Neurochemical characterization of the release and uptake of dopamine in ventral tegmental area and serotonin in substantia nigra of the mouse

In the present report, fast-scan cyclic voltammetry was used to identify the monoamines that were released by electrical stimulation in mouse brain slices containing ventral tegmental area (VTA), substantia nigra (SN) -pars compacta (SNc) and -pars reticulata (SNr). We showed that voltammograms obtained in mouse VTA were consistent with detection of a catecholamine, while those in both subregions of the SN were consistent with detection of an indolamine, based on the reduction peak potentials. We used pharmacological blockade and genetic deletion of monoamine transporters to further confirm the identity of released monoamines in mouse midbrain and to assess the control of monoamines by their transporters in each brain region. Inhibition of dopamine and norepinephrine transporters by nomifensine (1 and 10 microm) decreased uptake rates in the VTA, but did not change uptake rates in either subregion of the SN. Serotonin transporter inhibition by fluoxetine (10 microm) decreased uptake rates in the SNc and SNr, but was without effect in the VTA. Selective inhibition of the norepinephrine transporter by desipramine (10 microm) had no effect in any brain region. Using dopamine transporter- and serotonin transporter-knockout mice, we found decreased uptake rates in VTA and SN subregions, respectively. Peak signals recorded in each midbrain region were pulse number dependent and exhibited limited frequency dependence. Thus, dopamine is predominately detected by voltammetry in mouse VTA, while serotonin is predominately detected in mouse SNc and SNr. Furthermore, active uptake occurs in these areas and can be altered only by specific uptake inhibitors, suggesting a lack of heterologous uptake. In addition, somatodendritic dopamine release in VTA was not mediated by monoamine transporters. This work offers an initial characterization of voltammetric signals in the midbrain of the mouse and provides insight into the regulation of monoamine neurotransmission in these areas.     

Factors affecting in vivo electrochemistry: electrode-tissue interaction and the ascorbate amplification effect

While in vivo electrochemistry has been shown to be useful for discovering new neurophysiological phenomena, there is still considerable controversy about the identity of the compounds being measured and the concentration of those compounds in extracellular fluid in brain. We have found that carbon paste electrodes undergo changes in sensitivity and specificity for dopamine and other compounds after being implanted in brain. We have also examined the effect of ascorbate on the selective enhancement of catecholamine peaks to provide an explanation for the apparently very high concentrations of dopamine measured in the extracellular fluid space. After temporary brain implantation (20 min), carbon paste electrodes tested in vitro showed increased sensitivity and lower oxidation potentials for dopamine, norepinephrine and serotonin. These brain-treated electrodes also detected 3,4-dihydroxyphenylacetic acid (DOPAC) as a distinct peak at +0.16 V, although the electrode sensitivity for DOPAC was some 25 times lower than that for dopamine. Brain treatment did not alter electrode sensitivity or oxidation potential for 5-HIAA. The oxidation current for ascorbic acid when processed as the semiderivative showed no distinct peak in the potential range -0.2 to +0.4V for either untreated or brain-treated electrodes. However ascorbic acid amplified the electrochemical peaks of catechols in direct proportion to the ratio of the concentration of ascorbate to the concentration of the catechol. In the physiologic concentration range of 300 microM ascorbate, the electrochemical signal for 1 microM dopamine was amplified 4250%. While ascorbate amplification improves detectability of dopamine and norepinephrine, it also introduces ambiguity since changing catechol concentrations cannot be distinguished from changing ascorbate concentrations.     

2-Guanidinoethanol increased dopamine release and 3,4-dihydroxyphenylacetic acid content,but not homovanillic acid content in the rat brain: Electroneurochemical and enzymological studies

