Locomotor Activity In Mice Research Articles

Characterization of novel nitazene recreational drugs: Insights into their risk potential from in vitro µ-opioid receptor assays and in vivo behavioral studies in mice

2-Benzylbenzimidazole derivatives or ‘nitazenes’ are increasingly present on the recreational drug market. Here, we report the synthesis and pharmacological characterization of 15 structurally diverse nitazenes that might be predicted to emerge or grow in popularity. This work expands the existing knowledge about 2-benzylbenzimidazole structure-activity relationships (SARs), while also helping stakeholders (e.g., forensic toxicologists, clinicians, policymakers) in their risk assessment and preparedness for the potential next generation of nitazenes. In vitro µ-opioid receptor (MOR) affinity was determined via competition radioligand (3[H]DAMGO) binding assays in rat brain tissue. MOR activation (potency and efficacy) was studied by means of a cell-based β-arrestin 2 recruitment assay. For seven nitazenes, including etonitazene, opioid-like pharmacodynamic effects (antinociception, locomotor activity, body temperature changes) were evaluated after subcutaneous administration in male C57BL/6J mice. The results showed that all nitazenes bound to MOR with nanomolar affinities, and the functional potency of several of them was comparable to or exceeded that of fentanyl. In vivo, dose-dependent effects were observed for antinociception, locomotor activity, and body temperature changes in mice. SAR insights included the high opioid-like activity of methionitazene, iso-butonitazene, sec-butonitazene, and the etonitazene analogues 1-ethyl-pyrrolidinylmethyl N-desalkyl etonitazene and ethylene etonitazene. The most potent analogue of the panel across all functional assays was α’-methyl etonitazene. Taken together, through critical pharmacological evaluation, this work provides a framework for strengthened preparedness and risk assessments of current and future nitazenes that have the potential to cause harm to users.

Curcumin alleviates arsenic trioxide-induced neural damage in the murine striatal region.

Arsenic-induced neurotoxicity, with dose-dependent effects, is well-documented in rodents. Curcumin (CUR), a cost-effective plant polyphenol, shows neuroprotective effects by modulating oxidative stress, apoptosis, and neurochemistry. This study evaluates curcumin's neuroprotective potential against arsenic trioxide (As2O3) in the mouse striatal region. Healthy adult male mice were chronically administered with varying concentrations of As2O3 (2, 4 and 8mg/kg bw) alone and along with CUR (100mg/kg bw) orally for 45days.Towards the end of the experimental period, the animals were subjected to behavioural paradigms including open field task, novel object recognition, rota-rod, and Morris water maze. Striatal tissues were freshly collected from the animals on day 46 for biochemical analyses (MDA, GPx, and GSH). Additionally, perfusion-fixed brains were processed for morphological observations. Behavioural study showed an apparent decrease in certain cognitive functions (learning and memory) and locomotor activity in mice exposed to As2O3 compared to controls. Simultaneous treatment of As2O3 (2, 4 and 8mg/kg bw) and curcumin (100mg/kg bw) alleviated the As-induced locomotor and cognitive deficits. As2O3 alone exposure also exhibited a significant increase in oxidative stress marker (MDA) and a decrease in antioxidant enzyme levels (GPx, GSH). Morphological alterations were noted in mice subjected to elevated doses of As2O3 (4 and 8mg/kg bw). However, these changes were reversed in mice who received As2O3 + CUR co-treatment. Collectively, our findings indicate that curcumin offers neuroprotection to the striatal region against As2O3-induced behavioral deficits, as well as biochemical and morphological alterations.

Behavioral effects of two cannabidiol and cannabigerol-rich formulas on mice

Cannabis sativa L. produces more than 100 specific bioactive compounds, known as cannabinoids. The major non-psychotropic Cannabis constituent is cannabidiol (CBD), which displays beneficial properties in a variety of medical conditions. However, the potential therapeutic role of other minor phytocannabinoids, such as cannabigerol (CBG), and their use in combination with CBD, has remained largely unexplored. In this study, we wanted to assess the in vivo effects of two novel non-psychotropic cannabinoid formulas, both containing relatively high percentages of CBD but differing mainly for CBG content, hereafter called CBG+ and CBG- formulas. We employed different behavioral tests to evaluate the effects of these formulas at three different dosages on mice locomotor activity, anxiety-related behaviors, short-term memory and sociability. We found that these two formulas display unique behavioral profiles: CBG+ formula produced an increase in mice locomotor activity and displayed anxiolytic properties, whereas both formulas improved spatial short-term memory and social interactions. The results obtained suggest that different combinations of phytocannabinoids are able to determine different behavioral effects and highlight the importance of studying the effects of less known phytocannabinoids (like CBG), which used in combination with other phytocannabinoids can change the profile of action of other active compounds (such as CBD).

