Endogenous morphine-like compound immunoreactivity increases in parkinsonism

Discovering Hair Biomarkers of Alzheimer's Disease Using High Resolution Mass Spectrometry-Based Untargeted Metabolomics

Hair may be a potential biospecimen to discover biomarkers for Alzheimer's disease (AD) since it reflects the integral metabolic profiles of body burden over several months. Here, we described the AD biomarker discovery in the hair using a high-resolution mass spectrometry (HRMS)-based untargeted metabolomics approach. A total of 24 patients with AD and 24 age- and sex-matched cognitively healthy controls were recruited. The hair samples were collected 0.1-cm away from the scalp and further cut into 3-cm segments. Hair metabolites were extracted by ultrasonication with methanol/phosphate-buffered saline 50/50 (v/v) for 4 h. A total of 25 discriminatory chemicals in hair between the patients with AD and controls were discovered and identified. The AUC value achieved 0.85 (95% CI: 0.72~0.97) in patients with very mild AD compared to healthy controls using a composite panel of the 9 biomarker candidates, indicating high potential for the initiation or promotion phase of AD dementia in the early stage. A metabolic panel combined with the nine metabolites may be used as biomarkers for the early detection of AD. The hair metabolome can be used to reveal metabolic perturbations for biomarker discovery. Investigating perturbations of the metabolites will offer insight into the pathogenesis of AD.

Determination of morphine and norlaudanosoline in murine brain regions by dispersive liquid-liquid micro-extraction and liquid chromatograpy-electrochemical detection

Morphine can be synthesized endogenously by mammals from dopamine via the intermediate norlaudanosoline. Previously, both compounds have been detected separately in whole brains of mice and brain regions of rats, and in urine of humans. Here, we report a novel method for the analysis of both compounds in single murine brain regions. Initially, a variant of dispersive liquid-liquid microextraction was established by using methanol as an extractant, cyclohexane as solvent, and tributylphosphate as disperser. The extraction method was applied to murine brain regions homogenized with perchloric acid while the subsequent detection was carried out by HPLC with electrochemical detection. In the thalamus of C57Bl/6J mice (n = 3, male, age 4-8 months), morphine and norlaudanosoline could be detected at levels of 19 ± 3.9 and 7.2 ± 2.3 pg/mg, respectively. Overall, we provide a novel method for the simultaneous extraction and detection of both morphine and norlaudanosoline in single murine brain regions.

Neuroprotection or Neurotoxicity of Illicit Drugs on Parkinson's Disease

Parkinson's Disease (PD) is currently the most rapid growing neurodegenerative disease and over the past generation, its global burden has more than doubled. The onset of PD can arise due to environmental, sporadic or genetic factors. Nevertheless, most PD cases have an unknown etiology. Chemicals, such as the anthropogenic pollutant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and amphetamine-type stimulants, have been associated with the onset of PD. Conversely, cannabinoids have been associated with the treatment of the symptoms'. PD and medical cannabis is currently under the spotlight, and research to find its benefits on PD is on-going worldwide. However, the described clinical applications and safety of pharmacotherapy with cannabis products are yet to be fully supported by scientific evidence. Furthermore, the novel psychoactive substances are currently a popular alternative to classical drugs of abuse, representing an unknown health hazard for young adults who may develop PD later in their lifetime. This review addresses the neurotoxic and neuroprotective impact of illicit substance consumption in PD, presenting clinical evidence and molecular and cellular mechanisms of this association. This research area is utterly important for contemporary society since illicit drugs' legalization is under discussion which may have consequences both for the onset of PD and for the treatment of its symptoms.

