Dopamine and Noradrenaline in the Brain; Overlapping or Dissociate Functions?

Microbiota-gut-brain axis: Natural antidepressants molecular mechanism

BACKGROUND

Major depressive disorder (MDD) is a severe mental health condition characterized by persistent depression, impaired cognition, and reduced activity. Increasing evidence suggests that gut microbiota (GM) imbalance is closely linked to the emergence and advancement of MDD, highlighting the potential significance of regulating the "Microbiota-Gut-Brain" (MGB) axis to impact the development of MDD. Natural products (NPs), characterized by broad biological activities, low toxicity, and multi-target characteristics, offer unique advantages in antidepressant treatment by regulating MGB axis.

PURPOSE

This review was aimed to explore the intricate relationship between the GM and the brain, as well as host responses, and investigated the mechanisms underlying the MGB axis in MDD development. It also explored the pharmacological mechanisms by which NPs modulate MGB axis to exert antidepressant effects and addressed current research limitations. Additionally, it proposed new strategies for future preclinical and clinical applications in the MDD domain.

METHODS

To study the effects and mechanism by which NPs exert antidepressant effects through mediating the MGB axis, data were collected from Web of Science, PubMed, ScienceDirect from initial establishment to March 2024. NPs were classified and summarized by their mechanisms of action.

RESULTS

NPs, such as flavonoids,alkaloids,polysaccharides,saponins, terpenoids, can treat MDD by regulating the MGB axis. Its mechanism includes balancing GM, regulating metabolites and neurotransmitters such as SCAFs, 5-HT, BDNF, inhibiting neuroinflammation, improving neural plasticity, and increasing neurogenesis.

CONCLUSIONS

NPs display good antidepressant effects, and have potential value for clinical application in the prevention and treatment of MDD by regulating the MGB axis. However, in-depth study of the mechanisms by which antidepressant medications affect MGB axis will also require considerable effort in clinical and preclinical research, which is essential for the development of effective antidepressant treatments.

Hypocretin-1 receptor antagonism improves inhibitory control during the Go/No-Go task in highly motivated, impulsive male mice

RATIONALE

Motivation and inhibitory control are dominantly regulated by the dopaminergic (DA) and noradrenergic (NA) systems, respectively. Hypothalamic hypocretin (orexin) neurons provide afferent inputs to DA and NA nuclei and hypocretin-1 receptors (HcrtR1) are implicated in reward and addiction. However, the role of the HcrtR1 in inhibitory control is not well understood.

OBJECTIVES

To determine the effects of HcrtR1 antagonism and motivational state in inhibitory control using the go/no-go task in mice.

METHODS

n = 23 male C57Bl/6JArc mice were trained in a go/no-go task. Decision tree dendrogram analysis of training data identified more and less impulsive clusters of animals. A HcrtR1 antagonist (BI001, 12.5 mg/kg, per os) or vehicle were then administered 30 min before go/no-go testing, once daily for 5 days, under high (food-restricted) and low (free-feeding) motivational states in a latin-square crossover design. Compound exposure levels were assessed in a satellite group of animals.

RESULTS

HcrtR1 antagonism increased go accuracy and decreased no-go accuracy in free-feeding animals overall, whereas it decreased go accuracy and increased no-go accuracy only in more impulsive, food restricted mice. HcrtR1 antagonism also showed differential effects in premature responding, which was increased in response to the antagonist in free-feeding, less impulsive animals, and decreased in food restricted, more impulsive animals. HcrtR1 receptor occupancy by BI001 was estimated at ~ 66% during the task.

CONCLUSIONS

These data indicate that hypocretin signalling plays roles in goal-directed behaviour and inhibitory control in a motivational state-dependant manner. While likely not useful in all settings, HcrtR1 antagonism may be beneficial in improving inhibitory control in impulsive subpopulations.

Simulating combined monoaminergic depletions in a PD animal model through a bio-constrained differential equations system

Introduction

Historically, Parkinson's Disease (PD) research has focused on the dysfunction of dopamine-producing cells in the substantia nigra pars compacta, which is linked to motor regulation in the basal ganglia. Therapies have mainly aimed at restoring dopamine (DA) levels, showing effectiveness but variable outcomes and side effects. Recent evidence indicates that PD complexity implicates disruptions in DA, noradrenaline (NA), and serotonin (5-HT) systems, which may underlie the variations in therapy effects.

Methods

We present a system-level bio-constrained computational model that comprehensively investigates the dynamic interactions between these neurotransmitter systems. The model was designed to replicate experimental data demonstrating the impact of NA and 5-HT depletion in a PD animal model, providing insights into the causal relationships between basal ganglia regions and neuromodulator release areas.

Results

The model successfully replicates experimental data and generates predictions regarding changes in unexplored brain regions, suggesting avenues for further investigation. It highlights the potential efficacy of alternative treatments targeting the locus coeruleus and dorsal raphe nucleus, though these preliminary findings require further validation. Sensitivity analysis identifies critical model parameters, offering insights into key factors influencing brain area activity. A stability analysis underscores the robustness of our mathematical formulation, bolstering the model validity.

Discussion

Our holistic approach emphasizes that PD is a multifactorial disorder and opens promising avenues for early diagnostic tools that harness the intricate interactions among monoaminergic systems. Investigating NA and 5-HT systems alongside the DA system may yield more effective, subtype-specific therapies. The exploration of multisystem dysregulation in PD is poised to revolutionize our understanding and management of this complex neurodegenerative disorder.

The Locus Coeruleus in Chronic Pain

Pain perception is the consequence of a complex interplay between activation and inhibition. Noradrenergic pain modulation inhibits nociceptive transmission and pain perception. The main source of norepinephrine (NE) in the central nervous system is the Locus Coeruleus (LC), a small but complex cluster of cells in the pons. The aim of this study is to review the literature on the LC-NE inhibitory system, its influence on chronic pain pathways and its frequent comorbidities. The literature research showed that pain perception is the consequence of nociceptive and environmental processing and is modulated by the LC-NE system. If perpetuated in time, nociceptive inputs can generate neuroplastic changes in the central nervous system that reduce the inhibitory effects of the LC-NE complex and facilitate the development of chronic pain and frequent comorbidities, such as anxiety, depression or sleeping disturbances. The exact mechanisms involved in the LC functional shift remain unknown, but there is some evidence that they occur through plastic changes in the medial and lateral pathways and their brain projections. Additionally, there are other influencing factors, like developmental issues, neuroinflammatory glial changes, NE receptor affinity and changes in LC neuronal firing rates.

To update or to create? The influence of novelty and prior knowledge on memory networks

Schemas are foundational mental structures shaped by experience. They influence behaviour, guide the encoding of new memories and are shaped by associated information. The adaptability of memory schemas facilitates the integration of new information that aligns with existing knowledge structures. First, we discuss how novel information consistent with an existing schema can be swiftly assimilated when presented. This cognitive updating is facilitated by the interaction between the hippocampus and the prefrontal cortex. Second, when novel information is inconsistent with the schema, it likely engages the hippocampus to encode the information as part of an episodic memory trace. Third, novelty may enhance hippocampal dopamine through either the locus coeruleus or ventral tegmental area pathways, with the pathway involved potentially depending on the type of novelty encountered. We propose a gradient theory of schema and novelty to elucidate the neural processes by which schema updating or novel memory traces are formed. It is likely that experiences vary along a familiarity-novelty continuum, and the degree to which new experiences are increasingly novel will guide whether memory for a new experience either integrates into an existing schema or prompts the creation of a new cognitive framework. This article is part of the theme issue 'Long-term potentiation: 50 years on'.

Effects of voluntary exercise and electrical muscle stimulation on reaction time in the Go/No-Go task

INTRODUCTION

Acute exercise improves cognitive performance. However, it remains unclear what triggers cognitive improvement. Electrical muscle stimulation (EMS) facilitates the examination of physiological changes derived from peripheral muscle contraction during exercise. Thus, we compared the effects of EMS and voluntary exercise at low- or moderate-intensity on reaction time (RT) in a cognitive task to understand the contribution of central and peripheral physiological factors to RT improvement.

METHODS

Twenty-four young, healthy male participants performed a Go/No-Go task before and after EMS/exercise. In the EMS condition, EMS was applied to the lower limb muscles. In the low-intensity exercise condition, the participants cycled an ergometer while maintaining their heart rate (HR) at the similar level during EMS. In the moderate-intensity exercise condition, exercise intensity corresponded to ratings of perceived exertion of 13/20. The natural log-transformed root mean square of successive differences between adjacent inter-beat (R-R) intervals (LnRMSSD), which predominantly reflects parasympathetic HR modulation, was calculated before and during EMS/exercise.