Anti-inflammatory and antinociceptive effects of Aloysia gratissima leaves essential oil: An in vivo study

Background and aimAloysia gratissima is used in popular medicine as an analgesic and sedative. However, studies on its biological activities are still scarce. Therefore, this work aimed to evaluate the antinociceptive and anti-inflammatory effect of A. gratissima leaves essential oil (OAG) in mice. Experimental procedureThe OAG was obtained by hydrodistillation and its composition was determined by gas chromatography-mass spectrometry. The sesquiterpenes pinocamphone, β-pinene, and guaiol were the major constituents of OAG. The effect of OAG (1, 10, and 30 mg/kg, p.o.) was assessed by pre-treating male mice 1h before the formalin assay, carrageenan-induced peritonitis test, or the paw edema induced by arachidonic acid (AA). The acute toxicity of OAG (2000 mg/kg, p.o.) was also investigated. Results and conclusionThe minimum effective dose of OAG in the formalin test was 1 mg/kg. This dose did not affect the locomotor activity of mice. The OAG decreased the number of leukocytes/mm³ in the peritoneal exudate of mice and reduced paw edema 45 min after the arachidonic acid injection. OAG treatment elicited a reduction in NPSH levels in the paw tissue and increased NPSH levels in mice blood plasma and did not cause mice mortality. The OAG is devoid of acute toxicity and shows anti-inflammatory activity, which can be related to the presence of pinocamphone, guaiol, and β-pinene and is mediated, at least in part, by mechanisms that involve the participation of NPSH.

Aberrant copper metabolism and hepatic inflammation cause neurological manifestations in a mouse model of Wilson’s disease

Pathogenic germline mutations in the P-type copper-transporting ATPase (ATP7B) gene cause Wilson’s disease (WD), a hereditary disorder characterized by disrupted copper metabolism. The Arg778Leu (R778L) mutation in exon 8 is prevalent among individuals with WD in East Asia and is associated with more severe phenotypes. In this study, we generated a WD mouse model harboring R778L mutation (R778L mice) using CRISPR/Cas9. R778L mice exhibit a range of pathological characteristics resembling those of patients with WD and the same point mutations, including aberrant copper metabolism, pathological cellular injury, inflammation, and severe hepatic fibrosis. At 3–5 months of age, these mice started to display neurological deficits in motor coordination and cognitive dysfunction, accompanied by increased expression of inflammatory cytokines in the central nervous system. Microglia in the striatum and cortex exhibit significant activation, shorter processes, and decreased branch points. However, the Cu2+ levels in the brain tissue of R778L mice did not differ significantly from those of wild-type mice. Notably, inhibition of hepatic inflammation with PJ34 or siNfkb markedly alleviated the deficiencies in cognitive performance and improved locomotor activity in R778L mice. Thus, this study establishes a novel murine model to investigate the pathophysiology of WD, highlights the liver-brain crosstalk responsible for neurological manifestations in individuals with WD caused by the R778L point mutation, and demonstrates the potential of modulating liver inflammation as a therapeutic strategy for alleviating the neurological manifestations of WD.

A repeatedly evolved mutation in Cryptochrome-1 of subterranean animals alters behavioral and molecular circadian rhythms.