Vector-mediated l-3,4-dihydroxyphenylalanine delivery reverses motor impairments in a primate model of Parkinson's disease

Ever since its introduction 40 years ago l-3,4-dihydroxyphenylalanine (l-DOPA) therapy has retained its role as the leading standard medication for patients with Parkinson's disease. With time, however, the shortcomings of oral l-DOPA treatment have become apparent, particularly the motor fluctuations and troublesome dyskinetic side effects. These side effects, which are caused by the excessive swings in striatal dopamine caused by intermittent oral delivery, can be avoided by delivering l-DOPA in a more continuous manner. Local gene delivery of the l-DOPA synthesizing enzymes, tyrosine hydroxylase and guanosine-tri-phosphate-cyclohydrolase-1, offers a new approach to a more refined dopaminergic therapy where l-DOPA is delivered continuously at the site where it is needed i.e. the striatum. In this study we have explored the therapeutic efficacy of adeno-associated viral vector-mediated l-DOPA delivery to the putamen in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated rhesus monkeys, the standard non-human primate model of Parkinson's disease. Viral vector delivery of the two enzymes, tyrosine hydroxylase and guanosine-5'-tri-phosphate-cyclohydrolase-1, bilaterally into the dopamine-depleted putamen, induced a significant, dose-dependent improvement of motor behaviour up to a level identical to that obtained with the optimal dose of peripheral l-DOPA. Importantly, this improvement in motor function was obtained without any adverse dyskinetic effects. These results provide proof-of-principle for continuous vector-mediated l-DOPA synthesis as a novel therapeutic strategy for Parkinson's disease. The constant, local supply of l-DOPA obtained with this approach holds promise as an efficient one-time treatment that can provide long-lasting clinical improvement and at the same time prevent the appearance of motor fluctuations and dyskinetic side effects associated with standard oral dopaminergic medication.

The levels of the NMDA receptor co-agonist D-serine are reduced in the substantia nigra of MPTP-lesioned macaques and in the cerebrospinal fluid of Parkinson's disease patients

Dysfunction of NMDA receptor (NMDAR)-mediated transmission is supposed to contribute to the motor and non-motor symptoms of Parkinson’s Disease (PD), and to L-DOPA-induced dyskinesia. Besides the main agonist L-glutamate, two other amino acids in the atypical D-configuration, D-serine and D-aspartate, activate NMDARs. In the present work, we investigated the effect of dopamine depletion on D-amino acids metabolism in the brain of MPTP-lesioned Macaca mulatta, and in the serum and cerebrospinal fluid of PD patients. We found that MPTP treatment increases D-aspartate and D-serine in the monkey putamen while L-DOPA rescues both D-amino acids levels. Conversely, dopaminergic denervation is associated with selective D-serine reduction in the substantia nigra. Such decrease suggests that the beneficial effect of D-serine adjuvant therapy previously reported in PD patients may derive from the normalization of endogenous D-serine levels and consequent improvement of nigrostriatal hypoglutamatergic transmission at glycine binding site. We also found reduced D-serine concentration in the cerebrospinal fluid of L-DOPA-free PD patients. These results further confirm the existence of deep interaction between dopaminergic and glutamatergic neurotransmission in PD and disclose a possible direct influence of D-amino acids variations in the changes of NMDAR transmission occurring under dopamine denervation and L-DOPA therapy.

Effects of subthalamic deep brain stimulation with gabapentin and morphine on mechanical and thermal thresholds in 6-hydroxydopamine lesioned rats

Chronic pain is the most common non-motor symptom among Parkinson's disease (PD) patients, with 1.85 million estimated to be in debilitating pain by 2030. Subthalamic deep brain stimulation (STN DBS) programmed for treating PD motor symptoms has also been shown to significantly improve pain scores. However, even though most patients' pain symptoms improve or disappear, 74% of patients treated develop new pain symptoms within 8 years. Previously we have shown that duloxetine and STN high frequency stimulation (HFS) significantly increase mechanical thresholds more than either alone. The current project specifically investigates the effects of gabapentin and morphine alone and with high (150 Hz; HFS) and low (50 Hz; LFS) frequency stimulation in the 6-hydroxydopamine rat model for PD. We found that HFS, LFS, gabapentin 15 mg/kg and morphine 1 mg/kg all independently improve von Frey (VF) thresholds. Neither drug augments the HFS response significantly. Morphine at 1 mg/kg showed a trend to increasing thresholds compared to LFS alone (p = 0.062). Interestingly, gabapentin significantly reduced (p = 0.019) the improved VF thresholds and Randall Selitto thresholds seen with LFS. Thus, though neither drug augments DBS, we found effects of both compounds independently increase VF thresholds, informing use of our model of chronic pain in PD. Gabapentin's reversal of LFS effects warrants further exploration.