RESULTS

RT improved following moderate-intensity exercise (p = 0.002, Cohen' d = 0.694), but not following EMS (p = 0.107, Cohen' d = 0.342) and low-intensity exercise (p = 0.076, Cohen' d = 0.380). Repeated measures correlation analysis revealed that RT was correlated with LnRMSSD (Rrm(23) = 0.599, p = 0.002) in the moderate-intensity exercise condition.

CONCLUSION

These findings suggest that the amount of central neural activity and exercise pressor reflex may be crucial for RT improvement. RT improvement following moderate-intensity exercise may, at least partly, be associated with enhanced sympathetic nervous system activity.

A combination treatment based on drug repurposing demonstrates mutation-agnostic efficacy in pre-clinical retinopathy models

Inherited retinopathies are devastating diseases that in most cases lack treatment options. Disease-modifying therapies that mitigate pathophysiology regardless of the underlying genetic lesion are desirable due to the diversity of mutations found in such diseases. We tested a systems pharmacology-based strategy that suppresses intracellular cAMP and Ca2+ activity via G protein-coupled receptor (GPCR) modulation using tamsulosin, metoprolol, and bromocriptine coadministration. The treatment improves cone photoreceptor function and slows degeneration in Pde6βrd10 and RhoP23H/WT retinitis pigmentosa mice. Cone degeneration is modestly mitigated after a 7-month-long drug infusion in PDE6A-/- dogs. The treatment also improves rod pathway function in an Rpe65-/- mouse model of Leber congenital amaurosis but does not protect from cone degeneration. RNA-sequencing analyses indicate improved metabolic function in drug-treated Rpe65-/- and rd10 mice. Our data show that catecholaminergic GPCR drug combinations that modify second messenger levels via multiple receptor actions provide a potential disease-modifying therapy against retinal degeneration.

Exploring the Therapeutic Potential of Terpenoids for Depression and Anxiety

This review focus on the terpenoids as potential therapeutic agents for depression and anxiety disorders, which naturally found in a variety of plants and exhibit a wide range of biological activities. Among the terpenoids discussed in this review are α-pinene, β-caryophyllene, α-phellandrene, limonene, β-linalool, 1, 8-cineole, β-pinene, caryophyllene oxide, p-cymene, and eugenol. All of these compounds have been studied extensively regarding their pharmacological properties, such as neuroprotective effect, anti-inflammation, antibacterial, regulation of neurotransmitters and antioxidant effect. Preclinical evidence are reviewed to highlight their diverse mechanisms of action and therapeutic potential to support antidepressant and anxiolytic properties. Additionally, challenges and future directions are also discussed to emphasize therapeutic utility of terpenoids for mental health disorders. Overall, this review provides a promising role of terpenoids as novel therapeutic agents for depression and anxiety, with potential implications for the development of more effective and well-tolerated treatments in the field of psychopharmacology.

A biphasic response to blueberry supplementation on depressive symptoms in emerging adults: a double-blind randomized controlled trial

PURPOSE

The aim of the present study was to examine the acute and chronic effects of wild blueberry supplementation on mood, executive function, and serum biomarkers of neuroplasticity, inflammation, and oxidative stress in emerging adults with moderate-to-severe depressive symptoms.

METHODS

In this double-blind trial, 60 emerging adults (Mage = 20.0 years, 32% male) with self-reported depressive symptoms were randomly assigned to receive a single blueberry drink (acute phase), followed by 6 weeks of daily blueberry supplementation (chronic phase), or a matched placebo drink. The primary outcome was Beck Depression Inventory-II (BDI-II) scores at 6-week follow-up. Further measures included momentary affect (PANAS-X) and accuracy on an executive function task. The data were analyzed using ANCOVAs adjusted for baseline values, sex, and habitual fruit and vegetable intake. Estimated marginal means were calculated to compare the treatment arms.

RESULTS

The blueberry drink significantly improved positive affect (p = 0.026) and executive function (p = 0.025) at 2 h post-ingestion, with change scores being positively correlated in the blueberry group (r = 0.424, p = 0.017). However, after six weeks of supplementation the reduction in BDI-II scores was greater in the placebo group by 5.8 points (95% CI: 0.8-10.7, p = 0.023). Generalized anxiety and anhedonia also decreased significantly more in the placebo group. No significant differences were found for any of the biomarkers.

CONCLUSIONS

Six weeks of wild blueberry supplementation were inferior to placebo in reducing depressive symptoms. Nevertheless, the correlated improvements in positive affect and executive function after a single dose of blueberries point to a beneficial, albeit transient, psychological effect. These contrasting results suggest a biphasic, hormetic-like response that warrants further investigation.

TRIAL REGISTRATION

NCT04647019, dated 30 November, 2020.

A Computational Model for the Simulation of Prepulse Inhibition and Its Modulation by Cortical and Subcortical Units

The sensorimotor gating is a nervous system function that modulates the acoustic startle response (ASR). Prepulse inhibition (PPI) phenomenon is an operational measure of sensorimotor gating, defined as the reduction of ASR when a high intensity sound (pulse) is preceded in milliseconds by a weaker stimulus (prepulse). Brainstem nuclei are associated with the mediation of ASR and PPI, whereas cortical and subcortical regions are associated with their modulation. However, it is still unclear how the modulatory units can influence PPI. In the present work, we developed a computational model of a neural circuit involved in the mediation (brainstem units) and modulation (cortical and subcortical units) of ASR and PPI. The activities of all units were modeled by the leaky-integrator formalism for neural population. The model reproduces basic features of PPI observed in experiments, such as the effects of changes in interstimulus interval, prepulse intensity, and habituation of ASR. The simulation of GABAergic and dopaminergic drugs impaired PPI by their effects over subcortical units activity. The results show that subcortical units constitute a central hub for PPI modulation. The presented computational model offers a valuable tool to investigate the neurobiology associated with disorder-related impairments in PPI.

Functionality of arousal-regulating brain circuitry at rest predicts human cognitive abilities

Arousal state is regulated by subcortical neuromodulatory nuclei, such as locus coeruleus, which send wide-reaching projections to cortex. Whether higher-order cortical regions have the capacity to recruit neuromodulatory systems to aid cognition is unclear. Here, we hypothesized that select cortical regions activate the arousal system, which, in turn, modulates large-scale brain activity, creating a functional circuit predicting cognitive ability. We utilized the Human Connectome Project 7T functional magnetic resonance imaging dataset (n = 149), acquired at rest with simultaneous eye tracking, along with extensive cognitive assessment for each subject. First, we discovered select frontoparietal cortical regions that drive large-scale spontaneous brain activity specifically via engaging the arousal system. Second, we show that the functionality of the arousal circuit driven by bilateral posterior cingulate cortex (associated with the default mode network) predicts subjects' cognitive abilities. This suggests that a cortical region that is typically associated with self-referential processing supports cognition by regulating the arousal system.

Trigeminal nerve direct current stimulation causes sustained increase in neural activity in the rat hippocampus

BACKGROUND

Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation method that can modulate many brain functions including learning and memory. Recent evidence suggests that tDCS memory effects may be caused by co-stimulation of scalp nerves such as the trigeminal nerve (TN), and not the electric field in the brain. The TN gives input to brainstem nuclei, including the locus coeruleus that controls noradrenaline release across brain regions, including hippocampus. However, the effects of TN direct current stimulation (TN-DCS) are currently not well understood.

HYPOTHESIS

In this study we tested the hypothesis that stimulation of the trigeminal nerve with direct current manipulates hippocampal activity via an LC pathway.

METHODS

We recorded neural activity in rat hippocampus using multichannel silicon probes. We applied 3 min of 0.25 mA or 1 mA TN-DCS, monitored hippocampal activity for up to 1 h and calculated spikes-rate and spike-field coherence metrics. Subcutaneous injections of xylocaine were used to block TN, while intraperitoneal and intracerebral injection of clonidine were used to block the LC pathway.

RESULTS

We found that 1 mA TN-DCS caused a significant increase in hippocampal spike-rate lasting 45 min in addition to significant changes in spike-field coherence, while 0.25 mA TN-DCS did not. TN blockage prevented spike-rate increases, confirming effects were not caused by the electric field in the brain. When 1 mA TN-DCS was delivered during clonidine blockage no increase in spike-rate was observed, suggesting an important role for the LC-noradrenergic pathway.

CONCLUSION

These results support our hypothesis and provide a neural basis to understand the tDCS TN co-stimulation mechanism. TN-DCS emerges as an important tool to potentially modulate learning and memory.