The repeated evolution of similar phenotypes in independent lineages often occurs in response to similar environmental pressures, through similar or different molecular pathways. Recently, a repeatedly occurring mutation R263Q in a conserved domain of the protein Cryptochrome-1 (CRY1) was reported in multiple species inhabiting subterranean environments. Cryptochromes regulate circadian rhythms, and glucose and lipid metabolism. Subterranean species show changes to their circadian rhythm and metabolic pathways, making it likely that this mutation in CRY1 contributes to adaptive phenotypic changes. To identify the functional consequences of the CRY1 R263Q mutation, we generated a mouse model homozygous for this mutation. Indirect calorimetry experiments revealed delayed energy expenditure, locomotor activity and feeding patterns of mutant mice in the dark phase, but no further metabolic phenotypes - unlike a full loss of function of CRY1. Gene expression analyses showed altered expression of several canonical circadian genes in the livers of the mutant mice, fortifying the notion that CRY1 R263Q impacts metabolism. Our data provide the first characterization of a novel mutation that has repeatedly evolved in subterranean environments, supporting the idea that shared environmental constraints can drive the evolution of similar phenotypes through similar genetic changes.

Endogenous Regulator of G protein Signaling 14 (RGS14) suppresses cocaine-induced emotionally motivated behaviors in female mice.

Addictive drugs hijack the neuronal mechanisms of learning and memory in motivation and emotion processing circuits to reinforce their own use. Regulator of G-protein Signaling 14 (RGS14) is a natural suppressor of post-synaptic plasticity underlying learning and memory in the hippocampus. The present study used immunofluorescence and RGS14 knockout mice to assess the role of RGS14 in behavioral plasticity and reward learning induced by chronic cocaine in emotional-motivational circuits. We report that RGS14 is strongly expressed in discrete regions of the ventral striatum and extended amygdala in wild-type mice, and is co-expressed with D1 and D2 dopamine receptors in neurons of the nucleus accumbens (NAc). Of note, we found that RGS14 is upregulated in the NAc in mice with chronic cocaine history following acute cocaine treatment. We found significantly increased cocaine-induced locomotor sensitization, as well as enhanced conditioned place preference and conditioned locomotor activity in RGS14-deficient mice compared to wild-type littermates. Together, these findings suggest that endogenous RGS14 suppresses cocaine-induced plasticity in emotional-motivational circuits, implicating RGS14 as a protective agent against the maladaptive neuroplastic changes that occur during addiction.

Reduced voluntary wheel running behaviour in Kiss1r knockout mice

Kisspeptin and its receptor, Kiss1r, are novel players in the central balance of energy intake and expenditure. Recent evidence also indicates that kisspeptin signalling is important in thermoregulation and generation of the circadian rhythm. We used global Kiss1r knockout mice (Kiss1r KO), which are hypogonadal and develop obesity, to determine the impact of kisspeptin on circadian related behaviour. Voluntary wheel running was examined in Kiss1r KO and wild-type (WT) mice, using gonad intact and gonadectomised (GDX) mice to account for the effects of kisspeptin on gonadal sex steroids. Intact male and female Kiss1r KO mice covered only 10% and 30% of the distance travelled each day by their respective WT controls. In all mice, most of the running activity occurred during the dark phase. GDX WT mice ran significantly less during dark periods than the intact WT. GDX Kiss1r KO male mice ran significantly less than the GDX WT male mice, but the decrease was attenuated compared to intact mice. There was no difference between the female GDX Kiss1r KO and GDX WT. In contrast to the obese phenotype that develops in Kiss1r KO mice, body mass at the end of the study was significantly lower in the GDX Kiss1r KO than it was in the GDX WT mice. The difference in wheel running activity was not associated with any histological change in WAT, BAT, or muscle diameter. No difference in immunohistochemistry expression was seen in lateral hypothalamic orexin neurons or dopamine neurons in the ventral tegmental area / substantia nigra. We observed increased Iba1 expression (activation of microglia) in the arcuate nucleus of male Kiss1r KO mice. Overall, the circadian locomotor activity in male Kiss1r KO mice appears dependent on kisspeptin signalling and the obese phenotype does not develop in Kiss1r KO mice when they engage in voluntary activity.