Systemic Gene Delivery by Single-Dose Intracardiac Administration of scAAV2/9 and scAAV2/rh10 Variants in Newborn Rats

Recombinant adeno-associated virus serotype 9 (rAAV2/9) and pseudotype rhesus-10 (rAAV2/rh10) are used for gene delivery, especially into the central nervous system. Both serotypes cross the blood-brain barrier and mediate stable long-term transduction in dividing and nondividing cells. Among possible routes of administration, intracardiac injection holds the potential for widespread vector diffusion associated with a relatively simple approach. In this study adopting the intracardiac route, we compare the cell-specific tropism and transfection efficacy of a panel of engineered rAAV2/9 and rAAV2/rh10 vectors encoding the enhanced green fluorescent protein. We observed transduction in the brain and peripherally, with a predominant neuronal tropism while the various serotypes achieved different expression patterns.

Serotonergic Approaches in Parkinson's Disease: Translational Perspectives, an Update

Parkinson's disease (PD) has long been seen as a disorder caused by degeneration of the dopaminergic system, leading to the classic motor manifestations of the disease. However, there is now overwhelming evidence that PD is more than a disease merely caused by dopamine depletion. It is well-known that a myriad of other neurotransmitters are affected by the disease process. One such neurotransmitter is serotonin (5-HT). 5-HT has been shown to play a role in several motor and nonmotor manifestations of PD, including tremor, cognition, depression and psychosis. 5-HT also seems to play a critical role in L-3,4-dihydroxyphenylalanine (L-DOPA)-induced dyskinesia. A breadth of preclinical studies and clinical trials have been conducted that aimed at modulating the 5-HT system in order to alleviate depression, cognitive deficits, psychosis, and dyskinesia. In this Review, we summarize recent advances in the 5-HT field in PD, but with a translational emphasis. We start by presenting a novel nonhuman primate model of PD that presents with dual dopamine and 5-HT lesions. We then present preclinical and clinical data that introduce new concepts, such as the use of biased and partial agonists, as well as molecules recently introduced to the field of PD, such as eltoprazine, pimavanserin, nelotanserin, and SYN-120, to enhance therapeutic benefit while minimizing adverse events, notably on parkinsonian disability.

Selective Inactivation of Striatal FosB/ΔFosB-Expressing Neurons Alleviates L-DOPA-Induced Dyskinesia

BACKGROUND

ΔFosB is a surrogate marker of L-DOPA-induced dyskinesia (LID), the unavoidable disabling consequence of Parkinson's disease L-DOPA long-term treatment. However, the relationship between the electrical activity of FosB/ΔFosB-expressing neurons and LID manifestation is unknown.

METHODS

We used the Daun02 prodrug-inactivation method associated with lentiviral expression of β-galactosidase under the control of the FosB promoter to investigate a causal link between the activity of FosB/ΔFosB-expressing neurons and dyskinesia severity in both rat and monkey models of Parkinson's disease and LID. Whole-cell recordings of medium spiny neurons (MSNs) were performed to assess the effects of Daun02 and daunorubicin on neuronal excitability.

RESULTS

We first show that daunorubicin, the active product of Daun02 metabolism by β-galactosidase, decreases the activity of MSNs in rat brain slices and that Daun02 strongly decreases the excitability of rat MSN primary cultures expressing β-galactosidase upon D1 dopamine receptor stimulation. We then demonstrate that the selective, and reversible, inhibition of FosB/ΔFosB-expressing striatal neurons with Daun02 decreases the severity of LID while improving the beneficial effect of L-DOPA.

CONCLUSIONS

These results establish that FosB/ΔFosB accumulation ultimately results in altered neuronal electrical properties sustaining maladaptive circuits leading not only to LID but also to a blunted response to L-DOPA. These findings further reveal that targeting dyskinesia can be achieved without reducing the antiparkinsonian properties of L-DOPA when specifically inhibiting FosB/ΔFosB-accumulating neurons.