Expression pattern of nicotinic acetylcholine receptor subunit transcripts in neurons and astrocytes in the ventral tegmental area and locus coeruleus

Acetylcholine is the endogenous agonist for the neuronal nicotinic acetylcholine receptor (nAChR) system, which is involved in attention, memory, affective behaviours and substance use disorders. Brain nAChRs are highly diverse with 11 different subunits that can form multiple receptor subtypes, each with distinct receptor and pharmacological properties. Different neuronal cell types can also express different nAChR subtypes, resulting in highly complex cholinergic signalling. Identifying which nAChR subunit transcripts are expressed in cell types can provide an indication of which nAChR combinations are possible and which receptor subtypes may be most pharmacologically relevant to target. In addition to differences in expression across cell types, nAChRs also undergo changes in expression levels from adolescence to adulthood. In this study, we used fluorescent in situ hybridization to identify and quantify the expression of α4, α5, α6, β2 and β3 nAChR subunit transcripts in dopaminergic, GABAergic, glutamatergic and noradrenergic neurons and astrocytes in the ventral tegmental area (VTA) and locus coeruleus (LC) in adult and adolescent, male and female C57BL/6J mice. There were distinct differences in the pattern of nAChR subunit transcript expression between the two brain regions. LC noradrenergic neurons had high prevalence of α6, β2 and β3 expression, with very low expression of α4, suggesting the α6(non-α4)β2β3 receptor as a main subtype in these neurons. VTA astrocytes from adult mice showed greater prevalence of α5, α6, β2 and β3 transcript compared with adolescent mice. These data highlight the complex nAChR expression patterns across brain region and cell type.

Ongoing effects of preterm birth on the dopaminergic and noradrenergic pathways in the frontal cortex and hippocampus of guinea pigs

Children born preterm have an increased likelihood of developing neurobehavioral disorders such as attention-deficit hyperactivity disorder (ADHD) and anxiety. These disorders have a sex bias, with males having a higher incidence of ADHD, whereas anxiety disorder tends to be more prevalent in females. Both disorders are underpinned by imbalances to key neurotransmitter systems, with dopamine and noradrenaline in particular having major roles in attention regulation and stress modulation. Preterm birth disturbances to neurodevelopment may affect this neurotransmission in a sexually dimorphic manner. Time-mated guinea pig dams were allocated to deliver by preterm induction of labor (gestational age 62 [GA62]) or spontaneously at term (GA69). The resultant offspring were randomized to endpoints as neonates (24 h after term-equivalence age) or juveniles (corrected postnatal day 40, childhood equivalence). Relative mRNA expressions of key dopamine and noradrenaline pathway genes were examined in the frontal cortex and hippocampus and quantified with real-time PCR. Myelin basic protein and neuronal nuclei immunostaining were performed to characterize the impact of preterm birth. Within the frontal cortex, there were persisting reductions in the expression of dopaminergic pathway components that occurred in preterm males only. Conversely, preterm-born females had increased expression of key noradrenergic receptors and a reduction of the noradrenergic transporter within the hippocampus. This study demonstrated that preterm birth results in major changes in dopaminergic and noradrenergic receptor, transporter, and synthesis enzyme gene expression in a sex- and region-based manner that may contribute to the sex differences in susceptibility to neurobehavioral disorders. These findings highlight the need for the development of sex-based treatments for improving these conditions.

Using caffeine as a chemical means to induce flow states

Flow is an intrinsically rewarding state characterised by positive affect and total task absorption. Because cognitive and physical performance are optimal in flow, chemical means to facilitate this state are appealing. Caffeine, a non-selective adenosine receptor antagonist, has been emphasized as a potential flow-inducer. Thus, we review the psychological and biological effects of caffeine that, conceptually, enhance flow. Caffeine may facilitate flow through various effects, including: i) upregulation of dopamine D1/D2 receptor affinity in reward-associated brain areas, leading to greater energetic arousal and 'wanting'; ii) protection of dopaminergic neurons; iii) increases in norepinephrine release and alertness, which offset sleep-deprivation and hypoarousal; iv) heightening of parasympathetic high frequency heart rate variability, resulting in improved cortical stress appraisal, v) modification of striatal endocannabinoid-CB1 receptor-signalling, leading to enhanced stress tolerance; and vi) changes in brain network activity in favour of executive function and flow. We also discuss the application of caffeine to treat attention deficit hyperactivity disorder and caveats. We hope to inspire studies assessing the use of caffeine to induce flow.

Functionality of arousal-regulating brain circuitry at rest predicts human cognitive abilities

Arousal state is regulated by subcortical neuromodulatory nuclei, such as locus coeruleus, which send wide-reaching projections to cortex. Whether higher-order cortical regions have the capacity to recruit neuromodulatory systems to aid cognition is unclear. Here, we hypothesized that select cortical regions activate the arousal system, which in turn modulates large-scale brain activity, creating a functional circuit predicting cognitive ability. We utilized the Human Connectome Project 7T functional magnetic resonance imaging dataset (N=149), acquired at rest with simultaneous eye tracking, along with extensive cognitive assessment for each subject. First, we discovered select frontoparietal cortical regions that drive large-scale spontaneous brain activity specifically via engaging the arousal system. Second, we show that the functionality of the arousal circuit driven by bilateral posterior cingulate cortex (associated with the default mode network) predicts subjects' cognitive abilities. This suggests that a cortical region that is typically associated with self-referential processing supports cognition by regulating the arousal system.

Combined and sequential exposure to prenatal second hand smoke and postnatal maternal distress is associated with cingulo-opercular global efficiency and attention problems in school-age children

BACKGROUND

Prenatal exposure to secondhand (environmental) tobacco smoke (SHS) is associated with adverse neurodevelopmental outcomes, including altered functional activation of cognitive control brain circuitry and increased attention problems in children. Exposure to SHS is more common among Black youth who are also disproportionately exposed to socioeconomic disadvantage and concomitant maternal distress. We examine the combined effects of exposure to prenatal SHS and postnatal maternal distress on the global efficiency (GE) of the brain's cingulo-opercular (CO) and fronto-parietal control (FP) networks in childhood, as well as associated attention problems.

METHODS

Thirty-two children of non-smoking mothers followed in a prospective longitudinal birth cohort at the Columbia Center for Children's Environmental Health (CCCEH) completed magnetic resonance imaging (MRI) at ages 7-9 years old. GE scores were extracted from general connectivity data collected while children completed the Simon Spatial Incompatibility functional magnetic resonance imaging (fMRI) task. Prenatal SHS was measured using maternal urinary cotinine from the third trimester; postnatal maternal distress was assessed at child age 5 using the Psychiatric Epidemiology Research Interview (PERI-D). The Child Behavior Checklist (CBCL) measured Attention and Attention Deficit Hyperactivity Disorder (ADHD) problems at ages 7-9. Linear regressions examined the interaction between prenatal SHS and postnatal maternal distress on the GE of the CO or FP networks, as well as associations between exposure-related network alterations and attention problems. All models controlled for age, sex, maternal education at prenatal visit, race/ethnicity, global brain correlation, and mean head motion.

RESULTS

The prenatal SHS by postnatal maternal distress interaction term associated with the GE of the CO network (β = 0.673, Bu = 0.042, t(22) = 2.427, p = .024, D = 1.42, 95% CI [0.006, 0.079], but not the FP network (β = 0.138, Bu = 0.006, t(22) = 0.434, p = .668, 95% CI [-0.022, 0.033]). Higher GE of the CO network was associated with more attention problems (β = 0.472, Bu = 43.076, t(23) = 2.780, p = .011, D = 1.74, n = 31, 95% CI [11.024, 75.128], n = 31) and ADHD risk (β = 0.436, Bu = 21.961, t(29) = 2.567, p = .018, D = 1.81, 95% CI [4.219, 39.703], n = 30).

CONCLUSIONS

These preliminary findings suggest that sequential prenatal SHS exposure and postnatal maternal distress could alter the efficiency of the CO network and increase risk for downstream attention problems and ADHD. These findings are consistent with prior studies showing that prenatal SHS exposure is associated with altered function of brain regions that support cognitive control and with ADHD problems. Our model also identifies postnatal maternal distress as a significant moderator of this association. These data highlight the combined neurotoxic effects of exposure to prenatal SHS and postnatal maternal distress. Critically, such exposures are disproportionately distributed among youth from minoritized groups, pointing to potential pathways to known mental health disparities.

Does gut brain axis has an impact on Parkinson's disease (PD)?

Parkinson's Disease (PD) is becoming a growing global concern by being the second most prevalent disease next to Alzheimer's Disease (AD). Henceforth new exploration is needed in search of new aspects towards the disease mechanism and origin. Evidence from recent studies has clearly stated the role of Gut Microbiota (GM) in the maintenance of the brain and as a root cause of various diseases and disorders including other neurological conditions. In the case of PD, with an unknown etiology, the GM is said to have a larger impact on the disease pathophysiology. Although GM and its metabolites are crucial for maintaining the normal physiology of the host, it is an undeniable fact that there is an influence of GM in the pathophysiology of PD. As such the Enteroendocrine Cells (EECs) in the epithelium of the intestine are one of the significant regulators of the gut-brain axis and act as a communication mediator between the gut and the brain. The communication is established via the molecules of neuroendocrine which are said to have a crucial part in neurological diseases such as AD, PD, and other psychiatry-related disorders. This review is focused on understanding the proper role of GM and EECs in PD. Here, we also focus on some of the metabolites and compounds that can interact with the PD genes causing various dysfunctions in the cell and facilitating the disease conditions using bioinformatical tools. Various mechanisms concerning EECs and PD, their identification, the latest studies, and available current therapies have also been discussed.