Scopoletin and rutin attenuate ethanol reward in mouse-conditioned place preference test

IntroductionIn Traditional Chinese Medicine (TCM), Morinda citrifolia Linn. (Hai ba ji), is utilized for its various parts such as leaves, fruits, flowers, roots, and bark, serving as a tonic and addressing ailments including fever, skin, eye, throat, and gum issues, as well as nausea, vomiting, and neurological diseases. Previous research indicated that M. citrifolia Linn. fruit and its juice reduced ethanol-conditioned place preference (CPP) in mice, with scopoletin (SCOP) and rutin (RUT) proposed as the main bioactive compounds responsible for this effect. This study aimed to evaluate the impact of SCOP and RUT on ethanol reward using the CPP test in mice. MethodsThe CPP protocol consisted of a habituation phase spanning 3 days, a 1-day preconditioning phase, 10 days of conditioning, a rest day, and a post-conditioning day. The vehicle-saline control and vehicle-ethanol control groups received oral administration of a 1 % w/v solution of sodium carboxymethyl cellulose (CMC) at a dosage of 10 ml/kg. SCOP and RUT were administered orally at doses ranging from 0.05 to 1 mg/kg body weight (bw), while acamprosate (ACAM) was administered at a dosage of 300 mg/kg bw, all one hour before postconditioning. Statistical analyses utilized both repeated measures two-way and one-way ANOVA. ResultsOral administration of SCOP (0.05, 0.1, and 0.5 mg/kg bw) and RUT (0.05 mg/kg bw) one hour before postconditioning testing on day 16 markedly reduced ethanol CPP in mice. Additionally, SCOP and RUT at all tested doses (0.05–1 mg/kg bw, p.o.) did not induce any changes in normal locomotor activity in mice. DiscussionThese results suggest that SCOP and RUT diminish ethanol reward in mice, underscoring the therapeutic potential of these phytochemicals in managing alcohol use disorder.

Dopaminergic REST/NRSF is protective against manganese-induced neurotoxicity in mice

Chronic exposure to elevated levels of manganese (Mn) may cause a neurological disorder referred to as manganism. The transcription factor REST is dysregulated in several neurodegenerative diseases, such as Alzheimer’s disease and Parkinson’s disease. REST upregulated tyrosine hydroxylase and induced protection against Mn toxicity in neuronal cultures. In the present study, we investigated if dopaminergic REST plays a critical role in protecting against Mn-induced toxicity in vivo using dopaminergic REST conditional knockout (REST-cKO) mice and REST loxP mice as wild-type (WT) controls. Restoration of REST in the substantia nigra (SN) with neuronal REST AAV vector infusion was performed to further support the role of REST in Mn toxicity. Mice were exposed to Mn (330 ug, intranasal, daily for 3 weeks), followed by behavioral tests and molecular biology experiments. Results showed that Mn decreased REST mRNA/protein levels in the SN-containing midbrain, as well as locomotor activity and motor coordination in WT mice, which were further decreased in REST-cKO. Mn-induced mitochondrial insults, such as impairment of fission/fusion and mitophagy, apoptosis, and oxidative stress, in the midbrain of WT mice were more pronounced in REST-cKO. However, REST restoration in the SN of REST cKO mice attenuated Mn-induced neurotoxicity. REST’s molecular target for its protection is unclear, but REST attenuated Mn-induced mitochondrial dysregulation, indicating that it is a primary intracellular target for both Mn and REST. These novel findings suggest that dopaminergic REST in the nigrostriatal pathway is critical in protecting against Mn toxicity, underscoring REST as a potential therapeutic target for treating manganism.

Anterior Cingulate Cortex Contributes to the Hyperlocomotion under Nitrogen Narcosis.

Nitrogen narcosis is a neurological syndrome that manifests when humans or animals encounter hyperbaric nitrogen, resulting in a range of motor, emotional, and cognitive abnormalities. The anterior cingulate cortex (ACC) is known for its significant involvement in regulating motivation, cognition, and action. However, its specific contribution to nitrogen narcosis-induced hyperlocomotion and the underlying mechanisms remain poorly understood. Here we report that exposure to hyperbaric nitrogen notably increased the locomotor activity of mice in a pressure-dependent manner. Concurrently, this exposure induced heightened activation among neurons in both the ACC and dorsal medial striatum (DMS). Notably, chemogenetic inhibition of ACC neurons effectively suppressed hyperlocomotion. Conversely, chemogenetic excitation lowered the hyperbaric pressure threshold required to induce hyperlocomotion. Moreover, both chemogenetic inhibition and genetic ablation of activity-dependent neurons within the ACC reduced the hyperlocomotion. Further investigation revealed that ACC neurons project to the DMS, and chemogenetic inhibition of ACC-DMS projections resulted in a reduction in hyperlocomotion. Finally, nitrogen narcosis led to an increase in local field potentials in the theta frequency band and a decrease in the alpha frequency band in both the ACC and DMS. These results collectively suggest that excitatory neurons within the ACC, along with their projections to the DMS, play a pivotal role in regulating the hyperlocomotion induced by exposure to hyperbaric nitrogen.

