Differential effects of dopamine-directed treatments on cognition

Benefits of exercise on cognitive impairment in alcohol use disorder following alcohol withdrawal

Although most cognitive impairments induced by prolonged alcohol consumption tend to improve within the initial months of abstinence, there is evidence suggesting certain cognitive deficits may persist. This study aimed to investigate the impact of aerobic exercise on learning and memory in alcohol use disorder (AUD) mice following a period of abstinence from alcohol. We also sought to assess the levels of monoamine neurotransmitters in the hippocampus. To this end, we established an AUD mouse model through a two-bottle choice (sucrose fading mode and normal mode) and chronic intermittent alcohol vapor (combined with intraperitoneal injection) and randomly allocated mice into exercise groups to undergo treadmill training. Learning and memory abilities were assessed through the Morris water maze test and spontaneous activity was evaluated using the open field test. The levels of dopamine, norepinephrine, serotonin, and brain-derived neurotrophic factor in the hippocampus were quantified using enzyme-linked immunoassay (ELISA) kits. The findings reveal that after cessation of alcohol consumption, learning and memory abilities in AUD mice did not completely return to normal levels. The observed enhancement of cognitive functions in AUD mice through aerobic exercise may be attributed to restoring levels of monoamine neurotransmitters in the hippocampus, boosting brain-derived neurotrophic factor (BDNF) concentrations, and facilitating an increase in hippocampal mass. These results offer empirical evidence to support aerobic exercise as a viable therapeutic strategy to alleviate cognitive deficits associated with AUD.

Structure-Activity Relationship Studies on 6-Chloro-1-phenylbenzazepines Leads to the Identification of a New Dopamine D1 Receptor Antagonist

The 1-phenylbenzazepine template has yielded a number of D1R-like ligands, which, though useful as pharmacological tools, have significant drawbacks in terms of selectivity versus D5R as well as pharmacokinetic behavior. A number of 1-phenylbenzazepines contain a 6-chloro functional group, but extensive SAR studies around the 6-chloro-1-phenylbenzazepine framework have not been reported in the literature. To further understand the tolerance of the 6-chloro-1-phenylbenzazepine template for various substituent groups towards affinity and selectivity at D1R, we synthesized two series of analogs with structural variations at the C-7, C-8, N-3, C-3' and C-4' positions. The series 2 analogs differed from series 1 analogs in possessing a nitrogenated functionality at C-8 and lacked a C-4' substituent, but were otherwise similar. Analogs were assessed for affinity at D1R, D2R and D5R. For both series, we found that the analogs lacked affinity for D2R and showed modest D1R versus D5R selectivity. For series 1 analogs, an N-3 methyl substituent group was better tolerated than N-H or an N-3 allyl substituent. The C-8 position appears to be tolerant of amino and methanesulfonamide substituents for high D1R affinity, but C-8 amides displayed low to moderate D1R affinities. A C-3' methyl substituent appeared to be critical for the D1R affinity of some analogs, but the C-4' substituents tried (hydroxy and methoxy; series 1) did not result in any significant boost in D1R affinity. Compound 15a was the most potent and selective D1R ligand identified from these studies (Ki at D1R = 30 nM; 6-fold selectivity versus D5R). Further functional activity assessments indicate that 15a functions as a D1R antagonist towards cAMP-mediated signaling. The predicted drug-like properties of 15a are encouraging for further pharmacological assessments on the compound.

Low-Affinity/High-Selectivity Dopamine Transport Inhibition Sufficient to Rescue Cognitive Functions in the Aging Rat

The worldwide increase in cognitive decline, both in aging and with psychiatric disorders, warrants a search for pharmacological treatment. Although dopaminergic treatment approaches represent a major step forward, current dopamine transporter (DAT) inhibitors are not sufficiently specific as they also target other transporters and receptors, thus showing unwanted side effects. Herein, we describe an enantiomerically pure, highly specific DAT inhibitor, S-CE-123, synthetized in our laboratory. Following binding studies to DAT, NET and SERT, GPCR and kinome screening, pharmacokinetics and a basic neurotoxic screen, S-CE-123 was tested for its potential to enhance and/or rescue cognitive functions in young and in aged rats in the non-invasive reward-motivated paradigm of a hole-board test for spatial learning. In addition, an open field study with young rats was carried out. We demonstrated that S-CE-123 is a low-affinity but highly selective dopamine reuptake inhibitor with good bioavailability. S-CE-123 did not induce hyperlocomotion or anxiogenic or stereotypic behaviour in young rats. Our compound improved the performance of aged but not young rats in a reward-motivated task. The well-described impairment of the dopaminergic system in aging may underlie the age-specific effect. We propose S-CE-123 as a possible candidate for developing a tentative therapeutic strategy for age-related cognitive decline and cognitive dysfunction in psychiatric disorders.