The neuromodulatory role of dopamine in improved reaction time by acute cardiovascular exercise

Acute cardiovascular physical exercise improves cognitive performance, as evidenced by a reduction in reaction time (RT). However, the mechanistic understanding of how this occurs is elusive and has not been rigorously investigated in humans. Here, using positron emission tomography (PET) with [11 C]raclopride, in a multi-experiment study we investigated whether acute exercise releases endogenous dopamine (DA) in the brain. We hypothesized that acute exercise augments the brain DA system, and that RT improvement is correlated with this endogenous DA release. The PET study (Experiment 1: n = 16) demonstrated that acute physical exercise released endogenous DA, and that endogenous DA release was correlated with improvements in RT of the Go/No-Go task. Thereafter, using two electrical muscle stimulation (EMS) studies (Experiments 2 and 3: n = 18 and 22 respectively), we investigated what triggers RT improvement. The EMS studies indicated that EMS with moderate arm cranking improved RT, but RT was not improved following EMS alone or EMS combined with no load arm cranking. The novel mechanistic findings from these experiments are: (1) endogenous DA appears to be an important neuromodulator for RT improvement and (2) RT is only altered when exercise is associated with central signals from higher brain centres. Our findings explain how humans rapidly alter their behaviour using neuromodulatory systems and have significant implications for promotion of cognitive health. KEY POINTS: Acute cardiovascular exercise improves cognitive performance, as evidenced by a reduction in reaction time (RT). However, the mechanistic understanding of how this occurs is elusive and has not been rigorously investigated in humans. Using the neurochemical specificity of [11 C]raclopride positron emission tomography, we demonstrated that acute supine cycling released endogenous dopamine (DA), and that this release was correlated with improved RT. Additional electrical muscle stimulation studies demonstrated that peripherally driven muscle contractions (i.e. exercise) were insufficient to improve RT. The current study suggests that endogenous DA is an important neuromodulator for RT improvement, and that RT is only altered when exercise is associated with central signals from higher brain centres.

Biochemical characterization of chamomile essential oil: Antioxidant, antibacterial, anticancer and neuroprotective activity and potential treatment for Alzheimer's disease

Alzheimer's disease (AD) causes dementia among older adults, increasing the global burden of dementia. Therefore, this study investigates the potential neuroprotective, antioxidant, and anticancer effects of chamomile essential oil (CCO) in Alzheimer's disease. CCO's main volatile compounds (VOCs) were α-bisabolol, camazulene, and bisabolol oxide A, representing 81 % of all VOCs. CCO scavenged 93 % of DPPH free radicals and inhibited the pathogenic bacteria, i.e., Staphylococcus aureus and Salmonella typhi, besides reducing 89 % of brain cancer cell lines (U87). Eighty albino rats were randomized into four groups: standard control, Alzheimer's disease group caused by AlCl3, and treated groups. The results indicated that the mean value of tumor necrosis factor α (TNF-α), amyloid precursor protein (APP), amyloid beta (Aβ), caspase-3, & B-cell lymphoma 2 (Bcl-2) was significantly elevated due to the harmful effect of AlCl3; however, CCO downregulated these values, and this effect was attributed to the considerable volatile compounds and phenolic compounds content. Additionally, CCO rats showed a significant increment in noradrenergic (NE), dopaminergic (DO), and serotoninergic systems with relative increases of 50, 50, and 14 % compared to diseased rats. The brain histology of CCO-treated rats showed a significant reduction in neuronal degeneration and improved brain changes, and its histology was close to that of the control brain. The results indicated that CCO offers a new strategy that could be used as an antioxidant and neuroprotective agent for AD due to its considerable contents of antioxidants and anti-inflammatory compounds.

Subsecond Codetection of Dopamine and Estradiol at a Modified Sharkfin Waveform

17β-Estradiol (E2) is a ubiquitously expressed hormone that is active in a wide range of neuroprotective and regenerative roles throughout the brain. In particular, it is a well-known dopamine (DA) regulator and is responsible for modulating the expression of dopaminergic receptors and transporters. Recent studies point to E2 release occurring on a rapid time scale and having impacts on DA activity within seconds to minutes. As such, tools capable of monitoring the release of both E2 and DA in real time are essential for developing an accurate understanding of their interactive roles in neurotransmission and regulation. Currently, no analytical techniques capable of codetection of both analytes with high sensitivity, spatiotemporal resolution, extended monitoring, and minimal tissue damage exist. We describe a modified waveform using fast-scan cyclic voltammetry that is capable of low nanomolar detection of both DA and E2 on a subsecond time scale. Both analytes have limits of detection at or below 30 nM and high sensitivity: 11.31 ± 0.55 nA/μM for DA and 9.47 ± 0.36 nA/μM for E2. The waveform is validated in a tissue matrix, confirming its viability for measurement in a biologically relevant setting. This is the first method capable of codetection of fluctuations in DA and E2 with the temporal, spatial, and sensitivity requirements necessary for studying real-time neurochemical signaling.

Fear extinction rescuing effects of dopamine and L-DOPA in the ventromedial prefrontal cortex

The ventromedial prefrontal cortex (vmPFC; rodent infralimbic cortex (IL)), is posited to be an important locus of fear extinction-facilitating effects of the dopamine (DA) bio-precursor, L-DOPA, but this hypothesis remains to be formally tested. Here, in a model of impaired fear extinction (the 129S1/SvImJ inbred mouse strain; S1), we monitored extracellular DA dynamics via in vivo microdialysis in IL during fear extinction and following L-DOPA administration. Systemic L-DOPA caused sustained elevation of extracellular DA levels in IL and increased neuronal activation in a subpopulation of IL neurons. Systemic L-DOPA enabled extinction learning and promoted extinction retention at one but not ten days after training. Conversely, direct microinfusion of DA into IL produced long-term fear extinction (an effect that was insensitive to ɑ-/ß-adrenoreceptor antagonism). However, intra-IL delivery of a D1-like or D2 receptor agonist did not facilitate extinction. Using ex vivo multi-electrode array IL neuronal recordings, along with ex vivo quantification of immediate early genes and DA receptor signalling markers in mPFC, we found evidence of reduced DA-evoked mPFC network responses in S1 as compared with extinction-competent C57BL/6J mice that were partially driven by D1 receptor activation. Together, our data demonstrate that locally increasing DA in IL is sufficient to produce lasting rescue of impaired extinction. The finding that systemic L-DOPA increased IL DA levels, but had only transient effects on extinction, suggests L-DOPA failed to reach a threshold level of IL DA or produced opposing behavioural effects in other brain regions. Collectively, our findings provide further insight into the neural basis of the extinction-promoting effects of DA and L-DOPA in a clinically relevant animal model, with possible implications for therapeutically targeting the DA system in anxiety and trauma-related disorders.

The Anti-Apoptotic Effect of Ranolazine on Cerebral Protection during Cardiopulmonary Bypass and Carotid Artery Surgery

Background

We aimed to determine the usability of ranolazine (Rn) as a neuroprotective during cardiac surgeries and carotid artery interventions where cerebral blood flow is interrupted.

Methods

Female Wistar albino rats were used. The rats were divided into 4 groups of 8 rats each. The first group (Group 1) was the control group. Group 2 underwent ischemia induction but was not treated with Rn. Group 3 received 25 mg/kg/day and Group 4 50 mg/kg/day Rn intraperitoneally, starting 3 days before ischemia induction. Bilateral carotid arteries were explored and clamped simultaneously. Ischemia was induced for 15 minutes. After 72 hours, the experimental animals were sacrificed.

Results

Superoxide dismutase, alkaline phosphatase, and interleukin 6 levels were similar among the 4 groups. Acetylcholine esterase (Group 3: p = 0.007, Group 4: p = 0.002), tumor necrosis factor-alpha (Group 4: p = 0.01), and annexin V (Group 3: p = 0.001) levels were statistically significantly lower in the Rn-treated groups. Malondialdehyde (Group 3: p = 0.003, Group 4: p = 0.009), reduced glutathione (Group 4: p = 0.04), acid phosphatase (Group 3: p = 0.04), noradrenaline (Group 3: p = 0.01), and Bcl-2 (Group 4: p = 0.004) levels were significantly higher in the Rn-treated groups.

Conclusions

The results of this study demonstrated the antiapoptotic effect of Rn in a brain ischemia-reperfusion model of rats receiving Rn before the procedure.