Human Circulatory/Respiratory-Inspired Comprehensive Air Purification System.

The circulatory and respiratory systems in humans are marvels of biological engineering that exhibit competence in maintaining homeostasis. These systems not only shield the organism from external contaminants but also orchestrate the vital gases via the bloodstream to sustain cellular respiration and metabolic processes across diverse tissues. It is noticed that spaces inhabited encounter challenges akin to those of the human body: protecting the indoor air from external pollutants while removing anthropogenic byproducts like carbon dioxide (CO2), particulate matters (PM), and volatile organic compounds (VOCs) tooutside. A biomimetic approach, composed of a microbubble-based gas exchanger and circulating liquid inspired by alveoli, capillary beds, and bloodstream of the human circulatory/respiratory system, offer an innovative solution for comprehensive air purification of hermetic spaces. Circulatory/respiratory-inspired air purification system (CAPS) ensure both continuous removal of PM and exchange of gas species between indoor and outdoor environments to maintain homeostasis. The effectiveness of this system is also supported by animal behavior experiments with and without CAPS, showing an effect of reducing CO2 concentration by 30% and increasing mice locomotor activity by 53%. CAPS is expected to evolve into robust and comprehensive air purification schemes through the networked integration of plural internal and external environments.

Abstract Tu044: Cardiac Mitochondrial Dysfunction Induces Region-Specific Mitochondrial Stress Response In The Brain To Adapt Neuronal Changes

Background: The hippocampus and cortex are susceptible to changes in blood supply, metabolites, and oxygenation. However, how disrupted cardiac function affects these critical areas of the brain, leading to the cognitive and neurological consequences of heart failure, remains unclear. Hypothesis: We hypothesize that disrupted cardiac function cross-talks with the brain by inducing region-specific mitochondrial stress responses, leading to adaptive changes. Methods: We utilized cardiac-specific LonP1 knockout (LonP1cKO) mice to induce heart failure within 21 days of birth. Alongside cre- control mice, we assessed cerebral blood flow using Laser speckle contrast imaging, locomotor activity through a comprehensive laboratory animal monitoring system (CLAMS), and gene expression profiles in the hippocampus and cortex by RT-PCR. Student’s ‘t’ test determined statistical significance with a p-value<0.05. Results: At 21 days, LonP1cKO mice demonstrated a significant (p<0.0001) reduction in cerebral blood flow (587.1±33.68, n=7) compared to the control (1034±31.26, n=5). Additionally, there were notable decreases in both X and Y-axis ambulatory and total locomotor activities in LonP1cKO mice [XAMB (100.3±6.6 vs 224±13.6 n=16), YAMB) (67.9±4.7 vs 150±8.5 n=16), XTOT (351.8±18.1 vs 534.4±26.3 n=16) and YTOT (190.7±9.6 vs 354.9±17.07 n=16). RT-PCR analysis revealed significant upregulation of genes related to hypoxia and cellular stress (Hif1a, FGf2, Atf6), mitochondrial biogenesis (mtDNA, Tfam, mt-COI, mt-COII), mitochondrial stress response proteases (LonP1, Afg3l2, Spg7, Yme1l1), and downregulation in neurotrophic factors (Bdnf, Ngf, Gfap) in the hippocampus and cortex. Conclusion: The study highlights that cardiac dysfunction in LonP1cKO mice leads to mitochondrial and cellular stress response in the brain to adapt neuronal changes, suggesting a critical link between cardiac health and brain function regulated through mitochondrial stress response pathways.

