Dopamine beta-hydroxylase in health and disease

The pharmacology of vitamin C

Ascorbic acid, the reduced form of vitamin C, is a ubiquitous small carbohydrate. Despite decades of focused research, new metabolic functions of this universal electron donor are still being discovered and add to the complexity of our view of vitamin C in human health. Although praised as an unsurpassed water-soluble antioxidant in plasma and cells, the most interesting functions of vitamin C seem to be its roles as specific electron donor in numerous biological reactions ranging from the well-known hydroxylation of proline to cofactor for the epigenetic master regulators ten-eleven translocation enzymes and Jumonji domain-containing histone-lysine demethylases. Some of these functions may have important implications for disease prevention and treatment and have spiked renewed interest in, eg, vitamin C's potential in cancer therapy. Moreover, some fundamental pharmacokinetic properties of vitamin C remain to be established including if other mechanisms than passive diffusion governs the efflux of ascorbate anions from the cell. Taken together, there still seems to be much to learn about the pharmacology of vitamin C and its role in health and disease. This review explores new avenues of vitamin C and integrates our present knowledge of its pharmacology. SIGNIFICANCE STATEMENT: Vitamin C is involved in multiple biological reactions of which most are essential to human health. Hundreds of millions of people are considered deficient in vitamin C according to accepted guidelines, but little is known about the long-term consequences. Although the complexity of vitamin C's physiology and pharmacology has been widely disregarded in clinical studies for decades, it seems clear that a deeper understanding of particularly its pharmacology holds the key to unravel and possibly exploit the potential of vitamin C in disease prevention and therapy.

Assessment of the relationship between the dopaminergic pathway and severe acute respiratory syndrome coronavirus 2 infection, with related neuropathological features, and potential therapeutic approaches in COVID-19 infection

Dopamine is a known catecholamine neurotransmitter involved in several physiological processes, including motor control, motivation, reward, cognition, and immune function. Dopamine receptors are widely distributed throughout the nervous system and in immune cells. Several viruses, including human immunodeficiency virus and Japanese encephalitis virus, can use dopaminergic receptors to replicate in the nervous system and are involved in viral neuropathogenesis. In addition, studies suggest that dopaminergic receptors may play a role in the progression and pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. When SARS-CoV-2 binds to angiotensin-converting enzyme 2 receptors on the surface of neuronal cells, the spike protein of the virus can bind to dopaminergic receptors on neighbouring cells to accelerate its life cycle and exacerbate neurological symptoms. In addition, recent research has shown that dopamine is an important regulator of the immune-neuroendocrine system. Most immune cells express dopamine receptors and other dopamine-related proteins, indicating the importance of dopaminergic immune regulation. The increase in dopamine concentration during SARS-CoV2 infection may reduce immunity (innate and adaptive) that promotes viral spread, which could lead to neuronal damage. In addition, dopaminergic signalling in the nervous system may be affected by SARS-CoV-2 infection. COVID -19 can cause various neurological symptoms as it interacts with the immune system. One possible treatment strategy for COVID -19 patients could be the use of dopamine antagonists. To fully understand how to protect the neurological system and immune cells from the virus, we need to study the pathophysiology of the dopamine system in SARS-CoV-2 infection.

Molecular Mechanism Biomarkers Predict Diagnosis in Schizophrenia and Schizoaffective Psychosis, with Implications for Treatment

Diagnostic uncertainty and relapse rates in schizophrenia and schizoaffective disorder are relatively high, indicating the potential involvement of other pathological mechanisms that could serve as diagnostic indicators to be targeted for adjunctive treatment. This study aimed to seek objective evidence of methylenetetrahydrofolate reductase MTHFR C677T genotype-related bio markers in blood and urine. Vitamin and mineral cofactors related to methylation and indolamine-catecholamine metabolism were investigated. Biomarker status for 67 symptomatically well-defined cases and 67 asymptomatic control participants was determined using receiver operating characteristics, Spearman's correlation, and logistic regression. The 5.2%-prevalent MTHFR 677 TT genotype demonstrated a 100% sensitive and specific case-predictive biomarkers of increased riboflavin (vitamin B2) excretion. This was accompanied by low plasma zinc and indicators of a shift from low methylation to high methylation state. The 48.5% prevalent MTHFR 677 CC genotype model demonstrated a low-methylation phenotype with 93% sensitivity and 92% specificity and a negative predictive value of 100%. This model related to lower vitamin cofactors, high histamine, and HPLC urine indicators of lower vitamin B2 and restricted indole-catecholamine metabolism. The 46.3%-prevalent CT genotype achieved high predictive strength for a mixed methylation phenotype. Determination of MTHFR C677T genotype dependent functional biomarker phenotypes can advance diagnostic certainty and inform therapeutic intervention.

Multifactor Dimensionality Reduction Analysis to Evaluate the Association of Dopamine Beta-Hydroxylase (DΒH) Polymorphisms with Susceptibility to Dementia (SADEM Study)

Dementia is a multifactorial disease in which environmental, lifestyle, and genetic factors intervene. Population studies have been used in looking for the susceptibility genes for this disease. Since the activity of dopamine b hydroxylase (DβH) is reduced in the hippocampus and neocortex in the brain, changes in the physiological status of dopamine have been reported in Alzheimer's disease (AD) induced by this enzyme. Therefore, DBH polymorphisms have been associated with susceptibility to some neurological diseases such as AD, but few studies have investigated the relationship between these polymorphisms with other types of dementia, especially in Mexican populations. The aim of this study was to evaluate the association between single-nucleotide polymorphism (SNP) in the dopamine b-hydroxylase (DBH gene (rs1611115) and their interactions with environmental factors and the dementia risk. We examined the genotype of the gene DBH (rs1611115) polymorphism in patients with dementia and healthy. The interaction and the impact of DBH (rs1611115) polymorphism on dementia were examined through multifactor dimensionality reduction (MDR) analysis, and the results were verified by the Chi-square test. Hardy-Weinberg equilibrium (HWE) was also checked by the Chi-square test. The relative risk was expressed by odds ratio (OR) and 95%. A total of 221 dementia patients and 534 controls met the inclusion criteria of MDR analyses. The results of the MDR analysis showed that the development of dementia was positively correlated with interaction between the TT genotype of the DBH1 locus rs1611115 TT and diabetes, hypertension, and alcohol consumption (OR = 6.5: 95% CI = 4.5-9.5), originating further cognitive damage. These findings provide insight into the positive correlation between the metabolism and cardiovascular disorders and the presence of the T allele by means of a recessive model of DBH rs1611115 polymorphism with the suspensibility of dementia.

Upregulations of α1 adrenergic receptors and noradrenaline synthases in the medial prefrontal cortex are associated with emotional and cognitive dysregulation induced by post-weaning social isolation in male rats

Early-life social isolation induces emotional and cognitive dysregulation, such as increased aggression and anxiety, and decreases neuron excitability in the medial prefrontal cortex (mPFC). The noradrenergic system in the mPFC regulates emotion and cognitive function via α₁ or α_2A adrenergic receptors, depending on noradrenaline levels. However, social isolation-induced changes in the mPFC noradrenergic system have not been reported. Here, male Wistar rats received post-weaning social isolation for nine consecutive weeks and were administered behavioral tests (novel object recognition, elevated plus maze, aggression, and forced swimming, sequentially). Protein expression levels in the mPFC noradrenergic system (α₁ and α_2A adrenergic receptors, tyrosine hydroxylase, and dopamine-β-hydroxylase used as indices of noradrenaline synthesis and release) were examined through western blotting. Social isolation caused cognitive dysfunction, anxiety-like behavior, and aggression, but not behavioral despair. Socially-isolated rats exhibited increased protein levels of the α₁ adrenergic receptor, tyrosine hydroxylase, and dopamine-β-hydroxylase in the mPFC; there was no significant difference between the groups in the α_2A adrenergic receptor expression levels. Preferential activation of the α₁ adrenergic receptor caused by high noradrenaline concentration in the mPFC may be involved in social isolation-induced emotional and cognitive regulation impairments. Targeting the α₁ adrenergic receptor signaling pathway is a potential therapeutic strategy for psychiatric disorders with symptomatic features such as emotional and cognitive dysregulation.