The effects of 2-guanidinoethanol (GEt) on the release of monoamines and on the activity of their degrading enzymes were studied in order to investigate why 3,4-dihydroxyphenylacetic acid (DOPAC) increased to a much greater extent than homovanillic acid (HVA) after GEt injection into rat brain. In differential pulse voltammograms recorded using an electrochemically treated carbon fiber electrode, two distinct oxidation peaks, one at 130mV (DOPAC peak) and the other at 300 mV (5-hydroxyindoleacetic acid (5-HIAA) peak), were observed. In the hippocampus, the DOPAC peak increased markedly compared to the peak height recorded prior to the intracerebroventricular injection of GEt (6mol). Although the DOPAC peak height increased to 350% 4 hours after GEt injection, the 5-HIAA peak showed no change. In the striatum, the DOPAC peak increased to 150% 3 hours after GEt injection. Serial changes in the extracellular levels of DOPAC, HVA, and 5-HIAA were monitored in the striatum after GEt injection, using an in vivo brain micro-dialysis technique. Although the DOPAC levels strated to increase 80 minutes after GEt injection, HVA and 5-HIAA levels showed no change. On the other hand, monoamineoxidase, which metabolizes dopamine to DOPAC, was not activated and catechol-0-methyltransferase, which metabolizes DOPAC to HVA, were not inhibited by 5 mM of GEt in vitro. These data suggested that GEt increased the release of dopamine, but not of serotonin, and that GEt might restrict the DOPAC transport system.     

Molecular and Cellular Mechanisms of Ecstasy-Induced Neurotoxicity: An Overview

“Ecstasy” [(±)-3,4-methylenedioxymethamphetamine, MDMA, XTC, X, E] is a psychoactive recreational hallucinogenic substance and a major worldwide drug of abuse. Several reports raised the concern that MDMA has the ability to induce neurotoxic effects both in laboratory animals and humans. Despite more than two decades of research, the mechanisms by which MDMA is neurotoxic are still to be fully elucidated. MDMA induces serotonergic terminal loss in rats and also in some mice strains, but also a broader neuronal degeneration throughout several brain areas such as the cortex, hippocampus, and striatum. Meanwhile, in human “ecstasy” abusers, there are evidences for deficits in seronergic biochemical markers, which correlate with long-term impairments in memory and learning. There are several factors that contribute to MDMA-induced neurotoxicity, namely, hyperthermia, monoamine oxidase metabolism of dopamine and serotonin, dopamine oxidation, the serotonin transporter action, nitric oxide, and the formation of peroxinitrite, glutamate excitotoxicity, serotonin 2A receptor agonism, and, importantly, the formation of MDMA neurotoxic metabolites. The present review covered the following topics: history and epidemiology, pharmacological mechanisms, metabolic pathways and the influence of isoenzyme genetic polymorphisms, as well as the acute effects of MDMA in laboratory animals and humans, with a special focus on MDMA-induced neurotoxic effects at the cellular and molecular level. The main aim of this review was to contribute to the understanding of the cellular and molecular mechanisms involved in MDMA neurotoxicity, which can help in the development of therapeutic approaches to prevent or treat the long-term neuropsychiatric complications of MDMA abuse in humans.     

Electrochemical reactions of horse heart cytochrome c at graphite electrodes

The interaction of cytochrome c with a paraffin-wax-impregnated spectroscopic graphite electrode (WISGE) was studied in a medium consisting of 0.1 M potassium phosphate, pH 7.0, by means of differential pulse and cyclic voltammetry. Ferricytochrome c yields on voltammograms a single cathodic peak C around a potential of -0.3 V (vs. Ag/AgCl) and two anodic peaks AI and AII around the potentials of 0.66 and 0.89 V, respectively. Cathodic peak C corresponds to a catalytic reaction during which ferricytochrome c is reduced to ferrocytochrome c: ferricytochrome c is then regenerated by chemical oxidation of ferrocytochrome c by oxygen adsorbed at the WISGE surface. The first, more negative anodic peak AI corresponds to anodic electrochemical oxidation of tyrosine residues, whereas the second, more positive anodic peak (peak AII) corresponds to an anodic reaction of haemin. Voltammetry at a WISGE may provide a valuable technique for obtaining data about cytochrome c properties on electrically charged surface.     