Oral berberine improves brain dopa/dopamine levels to ameliorate Parkinson's disease by regulating gut microbiota

The phenylalanine–tyrosine–dopa–dopamine pathway provides dopamine to the brain. In this process, tyrosine hydroxylase (TH) is the rate-limiting enzyme that hydroxylates tyrosine and generates levodopa (l-dopa) with tetrahydrobiopterin (BH₄) as a coenzyme. Here, we show that oral berberine (BBR) might supply H^• through dihydroberberine (reduced BBR produced by bacterial nitroreductase) and promote the production of BH₄ from dihydrobiopterin; the increased BH₄ enhances TH activity, which accelerates the production of l-dopa by the gut bacteria. Oral BBR acts in a way similar to vitamins. The l-dopa produced by the intestinal bacteria enters the brain through the circulation and is transformed to dopamine. To verify the gut–brain dialog activated by BBR’s effect, Enterococcus faecalis or Enterococcus faecium was transplanted into Parkinson’s disease (PD) mice. The bacteria significantly increased brain dopamine and ameliorated PD manifestation in mice; additionally, combination of BBR with bacteria showed better therapeutic effect than that with bacteria alone. Moreover, 2,4,6-trimethyl-pyranylium tetrafluoroborate (TMP-TFB)-derivatized matrix-assisted laser desorption mass spectrometry (MALDI-MS) imaging of dopamine identified elevated striatal dopamine levels in mouse brains with oral Enterococcus, and BBR strengthened the imaging intensity of brain dopamine. These results demonstrated that BBR was an agonist of TH in Enterococcus and could lead to the production of l-dopa in the gut. Furthermore, a study of 28 patients with hyperlipidemia confirmed that oral BBR increased blood/fecal l-dopa by the intestinal bacteria. Hence, BBR might improve the brain function by upregulating the biosynthesis of l-dopa in the gut microbiota through a vitamin-like effect.

Acting Before; A Combined Strategy to Counteract the Onset and Progression of Dementia

Brain aging and aging-related neurodegenerative disorders are posing a significant challenge for health systems worldwide. To date, most of the therapeutic efforts aimed at counteracting dementiarelated behavioral and cognitive impairment have been focused on addressing putative determinants of the disease, such as β-amyloid or tau. In contrast, relatively little attention has been paid to pharmacological interventions aimed at restoring or promoting the synaptic plasticity of the aging brain. The review will explore and discuss the most recent molecular, structural/functional, and behavioral evidence that supports the use of non-pharmacological approaches as well as cognitive-enhancing drugs to counteract brain aging and early-stage dementia.

Protective role of functional food in cognitive deficit in young and senile rats

Cognitive decline and neurodegenerative diseases pose a significant burden on healthcare resources both in developed and developing countries which is a major socio-economic and healthcare concern. Alzheimer's disease is the most common form of progressive neurodegenerative dementia of the aged brain. Aluminum is a constituent of antacids, deodorants, kitchenware and food additives which allows easy access into the body posing risk to development of senile dementia of Alzheimer's type. Virgin coconut oil was declared as a potential cognitive strengthener. Assessment of cognitive and memory-enhancing effects of virgin coconut oil in senile and young rats to gain vital insights into its effective use in the prevention of neurodegeneration in dementia/Alzheimer's disease-like manifestations and alleviate cognitive dysfunction and learning impairment with neuronal damage imparted by daily oral intake of aluminum. Alzheimer's disease-like symptoms and memory impairment were experimentally induced using oral anhydrous aluminum chloride given daily for five successive weeks in young and old age albino rats. Treatment groups received virgin coconut oil to assess protection during the experimental period. Behavioral test, Morris water maze was conducted before/after induction/treatment. At the end of the experimental period, cholinergic, dopaminergic, noradrenergic and serotonergic neurotransmission as well as brain-derived neurotrophic factor were being investigated, in addition to immunochemical and histopathological examination of targeted brain regions. Virgin coconut oil significantly improved cholinergic activity and monoaminergic neurotransmission. Moreover, immunochemical and histopathological examination revealed marked protection with virgin coconut oil against aluminum-induced Alzheimer's disease-like pathology and cognitive deficit.