Attenuation of Anxiety-Like Behavior by Helichrysum stoechas (L.) Moench Methanolic Extract through Up-Regulation of ERK Signaling Pathways in Noradrenergic Neurons

The long-term use of anxiolytic and antidepressant drugs can cause a plethora of side effects and the use of complementary and alternative medicine, which is generally considered safer than conventional medicine, is consistently increasing. Helichrysum stoechas (L.) Moench methanolic extract (HSE) has shown MAO-A inhibitory properties in previous studies. With the aim of obtaining innovative and safer therapies for mood disorders, this study investigated the potential activity of HSE in the management of anxiety- and depression-related symptoms. HSE showed dose-dependent (30-100 mg/kg p.o.) anxiolytic-like activity in the light dark box and marble burying tests, without any antidepressant-like activity, as shown by the results of the tail suspension test. Additionally, HSE did not have any effect on the modulation of pain, which highlights its selectivity in the control of anxiety-related behavior. At active doses, HSE did not produce any sedative effect or result in impaired motor coordination and memory functions. Western blotting experiments showed the ability of HSE to counteract the reduction in the phosphorylation of ERK44/42, to restore brain-derived neurotrophic factor (BDNF) expression and to return cyclic AMP response element binding (CREB) levels to basal levels in noradrenergic hippocampal neurons of mice exposed to an anxiety-related environment, which indicates a protective role against anxiety behavior. These results suggest that oral administration of HSE might represent an interesting opportunity for the management of anxiety disorders.

KiwiC for Vitality: Results of a Randomized Placebo-Controlled Trial Testing the Effects of Kiwifruit or Vitamin C Tablets on Vitality in Adults with Low Vitamin C Levels

Consumption of vitamin C-rich fruit and vegetables has been associated with greater feelings of vitality. However, these associations have rarely been tested in randomized controlled trials. The aim of the current study was to test the effects of eating a vitamin C-rich food (kiwifruit) on subjective vitality and whether effects are driven by vitamin C. Young adults (n = 167, 61.1% female, aged 18-35) with plasma vitamin C <40 µmol/L were randomized into three intervention conditions: kiwifruit (2 SunGold™ kiwifruit/day), vitamin C (250 mg tablet/day), placebo (1 tablet/day). The trial consisted of a two-week lead-in, four-week intervention, and two-week washout. Plasma vitamin C and vitality questionnaires (total mood disturbance, fatigue, and well-being) were measured fortnightly. Self-reported sleep quality and physical activity were measured every second day through smartphone surveys. Nutritional confounds were assessed using a three-day food diary during each study phase. Plasma vitamin C reached saturation levels within two weeks for the kiwifruit and vitamin C groups. Participants consuming kiwifruit showed significantly improved mood and well-being during the intervention period; improvements in well-being were sustained during washout. Decreased fatigue and increased well-being were observed following intake of vitamin C alone, but only for participants with consistently low vitamin C levels during lead-in. Diet records showed that participants consuming kiwifruit reduced their fat intake during the intervention period. Intervention effects remained significant when adjusting for age and ethnicity, and were not explained by sleep quality, physical activity, BMI, or other dietary patterns, including fat intake. There were no changes in plasma vitamin C status or vitality in the placebo group. Whole food consumption of kiwifruit improved subjective vitality in adults with low vitamin C status. Similar, but not identical, changes were found for vitamin C tablets suggesting that additional properties of kiwifruit may contribute to improved vitality.

Strategies to Combat Heat Stress in Broiler Chickens: Unveiling the Roles of Selenium, Vitamin E and Vitamin C

Heat stress compromises efficient poultry production by impairing growth performance and increasing mortality. Mechanisms to dissipate excess heat divert energy from efficient production. This includes increased energy expenditure for respiration, oxidative stress and micronutrient absorption. The fortification of diets with particular feed additives has been known as one of the most important approaches to minimize the negative impacts of heat stress on broiler production. In this context, the promising functional feed additives appeared to be selenium and vitamins E and C. The fortification of broiler diets with these feed additives has been proven to enhance the function of vital organs, immune system response and growth performance of broilers under heat stress. The current review highlights recent successful experiences in the alleviation of heat stress symptoms in broilers using the above-mentioned additives. Selenium and vitamins E and C enhanced production performance in broiler chickens challenged with acute heat stress. The combination of these additives, by employing multiple mechanisms and through synergistic effects, improves heat stress symptoms more efficiently than their individual forms. Emerging literature reveals that selenium and vitamins E and C are involved in close interactions to protect proteins and lipids from oxidative damage and boost immune system function.

Microbiota Alters Urinary Bladder Weight and Gene Expression

We studied the effect of microbiota on the transcriptome and weight of the urinary bladder by comparing germ-free (GF) and specific pathogen-free (SPF) housed mice. In total, 97 genes were differently expressed (fold change > ±2; false discovery rate (FDR) p-value < 0.01) between the groups, including genes regulating circadian rhythm (Per1, Per2 and Per3), extracellular matrix (Spo1, Spon2), and neuromuscular synaptic transmission (Slc18a3, Slc5a7, Chrnb4, Chrna3, Snap25). The highest increase in expression was observed for immunoglobulin genes (Igkv1-122, Igkv4-68) of unknown function, but surprisingly the absence of microbiota did not change the expression of the genes responsible for recognizing microbes and their products. We found that urinary bladder weight was approximately 25% lighter in GF mice (p = 0.09 for males, p = 0.005 for females) and in mice treated with broad spectrum of antibiotics (p = 0.0002). In conclusion, our data indicate that microbiota is an important determinant of urinary bladder physiology controlling its gene expression and size.

Persistent low body weight in humans is associated with higher mitochondrial activity in white adipose tissue

BACKGROUND

Constitutional thinness (CT) is a state of low but stable body weight (BMI ≤18 kg/m2). CT subjects have normal-range hormonal profiles and food intake but exhibit resistance to weight gain despite living in the modern world's obesogenic environment.

OBJECTIVE

The goal of this study is to identify molecular mechanisms underlying this protective phenotype against weight gain.

METHODS

We conducted a clinical overfeeding study on 30 CT subjects and 30 controls (BMI 20-25 kg/m2) matched for age and sex. We performed clinical and integrative molecular and transcriptomic analyses on white adipose and muscle tissues.

RESULTS

Our results demonstrate that adipocytes were markedly smaller in CT individuals (mean ± SEM: 2174 ± 142 μm 2) compared with controls (3586 ± 216 μm2) (P < 0.01). The mitochondrial respiratory capacity was higher in CT adipose tissue, particularly at the level of complex II of the electron transport chain (2.2-fold increase; P < 0.01). This higher activity was paralleled by an increase in mitochondrial number (CT compared with control: 784 ± 27 compared with 675 ± 30 mitochondrial DNA molecules per cell; P < 0.05). No evidence for uncoupled respiration or "browning" of the white adipose tissue was found. In accordance with the mitochondrial differences, CT subjects had a distinct adipose transcriptomic profile [62 differentially expressed genes (false discovery rate of 0.1 and log fold change >0.75)], with many differentially expressed genes associating with positive metabolic outcomes. Pathway analyses revealed an increase in fatty acid oxidation ( P = 3 × 10-04) but also triglyceride biosynthesis (P = 3.6 × 10-04). No differential response to the overfeeding was observed in the 2 groups.

CONCLUSIONS

The distinct molecular signature of the adipose tissue in CT individuals suggests the presence of augm ented futile lipid cycling, rather than mitochondrial uncoupling, as a way to increase energy expenditure in CT individuals. We propose that increased mitochondrial function in adipose tissue is an important mediator in sustaining the low body weight in CT individuals. This knowledge could ultimately allow more targeted approaches for weight management treatment strategies. This trial was registered at clinicaltrials.gov as NCT02004821.