Depression-reminiscent Behavior Induced by Chronic Unpredictable Mild Stress Paradigm in Mice Substantially Abrogated by Diosmin

Background: Diosmin has already been described and documented to be neuroprotective, antioxidant and anti-inflammatory. It may possess or hold depressionalleviating activity. Therefore, the purpose of the current research protocol is to investigate the depression-relieving proficiency of diosmin in stressed and unstressed mice. Methods: Male mice (Swiss albino) were imperiled to an unpredictable chronic stress paradigm every day for three sequential weeks, and depression-resembling behavioral despair was induced. Imipramine 15 mg/kg and diosmin (25, 50 and 100 mg/kg) were dispensed for 21 successive days to discrete groups of stressed and unstressed mice. Results: Both diosmin (100 mg/kg) and 15 mg/kg imipramine administration for 3 consecutive weeks substantially or significantly diminished the immobility period of mice imperiled to stress in comparison to stressed mice gauzed with the vehicle. Diosmin (25, 50 and 100 mg/kg) and imipramine considerably reinstated the diminished sucrose proclivity (sucrose preference percentage; %) in stressed mice, demonstrating their considerable or substantial depression-relieving effects. The locomotor activities of mice were not considerably altered by these drugs. Antidepressant-like activity of diosmin for immobility periods and preference for sucrose was observed to be analogous to imipramine. Diosmin (100 mg/kg) and imipramine substantially quashed CUMS- persuaded escalation of plasma corticosterone and nitrite levels, malondialdehyde levels and MAO-A activity in the brain of stressed mice. Both drugs also substantially reversed CUMS-prompted reduction in catalase activity and brain glutathione levels. Conclusion: Accordingly, diosmin revealed significant anti-depressive activity in mice imperiled to chronic mild unpredictable stress paradigm conceivably via mitigation of nitrosative and oxidative stress, reticence of brain MAO-A action, and sink drop of plasma corticosterone degrees.

Extracts of Prunella vulgaris Enhanced Pentobarbital-Induced Sleeping Behavior in Mice Potentially via Adenosine A2A Receptor Activity.

The increasing prevalence of sleep dysregulation cases has prompted the search for effective and safe sleep-enhancing agents. Numerous medications used in the treatment of sleep disorders function by enhancing γ-aminobutyric acid neurotransmitter activity. Unfortunately, these substances may induce significant adverse effects in chronic users, such as dependence and motor behavior impairments. Consequently, there is a growing interest in exploring therapeutic sleep-enhancing agents derived from natural sources, with the anticipation of causing less severe side effects. Prunella vulgaris (PV), a perennial plant indigenous to South Korea, exhibits various pharmacological effects, likely attributed to its chemical composition. Rosmarinic acid, one of its components, has previously demonstrated sleep-potentiating properties, suggesting the potential for PV to exhibit similar pharmacological effects. This study aims to investigate the potential effects of repeated administration of PV extract on the sleep behavior, brainwave activity, sleep-wake cycle, and physiological behavior of mice. Findings indicate that PV extracts exhibit sleep-enhancing effects in mice, characterized by prolonged sleep duration and a reduced onset time of pentobarbital-induced sleep. However, PV extracts only reduced alpha wave powers, with minor alterations in wakefulness and rapid-eye-movement sleep duration. In contrast to diazepam, PV extracts lack adverse effects on locomotor activity, motor coordination, or anxiety in mice. Receptor-binding assay and caffeine treatment support the potential involvement of adenosine A2A receptors in the effects of PV, suggesting distinct mechanisms of action compared to diazepam, despite both exhibiting sleep-altering effects. Overall, our results suggest that PV holds promise as a potential source of sleep-aiding agents.

Kisspeptins centrally modulate food intake and locomotor activity in mice independently of gonadal steroids in a sexually dimorphic manner.