On the role of synchrony for neuron–astrocyte interactions and perceptual conscious processing

Recent research on brain correlates of cognitive processes revealed the occurrence of global synchronization during conscious processing of sensory stimuli. In spite of technological progress in brain imaging, an explanation of the computational role of synchrony is still a highly controversial issue. In this study, we depart from an analysis of the usage of blood-oxygen-level-dependent functional magnetic resonance imaging for the study of cognitive processing, leading to the identification of evoked local field potentials as the vehicle for sensory patterns that compose conscious episodes. Assuming the “astrocentric hypothesis” formulated by James M. Robertson (astrocytes being the final stage of conscious processing), we propose that the role of global synchrony in perceptual conscious processing is to induce the transfer of information patterns embodied in local field potentials to astrocytic calcium waves, further suggesting that these waves are responsible for the “binding” of spatially distributed patterns into unitary conscious episodes.     

Fine steps of electrocatalytic oxidation and sensitive detection of some amino acids on copper nanoparticles

The electrocatalytic oxidation of five amino acids—glycine, aspartic acid, cysteine, glutamic acid, and tyrosine—on two copper-based electrodes comprising copper microparticle-modified carbon paste electrode (m-CPE) and copper nanoparticle-modified CPE (n-CPE) was investigated. In the voltammograms recorded using m-CPE, a single anodic peak related to the oxidation of amino acids appeared and was related to the electrocatalytic oxidation of the amino acids via the electrogenerated Cu(III) species. Using n-CPE, however, two overlapped anodic peaks in the voltammograms appeared and were related to two fine tunable steps of the oxidation process. The currents of the two peaks were controlled by diffusion and were confirmed by chronoamperometric measurements. The amino acids were oxidized on n-CPE at higher rates and at lower potentials compared with m-CPE. This was attributed to the nanosize of copper nanoparticles. Some primary linear-chain amines and primary branched-chain amines were oxidized on the copper-based electrodes as markers. The catalytic rate constants, the transfer coefficients, and the diffusion coefficients for the amino acids are reported. Simple, sensitive, and time-saving sensing procedures in both batch and flow systems were developed for the analysis of the amino acids, and the corresponding analytical parameters are reported.     

A Metabolic Biofuel Cell: Conversion of Human Leukocyte Metabolic Activity to Electrical Currents

An investigation of the electrochemical activity of human white blood cells (WBC) for biofuel cell (BFC) applications is described. WBCs isolated from whole human blood were suspended in PBS and introduced into the anode compartment of a proton exchange membrane (PEM) fuel cell. The cathode compartment contained a 50 mM potassium ferricyanide solution. Average current densities between 0.9 and 1.6 μA cm^-2 and open circuit potentials (V_oc) between 83 and 102 mV were obtained, which were both higher than control values. Cyclic voltammetry was used to investigate the electrochemical activity of the activated WBCs in an attempt to elucidate the mechanism of electron transfer between the cells and electrode. Voltammograms were obtained for the WBCs, including peripheral blood mononuclear cells (PBMCs - a lymphocyte-monocyte mixture isolated on a Ficoll gradient), a B lymphoblastoid cell line (BLCL), and two leukemia cell lines, namely K562 and Jurkat. An oxidation peak at about 363 mV vs. SCE for the PMA (phorbol ester) activated primary cells, with a notable absence of a reduction peak was observed. Oxidation peaks were not observed for the BLCL, K562 or Jurkat cell lines. HPLC confirmed the release of serotonin (5-HT) from the PMA activated primary cells. It is believed that serotonin, among other biochemical species released by the activated cells, contributes to the observed BFC currents.     

Voiceprint identification and its application to sociological studies of wild Japanese monkeys (Macaca fuscata yakui)

Japanese monkeys often exchange the particular vocal sound, “coo,” especially when they feed or move as a group. It was considered that the “coo” sound had no positive social meaning, perhaps because the “coo” sound network and its function were hidden behind other behavioral observations. For identification of the vocalizer only from hearing the “coo” sound, three phonetic values, i.e., the “fundamental,” “duration,” and “formants,” plus other characteristics were used as indices of voiceprints. The results indicated that these were effective for identifying the vocalizer in two-thirds of the adults in the study troop which was composed of 12 adults and 16 immature members. The “coo” sound exchange network among the troop members (adults) was drawn on the basis of the voiceprint identification. The network showed three characteristics as follows: (1) matriarchs of the kin-groups frequently exchanged “coo” sounds with each other; (2) the other females exchanged “coo” sounds mostly within their own kin-groups; and (3) males seldom participated in the “coo” sound exchange. This suggests that “coo” sound exchange plays a central role for the matriarch of kin-groups in binding each kin-group and, ultimately, in binding all members together into an organized troop.     