Synthesis and dopamine receptor pharmacological evaluations on ring C ortho halogenated 1-phenylbenzazepines

A series of 1-phenylbenzazepines containing bromine or chlorine substituents at the ortho position of the appended phenyl ring (2'-monosubstituted or 2',6'- disubstituted patterns) were synthesized and evaluated for affinity towards dopamine D₁R, D₂R and D₅R. As is typical of the 1-phenylbenzazepine scaffold, the compounds displayed selectivity towards D₁R and D₅R; analogs generally lacked affinity for D₂R. Interestingly, 2',6'-dichloro substituted analogs showed modest D₅R versus D₁R selectivity whereas this selectivity was reversed in compounds with a 2'-halo substitution pattern. Compound 10a was identified as a D₁R antagonist (K_i = 14 nM; IC₅₀ = 9.4 nM).

Synthesis, pharmacological evaluations, and molecular docking studies on a new 1,3,4,11b-tetrahydro-1H-fluoreno[9,1-cd]azepine framework: Rigidification of D1 receptor selective 1-phenylbenzazepines and discovery of a new 5-HT6 receptor scaffold

The novel 1,3,4,11b-tetrahydro-1H-fluoreno[9,1-cd]azepine framework, a structurally rigidified variant of the 1-phenylbenzazepine template, was synthesized via direct arylation as a key reaction. Evaluation of the binding affinities of the rigidified compounds across a battery of serotonin, dopamine, and adrenergic receptors indicates that this scaffold unexpectedly has minimal affinity for D₁ and other dopamine receptors and is selective for the 5-HT₆ receptor. The affinity of these systems at the 5-HT₆ receptor is significantly influenced by electronic and hydrophobic interactions as well as the enhanced rigidity of the ligands. Molecular docking studies indicate that the reduced D₁ receptor affinity of the rigidified compounds may be due in part to weaker H-bonding interactions between the oxygenated moieties on the compounds and specific receptor residues. Key receptor-ligand H-bonding interactions, salt bridges, and π-π interactions appear to be responsible for the 5-HT₆ receptor affinity of the compounds. Compounds 10 (6,7-dimethoxy-2,3,4,11b-tetrahydro-1H-fluoreno[9,1-cd]azepine) and 12 (6,7-dimethoxy-2-methyl-2,3,4,11b-tetrahydro-1H-fluoreno[9,1-cd]azepine) have been identified as structurally novel, high affinity (K_i  = 5 nM), selective 5-HT₆ receptor ligands.

Effects of NBI-98782, a selective vesicular monoamine transporter 2 (VMAT2) inhibitor, on neurotransmitter efflux and phencyclidine-induced locomotor activity: Relevance to tardive dyskinesia and antipsychotic action

Valbenazine, a vesicular monoamine transporter 2 (VMAT2, SLC18A2) inhibitor, is a newly approved treatment for tardive dyskinesia. VMAT2 is present in the membrane of secretory vesicles and transports dopamine (DA), norepinephrine (NE), serotonin (5-HT), histamine, glutamate (Glu), and GABA into vesicles for presynaptic release. We utilized microdialysis in awake, freely moving mice to determine the effect of NBI-98782, the active metabolite of valbenazine, alone, or in combination with several antipsychotic drugs (APDs), to influence neurotransmitter efflux in the medial prefrontal cortex (mPFC), dorsal striatum (dSTR), hippocampus and nucleus accumbens (NAC); we also compared it with tetrabenazine, the prototypical VMAT2 inhibitor. Acute NBI-98782 and tetrabenazine decreased mPFC, dSTR, hippocampus, and NAC DA, 5-HT, and NE efflux, while increasing that of DOPAC, HVA, and 5-HIAA. Sub-chronic NBI-98782 (7 days) decreased baseline DA and 5-HT efflux in both mPFC and dSTR. NBI-98782 elicited similar effects on neurotransmitter efflux in sub-chronic NBI-98782-treated mice but also enhanced ACh and GABA; the decrease in DA efflux in mPFC and dSTR was not significant in the sc-treated animals. NBI-98782 suppressed clozapine-, olanzapine- and risperidone-induced DA efflux in both mPFC and dSTR, and ACh efflux in mPFC. NBI-98782 suppressed the haloperidol-induced DA efflux in dSTR, with minimal effect on GABA efflux. NBI-98782 attenuated PCP-induced DA, 5-HT, NE and Glu efflux, and AMPH-induced DA and NE efflux, in both mPFC and dSTR, as well as PCP- and AMPH-induced hyperlocomotion, suggesting possible beneficial antipsychotic effects.