Kisspeptins are essential regulators of the reproductive axis, with capacity to potently activate gonadotropin-releasing hormoneneurons, acting also as central conduits for the metabolic regulation of fertility. Recent evidence suggests that kisspeptins per se may also modulate several metabolic parameters, including body weight, food intake or energy expenditure, but their actual roles and site(s) of action remain unclear. We present herein a series of studies addressing the metabolic effects of central and peripheral administration of kisspeptin-10 (Kp-10; 1 nmol and 3 nmol daily, respectively) for 11 days in mice of both sexes. To assess direct metabolic actions of Kp-10 versus those derived indirectly from its capacity to modulate gonadal hormone secretion, kisspeptin effects were tested in adult male and female mice gonadectomized and supplemented with fixed, physiological doses of testosterone or 17β-estradiol, respectively. Central administration of Kp-10 decreased food intake in male mice, especially during the dark phase (~50%), which was accompanied by a reduction in total and nocturnal energy expenditure (~16%) and locomotor activity (~70%). In contrast, opposite patterns were detected in female mice, with an increase in total and nocturnal locomotor activity (>65%), despite no changes in food intake or energy expenditure. These changes were independent of body weight, as no differences were detected in mice of both sexes at the end of Kp-10 treatments. Peripheral administration of Kp-10 failed to alter any of the metabolic parameters analyzed, except for a decrease in locomotor activity in male mice and a subtle increase in 24 h food intake in female mice, denoting a predominant central role of kisspeptins in the control of energy metabolism. Finally, glucose tolerance and insulin sensitivity were not significantly affected by central or peripheral treatment with Kp-10. In conclusion, our data reveal a potential role of kisspeptins in the control of key metabolic parameters, including food intake, energy expenditure and locomotor activity, with a preferential action at central level, which is sex steroid-independent but sexually dimorphic.

Effects of Selective and Mixed-Action Kappa and Delta Opioid Receptor Agonists on Pain-Related Behavioral Depression in Mice.

We recently developed a series of nalfurafine analogs (TK10, TK33, and TK35) that may serve as non-addictive candidate analgesics. These compounds are mixed-action agonists at the kappa and delta opioid receptors (KOR and DOR, respectively) and produce antinociception in a mouse warm-water tail-immersion test while failing to produce typical mu opioid receptor (MOR)-mediated side effects. The warm-water tail-immersion test is an assay of pain-stimulated behavior vulnerable to false-positive analgesic-like effects by drugs that produce motor impairment. Accordingly, this study evaluated TK10, TK33, and TK35 in a recently validated assay of pain-related behavioral depression in mice that are less vulnerable to false-positive effects. For comparison, we also evaluated the effects of the MOR agonist/analgesic hydrocodone (positive control), the neurokinin 1 receptor (NK1R) antagonist aprepitant (negative control), nalfurafine as a selective KOR agonist, SNC80 as a selective DOR agonist, and a nalfurafine/SNC80 mixture. Intraperitoneal injection of dilute lactic acid (IP lactic acid) served as a noxious stimulus to depress vertical and horizontal locomotor activity in male and female ICR mice. IP lactic acid-induced locomotor depression was alleviated by hydrocodone but not by aprepitant, nalfurafine, SNC80, the nalfurafine/SNC80 mixture, or the KOR/DOR agonists. These results suggest that caution is warranted in advancing mixed-action KOR/DOR agonists as candidate analgesics.

Combinatorial therapy with sub-effective Ro25-6981 and ZL006 ameliorates depressive-like behavior in single or combined stressed male mice

Major depression is a severe neuropsychiatric disorder that poses a significant challenge to health. However, development of an effective therapy for the disease has long been difficult. Here, we investigate the efficacy of a novel combinatorial treatment employing sub-effective doses of Ro25-6981, an antagonist targeting GluN2B-containing NMDA receptors, in conjunction with ZL006, an inhibitor of the PSD95/nNOS, on mouse models of depression. We employed social isolation, chronic restraint stress, or a combination of both to establish a depressed mouse model. Treatment with the drug combination reduced depressive-like behaviors without affecting locomotor activity in mice subjected to social isolation or chronic restraint stress. Furthermore, the combination therapy ameliorated depressive-like behaviors induced by combined stress of chronic restraint followed by social isolation. Mechanistic studies revealed that the combined treatment downregulated the hippocampal nitric oxide level. However, the therapeutic benefits of this combination were negated by the activation of NMDA receptors with a low dose of NMDA or by increasing nitric oxide levels with l-arginine. Moreover, the combinatorial treatment had negligible effects on object memory and contextual fear memory. Our data establish a combined therapy paradigm, providing a potential strategy targeting major depression.

The Discovery of Novel α2a Adrenergic Receptor Agonists Only Coupling to Gαi/O Proteins by Virtual Screening.