On the Structural Regularity in Nucleobases and Amino Acids and Relationship to the Origin and Evolution of the Genetic Code

To explore how chemical structures of both nucleobases and amino acids may have played a role in shaping the genetic code, numbers of sp² hybrid nitrogen atoms in nucleobases were taken as a determinative measure for empirical stereo-electronic property to analyze the genetic code. Results revealed that amino acid hydropathy correlates strongly with the sp² nitrogen atom numbers in nucleobases rather than with the overall electronic property such as redox potentials of the bases, reflecting that stereo-electronic property of bases may play a role. In the rearranged code, five simple but stereo-structurally distinctive amino acids (Gly, Pro, Val, Thr and Ala) and their codon quartets form a crossed intersection “core”. Secondly, a re-categorization of the amino acids according to their β-carbon stereochemistry, verified by charge density (at β-carbon) calculation, results in five groups of stereo-structurally distinctive amino acids, the group leaders of which are Gly, Pro, Val, Thr and Ala, remarkably overlapping the above “core”. These two lines of independent observations provide empirical arguments for a contention that a seemingly “frozen” “core” could have formed at a certain evolutionary stage. The possible existence of this codon “core” is in conformity with a previous evolutionary model whereby stereochemical interactions may have shaped the code. Moreover, the genetic code listed in UCGA succession together with this codon “core” has recently facilitated an identification of the unprecedented icosikaioctagon symmetry and bi-pyramidal nature of the genetic code.     

Electron Capture Dissociation Mass Spectrometry in Characterization of Peptides and Proteins

Electron capture dissociation (ECD) represents one of the most recent and significant advancements in tandem mass spectrometry (MS/MS) for the identification and characterization of polypeptides. In comparison with the conventional fragmentation techniques, such as collisionally activated dissociation (CAD), ECD provides more extensive sequence fragments, while allowing the labile modifications to remain intact during backbone fragmentation—an important attribute for characterizing post-translational modifications. Herein, we present a brief overview of the ECD technique as well as selected applications in characterization of peptides and proteins. Case studies including characterization and localization of amino acid glycosylation, methionine oxidation, acylation, and “top–down” protein mass spectrometry using ECD will be presented. A recent technique, coined as electron transfer dissociation (ETD), will be also discussed briefly.     

Agonistic behavior in a transplanted troop of Japanese macaques: Arashiyama west

Arashiyama A troop was transplanted from Japan to Texas, U.S.A. in February 1972 and released into a large outdoor enclosure (42 ha) in a semi-free ranging condition. Agonistic behavior was quantified during the first six months after the release. Agonistic interactions occurred at about one incident per 100 monkeys every 2 to 9 minutes. In general, peaks in frequency of agonistic interactions coincided with peaks in feeding activity. 97.5% of all incidents were of a “mild” type, and 85.7% were simple one-to-one, unidirectional interactions. “Severe” forms of agonistic behavior occurred only during the first month and then only rarely. Adult females and juveniles were initiators in about 93% of all cases. In general, the more severe the form of attack, the more pronounced was the form of submission.     

Correlations between the psychological peculiarities of an individual and the efficacy of a single neurofeedback session (by the EEG characteristics)