Exploring Shopper's Browsing Behavior and Attention Level with an EEG Biosensor Cap

The online shopping market is developing rapidly, meaning that it is important for retailers and manufacturers to understand how consumers behave online compared to when in brick-and-mortar stores. Retailers want consumers to spend time shopping, browsing, and searching for products in the hope a purchase is made. On the other hand, consumers may want to restrict their duration of stay on websites due to perceived risk of loss of time or convenience. This phenomenon underlies the need to reduce the duration of consumer stay (namely, time pressure) on websites. In this paper, the browsing behavior and attention span of shoppers engaging in online shopping under time pressure were investigated. The attention and meditation level are measured by an electroencephalogram (EEG) biosensor cap. The results indicated that when under time pressure shoppers engaging in online shopping are less attentive. Thus, marketers may need to find strategies to increase a shopper’s attention. Shoppers unfamiliar with product catalogs on shopping websites are less attentive, therefore marketers should adopt an interesting style for product catalogs to hold a shopper’s attention. We discuss our findings and outline their business implications.

Aripiprazole and haloperidol protect neurite lesions via reducing excessive D2R-DISC1 complex formation

Dopamine D2 receptor (D2R) hyperactivity causes altered brain development and later produces onset of symptoms mimicking schizophrenia. It is known that D2R interacts with disrupted in schizophrenia 1 (DISC1); however, the effect of D2R-DISC1 interaction in intracellular signalling and neurite growth has not been studied. This study investigated the effect of D2R over-activation on Akt-GSK3β signalling and neurite morphology in cortical neurons. Over-activation of D2Rs caused neurite lesions, which were associated with decreased protein kinase B (Akt) and glycogen synthase kinase 3 beta (GSK3β) phosphorylation in cortical neurons. The antipsychotic drug aripiprazole was more effective in the prevention of neurite lesions than haloperidol. Unlike haloperidol, aripiprazole prevented downregulation of phospho (p) Akt-pGSK3β induced by D2R hyperactivity, indicating involvement of different pathways. D2Rs were hyperactive in cortical neurons of mice with DISC1 mutation, which caused more severe neurite lesions in cortical neurons treated with quinpirole. Immunofluorescent staining for Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) confirmed that cortical pyramidal neurons were involved in the D2R hyperactivity-induced neurite lesions. Using the fluorescence resonance energy transfer (FRET) technique, we provide direct evidence that D2R hyperactivity led to D2R-DISC1 complex formation, which altered pGSK3β signalling. This study showed that D2R hyperactivity-induced D2R-DISC1 complex formation is associated with decreased pAkt-pGSK3β signalling and in turn, caused neurite impairment. Aripiprazole and haloperidol prevented the impairment of neurite growth but appeared to do so via different intracellular signalling pathways.

The expression of tyrosine hydroxylase and DARPP-32 in the house crow (Corvus splendens) brain