Autonomic regulation of T-lymphocytes: Implications in cardiovascular disease

The nervous and immune systems both serve as essential assessors and regulators of physiological function. Recently, there has been a great interest in how the nervous and immune systems interact to modulate both physiological and pathological states. In particular, the autonomic nervous system has a direct line of communication with immune cells anatomically, and moreover, immune cells possess receptors for autonomic neurotransmitters. This circumstantial evidence is suggestive of a functional interplay between the two systems, and extensive research over the past few decades has demonstrated neurotransmitters such as the catecholamines (i.e. dopamine, norepinephrine, and epinephrine) and acetylcholine have potent immunomodulating properties. Furthermore, immune cells, particularly T-lymphocytes, have now been found to express the cellular machinery for both the synthesis and degradation of neurotransmitters, which suggests the ability for both autocrine and paracrine signaling from these cells independent of the nervous system. The details underlying the functional interplay of this complex network of neuroimmune communication are still unclear, but this crosstalk is suggestive of significant implications on the pathogenesis of a number of autonomic-dysregulated and inflammation-mediated diseases. In particular, it is widely accepted that numerous forms of cardiovascular diseases possess imbalanced autonomic tone as well as altered T-lymphocyte function, but a paucity of literature exists discussing the direct role of neurotransmitters in shaping the inflammatory microenvironment during the progression or therapeutic management of these diseases. This review seeks to provide a fundamental framework for this autonomic neuroimmune interaction within T-lymphocytes, as well as the implications this may have in cardiovascular diseases.

Pharmacogenetics of Dopamine β-Hydroxylase in cocaine dependence therapy with doxazosin

The α₁ -adrenergic antagonist, doxazosin, has improved cocaine use disorder (CUD) presumably by blocking norepinephrine (NE) stimulation and reward from cocaine-induced NE increases. If the NE levels for release were lower, then doxazosin might more readily block this NE stimulation and be more effective. The NE available for release can be lower through a genetic polymorphism in dopamine β-hydroxylase (DBH) (C-1021T, rs1611115), which reduces DβH's conversion of dopamine to NE. We hypothesize that doxazosin would be more effective in CUD patients who have these genetically lower DβH levels. This 12-week, double-blind, randomized, placebo-controlled trial included 76 CUD patients: 49 with higher DβH levels from the DBH CC genotype and 27 with lower DβH levels from T-allele carriers (CT or TT). Patients were randomized to doxazosin (8 mg/day, N = 47) or placebo (N = 29) and followed with thrice weekly urine toxicology and once weekly cognitive behavioral psychotherapy. Cocaine use was reduced at a higher rate among patients in the doxazosin than in the placebo arm. We found significantly lower cocaine use rates among patients carrying the T-allele (CT/TT) than the CC genotype. The percentage of cocaine positive urines was reduced by 41 percent from baseline in the CT/TT group with low DβH and NE levels, as compared with no net reduction in the CC genotype group with normal DβH and NE levels. The DBH polymorphism appears play an important role in CUD patients' response to doxazosin treatment, supporting a pharmacogenetic association and potential application for personalized medicine.

A single nucleotide polymorphism in dopamine beta hydroxylase (rs6271(C>T)) is over-represented in inflammatory bowel disease patients and reduces circulating enzyme

Inflammatory bowel diseases (IBD) are associated with altered neuronal regulation of the gastrointestinal (GI) tract and release of norepinephrine (NE). As sympathetic innervation of the GI tract modulates motility, blood flow, and immune function, changes in NE signaling may alter the risk of developing IBD. Dopamine beta-hydroxylase (DβH), the enzyme responsible for NE production, has been suggested to play a critical role in IBD, however the exact mechanism is unknown. We hypothesized that genetic variants of DβH could increase the risk of IBD. We performed genetic analysis on 45 IBD patients and 74 controls. IBD patients were screened by targeted exome sequencing and compared with NeuroX DβH single nucleotide polymorphism (SNP) genotyping data of the controls. Serum DβH protein levels for 15 IBD patients and 13 controls were evaluated using immunoblots and competitive ELISA. Seven SNPs were observed from DβH targeted exome sequencing in the 45 IBD patients. A single non-synonymous SNP, rs6271 (Arg549Cys), had a significant association with IBD patients; the odds ratio was a 5.6 times higher SNP frequency in IBD patients compared to controls (p = 0.002). We also examined the function and availability of the protein in both the IBD and control patients' sera bearing DβH Arg549Cys. Both control and IBD subjects bearing the heterozygote allele had statistically lower DβH protein levels while the intrinsic enzyme activity was higher. This is the first report of a noradrenergic genetic polymorphism (rs6271; Arg549Cys) associated with IBD. This polymorphism is associated with significantly lower levels of circulating DβH.

Vitamin C Content in Fruits: Biosynthesis and Regulation

Throughout evolution, a number of animals including humans have lost the ability to synthesize ascorbic acid (ascorbate, vitamin C), an essential molecule in the physiology of animals and plants. In addition to its main role as an antioxidant and cofactor in redox reactions, recent reports have shown an important role of ascorbate in the activation of epigenetic mechanisms controlling cell differentiation, dysregulation of which can lead to the development of certain types of cancer. Although fruits and vegetables constitute the main source of ascorbate in the human diet, rising its content has not been a major breeding goal, despite the large inter- and intraspecific variation in ascorbate content in fruit crops. Nowadays, there is an increasing interest to boost ascorbate content, not only to improve fruit quality but also to generate crops with elevated stress tolerance. Several attempts to increase ascorbate in fruits have achieved fairly good results but, in some cases, detrimental effects in fruit development also occur, likely due to the interaction between the biosynthesis of ascorbate and components of the cell wall. Plants synthesize ascorbate de novo mainly through the Smirnoff-Wheeler pathway, the dominant pathway in photosynthetic tissues. Two intermediates of the Smirnoff-Wheeler pathway, GDP-D-mannose and GDP-L-galactose, are also precursors of the non-cellulosic components of the plant cell wall. Therefore, a better understanding of ascorbate biosynthesis and regulation is essential for generation of improved fruits without developmental side effects. This is likely to involve a yet unknown tight regulation enabling plant growth and development, without impairing the cell redox state modulated by ascorbate pool. In certain fruits and developmental conditions, an alternative pathway from D-galacturonate might be also relevant. We here review the regulation of ascorbate synthesis, its close connection with the cell wall, as well as different strategies to increase its content in plants, with a special focus on fruits.

Executive (dys)function after stroke: special considerations for behavioral pharmacology

Stroke is a worldwide leading cause of death and long-term disability with concurrent secondary consequences that are largely comprised of mood dysfunction, as well as sensory, motor, and cognitive deficits. This review focuses on the cognitive deficits associated with stroke specific to executive dysfunction (including decision making, working memory, and cognitive flexibility) in humans, nonhuman primates, and additional animal models. Further, we review some of the cellular and molecular underpinnings of the individual components of executive dysfunction and their neuroanatomical substrates after stroke, with an emphasis on the changes that occur during biogenic monoamine neurotransmission. We concentrate primarily on changes in the catecholaminergic (dopaminergic and noradrenergic) and serotonergic systems at the levels of neurotransmitter synthesis, distribution, reuptake, and degradation. We also discuss potential secondary stroke-related behavioral deficits (specifically, poststroke depression as well as drug-abuse potential and addiction) and their relationship with stroke-induced deficits in executive function, an especially important consideration given that the average age of the human stroke population is decreasing. In the final sections, we address pharmacological considerations for the treatment of ischemia and the subsequent functional impairment, as well as current limitations in the field of stroke and executive function research.

Cell-Type Identification in the Autonomic Nervous System

The autonomic nervous system controls various internal organs and executes crucial functions through sophisticated neural connectivity and circuits. Its dysfunction causes an imbalance of homeostasis and numerous human disorders. In the past decades, great efforts have been made to study the structure and functions of this system, but so far, our understanding of the classification of autonomic neuronal subpopulations remains limited and a precise map of their connectivity has not been achieved. One of the major challenges that hinder rapid progress in these areas is the complexity and heterogeneity of autonomic neurons. To facilitate the identification of neuronal subgroups in the autonomic nervous system, here we review the well-established and cutting-edge technologies that are frequently used in peripheral neuronal tracing and profiling, and discuss their operating mechanisms, advantages, and targeted applications.