Dopamine in the Brain: Hypothesizing Surfeit or Deficit Links to Reward and Addiction

Recently there has been debate concerning the role of brain dopamine in reward and addiction. David Nutt and associates eloquently proposed that dopamine (DA) may be central to psycho stimulant dependence and some what important for alcohol, but not important for opiates, nicotine or even cannabis. Others have also argued that surfeit theories can explain for example cocaine seeking behavior as well as non-substance-related addictive behaviors. It seems prudent to distinguish between what constitutes “surfeit” compared to” deficit” in terms of short-term (acute) and long-term (chronic) brain reward circuitry responsivity. In an attempt to resolve controversy regarding the contributions of mesolimbic DA systems to reward, we review the three main competing explanatory categories: “liking”, “learning”, and “wanting”. They are (a) the hedonic impact -liking reward, (b) the ability to predict rewarding effects-learning and (c) the incentive salience of reward-related stimuli -wanting. In terms of acute effects, most of the evidence seems to favor the “surfeit theory”. Due to preferential dopamine release at mesolimbic-VTA-caudate-accumbens loci most drugs of abuse and Reward Deficiency Syndrome (RDS) behaviors have been linked to heightened feelings of well-being and hyperdopaminergic states.The “dopamine hypotheses” originally thought to be simple, is now believed to be quite complex and involves encoding the set point of hedonic tone, encoding attention, reward expectancy, and incentive motivation. Importantly, Willuhn et al. shows that in a self-administration paradigm, (chronic) excessive use of cocaine is caused by decreased phasic dopamine signaling in the striatum. In terms of chronic addictions, others have shown a blunted responsivity at brain reward sites with food, nicotine, and even gambling behavior. Finally, we are cognizant of the differences in dopaminergic function as addiction progresses and argue that relapse may be tied to dopamine deficiency. Vulnerability to addiction and relapse may be the result of the cumulative effects of dopaminergic and other neurotransmitter genetic variants and elevated stress levels. We therefore propose that dopamine homeostasis may be a preferred goal to combat relapse.

Pathophysiology of L-dopa-induced motor and non-motor complications in Parkinson's disease

Involuntary movements, or dyskinesia, represent a debilitating complication of levodopa (L-dopa) therapy for Parkinson's disease (PD). L-dopa-induced dyskinesia (LID) are ultimately experienced by the vast majority of patients. In addition, psychiatric conditions often manifested as compulsive behaviours, are emerging as a serious problem in the management of L-dopa therapy. The present review attempts to provide an overview of our current understanding of dyskinesia and other L-dopa-induced dysfunctions, a field that dramatically evolved in the past twenty years. In view of the extensive literature on LID, there appeared a critical need to re-frame the concepts, to highlight the most suitable models, to review the central nervous system (CNS) circuitry that may be involved, and to propose a pathophysiological framework was timely and necessary. An updated review to clarify our understanding of LID and other L-dopa-related side effects was therefore timely and necessary. This review should help in the development of novel therapeutic strategies aimed at preventing the generation of dyskinetic symptoms.

Cytochrome P450 3A Enzymes Catalyze the O6-Demethylation of Thebaine, a Key Step in Endogenous Mammalian Morphine Biosynthesis

Morphine, first characterized in opium from the poppy Papaver somniferum, is one of the strongest known analgesics. Endogenous morphine has been identified in several mammalian cells and tissues. The synthetic pathway of morphine in the opium poppy has been elucidated. The presence of common intermediates in plants and mammals suggests that biosynthesis occurs through similar pathways (beginning with the amino acid L-tyrosine), and the pathway has been completely delineated in plants. Some of the enzymes in the mammalian pathway have been identified and characterized. Two of the latter steps in the morphine biosynthesis pathway are demethylation of thebaine at the O(3)- and the O(6)-positions, the latter of which has been difficult to demonstrate. The plant enzymes responsible for both the O(3)-demethylation and the O(6)-demethylation are members of the Fe(II)/α-ketoglutarate-dependent dioxygenase family. Previous studies showed that human cytochrome P450 (P450) 2D6 can catalyze thebaine O(3)-demethylation. We report that demethylation of thebaine at the O(6)-position is selectively catalyzed by human P450s 3A4 and 3A5, with the latter being more efficient, and rat P450 3A2. Our results do not support O(6)-demethylation of thebaine by an Fe(II)/α-ketoglutarate-dependent dioxygenase. In rat brain microsomes, O(6)-demethylation was inhibited by ketoconazole, but not sulfaphenazole, suggesting that P450 3A enzymes are responsible for this activity in the brain. An alternate pathway to morphine, oripavine O(6)-demethylation, was not detected. The major enzymatic steps in mammalian morphine synthesis have now been identified.