Modifications of different EEG rhythms induced by a single neurofeedback session (by the EEG characteristics) directed toward an increase in the ratio of the spectral powers (SPs) of the α vs θ oscillations were compared with the psychological characteristics of the tested subjects (the group included 30 persons). A generally accepted neurofeedback technique was used; the intensity of acoustic white noise served as the feedback signal. EEG potentials were recorded from the C3 and C4 leads. Psychological testing was carried out using Eysenck’s (EPQ), Rusalov’s (OST), and (16 PF) questionnaires. The directions of changes in the SPs of EEG frequency components were found to significantly correlate with some individuality-related peculiarities of the tested subjects. The SP of the δ rhythm correlated with the EPQ scale “neuroticism,” OST scale “social plasticity,” and 16 PF factors H (“parmia”), I (“premsia”), and Q₃ (“self-control of behavior”). The SP of the θ component demonstrated correlations with the OST scales “ergisity,” “plasticity,” and “social temp” and with 16 PF factors M (“autia”), Q₄ (“frustration”), and Q1 (“exvia”). The SP of the α rhythm correlated with 16 PF factors Q₃ (“self-control of behavior”), G (“strength of superEgo”), O (“hypothymia”), L (“protension”), and N (“shrewdness”). The SP of the β rhythm correlated with the OST scale “emotionality,” while that of the γ rhythm showed correlations with the 16 PF indices L (“protension”) and M (“autia”). Changes in the ratio of the α vs θ SPs correlated with the EPQ scale “neuroticism.” Thus, our data confirm the statement that a high individual variability of the results of a single (first in the series) neurofeedback session is to a great extent related to peculiarities of the individual psychological pattern of the subject. Neirofiziologiya/Neurophysiology, Vol. 38, No. 3, pp. 239–247, May–June, 2006.     

Biosemiosis and the Cellular Basis of Mind

The human brain is a complex organ made up of neurons and several other cell types, and whose role is processing information for use in elicitation of behaviors. To accomplish this, the brain requires large amounts of energy, and this energy is obtained by the oxidation of glucose (Glc). However, the question of how the oxidation of Glc by individual neurons in brain results in their collective ability to rapidly generate feats of cognition that allow them to recognize the nature of the universe in which they live and to communicate this information remains unclear. In this article, insights into this process are provided by first considering the brain’ s homeostatic “operating system” for supply of energy to stimulated neurons, and how this system defines the basic unit of brain “structure”. This is followed by consideration of the brain’s “two-cell” neuronal communication mechanism which defines the basic unit of brain “function”. Finally, an analysis of the nature of frequency-encoded “neuronal languages” that enable ensembles of neurons to translate energy derived from the oxidation of Glc into a collective “mind”, the aggregate of all brain processes including those involving perception, thought, insight, foresight, imagination and behavior.     

The visual ecology of Puerto Rican anoline lizards: habitat light and spectral sensitivity

The visual ecology of six closely related species of Puerto Rican anoline lizards was investigated and they were found to occupy four distinct habitat types in terms of light conditions: “full shade”, “partial shade”, “no shade”, and “forest canopy.”The habitats differed substantially in total radiance and irradiance as well as in the shape of the irradiance spectrum. The shape of the radiance spectrum was similar in all of the habitats. We used electroretinogram (ERG) flicker photometry to measure spectral sensitivity and found the curves for all six species to be similar. The spectral sensitivity peaked in the range 550–560 nm, which matched the peak in spectral radiance for all of the habitats. The shape of the spectral-sensitivity curve was similar to those of a number of other terrestrial vertebrates. We suggest that the convergence of the shape of the photopic ERG-determined spectral-sensitivity curve in many terrestrial vertebrates may, in part, be due to the fact that the background radiance of many terrestrial habitats is dominated by the reflectance spectrum of green vegetation which peaks at 550 nm. Accepted: 14 May 1997     

Functional changes in brainstem auditory structures in humans suffering from the Chernobyl’ catastrophe

We analyzed the temporal characteristics of short-latency auditory evoked potentials (SL AEP) in people involved in the cleanup work after the Chemobyl’ catastrophe (hereafter, cleanup workers), who now are living within the “clean” territories or remain within the radionuclide-contaminated area (groups 2 and 3, respectively), and in persons who were not involved in the cleanup works but are permanently living within the contaminated zone (group 4). The latencies of the SL AEP were peaks (peak latencies, PL) in all these groups regularly exceeded corresponding values in the control group 1. The increments were mild (several percent) but significant for the waves II–V. The most substantial PL increments were characteristic for group 3. Analysis of the interpeak intervals showed that an increase in the I–III interval provided the greatest contribution to modification of the SL AEP, temporal parameters. The mechanisms of influence of the Chernobyl’ catastrophe-related factors on the brainstem auditory structures are discussed. The data allow us to conclude that functional modifications in the above structures contribute to the hearing change for the worse observed in the people suffering from the Chernobyl’ catastrophe; a prolonged stay within the contaminated territories represents a considerable factor aggravating these changes.     