Coordinate expression of pan-neuronal and functional signature genes in sympathetic neurons

Neuron subtypes of the mature nervous system differ in the expression of characteristic marker genes while they share the expression of generic neuronal genes. The regulatory logic that maintains subtype-specific and pan-neuronal genes is not well understood. To begin to address this issue, we analyze RNA sequencing results from whole sympathetic ganglia and single sympathetic neurons in the mouse. We focus on gene products involved in the neuronal cytoskeleton, neurotransmitter synthesis and storage, transmitter release and reception and electrical information processing. We find a particular high correlation in the expression of stathmin 2 and several members of the tubulin beta family, classical pan-neuronal markers. Noradrenergic transmitter-synthesizing enzymes and transporters are also well correlated in their cellular transcript levels. In addition, noradrenergic marker transcript levels correlate well with selected pan-neuronal markers. Such a correlation in transcript levels is also seen between a number of selected ion channel, receptor and synaptic protein genes. These results provide the foundation for the analyses of the coordinated expression of downstream target genes in nerve cells.

Storage of neural histamine and histaminergic neurotransmission is VMAT2 dependent in the zebrafish

Monoaminergic neurotransmission is greatly dependent on the function of the vesicular monoamine transporter VMAT2, which is responsible for loading monoamines into secretory vesicles. The role of VMAT2 in histaminergic neurotransmission is poorly understood. We studied the structure and function of the histaminergic system in larval zebrafish following inhibition of VMAT2 function by reserpine. We found that reserpine treatment greatly reduced histamine immunoreactivity in neurons and an almost total disappearance of histamine-containing nerve fibers in the dorsal telencephalon and habenula, the most densely innervated targets of the hypothalamic histamine neurons. The reserpine treated larvae had an impaired histamine-dependent dark-induced flash response seen during the first second after onset of darkness, implying that function of the histaminergic network is VMAT2 dependent. Levels of histamine and other monoamines were decreased in reserpine treated animals. This study provides conclusive evidence of the relevance of VMAT2 in histaminergic neurotransmission, further implying that the storage and release mechanism of neural histamine is comparable to that of other monoamines. Our results also reveal potential new insights about the roles of monoaminergic neurotransmitters in the regulation of locomotion increase during adaptation to darkness.

Emerging Evidence on Neutrophil Motility Supporting Its Usefulness to Define Vitamin C Intake Requirements

Establishing intake recommendations for vitamin C remains a challenge, as no suitable functional parameter has yet been agreed upon. In this report, we review the emerging evidence on neutrophil motility as a possible marker of vitamin C requirements and put the results in perspective with other approaches. A recent in vitro study showed that adequate levels of vitamin C were needed for this function to work optimally when measured as chemotaxis and chemokinesis. In a human study, neutrophil motility was optimal at intakes ≥250 mg/day. Interestingly, a Cochrane review showed a significant reduction in the duration of episodes of common cold with regular vitamin C intakes in a similar range. Additionally, it was shown that at a plasma level of 75 µmol/L, which is reached with vitamin C intakes ≥200 mg/day, incidences of cardiovascular disease were lowest. This evidence would suggest that daily intakes of 200 mg vitamin C might be advisable for the general adult population, which can be achieved by means of a diverse diet. However, additional studies are warranted to investigate the usefulness of neutrophil motility as a marker of vitamin C requirements.

Association of Dopamine Beta-Hydroxylase (DBH) Polymorphisms with Susceptibility to Parkinson's Disease

Background

The purpose of this study was to explore the association between 2 single-nucleotide polymorphisms (SNPs) in the dopamine β-hydroxylase (DBH) gene (rs1611115 and rs732833) and the susceptibility to Parkinson’s disease (PD).

Material/Methods

Polymerase chain reaction direct sequencing (PCR-DS) was used to test the genotypes of DBH polymorphisms in 95 PD patients and 100 healthy examinees frequency-matched with the former by age and sex. The genotype and allele distribution differences between the case and control groups were analyzed by chi-square test, and the relative risk of PD in southern Chinese populations was expressed by odds ratio (OR) and 95% confidence interval (CI). Hardy-Weinberg equilibrium (HWE) was also checked by chi-square test.

Results

The genotype and allele distribution frequencies in rs1611115 were obviously different between PD patients and the healthy control group (P<0.05). The TT genotype may lead to a 2.95 times higher risk of PD occurrence compared with the common genotype CC (OR=2.95, 95%CI=1.02–8.51), and the C allele increased risk of onset of PD (OR=1.81, 95%CI=1.17–2.82). Cognition of the PD patients was different between CC and CT+TT genotypes of rs1611115 (P=0.047).

Conclusions

DBH rs1611115 polymorphism was likely to be associated with the susceptibility to PD, but we did not find that rs732833 is a susceptibility marker for PD.

Osteoblastic Actions of the Neuropeptide Y System to Regulate Bone and Energy Homeostasis

Neural pathways are now a well-appreciated factor in the regulatory milieu controlling the maintenance of bone mass. A number of neural pathways from the brain to bone have been identified. These pathways often involve elements of the energy homeostatic apparatus, indicating links between the regulation of bone metabolism and energy balance. Neuropeptide Y is one such factor that co-regulates these two processes. Initial studies outlined the skeletal actions of NPY from within the brain and the interactions with energy homeostatic processes. However, in recent years, an appreciation for the actions of NPY within bone cells has expanded. Cells of the osteoblastic lineage express both NPY ligand and a cognate receptor NPY, Y1R. Murine studies have demonstrated that both ligand and receptor actively control bone mass and osteoblast activity and interact with mechanical signals to integrate with the local loading environment. Local NPY signalling regulates osteoprogenitor production and differentiation, to cover the entire osteoblastic lineage. In addition, several recent studies have demonstrated extra-skeletal actions of osteoblastic NPY signalling, to regulate energy expenditure and with it adiposity, and in a separate study, to control release of a factor-controlling beta cell mass and insulin production/release and with it glucose tolerance. Thus, osteoblastic neuropeptide production and signalling illustrates the rapidly widening sphere of influence of skeletal tissue, and suggests a far more complex and interconnected physiology then is currently appreciated.

Central adiponectin administration reveals new regulatory mechanisms of bone metabolism in mice

Adiponectin (APN), the most abundant adipocyte-secreted adipokine, regulates energy homeostasis and exerts well-characterized insulin-sensitizing properties. The peripheral or central effects of APN regulating bone metabolism are beginning to be explored but are still not clearly understood. In the present study, we found that APN-knockout (APN-KO) mice fed a normal diet exhibited decreased trabecular structure and mineralization and increased bone marrow adiposity compared with wild-type (WT) mice. APN intracerebroventricular infusions decreased uncoupling protein 1 (UCP1) expression in brown adipose tissue, epinephrine and norepinephrine serum levels, and osteoclast numbers, whereas osteoblast osteogenic marker expression and trabecular bone mass increased in APN-KO and WT mice. In addition, centrally administered APN increased hypothalamic tryptophan hydroxylase 2 (TPH2), cocaine- and amphetamine-regulated transcript (CART), and 5-hydroxytryptamine (serotonin) receptor 2C (Htr2C) expressions but decreased hypothalamic cannabinoid receptor-1 expression. Treatment of immortalized mouse neurons with APN demonstrated that APN-mediated effects on TPH2, CART, and Htr2C expression levels were abolished by downregulating adaptor protein containing pleckstrin homology domain, phosphotyrosine domain, and leucine zipper motif (APPL)-1 expression. Pharmacological increase in sympathetic activity stimulated adipogenic differentiation of bone marrow stromal cells (BMSC) and reversed APN-induced expression of the lysine-specific demethylases involved in regulating their commitment to the osteoblastic lineage. In conclusion, we found that APN regulates bone metabolism via central and peripheral mechanisms to decrease sympathetic tone, inhibit osteoclastic differentiation, and promote osteoblastic commitment of BMSC.

