Social cognition guides social behavior. Subjects with proper social cognition should be able to: (1) have reasonable social motivation, (2) recognize other people and infer their intentions, and (3) weigh social hierarchies and other values. The choice of appropriate behavioral paradigms enables the use of rodents to study social behavior disorders in humans, thus enabling research to go deeper into neural mechanisms. This paper reviews commonly used rodent behavioral paradigms in studies of social behavior disorders. We focused specifically on sorting out ways to transfer the study of human social behavior to rodents through behavioral paradigms.

Amelioration of cognition impairments in the valproic acid-induced animal model of autism by ciproxifan, a histamine H3-receptor antagonist

Autism spectrum disorder is a neurodevelopmental disorder characterized by deficits in social communication and repetitive behavior. Many studies show that the number of cognitive impairmentscan be reduced by antagonists of the histamine H3 receptor (H3R). In this study, the effects of ciproxifan (CPX) (1 and 3 mg/kg, intraperitoneally) on cognitive impairments in rat pups exposed to valproic acid (VPA) (600 mg/kg, intraperitoneally) wereexamined on postnatal day 48-50 (PND 48-50) using marble-burying task (MBT), open field, novel object recognition (NOR), and Passive avoidance tasks. Famotidine (FAM) (10, 20, and 40 mg/kg, intraperitoneally) was also used to determine whether histaminergic neurotransmission exerts its procognitive effects via H2 receptors (H2Rs). Furthermore, a histological investigation was conducted to assess the degree of degeneration of hippocampal neurons. The results revealed that repetitive behaviors increased in VPA-exposed rat offspring in the MBT. In addition, VPA-exposed rat offspring exhibited more anxiety-like behaviors in the open field than saline-treated rats. It was found that VPA-exposed rat offspring showed memory deficits in NOR and Passive avoidance tasks. Our results indicated that 3 mg/kg CPX improved cognitive impairments induced by VPA, while 20 mg/kg FAM attenuated them. We concluded that 3 mg/kg CPX improved VPA-induced cognitive impairments through H3Rs. The histological assessment showed that the number of CA1 neurons decreased in the VPA-exposed rat offspring compared to the saline-exposed rat offspring, but this decrease was not significant. The histological assessment also revealed no significant differences in CA1 neurons in VPA-exposed rat offspring compared to saline-exposed rat offspring. However, CPX3 increased the number of CA1 neurons in the VPA + CPX3 group compared to the VPA + Saline group, but this increase was not significant. This study showed that rats prenatally exposed to VPA exhibit cognitive impairments in the MBT, open field, NOR, and Passive avoidance tests, which are ameliorated by CPX treatment on PND 48-50. In addition, morphological investigations showed that VPA treatment did not lead to neuronal degeneration in the CA1 subfield of the hippocampus in rat pups.

Sublethal ammonia induces alterations of emotions, cognition, and social behaviors in zebrafish (Danio rerio)

Ammonia pollutants were usually found in aquatic environments is due to urban sewage, industrial wastewater discharge, and agricultural runoff and concentrations as high as 180 mg/L (NH₄⁺) have been reported in rivers. High ammonia levels are known to impair multiple tissue and cell functions and cause fish death. Although ammonia is a potent neurotoxin, how sublethal concentrations of ammonia influence the central nervous system (CNS) and the complex behaviors of fish is still unclear. In the present study, we demonstrated that acute sublethal ammonia exposure can change social behavior of adult zebrafish. The exposure to 90 mg /L of (NH₄⁺) for 4 h induced a strong fear response and lower shoaling cohesion; exposure to 180 mg /L of (NH₄⁺) for 4 h reduced the aggressiveness, and social recognition, while the anxiety, social preference, learning, and short-term memory were not affected. Messenger RNA expressions of glutaminase and glutamate dehydrogenase in the brain were induced, suggesting that ammonia exposure altered glutamate neurotransmitters in the CNS. Our findings in zebrafish provided delicate information of ammonia neurotoxicity in complex higher-order social behaviors, which has not been revealed previously. In conclusion, sublethal and acute ammonia exposure can change specific behaviors of fish, which might lead to reductions in individual and population fitness levels.

Histamine H3 receptor antagonist, ciproxifan, alleviates cognition and synaptic plasticity alterations in a valproic acid-induced animal model of autism

RATIONALE

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social communication and cognitive behaviors. Histamine H3 receptor (H3R) antagonists are considered as therapeutic factors for treating cognitive impairments.

OBJECTIVES

The aim of the present study was to evaluate the effects of the H3R antagonist, ciproxifan (CPX), on cognition impairment especially, spatial learning memory, and synaptic plasticity in the CA1 region of the hippocampus in autistic rats.

METHODS

Pregnant rats were injected with either valproic acid (VPA) (600 mg/kg, i.p.) or saline on an embryonic day 12.5 (E12.5). The effects of the H3R antagonist, ciproxifan (CPX) (1, 3 mg/kg, i.p.), were investigated on learning and memory in VPA-exposed rat pups and saline-exposed rat pups using Morris water maze (MWM) and social interaction tasks. The H2R antagonist, famotidine (FAM) (10, 20, 40 mg/kg, i.p.), was used to determine whether brain histaminergic neurotransmission exerted its procognitive effects through the H2R. In addition, synaptic reinforcement was evaluated by in vivo field potential recording.