Atomoxetine and reward size equally improve task engagement and perceptual decisions but differently affect movement execution

Our ability to engage and perform daily activities relies on balancing the associated benefits and costs. Rewards, as benefits, act as powerful motivators that help us stay focused for longer durations. The noradrenergic (NA) system is thought to play a significant role in optimizing our performance. Yet, the interplay between reward and the NA system in shaping performance remains unclear, particularly when actions are driven by external incentives (reward). To explore this interaction, we tested four female rhesus monkeys performing a sustained Go/NoGo task under two reward sizes (low/high) and three pharmacological conditions (saline and two doses of atomoxetine, a NA reuptake inhibitor: ATX-0.5 mg/kg and ATX-1 mg/kg). We found that increasing either reward or NA levels equally enhanced the animal's engagement in the task compared to low reward saline; the animals also responded faster and more consistently under these circumstances. Notably, we identified differences between reward size and ATX. When combined with ATX, high reward further reduced the occurrence of false alarms (i.e., incorrect go trials on distractors), implying that it helped further suppress impulsive responses. In addition, ATX (but not reward size) consistently increased movement duration dose-dependently, while high reward did not affect movement duration but decreased its variability. We conclude that noradrenaline and reward modulate performance, but their effects are not identical, suggesting differential underlying mechanisms. Reward might energize/invigorate decisions and action, while ATX might help regulate energy expenditure, depending on the context, through the NA system.

Trigeminal nerve direct current stimulation causes sustained increase in neural activity in the rat hippocampus

Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation method that can modulate many brain functions including learning and memory. Recent evidence suggests that tDCS memory effects may be caused by co-stimulation of scalp nerves such as the trigeminal nerve (TN), and not the electric field in the brain. The TN gives input to brainstem nuclei, including the locus coeruleus that controls noradrenaline release across brain regions, including hippocampus. However, the effects of TN direct current stimulation (TN-DCS) are currently not well understood. In this study we hypothesized that TN-DCS manipulates hippocampal activity via an LC-noradrenergic bottom-up pathway. We recorded neural activity in rat hippocampus using multichannel silicon probes. We applied 3 minutes of 0.25 mA or 1 mA TN-DCS, monitored hippocampal activity for up to 1 hour and calculated spikes-rate and spike-field coherence metrics. Subcutaneous injections of xylocaine were used to block TN and intraperitoneal injection of clonidine to block the LC pathway. We found that 1 mA TN-DCS caused a significant increase in hippocampal spike-rate lasting 45 minutes in addition to significant changes in spike-field coherence, while 0.25 mA TN-DCS did not. TN blockage prevented spike-rate increases, confirming effects were not caused by the electric field in the brain. When 1 mA TN-DCS was delivered during clonidine blockage no increase in spike-rate was observed, suggesting an important role for the LC-noradrenergic pathway. These results provide a neural basis to support a tDCS TN co-stimulation mechanism. TN-DCS emerges as an important tool to potentially modulate learning and memory.

Highlights

Trigeminal nerve direct current stimulation (TN-DCS) boosts hippocampal spike ratesTN-DCS alters spike-field coherence in theta and gamma bands across the hippocampus.Blockade experiments indicate that TN-DCS modulated hippocampal activity via the LC-noradrenergic pathway.TN-DCS emerges as a potential tool for memory manipulation.

Figure Graphic Abstract

Geraniol attenuates behavioral and neurochemical impairments by inhibitions of HPA-axis and oxido-inflammatory perturbations in mice exposed to post-traumatic stress disorder

Geraniol is an acyclic isoprenoid monoterpenoid analogue that has been shown to elicit neuroprotective functions, primarily through its ability to stimulate antioxidant and anti-inflammatory systems. An increase in inflammatory cytokines and oxidative stress exacerbate activation hypothalamic-pituitary-adrenal axis (HPA), leading to neurochemical dysfunction, which has important roles in the pathogenesis of post-traumatic disorder (PTSD), a mental health disorder characterized of post-trauma-induced intense fear. The aim of this study was to evaluate the anti-PTSD-like effects and underlying mechanisms of geraniol against single-prolonged-stress (SPS)-induced PTSD in mice. Following concomitant exposure to SPS (triple-paradigm traumatic events) and isolation for 7 days, mice (n = 9) were treated with geraniol (50 and 100 mg/kg, p.o.) or fluoxetine (10 mg/kg, p.o.) from days 8-21. Mice were assessed for behavioral changes. Neurochemical changes, inflammatory, oxido-nitrergic markers, adrenal weight, serum glucose and corticosterone concentrations were assayed. Geraniol inhibits SPS-induced anxiety- and depressive-like features as well as behavioral despair in the depression paradigms. SPS-induced locomotor and memory impairments were also abated by geraniol treatment similarly to fluoxetine. SPS-induced adrenal hypertrophy and increased blood glucose and corticosterone concentrations, were attenuated by the geraniol treatment. Elevated levels of TNF-α and IL-6, and malondialdehyde, nitrite, acetylcholinesterase enzyme were reduced by geraniol. Geraniol also increased glutathione, superoxide-dismutase, and catalase levels as well as dopamine, serotonin concentrations and GABAergic glutamic acid decarboxylase enzyme activity in the striatum, prefrontal cortex and hippocampus in the PTSD-mice relative to SPS control. In conclusion, geraniol attenuates behavioral impairments and neurochemical dysregulations by inhibitions of HPA-axis and oxido-inflammatory perturbations in mice exposed to PTSD.

Systemic perturbations in amino acids/amino acid derivatives and tryptophan pathway metabolites associated with murine influenza A virus infection

BACKGROUND

Influenza A virus (IAV) is the only influenza virus causing flu pandemics (i.e., global epidemics of flu disease). Influenza (the flu) is a highly contagious disease that can be deadly, especially in high-risk groups. Worldwide, these annual epidemics are estimated to result in about 3 to 5 million cases of severe illness and in about 290,000 to 650,000 respiratory deaths. We intend to reveal the effect of IAV infection on the host's metabolism, immune response, and neurotoxicity by using a mouse IAV infection model.

METHODS

51 metabolites of murine blood plasma (33 amino acids/amino acid derivatives (AADs) and 18 metabolites of the tryptophan pathway) were analyzed by using Ultra-High-Performance Liquid Chromatography-Mass Spectrometry with Electrospray Ionization at the acute (7 days post-infection (dpi)), resolution (14 dpi), and recovery (21 dpi) stages of the virus infection in comparison with controls.

RESULTS

Among the 33 biogenic amino acids/AADs, the levels of five amino acids/AADs (1-methylhistidine, 5-oxoproline, α-aminobutyric acid, glutamine, and taurine) increased by 7 dpi, whereas the levels of ten amino acids/AADs (4-hydroxyproline, alanine, arginine, asparagine, cysteine, citrulline, glycine, methionine, proline, and tyrosine) decreased. By 14 dpi, the levels of one AAD (3-methylhistidine) increased, whereas the levels of five amino acids/AADs (α-aminobutyric acid, aminoadipic acid, methionine, threonine, valine) decreased. Among the 18 metabolites from the tryptophan pathway, the levels of kynurenine, quinolinic acid, hydroxykynurenine increased by 7 dpi, whereas the levels of indole-3-acetic acid and nicotinamide riboside decreased.

CONCLUSIONS

Our data may facilitate understanding the molecular mechanisms of host responses to IAV infection and provide a basis for discovering potential new mechanistic, diagnostic, and prognostic biomarkers and therapeutic targets for IAV infection.

Measuring neuron-regulated immune cell physiology via the alpha-2 adrenergic receptor in an ex vivo murine spleen model

The communication between the nervous and immune systems plays a crucial role in regulating immune cell function and inflammatory responses. Sympathetic neurons, which innervate the spleen, have been implicated in modulating immune cell activity. The neurotransmitter norepinephrine (NE), released by sympathetic neurons, influences immune cell responses by binding to adrenergic receptors on their surface. The alpha-2 adrenergic receptor (α2AR), expressed predominantly on sympathetic neurons, has received attention due to its autoreceptor function and ability to modulate NE release. In this study, we used fast-scan cyclic voltammetry (FSCV) to provide the first subsecond measurements of NE released in the white pulp region of the spleen and validated it with yohimbine, a known antagonist of α2AR. For further application of FSCV in neuroimmunology, we investigated the extent to which subsecond NE from sympathetic neurons is important for immune cell physiology and cytokine production, focusing on tumor necrosis factor-alpha (TNF-α), interleukin-10 (IL-10), and interleukin-6 (IL-6). Our findings provide insights into the regulatory mechanisms underlying sympathetic-immune interactions and show the significance of using FSCV, a traditional neurochemistry technique, to study these neuroimmune mechanisms.