Polymorphisms in genes encoding dopamine signalling pathway and risk of alcohol dependence: a systematic review

BACKGROUND

Alcohol dependence (AD) is one of the major elements that significantly influence drinking pattern that provoke the alcohol-induced organ damage. The structural and neurophysiologic abnormalities in the frontal lobes of chronic alcoholics were revealed by magnetic resonance imaging scans. It is well known that candidate genes involved in dopaminergic pathway are of immense interest to the researchers engaged in a wide range of addictive disorders. Dopaminergic pathway gene polymorphisms are being extensively studied with respect to addictive and behavioral disorders.

METHODS

From the broad literature available, the current review summarizes the specific polymorphisms of dopaminergic genes that play a role in alcohol dependence.

RESULTS

No evidence indicating any strong association between AD and polymorphisms of dopamine pathway genes has emerged from the literature.

DISCUSSION

Further studies are warranted, considering a range of alcohol-related traits to determine the genes that influence alcohol dependence.

Low dopamine function in attention deficit/hyperactivity disorder: should genotyping signify early diagnosis in children?

Attention deficit/hyperactivity disorder (ADHD) is present in 8% to 12% of children, and 4% of adults worldwide. Children with ADHD can have learning impairments, poor selfesteem, social dysfunction, and an increased risk of substance abuse, including cigarette smoking. Overall, the rate of treatment with medication for patients with ADHD has been increasing since 2008, with ≥ 2 million children now being treated with stimulants. The rise of adolescent prescription ADHD medication abuse has occurred along with a concomitant increase of stimulant medication availability. Of adults presenting with a substance use disorder (SUD), 20% to 30% have concurrent ADHD, and 20% to 40% of adults with ADHD have a history of SUD. Following a brief review of the etiology of ADHD, its diagnosis and treatment, we focus on the benefits of early and appropriate testing for a predisposition to ADHD. We suggest that by genotyping patients for a number of known, associated dopaminergic polymorphisms, especially at an early age, misdiagnoses and/or over-diagnosis can be reduced. Ethical and legal issues of early genotyping are considered. As many as 30% of individuals with ADHD are estimated to either have secondary side-effects or are not responsive to stimulant medication. We also consider the benefits of non-stimulant medication and alternative treatment modalities, which include diet, herbal medications, iron supplementation, and neurofeedback. With the goals of improving treatment of patients with ADHD and SUD prevention, we encourage further work in both genetic diagnosis and novel treatment approaches.

Peptidylglycine α-amidating monooxygenase heterozygosity alters brain copper handling with region specificity

Copper (Cu), an essential trace element present throughout the mammalian nervous system, is crucial for normal synaptic function. Neuronal handling of Cu is poorly understood. We studied the localization and expression of Atp7a, the major intracellular Cu transporter in the brain, and its relation to peptidylglycine α-amidating monooxygenase (PAM), an essential cuproenzyme and regulator of Cu homeostasis in neuroendocrine cells. Based on biochemical fractionation and immunostaining of dissociated neurons, Atp7a was enriched in post-synaptic vesicular fractions. Cu followed a similar pattern, with ~ 20% of total Cu in synaptosomes. A mouse model heterozygous for the Pam gene (PAM+/−) was selectively Cu deficient in the amygdala. As in cortex and hippocampus, Atp7a and PAM expression overlap in the amygdala, with highest expression in interneurons. Messenger RNA levels of Atox-1 and Atp7a, which deliver Cu to the secretory pathway, were reduced in the amygdala but not in the hippocampus in PAM+/− mice, GABAB receptor mRNA levels were similarly affected. Consistent with Cu deficiency, dopamine β-monooxygenase function was impaired as evidenced by elevated dopamine metabolites in the amygdala, but not in the hippocampus, of PAM+/− mice. These alterations in Cu delivery to the secretory pathway in the PAM+/− amygdala may contribute to the physiological and behavioral deficits observed. Atp7a, a Cu-transporting P-type ATPase, is localized to the trans-Golgi network and to vesicles distributed throughout the dendritic arbor. Tissue-specific alterations in Atp7a expression were found in mice heterozygous for peptidylglycine α-amidating monooxygenase (PAM), an essential neuropeptide-synthesizing cuproenzyme. Atp7a and PAM are highly expressed in amygdalar interneurons. Reduced amygdalar expression of Atox-1 and Atp7a in PAM heterozygous mice may lead to reduced synaptic Cu levels, contributing to the behavioral and neurochemical alterations seen in these mice.

Adiponectin regulates bone mass via opposite central and peripheral mechanisms through FoxO1

The synthesis of adiponectin, an adipokine with ill-defined functions in animals fed a normal diet, is enhanced by the osteoblast-derived hormone osteocalcin. Here we show that adiponectin signals back in osteoblasts to hamper their proliferation and favor their apoptosis, altogether decreasing bone mass and circulating osteocalcin levels. Adiponectin fulfills these functions, independently of its known receptors and signaling pathways, by decreasing FoxO1 activity in a PI3-kinase-dependent manner. Over time, however, these local effects are masked because adiponectin signals in neurons of the locus coeruleus, also through FoxO1, to decrease the sympathetic tone, thereby increasing bone mass and decreasing energy expenditure. This study reveals that adiponectin has the unusual ability to regulate the same function in two opposite manners depending on where it acts and that it opposes, partially, leptin's influence on the sympathetic nervous system. It also proposes that adiponectin regulation of bone mass occurs through a PI3-kinase-FoxO1 pathway.

Docking studies and network analyses reveal capacity of compounds from Kandelia rheedii to strengthen cellular immunity by interacting with host proteins during tuberculosis infection

Kandelia rheedii (locally known as Guria or Rasunia), widely found and used in Indian subcontinent, is a well-known herbal cure to tuberculosis. However, neither the mechanism nor the active components of the plant extract responsible for mediating this action has yet been confirmed. Here in this study, molecular interactions of three compounds (emodin, fusaric acid and skyrin) from the plant extract with the host protein targets (casein kinase (CSNK), estrogen receptor (ERBB), dopamine β-hydroxylase (DBH) and glucagon receptor (Gcgr)) has been found. These protein targets are known to be responsible for strengthening cellular immunity against Mycobacteria tuberculosis. The specific interactions of these three compounds with the respective protein targets have been discussed here. The insights from study should further help us designing molecular medicines against tuberculosis.

Dopamine-β-hydroxylase in postural tachycardia syndrome

Norepinephrine is frequently elevated in postural tachycardia syndrome (POTS), a syndrome of heterogeneous etiology characterized by a >30 beats/min increase in heart rate with standing. Norepinephrine is synthesized from dopamine by dopamine-β-hydroxylase (DBH). The results of a preliminary study suggested that the T allele frequency of the DBH −1021C→T polymorphism is elevated in POTS. This allele correlates with low DBH activity and might predict reduced serum DBH activity in patients with POTS. To test the hypothesis that low DBH activity and the underlying −1021C→T polymorphism are associated with increased susceptibility to POTS, we measured serum DBH activity in POTS and determined its relationship to the DBH genotype and plasma norepinephrine. Serum DBH was similar for 83 normal volunteers and 42 patients with POTS: median (range) = 22.5 (0.5–94.2) and 19.6 (0.1–68.8) nmol·min−1·ml−1, respectively ( P = 0.282). The genotype frequencies for 254 control and 157 POTS patients were not different between groups (∼63% CC genotype and ∼5% TT genotype, P = 0.319). The T allele associated with lower serum DBH in both groups [control serum DBH = 15.7 (SD 12.3) and 35.1 nmol·min−1·ml−1(SD 18.6) for T carriers and noncarriers, respectively; POTS serum DBH = 8.2 (SD 5.6) and 28.5 nmol·min−1·ml−1(SD 14.7) for T carriers and noncarriers, respectively]. High DBH in POTS was linked to elevated plasma levels of norepinephrine. Although DBH activity and genotype are unlikely to be primary determinants of susceptibility to POTS, differences in DBH activity in POTS may reflect differences in the level of sympathetic activation.