Modifications of event-related evoked potentials in physiological and pathological aging of the brain

We compared the parameters of acoustic event-related evoked potentials (ERP; tone stimulation) in healthy young and healthy aged persons with those in patients suffering from Alzheimer’s disease (groups 1–3, respectively). It was found that the mean peak latencies (PL) of the components P1-N2 in group 1 were longer than those in group 2, and the absolute values of the amplitudes of these components were more negative. In Alzheimer patients (group 3), the PL of the components P1–P2 were much longer than those in group 2, and their peak-to-peak amplitudes dropped. The latencies of a simple sensorimotor reaction in groups 1–3 progressively increased (about three times). The ERP observed in two modes (“blackground” and “attention,” the latter with the performance of the sensorimotor reaction) were subjected to spectral analysis. Possible reasons for and mechanisms of those modifications of evoked potentials, which relate to physiological and pathological aging of the brain, are discussed.     

Identification of Barley Varieties Tolerant to Cadmium Toxicity

Two successive hydroponic experiments were carried out to identify barley varieties tolerant to Cd toxicity via examining Soil–Plant Analyses Development (SPAD) value, plant height, leaves and tillers per plant, root number and volume, and biomass accumulation. The results showed that SPAD values (chlorophyll meter readings), plant height, leaf number, root number and volume, and biomass accumulation of shoot/root were significantly reduced in the plants grown in 20 μM Cd nutrient solution compared with control, and the uptake and translocation of Zn, Mn, and Cu was also strictly hindered. Furthermore, there was a highly significant difference in the reduction in these growth parameters among varieties, and varieties “Weisuobuzhi” and “Jipi 1” showed the least reduction both in the two experiments, suggesting their high tolerance to Cd toxicity, while “Dong 17” and “Suyinmai 2” with the greatest reduction and the toxicity symptoms appeared rapidly and severely, denoting as Cd-sensitive varieties. Significant variety difference in Cd concentration was also found, with Weisuobuzhi containing the highest and Jipi 1 the lowest Cd concentration in shoots.     

Association between contrasting methane emissions of two rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) cultivars from the irrigated agroecosystem of northeast India and their growth and photosynthetic characteristics

Over two consecutive years in the North Bank Plain Zone of Assam, India, during the spring growing season (February–June) of- 2006 and 2007 we examined effects of morpho-physiological characteristics of rice (Oryza sativa L.) plants in relation to methane (CH₄) emission from paddy fields. Traditional cultivar “Agni” and modern improved cultivar “Ranjit” were grown in light textured loamy soil under irrigation. A higher seasonal integrated methane flux (E _sif) was recorded from “Agni” compared to “Ranjit”. Both cultivars exhibited an emission peak during active vegetative growth and a second peak at panicle initiation. Leaf and tiller number, leaf area, length, and volume of root were greater in “Agni”, but grain yield and yield-related parameters such as increased photosynthate partitioning to panicles at the expense of roots were greater in “Ranjit”. “Ranjit” also photosynthesed faster than “Agni” during panicle development but slower than “Agni” at tillering. In both the years, a higher soil organic carbon content was recorded in plots of “Agni”. Our results suggest that in “Agni” enhanced diversion of photosynthate to roots resulted in more substrate being available to methanogenic bacteria in the rhizosphere. Additionally, the more extensive vegetative growth of this cultivar may enhance methane transport from the soil to the above-ground atmosphere.     

Patterns of orientation behavior in marsh frogs (Rana ridibunda Pall.) of southern populations

The behavior of frogs from southern areas with an arid climate released during the reproductive period between their “home” pond and a less distant river is shown to be independent of weather conditions. The experiments were performed on frogs living near the village of Dosang, Astrakhan oblast. The frogs were released 60 to 150 m from their “home” breeding waterbody and 60 to 80 m from an “alien” waterbody. Four experiments were performed on 27 individuals. The movements of the frogs were traced by the method of “tracking by a thread.” The results revealed no preference in the frogs to return to their own breeding ponds, rather than to the nearby river. This behavior is peculiar to frogs of southern populations.