Synergistic photoactivation of VTA-catecholaminergic and BLA-glutamatergic projections induces long-term potentiation in the insular cortex

The presentation of novel stimuli induces a reliable dopamine release in the insular cortex (IC) from the ventral tegmental area (VTA). The novel stimuli could be associated with motivational and emotional signals induced by cortical glutamate release from the basolateral amygdala (BLA). Dopamine and glutamate are essential for acquiring and maintaining behavioral tasks, including visual and taste recognition memories. In this study, we hypothesize that the simultaneous activation of dopaminergic and glutamatergic projections to the neocortex can underlie synaptic plasticity. High-frequency stimulation of the BLA-IC circuit has demonstrated a reliable long-term potentiation (LTP), a widely acknowledged synaptic plasticity that underlies memory consolidation. Therefore, the concurrent optogenetic stimulation of the insula's glutamatergic and dopaminergic terminal fibers would induce reliable LTP. Our results confirmed that combined photostimulation of the VTA and BLA projections to the IC induces a slow-onset LTP. We also found that optogenetically-induced LTP in the IC relies on both glutamatergic NMDA receptors and dopaminergic D1/D5 receptors, suggesting that the combined effects of these neurotransmitters can trigger synaptic plasticity in the neocortex. Overall, our findings provide compelling evidence supporting the essential role of both dopaminergic and glutamatergic projections in modulating synaptic plasticity within the IC. Furthermore, our results suggest that the synergistic actions of these projections have a pivotal influence on the formation of motivational memories.

Knowledge mapping of the relationship between norepinephrine and memory: a bibliometric analysis

Introduction

Memory is a fundamental cognitive function for successful interactions with a complex environment. Norepinephrine (NE) is an essential component of catecholamine induced by emotional arousal, and numerous studies have demonstrated that NE is a key regulator in memory enhancement. We therefore conducted a bibliometric analysis to represent the knowledge pattern of the literature on the theme of NE-memory relationship.

Methods

The WOSCC database was selected to extract literature published during 2003-2022. The collected data of annual production, global cooperation, research structure and hotspots were analyzed and visualized.

Results

Our results showed that research on the links between NE and memory displayed a considerable development trend over the last two decades. The USA had a leading position in terms of scientific outputs and collaborations. Meanwhile, University of California Irvine contributed the most publications. Benno Roozendaal and James McGaugh were the most prolific authors in this field, and Neurobiology of Learning and Memory had the highest number of publications on this topic. The research emphasis has evolved from memory-related diseases and brain regions to neural mechanisms for different types of memory at neural circuit levels.

Conclusion

Our bibliometric analysis systematically analyzed the literature on the links between NE and memory from a bibliometric perspective. The demonstrated results of the knowledge mapping would provide valuable insights into the global research landscape.

Addictive drugs modify neurogenesis, synaptogenesis and synaptic plasticity to impair memory formation through neurotransmitter imbalances and signaling dysfunction

Drug abuse changes neurophysiological functions at multiple cellular and molecular levels in the addicted brain. Well-supported scientific evidence suggests that drugs negatively affect memory formation, decision-making and inhibition, and emotional and cognitive behaviors. The mesocorticolimbic brain regions are involved in reward-related learning and habitual drug-seeking/taking behaviors to develop physiological and psychological dependence on the drugs. This review highlights the importance of specific drug-induced chemical imbalances resulting in memory impairment through various neurotransmitter receptor-mediated signaling pathways. The mesocorticolimbic modifications in the expression levels of brain-derived neurotrophic factor (BDNF) and the cAMP-response element binding protein (CREB) impair reward-related memory formation following drug abuse. The contributions of protein kinases and microRNAs (miRNAs), along with the transcriptional and epigenetic regulation have also been considered in memory impairment underlying drug addiction. Overall, we integrate the research on various types of drug-induced memory impairment in distinguished brain regions and provide a comprehensive review with clinical implications addressing the upcoming studies.

A miniaturized nigrostriatal-like circuit regulating locomotor performance in a protochordate

To gain insight into the evolution of motor control systems at the origin of vertebrates, we have investigated higher-order motor circuitry in the protochordate Oikopleura dioica. We have identified a highly miniaturized circuit in Oikopleura with a projection from a single pair of dopaminergic neurons to a small set of synaptically coupled GABAergic neurons, which in turn exert a disinhibitory descending projection onto the locomotor central pattern generator. The circuit is reminiscent of the nigrostriatopallidal system in the vertebrate basal ganglia, in which disinhibitory circuits release specific movements under the modulatory control of dopamine. We demonstrate further that dopamine is required to optimize locomotor performance in Oikopleura, mirroring its role in vertebrates. A dopamine-regulated disinhibitory locomotor control circuit reminiscent of the vertebrate nigrostriatopallidal system was thus already present at the origin of ancestral chordates and has been maintained in the face of extreme nervous system miniaturization in the urochordate lineage.

Beyond Motor Deficits: Environmental Enrichment Mitigates Huntington's Disease Effects in YAC128 Mice

Huntington's disease (HD) is a neurodegenerative genetic disorder characterized by motor, psychiatric, cognitive, and peripheral symptoms without effective therapy. Evidence suggests that lifestyle factors can modulate disease onset and progression, and environmental enrichment (EE) has emerged as a potential approach to mitigate the progression and severity of neurodegenerative processes. Wild-type (WT) and yeast artificial chromosome (YAC) 128 mice were exposed to different EE conditions. Animals from cohort 1 were exposed to EE between postnatal days 21 and 60, and animals from cohort 2 were exposed to EE between postnatal days 60 and 120. Motor and non-motor behavioral tests were employed to evaluate the effects of EE on HD progression. Monoamine levels, hippocampal cell proliferation, neuronal differentiation, and dendritic arborization were also assessed. Here we show that EE had an antidepressant-like effect and slowed the progression of motor deficits in HD mice. It also reduced monoamine levels, which correlated with better motor performance, particularly in the striatum. EE also modulated neuronal differentiation in the YAC128 hippocampus. These results confirm that EE can impact behavior, hippocampal neuroplasticity, and monoamine levels in YAC128 mice, suggesting this could be a therapeutic strategy to modulate neuroplasticity deficits in HD. However, further research is needed to fully understand EE's mechanisms and long-term effects as an adjuvant therapy for this debilitating condition.

Neurotransmitter systems in the etiology of major neurological disorders: Emerging insights and therapeutic implications

Neurotransmitters serve as chemical messengers playing a crucial role in information processing throughout the nervous system, and are essential for healthy physiological and behavioural functions in the body. Neurotransmitter systems are classified as cholinergic, glutamatergic, GABAergic, dopaminergic, serotonergic, histaminergic, or aminergic systems, depending on the type of neurotransmitter secreted by the neuron, allowing effector organs to carry out specific functions by sending nerve impulses. Dysregulation of a neurotransmitter system is typically linked to a specific neurological disorder. However, more recent research points to a distinct pathogenic role for each neurotransmitter system in more than one neurological disorder of the central nervous system. In this context, the review provides recently updated information on each neurotransmitter system, including the pathways involved in their biochemical synthesis and regulation, their physiological functions, pathogenic roles in diseases, current diagnostics, new therapeutic targets, and the currently used drugs for associated neurological disorders. Finally, a brief overview of the recent developments in neurotransmitter-based therapeutics for selected neurological disorders is offered, followed by future perspectives in that area of research.

Molecular-enriched functional connectivity in the human brain using multiband multi-echo simultaneous ASL/BOLD fMRI

Receptor-enriched analysis of functional connectivity by targets (REACT) is a strategy to enrich functional MRI (fMRI) data with molecular information on the neurotransmitter distribution density in the human brain, providing a biological basis to the functional connectivity (FC) analysis. Although this approach has been used in BOLD fMRI studies only so far, extending its use to ASL imaging would provide many advantages, including the more direct link of ASL with neuronal activity compared to BOLD and its suitability for pharmacological MRI studies assessing drug effects on baseline brain function. Here, we applied REACT to simultaneous ASL/BOLD resting-state fMRI data of 29 healthy subjects and estimated the ASL and BOLD FC maps related to six molecular systems. We then compared the ASL and BOLD FC maps in terms of spatial similarity, and evaluated and compared the test-retest reproducibility of each modality. We found robust spatial patterns of molecular-enriched FC for both modalities, moderate similarity between BOLD and ASL FC maps and comparable reproducibility for all but one molecular-enriched functional networks. Our findings showed that ASL is as informative as BOLD in detecting functional circuits associated with specific molecular pathways, and that the two modalities may provide complementary information related to these circuits.