Catecholamine release in human skin--a microdialysis study

Dermal microdialysis might be a promising tool to investigate properties of sympathetic neurons in the skin as investigation of peripheral noradrenergic neurons in humans usually relies on highly variable vasoconstrictor reflexes or on indirect measurements like skin temperature recordings. To evaluate this technique, 21 experiments were performed in 15 healthy subjects with four intracutaneous microdialysis fibers (diameter, 200 microm; cutoff, 5 kDa) at hands or feet. After 60 min, saline perfusion tyramine at concentrations of 0.195 to 200 microg/ml was applied for 15 min followed by a 15-min saline perfusion again. Catecholamine concentrations were detected through high-performance liquid chromatography with electrochemical detection. Control experiments were performed in human skin homogenates with and without tyramine incubation. In vivo, norepinephrine (NE) concentration increased from 36.3 +/- 10.2 pg/ml to 84.4 +/- 18.4 pg/ml (P < 0.001) during stimulation with tyramine, dialysate dopamine (DA) concentration increased from 105.2 +/- 36.5 pg/ml to 7162.4 +/- 3972.4 pg/ml (P < 0.001). Both tyramine-induced NE and DA release were dose-dependent (NE: r = 0.438, P < 0.05; DA: r = 0.894, P < 0.001). In skin homogenates, tyramine incubation led to a significant increase of DA concentrations (387.0 +/- 34.8 pg/ml, controls: 13.2 +/- 2.4 pg/ml; P < 0.05), while NE and epinephrine levels remained unchanged. In conclusion, our experiments show that dermal microdialysis is capable of locally measuring catecholamines in human skin. This offers the opportunity to investigate the function of the peripheral sympathetic nervous system. Additional to non-enzymatic oxidation, DA increase probably reflects metabolic degradation of tyramine by non-neuronal pathways and therefore does not reflect local sympathetic innervation.

The Hippocampal Cholinergic Neurostimulating Peptide, the N-terminal Fragment of the Secreted Phosphatidylethanolamine-binding Protein, Possesses a New Biological Activity on Cardiac Physiology

Phosphatidylethanolamine-binding protein (PEBP), alternatively named Raf-1 kinase inhibitor protein, is the precursor of the hippocampal cholinergic neurostimulating peptide (HCNP) corresponding to its natural N-terminal fragment, previously described to be released by hippocampal neurons. PEBP is a soluble cytoplasmic protein, also associated with plasma and reticulum membranes of numerous cell types. In the present report, using biochemistry and cell biology techniques, we report for the first time the presence of PEBP in bovine chromaffin cell, a well described secretion model. We have examined its presence at the subcellular level and characterized this protein on both secretory granule membranes and intragranular matrix. In addition, its presence in bovine chromaffin cell and platelet exocytotic medium, as well as in serum, was reported showing that it is secreted. Like many other proteins that lack signal sequence, PEBP may be secreted through non-classic signal secretory mechanisms, which could be due to interactions with granule membrane lipids and lipid rafts. By two-dimensional liquid chromatography-tandem mass spectrometry, HCNP was detected among the intragranular matrix components. The observation that PEBP and HCNP were secreted with catecholamines into the circulation prompted us to investigate endocrine effects of this peptide on cardiovascular system. By using as bioassay an isolated and perfused frog (Rana esculenta) heart preparation, we show here that HCNP acts on the cardiac mechanical performance exerting a negative inotropism and counteracting the adrenergic stimulation of isoproterenol. All together, these data suggest that PEBP and HCNP might be considered as new endocrine factors involved in cardiac physiology.

The influence of noradrenergic blockade on vasospasm and the quantity of cerebral dopamine ß-hydroxylase following subarachnoid haemorrhage in rabbits

BACKGROUND

The aim of this study of experimental subarachnoid haemorrhage (SAH) and exclusion of the sympathetic nervous system (SNS) in rabbits was to find out if changes in the central noradrenergic areas of the hypothalamus and brain stem could be ascertained, in parallel with measurement of the intensity of chronic cerebral vasospasm in the basilar arteries.

METHODS

Histologic specimens were prepared by perfusion fixation on day 8 after the SAH. The spastic effect of experimentally induced SAH in New Zealand rabbits was investigated: firstly, using our previously developed method for measuring the corrugation coefficient (CC) of the vessel intima on precisely defined locations of the basilar artery (BA) with the aid of computer image analysis; and secondly, by immunohistochemical assessment of the concentration and localization of dopamine beta-hydroxylase (DBH), using anti-DBH, at precisely defined sites of the hypothalamus and brain stem of the same rabbit.

RESULTS

The intima of the BA, assessed by CC, was significantly less corrugated and had significantly less DBH in group A (the control group without SAH and without additional interventions; mean CC = 1.192, P = 0.004; median DBH = 0.50, P = 0.044), in group C (SAH and alpha-blocker phenoxybenzamine; mean CC = 1.142, P = 0.000; median DBH = 0.75, P = 0.001), and in group D (SAH and cervical gangliectomy; mean CC = 1.210, P = 0.003; median DBH = 0.50, P = 0.002) compared with group B (rabbits with SAH and without medication). Group B showed a significantly more intensive accumulation of DBH (median DBH = 1.15) and, according to the CC (mean CC = 1.369), more intensive corrugation of the intima of BA than all other groups. The correlation between CC and DBH for all the rabbits (groups A, B, C and D together) was significantly positive (Spearman Rho = 0.470; p = 0.010).

CONCLUSIONS

The results of this study demonstrated: firstly, an intensive excitatory influence of SAH on the quantity of DBH in central noradrenergic areas in the hypothalamus and brain stem; secondly, a very effective influence of peripheral and systemic sympathetic exclusion on lowering the quantity of central sympathetic DBH; thirdly, that the changes in the BA of individual rabbits occur simultaneously with corresponding changes in DBH-containing neurons, thus suggesting the likelihood of SNS involvement in the pathogenesis of post-SAH vasospasm in rabbits.

Inhibitory effects of nitric oxide and nitrosative stress on dopamine-beta-hydroxylase

Dopamine-beta-hydroxylase (DbetaH) is a copper-containing enzyme that uses molecular oxygen and ascorbate to catalyze the addition of a hydroxyl group on the beta-carbon of dopamine to form norepinephrine. While norepinephrine causes vasoconstriction following reflex sympathetic stimulation, nitric oxide (NO) formation results in vasodilatation via a guanylyl cyclase-dependent mechanism. In this report, we investigated the relationship between NO and DbetaH enzymatic activity. In the initial in vitro experiments, the activity of purified DbetaH was inhibited by the NO donor, diethylamine/NO (DEA/NO), with an IC(50) of 1 mm. The inclusion of either azide or GSH partially restored DbetaH activity, suggesting the involvement of the reactive nitrogen oxide species, N(2)O(3). Treatment of human neuroblastoma cells (SK-N-MC) with diethylamine/NO decreased cellular DbetaH activity without affecting their growth rate and was augmented by the depletion of intracellular GSH. Co-culture of the SK-N-MC cells with interferon-gamma and lipopolysaccharide-activated macrophages, which release NO, also reduced the DbetaH activity in the neuroblastoma cells. Our results are consistent with the hypothesis that nitrosative stress, mediated by N(2)O(3), can result in the inhibition of norepinephrine biosynthesis and may contribute to the regulation of neurotransmission and vasodilatation.

Origin and peptide content of nerve fibers in the nasal mucosa of rats

Injection of the retrograde neuronal tracer True blue into the anterior-lateral part of the nasal mucosa of rats labeled nerve cell bodies in the superior cervical ganglion, the sphenopalatine ganglion, the otic ganglion and the trigeminal ganglion on the ipsilateral side. In the superior cervical ganglion, the sphenopalatine ganglion and the trigeminal ganglion on the contralateral side, very few nerve cell bodies were labeled, indicating that these ganglia provide minor contributions only. The number of labeled cell bodies indicates that the superior cervical ganglion, the sphenopalatine ganglion and the trigeminal ganglion contribute most to the innervation of the nose, while the contribution from the otic ganglion is minor. Cell bodies in the superior cervical ganglion harbored noradrenaline (NA) or NA/neuropeptide Y (NPY); in the sphenopalatine ganglion vasoactive intestinal peptide (VIP) or VIP/NPY; in the otic ganglion VIP, VIP/NPY or VIP/substance P (SP) and in the trigeminal ganglion calcitonin gene-related peptide (CGRP) or CGRP/SP. The results from denervations and tracer experiments suggest that all NA-containing and the majority of NPY-containing fibers in the nasal mucosa are derived from the superior cervical ganglion (sympathetic nerve supply). VIP- and VIP/NPY-containing fibers originate from the sphenopalatine and optic ganglia (parasympathetic nerve supply). Nerve fibers containing CGRP and CGRP/SP emanate from the trigeminal ganglion (sensory nerve supply).