Most α2-AR agonists derived from dexmedetomidine have few structural differences between them and have no selectivity for α2A/2B-AR or Gi/Gs, which can lead to side effects in drugs. To obtain novel and potent α2A-AR agonists, we performed virtual screening for human α2A-AR and α2B-AR to find α2A-AR agonists with higher selectivity. Compound P300-2342 and its three analogs significantly decreased the locomotor activity of mice (p < 0.05). Furthermore, P300-2342 and its three analogs inhibited the binding of [3H] Rauwolscine with IC50 values of 7.72 ± 0.76 and 12.23 ± 0.11 μM, respectively, to α2A-AR and α2B-AR. In α2A-AR-HEK293 cells, P300-2342 decreased forskolin-stimulated cAMP production without increasing cAMP production, which indicated that P300-2342 activated α2A-AR with coupling to the Gαi/o pathway but without Gαs coupling. P300-2342 exhibited no agonist but slight antagonist activities in α2B-AR. Similar results were obtained for the analogs of P300-2342. The docking results showed that P300-2342 formed π-hydrogen bonds with Y394, V114 in α2A-AR, and V93 in α2B-AR. Three analogs of P300-2342 formed several π-hydrogen bonds with V114, Y196, F390 in α2A-AR, and V93 in α2B-AR. We believe that these molecules can serve as leads for the further optimization of α2A-AR agonists with potentially few side effects.

5-hydroxytryptamine 2C/1A receptors modulate the biphasic dose response of the head twitch response and locomotor activity induced by DOM in mice.

The phenylalkylamine hallucinogen (-)-2,5-dimethoxy-4-methylamphetamine (DOM) exhibits an inverted U-shaped dose-response curve for both head twitch response (HTR) and locomotor activity in mice. Accumulated studies suggest that HTR and locomotor hyperactivity induced by DOM are mainly caused by the activation of serotonin 5-hydroxytryptamine 2A receptor (5-HT2A receptor). However, the mechanisms underlying the biphasic dose response of HTR and locomotor activity induced by DOM, particularly at high doses, remain unclear. The primary objective of this study is to investigate the modulation of 5-HT2A/2C/1A receptors in HTR and locomotor activity, while also exploring the potential receptor mechanisms underlying the biphasic dose response of DOM. In this study, we employed pharmacological methods to identify the specific 5-HT receptor subtypes responsible for mediating the biphasic dose-response effects of DOM on HTR and locomotor activity in C57BL/6J mice. The 5-HT2A receptor selective antagonist (R)-[2,3-di(methoxy)phenyl]-[1-[2-(4-fluorophenyl)ethyl]piperidin-4-yl]methanol (M100907) (500µg/kg, i.p.) fully blocked the HTR at every dose of DOM (0.615-10mg/kg, i.p.) in C57BL/6J mice. M100907 (50µg/kg, i.p.) decreased the locomotor hyperactivity induced by a low dose of DOM (0.625, 1.25mg/kg, i.p.), but had no effect on the locomotor hypoactivity induced by a high dose of DOM (10mg/kg) in C57BL/6J mice. The 5-HT2C antagonist 6-chloro-5-methyl-1-[(2-[2-methylpyrid-3yloxy]pyrid-5yl)carbamoyl]indoline (SB242084) (0.3, 1mg/kg, i.p.) reduced the HTR induced by a dose of 2.5mg/kg DOM, but did not affect the response to other doses. SB242084 (1mg/kg, i.p.) significantly increased the locomotor activity induced by DOM (0.615-10mg/kg, i.p.) in mice. The 5-HT1A antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]N-(2-pyridinyl) cyclohexane carboxamide maleate (WAY100635) (1mg/kg, i.p.) increased both HTR and locomotor activity induced by DOM in mice. The 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (1mg/kg, i.p.) significantly reduced both the HTR and locomotor activity induced by DOM in mice. Additionally, pretreatment with the Gαi/o inhibitor PTX (0.25µg/mouse, i.c.v.) enhanced the HTR induced by DOM and attenuated the effect of DOM on locomotor activity in mice. Receptor subtypes 5-HT2C and 5-HT1A are implicated in the inverted U-shaped dose-response curves of HTR and locomotor activity induced by DOM in mice. The biphasic dose-response function of HTR and locomotor activity induced by DOM has different mechanisms in mice.