Dopamine and norepinephrine differentially mediate the exploration-exploitation tradeoff

The catecholamines dopamine (DA) and norepinephrine (NE) have been repeatedly implicated in neuropsychiatric vulnerability, in part via their roles in mediating the decision making processes. Although the two neuromodulators share a synthesis pathway and are co-activated under states of arousal, they engage in distinct circuits and roles in modulating neural activity across the brain. However, in the computational neuroscience literature, they have been assigned similar roles in modulating the latent cognitive processes of decision making, in particular the exploration-exploitation tradeoff. Revealing how each neuromodulator contributes to this explore-exploit process will be important in guiding mechanistic hypotheses emerging from computational psychiatric approaches. To understand the differences and overlaps of the roles of these two catecholamine systems in regulating exploration and exploitation, a direct comparison using the same dynamic decision making task is needed. Here, we ran mice in a restless two-armed bandit task, which encourages both exploration and exploitation. We systemically administered a nonselective DA receptor antagonist (flupenthixol), a nonselective DA receptor agonist (apomorphine), a NE beta-receptor antagonist (propranolol), and a NE beta-receptor agonist (isoproterenol), and examined changes in exploration within subjects across sessions. We found a bidirectional modulatory effect of dopamine receptor activity on the level of exploration. Increasing dopamine activity decreased exploration and decreasing dopamine activity increased exploration. Beta-noradrenergic receptor activity also modulated exploration, but the modulatory effect was mediated by sex. Reinforcement learning model parameters suggested that dopamine modulation affected exploration via decision noise and norepinephrine modulation affected exploration via outcome sensitivity. Together, these findings suggested that the mechanisms that govern the transition between exploration and exploitation are sensitive to changes in both catecholamine functions and revealed differential roles for NE and DA in mediating exploration.

Altered structural covariance of locus coeruleus in individuals with significant memory concern and patients with mild cognitive impairment

The locus coeruleus (LC) is the site where tau accumulation is preferentially observed pathologically in Alzheimer's disease (AD) patients, but the changes in gray matter co-alteration patterns between the LC and the whole brain in the predementia phase of AD remain unclear. In this study, we estimated and compared the gray matter volume of the LC and its structural covariance (SC) with the whole brain among 161 normal healthy controls (HCs), 99 individuals with significant memory concern (SMC) and 131 patients with mild cognitive impairment (MCI). We found that SC decreased in MCI groups, which mainly involved the salience network and default mode network. These results imply that seeding from LC, the gray matter network disruption and disconnection appears early in the MCI group. The altered SC network seeding from the LC can serve as an imaging biomarker for discriminating the patients in the potential predementia phase of AD from the normal subjects.

G protein-coupled receptors in neurodegenerative diseases and psychiatric disorders

Neuropsychiatric disorders are multifactorial disorders with diverse aetiological factors. Identifying treatment targets is challenging because the diseases are resulting from heterogeneous biological, genetic, and environmental factors. Nevertheless, the increasing understanding of G protein-coupled receptor (GPCR) opens a new possibility in drug discovery. Harnessing our knowledge of molecular mechanisms and structural information of GPCRs will be advantageous for developing effective drugs. This review provides an overview of the role of GPCRs in various neurodegenerative and psychiatric diseases. Besides, we highlight the emerging opportunities of novel GPCR targets and address recent progress in GPCR drug development.

The role of biofield energy treatment on psychological symptoms, mental health disorders, and stress-related quality of life in adult subjects: A randomized controlled clinical trial

Background

Western and Eastern cultures have practiced biofield energy therapy for thousands of years, but empirical research on effectiveness of this therapy is relatively nascent. Study was aimed to assess the safety and efficacy of biofield therapy on psychological symptoms and mental health disorders in adult subjects.

Methods

Seventy-seven participants (39 male and 38 female) underwent clinical trial. This trial was simple randomized, placebo-controlled, parallel-group, open-label, and single-center with subjects, who have one or more psychological symptoms. Two sessions of biofield energy attunement were given in-person at day 0 and 90 for 3 min (treatment group, n = 35) and others allocated to naive attunement (placebo group, n = 42). Subjects were assessed psychological questionnaire scoring using standard scale of assessment and levels of physiological biomarkers in serum were determined by parameter-specific ELISA.

Results

Perceived psychological symptoms/scores (asthenia, sleep disturbances, anxiety, depression, stress, confusion, future fearness, sexual desireness, motivation, confidence, emotional trauma, etc.) were significantly (p ≤ 0.0001) improved in the treatment group than placebo control group. Furthermore, physiological biomarkers: vitamins (B12, C, and D3 metabolites), immune biomarker (CD8+CD28-), neurotransmitters (acetylcholine, noradrenaline, and dopamine), hormones (oxytocin, 17-β-estradiol, and insulin), and antiaging protein (klotho) levels were significantly (p ≤ 0.001) increased in treatment group than placebo. Proinflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-8) and oxidative stress biomarkers (isoprostane and oxidized LDL) were reduced in treatment group compared with placebo.

Conclusions

Results suggest that experimenter's biofield energy plays a significant role in information transfer processes that contribute to individual's state of physical, mental, emotional, and spiritual well-being as well as improved overall health and quality of life.

Locus coeruleus ablation in mice: protocol optimization, stereology and behavioral impact

The Locus Coeruleus (LC) is in the brainstem and supplies key brain structures with noradrenaline, including the forebrain and hippocampus. The LC impacts specific behaviors such as anxiety, fear, and motivation, as well as physiological phenomena that impact brain functions in general, including sleep, blood flow regulation, and capillary permeability. Nevertheless, the short- and long-term consequences of LC dysfunction remain unclear. The LC is among the brain structures first affected in patients suffering from neurodegenerative diseases such as Parkinson's disease and Alzheimer's Disease, hinting that LC dysfunction may play a central role in disease development and progression. Animal models with modified or disrupted LC function are essential to further our understanding of LC function in the normal brain, the consequences of LC dysfunction, and its putative roles in disease development. For this, well-characterized animal models of LC dysfunction are needed. Here, we establish the optimal dose of selective neurotoxin N-(2-chloroethyl)-N-ethyl-bromo-benzylamine (DSP-4) for LC ablation. Using histology and stereology, we compare LC volume and neuron number in LC ablated (LCA) mice and controls to assess the efficacy of LC ablation with different numbers of DSP-4 injections. All LCA groups show a consistent decrease in LC cell count and LC volume. We then proceed to characterize the behavior of LCA mice using a light-dark box test, Barnes maze test, and non-invasive sleep-wakefulness monitoring. Behaviorally, LCA mice differ subtly from control mice, with LCA mice generally being more curious and less anxious compared to controls consistent with known LC function and projections. We note an interesting contrast in that control mice have varying LC size and neuron count but consistent behavior whereas LCA mice (as expected) have consistently sized LC but erratic behavior. Our study provides a thorough characterization of an LC ablation model, firmly consolidating it as a valid model system for the study of LC dysfunction.

Purkinje cell dopaminergic inputs to astrocytes regulate cerebellar-dependent behavior

Dopamine has a significant role in motor and cognitive function. The dopaminergic pathways originating from the midbrain have received the most attention; however, the relevance of the cerebellar dopaminergic system is largely undiscovered. Here, we show that the major cerebellar astrocyte type Bergmann glial cells express D1 receptors. Dopamine can be synthesized in Purkinje cells by cytochrome P450 and released in an activity-dependent fashion. We demonstrate that activation of D1 receptors induces membrane depolarization and Ca2+ release from the internal store. These astrocytic activities in turn modify Purkinje cell output by altering its excitatory and inhibitory synaptic input. Lastly, we show that conditional knockout of D1 receptors in Bergmann glial cells results in decreased locomotor activity and impaired social activity. These results contribute to the understanding of the molecular, cellular, and circuit mechanisms underlying dopamine function in the cerebellum, revealing a critical role for the cerebellar dopaminergic system in motor and social behavior.

Norepinephrine system at the interface of attention and reward

Reward learning is key to survival for individuals. Attention plays an important role in the rapid recognition of reward cues and establishment of reward memories. Reward history reciprocally guides attention to reward stimuli. However, the neurological processes of the interplay between reward and attention remain largely elusive, due to the diversity of the neural substrates that participate in these two processes. In this review, we delineate the complex and differentiated locus coeruleus norepinephrine (LC-NE) system in relation to different behavioral and cognitive substrates of reward and attention. The LC receives reward related sensory, perceptual, and visceral inputs, releases NE, glutamate, dopamine and various neuropeptides, forms reward memories, drives attentional bias and selects behavioral strategies for reward. Preclinical and clinical studies have found that abnormalities in the LC-NE system are involved in a variety of psychiatric conditions marked by disturbed functions in reward and attention. Therefore, we propose that the LC-NE system is an important hub in the interplay between reward and attention as well as a critical therapeutic target for psychiatric disorders characterized by compromised functions in reward and attention.

Therapeutic Potential of Dopamine and Related Drugs as Anti-Inflammatories and Antioxidants in Neuronal and Non-Neuronal Pathologies

Dopamine (DA), its derivatives, and dopaminergic drugs are compounds widely used in the management of diseases related to the nervous system. However, DA receptors have been identified in nonneuronal tissues, which has been related to their therapeutic potential in pathologies such as sepsis or septic shock, blood pressure, renal failure, diabetes, and obesity, among others. In addition, DA and dopaminergic drugs have shown anti-inflammatory and antioxidant properties in different kinds of cells.