Birds of the family Corvidae which includes diverse species such as crows, rooks, ravens, magpies, jays, and jackdaws are known for their amazing abilities at problem-solving. Since the catecholaminergic system, especially the neurotransmitter dopamine, plays a role in cognition, we decided to study the distribution of tyrosine hydroxylase (TH), the rate-limiting enzyme in the synthesis of catecholamines in the brain of house crows (Corvus splendens). We also studied the expression of DARPP-32 (dopamine and cAMP-regulated phosphoprotein), which is expressed in dopaminoceptive neurons. Our results demonstrated that as in other avian species, the expression of both TH and DARPP-32 was highest in the house crow striatum. The caudolateral nidopallium (NCL, the avian analogue of the mammalian prefrontal cortex) could be differentiated from the surrounding pallial regions based on a larger number of TH-positive "baskets" of fibers around neurons in this region and greater intensity of DARPP-32 staining in the neuropil in this region. House crows also possessed distinct nuclei in their brains which corresponded to song control regions in other songbirds. Whereas immunoreactivity for TH was higher in the vocal control region Area X compared to the surrounding MSt (medial striatum) in house crows, staining in RA and HVC was not as prominent. Furthermore, the arcopallial song control regions RA (nucleus robustus arcopallialis) and AId (intermediate arcopallium) were strikingly negative for DARPP-32 staining, in contrast to the surrounding arcopallium. Patterns of immunoreactivity for TH and DARPP-32 in "limbic" areas such as the hippocampus, septum, and extended amygdala have also been described.

Role of Descending Dopaminergic Pathways in Pain Modulation

Pain, especially when chronic, is a common reason patients seek medical care and it affects the quality of life and well-being of the patients. Unfortunately, currently available therapies for chronic pain are often inadequate because the neurobiological basis of such pain is still not fully understood. Although dopamine has been known as a neurotransmitter to mediate reward and motivation, accumulating evidence has shown that dopamine systems in the brain are also involved in the central regulation of chronic pain. Most importantly, descending dopaminergic pathways play an important role in pain modulation. In this review, we discuss dopamine receptors, dopaminergic systems in the brain, and the role of descending dopaminergic pathways in the modulation of different types of pain.

Human behavioral assessments in current research of Parkinson's disease

Parkinson's disease (PD) is traditionally classified as a movement disorder because patients mainly complain about motor symptoms. Recently, non-motor symptoms of PD have been recognized by clinicians and scientists as early signs of PD, and they are detrimental factors in the quality of life in advanced PD patients. It is crucial to comprehensively understand the essence of behavioral assessments, from the simplest measurement of certain symptoms to complex neuropsychological tasks. We have recently reviewed behavioral assessments in PD research with animal models (Asakawa et al., 2016). As a companion volume, this article will systematically review the behavioral assessments of motor and non-motor PD symptoms of human patients in current research. The major aims of this article are: (1) promoting a comparative understanding of various behavioral assessments in terms of the principle and measuring indexes; (2) addressing the major strengths and weaknesses of these behavioral assessments for a better selection of tasks/tests in order to avoid biased conclusions due to inappropriate assessments; and (3) presenting new concepts regarding the development of wearable devices and mobile internet in future assessments. In conclusion we emphasize the importance of improving the assessments for non-motor symptoms because of their complex and unique mechanisms in human PD brains.

The misfolded pro-inflammatory protein S100A9 disrupts memory via neurochemical remodelling instigating an Alzheimer's disease-like cognitive deficit

Memory deficits may develop from a variety of neuropathologies including Alzheimer's disease dementia. During neurodegenerative conditions there are contributory factors such as neuroinflammation and amyloidogenesis involved in memory impairment. In the present study, dual properties of S100A9 protein as a pro-inflammatory and amyloidogenic agent were explored in the passive avoidance memory task along with neurochemical assays in the prefrontal cortex and hippocampus of aged mice. S100A9 oligomers and fibrils were generated in vitro and verified by AFM, Thioflavin T and A11 antibody binding. Native S100A9 as well as S100A9 oligomers and fibrils or their combination were administered intranasally over 14 days followed by behavioral and neurochemical analysis. Both oligomers and fibrils evoked amnestic activity which correlated with disrupted prefrontal cortical and hippocampal dopaminergic neurochemistry. The oligomer-fibril combination produced similar but weaker neurochemistry to the fibrils administered alone but without passive avoidance amnesia. Native S100A9 did not modify memory task performance even though it generated a general and consistent decrease in monoamine levels (DA, 5-HT and NA) and increased metabolic marker ratios of DA and 5-HT turnover (DOPAC/DA, HVA/DA and 5-HIAA) in the prefrontal cortex. These results provide insight into a novel pathogenetic mechanism underlying amnesia in a fear-aggravated memory task based on amyloidogenesis of a pro-inflammatory factor leading to disrupted brain neurochemistry in the aged brain. The data further suggests that amyloid species of S100A9 create deleterious effects principally on the dopaminergic system and this novel finding might be potentially exploited during dementia management through a neuroprotective strategy.