Peptide-containing nerve fibers in the parathyroid glands of different species

Several neuropeptides, calcitonin gene-related peptide (CGRP), galanin, neuropeptide Y (NPY), pituitary adenylate cyclase activating peptide (PACAP), substance P (SP), vasoactive intestinal polypeptide (VIP), the noradrenergic marker dopamine beta-hydroxylase (DBH) and the general neuroendocrine marker PGP 9.5 were localized by immunocytochemistry in the parathyroid glands of chicken, rat, guinea-pig, cat, dog and sheep. The general density of innervation varied markedly among the species. Nerve fibers storing CGRP, NPY, PACAP, SP and VIP were present in all species examined. Galanin-containing fibers occurred in all species except guinea-pig and adrenergic (DBH-containing) fibers in all species except chicken and guinea-pig. Generally, the nerve fibers were distributed around blood vessels, in the parenchyma as single scattered fibers, and often also within the capsule. Coexistence studies were performed in cat and sheep. CGRP and SP invariably coexisted in the same nerve fibers. Further, CGRP partially coexisted with PACAP, NPY was observed in the same nerve fibers as DBH. A small population of NPY-containing fibers also seemed to contain galanin (cat only). VIP and NPY coexisted in a population of nerve fibers in the parenchyma. A population of VIP-containing fibers also seemed to contain PACAP. The results indicate the presence of several neuropeptides in the parathyroid glands. As judged by their distribution patterns they may regulate both secretory activity and blood flow, some of them possibly in a cooperative manner.

Effect of chronic DDC treatment on LHRH and substance P amidation processes in the rat

We examined the effects of chronic diethyldithiocarbamate (DDC) treatment on the concentrations of methionine-enkephalin, mature and unamidated forms (-Gly) of luteinizing hormone releasing hormone (LHRH) and substance P (SP) in various regions of the central nervous system (CNS). Chronic DDC treatment resulted in elevations of LHRH-Gly like immunoreactivity in the preoptic area (POA) and the medial basal hypothalamus (MBH), as well as elevations in SP-Gly like immunoreactivity in all areas of the CNS examined. Castration altered the ratios of SP-G-like/SP-like immunoreactivity in the pons, and LHRH-Gly like immunoreactivity in the MBH. Met-enkephalin concentrations were significantly elevated in the pons and medulla of intact DDC-treated animals, and in the POA of both intact- and castrated DDC-treated animals. Results demonstrate that it is possible to detect basal levels of unamidated LHRH and SP in many areas of the CNS, with ratios of unamidated/amidated peptides representing a unique and sensitive method for determining altered posttranslational processing of these transmitters, especially under altered endocrine states such as castration. Pharmacological blockade of terminal enzymatic processing of these peptides may be useful in studying upstream regulatory events in peptidergic neurons.

Peptide-containing nerve fibers in the fungiform papillae of pigs and rats

The occurrence and distribution of an array of neuropeptides and dopamine-beta-hydroxylase in the fungiform papillae of pigs and rats were studied by immunocytochemistry. Structural differences between the fungiform papillae of the two species were correlated to differences in the occurrence and distribution of neuropeptides. Calcitonin gene-related peptide-, substance P- and neurokinin A-containing fibers were numerous in the fungiform papillae of both species, although their distribution within the papilla differed. In the pig, the majority of these fibers ended within the taste buds, while in the rat numerous fibers also penetrated the adjacent epithelium. Galanin- and bombesin-immunoreactive nerve fibers could not be detected in the rat fungiform papillae, while in the pig many, but not all, of the fungiform papillae contained bombesin- and galanin-positive nerve fibers. Vasoactive intestinal peptide- and peptide histidine isoleucine-immunoreactive fibers occurred in the fungiform papillae of both species. A few neuropeptide Y-containing fibers and dopamine-beta-hydroxylase-positive (presumably adrenergic) fibers could be observed in the porcine papillae only.

Catecholamines and catecholamine-synthesizing enzymes in guinea-pig sensory ganglia

Cranial and spinal sensory ganglia of the guinea-pig were investigated by means of histochemistry and biochemistry for the presence of catecholamines and catecholamine-synthesizing enzymes. Sensory neurons exhibiting immunoreactivity to the rate-limiting enzyme of catecholamine synthesis, tyrosine hydroxylase (TH), were detected by immunohistochemistry in lumbo-sacral dorsal root ganglia, the nodose ganglion and the petrosal/jugular ganglion complex. The carotid body was identified as a target of TH-like-immunoreactive (TH-LI) neurons by the use of combined retrograde tracing and immunohistochemistry. Double-labelling immunofluorescence revealed that most TH-LI neurons also contained somatostatin-LI, but TH-LI did not coexist with either calcitonin gene-related peptide- or substance P-LI. TH-LI neurons did not react with antibodies to other enzymes involved in catecholamine synthesis, i.e., aromatic amino acid decarboxylase (AADC), dopamine-beta-hydroxylase (D beta H), and phenylethanolamine-N-methyl-transferase (PNMT). Petrosal neurons as well as their endings in the carotid body lacked dopamine- and L-DOPA-LI. Sensory neurons did not display glyoxylic acid-induced catecholamine fluorescence. Ganglia containing TH-LI neurons were kept in short-term organ culture after crushing their roots and the exiting nerve in order to enrich intra-axonal transmitter content at the ganglionic side of the crush. However, even under these conditions, catecholamine fluorescence was not detected in axons projecting peripherally or centrally from the ganglia. Sympathetic noradrenergic nerves entered the ganglia and terminated within them. Accordingly, biochemical analyses of guinea-pig sensory ganglia revealed noradrenaline but no dopamine. In conclusion, catecholamines within guinea-pig sensory ganglia are confined to sympathetic nerves, which fulfill presently unknown functions. The TH-LI neurons themselves, however, lack any additional sign of catecholamine synthesis, and the presence of enzymatically active TH within these neurons is questionable.

Peptide-containing neurons projecting to the vocal cords of the rat: retrograde tracing and immunocytochemistry

The distribution and origin of neuropeptide Y-, vasoactive intestinal peptide- and calcitonin gene-related peptide-containing nerve fibers and adrenergic (dopamine-beta-hydroxylase-containing) fibers in the rat larynx were studied by retrograde tracing and selective denervations in combination with immunocytochemistry. An injection of the retrograde tracer True Blue to the right vocal cord resulted in the appearance of labelled nerve cell bodies in the ipsi- and contralateral superior cervical and stellate ganglia, the thyroid ganglia, the jugular-nodose ganglionic complexes, in the ipsilateral trigeminal and dorsal root ganglia at levels C2 and C3 and in local tracheal ganglia. Judging from the number of labelled nerve cell bodies, the jugular-nodose ganglionic complexes, dorsal root ganglia and superior cervical ganglia provide the greater part of the vocal cord innervation. Most of the True Blue-labelled nerve cell bodies in the superior cervical and stellate ganglia contained neuropeptide Y. In the thyroid ganglia the majority of labelled nerve cell bodies contained vasoactive intestinal peptide. In the jugular-nodose ganglionic complex and the dorsal root ganglia the majority of the labelled nerve cell bodies stored calcitonin gene-related peptide. Retrograde tracing and denervation studies revealed that all noradrenaline- and the majority of neuropeptide Y-containing nerve fibers emanate from the superior cervical and stellate ganglia. A minor population of neuropeptide Y-containing nerve fibers originate in local tracheal ganglia. The vasoactive intestinal peptide-containing nerve fibers originate in the thyroid ganglion and local tracheal ganglia, whereas calcitonin gene-related peptide-containing nerve fibres emanate from the dorsal root ganglia (C2-C3), the trigeminal ganglia and the jugular-nodose ganglia.