AIM

To compile the mechanism of action of DA and the main dopaminergic drugs and show the findings that support the therapeutic potential of these molecules for the treatment of neurological and non-neurological diseases considering their antioxidant and anti-inflammatory actions.

METHOD

We performed a review article. An exhaustive search for information was carried out in specialized databases such as PubMed, PubChem, ProQuest, EBSCO, Scopus, Science Direct, Web of Science, Bookshelf, DrugBank, Livertox, and Clinical Trials.

RESULTS

We showed that DA and dopaminergic drugs have emerged for the management of neuronal and nonneuronal diseases with important therapeutic potential as anti-inflammatories and antioxidants.

CONCLUSIONS

DA and DA derivatives can be an attractive treatment strategy and a promising approach to slowing the progression of disorders through repositioning.

Exercising is good for the brain but exercising outside is potentially better

It is well known that exercise increases cognitive function. However, the environment in which the exercise is performed may be just as important as the exercise itself. Time spent in natural outdoor environments has been found to lead to increases in cognition similar to those resulting from acute exercise. Therefore, the benefits of both exercise and nature exposure suggest an additive impact on brain function when both factors are combined. This raises the question: what is the interaction between acute exercise and environment on cognition? We answered this question using electroencephalography to probe cognitive function using the oddball task before and after brief indoor and outdoor walks on 30 participants (average 21 years old, 95% CI [20, 22]). Our results demonstrate improved performance and an increase in the amplitude of the P300, an event-related neural response commonly associated with attention and working memory, following a 15-min walk outside; a result not seen following a 15-min walk inside. Importantly, this finding indicates that the environment may play a more substantial role in increasing cognitive function such as attention than exercise, at least in terms of acute exercise (i.e., a brief walk). With the world's growing urbanization and the associated increase in sedentary time indoors, a deeper understanding of how these factors interact and influence cognition may be critical to combat adverse health effects.

Noradrenergic Modulation of Learned and Innate Behaviors in Dopamine Transporter Knockout Rats by Guanfacine

Investigation of the precise mechanisms of attention deficit and hyperactivity disorder (ADHD) and other dopamine-associated conditions is crucial for the development of new treatment approaches. In this study, we assessed the effects of repeated and acute administration of α2A-adrenoceptor agonist guanfacine on innate and learned forms of behavior of dopamine transporter knockout (DAT-KO) rats to evaluate the possible noradrenergic modulation of behavioral deficits. DAT-KO and wild type rats were trained in the Hebb-Williams maze to perform spatial working memory tasks. Innate behavior was evaluated via pre pulse inhibition (PPI). Brain activity of the prefrontal cortex and the striatum was assessed. Repeated administration of GF improved the spatial working memory task fulfillment and PPI in DAT-KO rats, and led to specific changes in the power spectra and coherence of brain activity. Our data indicate that both repeated and acute treatment with a non-stimulant noradrenergic drug lead to improvements in the behavior of DAT-KO rats. This study further supports the role of the intricate balance of norepinephrine and dopamine in the regulation of attention. The observed compensatory effect of guanfacine on the behavior of hyperdopaminergic rats may be used in the development of combined treatments to support the dopamine-norepinephrine balance.

Role of G-Proteins and GPCRs in Cardiovascular Pathologies

Cell signaling is a fundamental process that enables cells to survive under various ecological and environmental contexts and imparts tolerance towards stressful conditions. The basic machinery for cell signaling includes a receptor molecule that senses and receives the signal. The primary form of the signal might be a hormone, light, an antigen, an odorant, a neurotransmitter, etc. Similarly, heterotrimeric G-proteins principally provide communication from the plasma membrane G-protein-coupled receptors (GPCRs) to the inner compartments of the cells to control various biochemical activities. G-protein-coupled signaling regulates different physiological functions in the targeted cell types. This review article discusses G-proteins' signaling and regulation functions and their physiological relevance. In addition, we also elaborate on the role of G-proteins in several cardiovascular diseases, such as myocardial ischemia, hypertension, atherosclerosis, restenosis, stroke, and peripheral artery disease.

Spatial contextual recognition memory updating is modulated by dopamine release in the dorsal hippocampus from the locus coeruleus

Detecting novelty is critical to consolidate declarative memories, such as spatial contextual recognition memory. It has been shown that stored memories, when retrieved, are susceptible to modification, incorporating new information through an updating process. Catecholamine release in the hippocampal CA1 region consolidates an object location memory (OLM). This work hypothesized that spatial contextual memory updating could be changed by decreasing catecholamine release in the hippocampal CA1 terminals from the locus coeruleus (LC). In a mouse model expressing Cre-recombinase under the control of the tyrosine hydroxylase (TH) promoter, memory updating was impaired by photoinhibition of the CA1 catecholaminergic terminals from the LC (LC-CA1) but not from the ventral tegmental area (VTA-CA1). In vivo microdialysis confirmed that the extracellular concentration of both dopamine (DA) and noradrenaline (NA) decreased after photoinhibition of the LC-CA1 terminals (but not VTA-CA1) during the OLM update session. Furthermore, DA D1/D5 and beta-adrenergic receptor antagonists disrupted behavior, but only the former impaired memory updating. Finally, photoinhibition of LC-CA1 terminals suppressed long-term potentiation (LTP) induction in Schaffer's collaterals as a plausible mechanism for memory updating. These data will help understand the underpinning mechanisms of DA in spatial contextual memory updating.

Ignore the glitch but mind the switch: Positive effects of methylphenidate on cognition in attention deficit hyperactivity disorder are related to prediction gain

Neuropsychological symptoms such as inattention and distractibility constitute a core characteristic of attention deficit hyperactivity disorder (ADHD). Here, we tested the hypothesis that attentional dysfunctions result from a deficit in neural gain modulation, which translates into difficulty in predictively weighting relevant sensory input while ignoring distraction. We compared thirty-seven hitherto untreated adults diagnosed with ADHD and thirty-eight healthy participants with a serial switch-drift task that requires internal models of predictable digit sequences to be either updated or stabilized. Switches between sequences that had to be indicated by key presses and digit omissions within a sequence (drifts) that should be ignored varied by stimulus-bound surprise quantified as Shannon information. To investigate whether catecholaminergic modulation by increasing extracellular norepinephrine and dopamine levels leads to an amelioration in prediction gain, participants were tested twice, with patients receiving a single dose of methylphenidate, a norepinephrine/dopamine reuptake inhibitor, in the second session. Patients and controls differed in both updating and stabilizing, depending on the respective event surprise. Specifically, patients showed difficulty in detecting expectable switches, while having greater difficulty to ignore surprising distractions. Thus, underconfident prior beliefs in ADHD may fail to appropriately weight expected relevant input, whereas the gain of neural responses to unexpected irrelevant distractors is increased. Methylphenidate improved both flexibility and stability of prediction and had a positive effect on selective responding over time. Our results suggest that ADHD is associated with an impairment in the use of prior expectations to optimally weight sensory inputs, which is improved by increasing catecholaminergic neurotransmission.

Catecholaminergic cell type-specific expression of Cre recombinase in knock-in transgenic rats generated by the Combi-CRISPR technology

BACKGROUND

Cell groups containing catecholamines provide a useful model to study the molecular and cellular mechanisms underlying the morphogenesis, physiology, and pathology of the central nervous system. For this purpose, it is necessary to establish a system to induce catecholaminergic group-specific expression of Cre recombinase. Recently, we introduced a gene cassette encoding 2A peptide fused to Cre recombinase into the site between the C-terminus and translational termination codons of the rat tyrosine hydroxylase (TH) open reading frame by the Combi-CRISPR technology, which is a genomic editing method to enable an efficient knock-in (KI) of long DNA sequence into a target site. However, the expression patterns of the transgene and its function as well as the effect of the mutation on the biochemical and behavioral phenotypes in the KI strains have not been characterized yet.

NEW METHOD

We aimed to evaluate the usefulness of TH-Cre KI rats as an experimental model for investigating the structure and function of catecholaminergic neurons in the brain.

RESULTS

We detected cell type-specific expression of Cre recombinase and site-specific recombination activity in the representative catecholaminergic groups in the TH-Cre KI rat strains. In addition, we measured TH protein levels and catecholamine accumulation in the brain regions, as well as motor, reward-related, and anxiety-like behaviors, indicating that catecholamine metabolism and general behavior are apparently normal in these KI rats.

CONCLUSIONS

TH-Cre KI rat strains produced by the Combi-CRISPR system offer a beneficial model to study the molecular and cellular mechanics for the morphogenesis, physiology, and pathology of catecholamine-containing neurons in the brain.