RESULTS

The results showed that VPA-exposed rat pups had significantly lower sociability and social memory performance compared to the saline rats. VPA-exposed rat pups exhibited learning and memory impairments in the MWM task. In addition, VPA caused suppression of long-term potentiation (LTP) in the CA1 area of the hippocampus. Our results demonstrated that CPX 3 mg/kg improved VPA-induced cognitive impairments and FAM 20 mg/kg attenuated cognitive behaviors as well as electrophysiological properties.

CONCLUSIONS

CPX 3 mg/kg improved VPA-induced impairments of LTP as well as learning and memory deficits through H2R.

Revisiting Preclinical Observations of Several Histamine H3 Receptor Antagonists/Inverse Agonists in Cognitive Impairment, Anxiety, Depression, and Sleep-Wake Cycle Disorder

A relationship appears to exist between dysfunction of brain histamine (HA) and various neuropsychiatric brain disorders. The possible involvement of brain HA in neuropathology has gained attention recently, and its role in many (patho)physiological brain functions including memory, cognition, and sleep-wake cycle paved the way for further research on the etiology of several brain disorders. Histamine H3 receptor (H3R) evidenced in the brains of rodents and humans remains of special interest, given its unique position as a pre- and postsynaptic receptor, controlling the synthesis and release of HA as well as different other neurotransmitters in different brain regions, respectively. Despite several disappointing outcomes for several H3R antagonists/inverse agonists in clinical studies addressing their effectiveness in Alzheimer's disease (AD), Parkinson's disease (PD), and schizophrenia (SCH), numerous H3R antagonists/inverse agonists showed great potentials in modulating memory and cognition, mood, and sleep-wake cycle, thus suggesting its potential role in neurocognitive and neurodegenerative diseases such as AD, PD, SCH, narcolepsy, and major depression in preclinical rodent models. In this review, we present preclinical applications of selected H3R antagonists/inverse agonists and their pharmacological effects on cognitive impairment, anxiety, depression, and sleep-wake cycle disorders. Collectively, the current review highlights the behavioral impact of developments of H3R antagonists/inverse agonists, aiming to further encourage researchers in the preclinical drug development field to profile the potential therapeutic role of novel antagonists/inverse agonists targeting histamine H3Rs.

Intranasal application of stem cells and their derivatives as a new hope in the treatment of cerebral hypoxia/ischemia: a review

Intranasal delivery of stem cells and conditioned medium to target the brain has attracted major interest in the field of regenerative medicine. In pre-clinical investigations during the last ten years, several research groups focused on this strategy to treat cerebral hypoxia/ischemia in neonates as well as adults. In this review, we discuss the curative potential of stem cells, stem cell derivatives, and their delivery route via intranasal application to the hypoxic/ischemic brain. After intranasal application, stem cells migrate from the nasal cavity to the injured area and exert therapeutic effects by reducing brain tissue loss, enhancing endogenous neurogenesis, and modulating cerebral inflammation that leads to functional improvements. However, application of this administration route for delivering stem cells and/or therapeutic substances to the damaged sites requires further optimization to translate the findings of animal experiments to clinical trials.

Bionanohybrid composed of metalloprotein/DNA/MoS2/peptides to control the intracellular redox states of living cells and its applicability as a cell-based biomemory device

The development of cell-based bioelectronic devices largely depends on the direct control of intracellular redox states. However, most related studies have focused on the accurate measurement of electrical signals from living cells, whereas direct intracellular state control remains largely unexplored. Here, we developed a biocompatible transmembranal bionanohybrid structure composed of a recombinant metalloprotein, DNA, molybdenum disulfide nanoparticles (MoS₂), and peptides to control intracellular redox states, which can be used as a cell-based biomemory device. Using the capacitance of MoS₂ located inside the cell, the bionanohybrid controled the intracellular redox states of living cells by recording and extracting intracellular charges, which inturn was achieved by activating (writing) and deactivating (erasing) the cells. As a proof of concept, cell-based biomemory functions including writing, reading, and erasing were successfully demonstrated and confirmed via electrochemical methods and patch-clamp analyses, resulting in the development of the first in vitro cell-based biomemory device. This newly developed bionanohybrid provides a novel approach to control cellular redox states for cell-based bioelectronic applications, and can be applicable in a wide range of biological fields including bioelectronic medicine and intracellular redox status regulation.

A Duet Between Histamine and Oleoylethanolamide in the Control of Homeostatic and Cognitive Processes

In ballet, a pas de deux (in French it means "step of two") is a duet in which the two dancers perform ballet steps together. The suite of dances shares a common theme of partnership. How could we better describe the fine interplay between oleoylethanolamide (OEA) and histamine, two phylogenetically ancient molecules controlling metabolic, homeostatic and cognitive processes? Contrary to the pas de deux though, the two dancers presumably never embrace each other as a dancing pair but execute their "virtuoso solo" constantly exchanging interoceptive messages presumably via vagal afferents, the blood stream, the neuroenteric system. With one exception, which is in the control of liver ketogenesis, as in hepatocytes, OEA biosynthesis strictly depends on the activation of histaminergic H₁ receptors. In this review, we recapitulate our main findings that evidence the interplay of histamine and OEA in the control of food consumption and eating behaviour, in the consolidation of emotional memory and mood, and finally, in the synthesis of ketone bodies. We will also summarise some of the putative underlying mechanisms for each scenario.