Peptide-containing nerve fibers in the circumvallate papillae

The occurrence and distribution of an array of neuropeptides and dopamine-beta-hydroxylase in the circumvallate papillae of monkey, pig, cow, ferret, cat, rat and mouse was studied by immunocytochemistry. The animals were chosen to represent species with different diets. Substance P/neurokinin A- and calcitonin gene-related peptide-containing fibers were numerous in the circumvallate papillae of all animals examined, with the highest frequency in monkey, pig, cow, rat and mouse; in ferret and cat moderate numbers were detected. Vasoactive intestinal peptide/peptide histidine isoleucine amide-containing fibers were numerous in the circumvallate papillae of pig, while they were moderate in number in monkey, ferret and mouse. Neuropeptide Y-containing fibers were few to moderate in number in the circumvallate papillae of all species. Galanin-containing fibers were numerous in the pig circumvallate papillae, while only a few fibers could be detected in monkey, cow, cat, rat and mouse. Somatostatin-containing fibers were seen only in the cat circumvallate papillae, gastrin-releasing peptide-containing fibers in the cow and cat, cholecystokinin/gastrin-containing fibers in the pig and cow. Dopamine-beta-hydroxylase-containing fibers were detected in all animals studied. They were few to moderate in number in the circumvallate papillae. There was no obvious link between the peptidergic innervation pattern and the food habits.

Neuropeptide Y and vasoactive intestinal peptide coexist in rat thyroid nerve fibers emanating from the thyroid ganglion

Neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) occur in nerve fibers around blood vessels and between follicles in the thyroid gland of the mouse and rat. VIP-immunoreactive fibers are numerous, while NPY-immunoreactive fibers are fewer. Most of the latter fibers contain noradrenaline (NA) as well as NPY, while a subpopulation was found to contain VIP instead of NA. We have determined the origins of rat thyroid nerve fibers containing NPY, VIP or NPY/VIP by investigating 3 conceivable sources, i.e. the superior cervical ganglion, the nodose ganglion and the thyroid ganglion. Chemical sympathectomy or removal of the superior cervical ganglion did not affect the frequency of VIP-immunoreactive fibers but eliminated most of the NPY-immunoreactive fibers as well as all NA-containing nerve fibers (recognized by antibodies to dopamine-beta-hydroxylase). The NPY-immunoreactive fibers that remained after sympathectomy occurred around blood vessels and between follicles and contained VIP. Cervical vagotomy (removal of the nodose ganglion including the adjacent vagus) did not overtly affect the frequency of NPY/VIP-, VIP-, or NPY/NA-containing fibers in the thyroid. In contrast, extirpation of the thyroid ganglion, which is situated immediately outside the thyroid capsule, greatly reduced the number of VIP- and NPY/VIP-containing fibers in the rat thyroid. On the whole, the results of radioimmunoassay of NPY and VIP agreed well with the immunocytochemical findings. High performance liquid chromatography confirmed the identity of NPY and VIP. The present findings suggest the existence in the rat thyroid of one NPY-containing nerve fiber population that harbours NA and emanates from the superior cervical ganglion; one NPY-containing fiber population that is non-adrenergic, harbours VIP and originates in the thyroid ganglion; and a second VIP-containing fiber population that is devoid of NPY and appears to derive from the thyroid ganglion.

Projections of peptide-containing neurons in rat colon

The distribution, origin and projections of nerve fibers containing vasoactive intestinal peptide, substance P, neuropeptide Y, galanin, gastrin-releasing peptide, calcitonin gene-related peptide, somatostatin or enkephalin were studied in the midcolon of the rat by immunocytochemistry and immunochemistry. Most of these nerve fibers had an intramural origin as was established by extrinsic denervation (serving of mesenterial nerves). Extrinsic denervation eliminated neuropeptide Y-containing fibers of presumably sympathetic origin together with sensory nerve fibers containing both substance P and calcitonin gene-related peptide. Co-existence of two peptides in the same neuron was studied by double immunostaining. This revealed co-existence of neuropeptide Y and vasoactive intestinal peptide in one population of intramural neurons; an additional population of intramural neurons was found to contain vasoactive intestinal peptide but not neuropeptide Y. All somatostatin-containing neurons in the submucous ganglia were found to harbor calcitonin gene-related peptide. A much larger population of submucous neurons containing calcitonin gene-related but not somatostatin was also detected. Some perivascular calcitonin gene-related peptide-containing nerve fibers (of intrinsic origin) harbored vasoactive intestinal peptide while others (of extrinsic origin) harbored substance P. The polarities and projections of the various peptide-containing intramural neurons in the transverse colon were studied by analysing the loss of nerve fibers upon local disruption of enteric nervous pathways (myectomy or intestinal clamping). Myenteric neurons containing vasoactive intestinal peptide, galanin, gastrin-releasing peptide, calcitonin gene-related peptide, somatostatin or vasoactive intestinal peptide/neuropeptide Y gave off 5-10-mm-long descending projections while those containing substance P or enkephalin issued approx. 5-mm-long ascending projections. Submucous neurons containing calcitonin gene-related peptide, somatostatin/calcitonin gene-related peptide or gastrin-releasing peptide issued both ascending (2-6 mm) and descending (2-6 mm) projections, those containing vasoactive intestinal peptide issued ascending (approx. 2 mm) projections, while those containing galanin or vasoactive intestinal peptide/neuropeptide Y lacked demonstrable oro-anal projections. Enkephalin-containing fibers could not be detected in the mucosa and the mucosal substance P-containing nerve fibers were too few to enable us to delineate their projections.

Changes in surviving nerve fibers associated with submucosal arteries following extrinsic denervation of the small intestine

The neuropeptide content of nerve fibers associated with submucosal arteries in the small intestine of guinea pigs was studied in whole-mount preparations using immunohistochemical methods. Tissues were obtained from normal animals or animals in which the small intestine had been extrinsically denervated. In normal animals, submucosal arteries are innervated by extrinsic sensory nerve fibers which contain both substance P and calcitonin gene-related peptide, and by sympathetic noradrenergic nerve fibers. In preparations obtained from animals 5-9 days after denervation, nerve fibers which contained substance P without detectable calcitonin gene-related peptide were associated with a few submucosal arteries. Nerve fibers which contained vasoactive intestinal peptide were also associated with some arteries. By 42-48 days after extrinsic denervation, substance P-containing fibers (without calcitonin gene-related peptide) and vasoactive intestinal peptide-containing fibers were associated with nearly every blood vessel. The extrinsic sympathetic nerve fibers did not regenerate during the course of this study. The nerve fibers associated with submucosal arteries in denervated tissues were not sensitive to capsaicin treatment. The alteration in the innervation of submucosal arterioles that follows extrinsic denervation of the gut may reflect either an increase in the neuropeptide content of the fibers, synthesis of a new peptide, or an increase in the number of fibers as a result of axonal sprouting.

Evidence for coexistence of serotonin and noradrenaline in sympathetic nerves supplying brain vessels of guinea pig

Nerve fibers containing 5-hydroxytryptamine (5-HT) were demonstrated immunohistochemically in the wall of pial vessels associated with the circle of Willis in the guinea pig. The fibers formed a network structure which was more dense in the rostral part of the arterial circle and its branches than in the caudal part. The 5-HT immunoreactive fibers disappeared in all arteries studied after bilateral superior cervical ganglionectomy, and unilateral ganglionectomy eliminated the 5-HT immunoreactivity in the ipsilateral part of the middle cerebral, posterior cerebral and superior cerebellar arteries. Decentralization of the superior cervical ganglion had no effect on the perivascular nerve plexus. Subsequent staining with dopamine-beta-hydroxylase (DBH) antiserum following elution of the first antibody revealed that 5-HT was present in the noradrenergic nerve fibers. Small intensive fluorescent cells with positive immunoreaction for 5-HT and DBH, respectively, were located in clusters within the ganglion, which showed no immunohistochemical evidence for the presence of serotonergic neurons. It is concluded that 5-HT is probably not synthesized in truly serotonergic fibers but rather taken up and stored together with noradrenaline in cerebrovascular sympathetic nerves originating in the superior cervical ganglia.