Targeting β-arrestin2 in the treatment of L-DOPA-induced dyskinesia in Parkinson's disease

Parkinson's disease (PD) is characterized by severe locomotor deficits and is commonly treated with the dopamine (DA) precursor l-3,4-dihydroxyphenylalanine (L-DOPA), but its prolonged use causes dyskinesias referred to as L-DOPA-induced dyskinesias (LIDs). Recent studies in animal models of PD have suggested that dyskinesias are associated with the overactivation of G protein-mediated signaling through DA receptors. β-Arrestins desensitize G protein signaling at DA receptors (D1R and D2R) in addition to activating their own G protein-independent signaling events, which have been shown to mediate locomotion. Therefore, targeting β-arrestins in PD L-DOPA therapy might prove to be a desirable approach. Here we show in a bilateral DA-depletion mouse model of Parkinson's symptoms that genetic deletion of β-arrestin2 significantly limits the beneficial locomotor effects while markedly enhancing the dyskinesia-like effects of acute or chronic L-DOPA treatment. Viral rescue or overexpression of β-arrestin2 in knockout or control mice either reverses or protects against LIDs and its key biochemical markers. In other more conventional animal models of DA neuron loss and PD, such as 6-hydroxydopamine-treated mice or rats and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated nonhuman primates, β-arrestin2 overexpression significantly reduced dyskinesias while maintaining the therapeutic effect of L-DOPA. Considerable efforts are being spent in the pharmaceutical industry to identify therapeutic approaches to block LIDs in patients with PD. Our results point to a potential therapeutic approach, whereby development of either a genetic or pharmacological intervention to enhance β-arrestin2- or limit G protein-dependent D1/D2R signaling could represent a more mechanistically informed strategy.

The UDP-glucuronosyltransferases of the blood-brain barrier: their role in drug metabolism and detoxication

UDP-glucuronosyltransferases (UGTs) form a multigenic family of membrane-bound enzymes expressed in various tissues, including brain. They catalyze the formation of β-D-glucuronides from structurally unrelated substances (drugs, other xenobiotics, as well as endogenous compounds) by the linkage of glucuronic acid from the high energy donor, UDP-α-D-glucuronic acid. In brain, UGTs actively participate to the overall protection of the tissue against the intrusion of potentially harmful lipophilic substances that are metabolized as hydrophilic glucuronides. These metabolites are generally inactive, except for important pharmacologically glucuronides such as morphine-6-glucuronide. UGTs are mainly expressed in endothelial cells and astrocytes of the blood brain barrier (BBB). They are also associated to brain interfaces devoid of BBB, such as circumventricular organ, pineal gland, pituitary gland and neuro-olfactory tissues. Beside their key-role as a detoxication barrier, UGTs play a role in the steady-state of endogenous compounds, like steroids or dopamine (DA) that participate to the function of the brain. UGT isoforms of family 1A, 2A, 2B and 3A are expressed in brain tissues to various levels and are known to present distinct but overlapping substrate specificity. The importance of these enzyme species with regard to the formation of toxic, pharmacologically or physiologically relevant glucuronides in the brain will be discussed.

Astrocytosis in parkinsonism: considering tripartite striatal synapses in physiopathology?

The current concept of basal ganglia organization and function in physiological and pathophysiological conditions excludes the most numerous cells in the brain, i.e., the astrocytes, present with a ratio of 10:1 neuron. Their role in neurodegenerative condition such as Parkinson's disease (PD) remains to be elucidated. Before embarking into physiological investigations of the yet-to-be-identified "tripartite" synapses in the basal ganglia in general and the striatum in particular, we therefore characterized anatomically the PD-related modifications in astrocytic morphology, the changes in astrocytic network connections and the consequences on the spatial relationship between astrocytic processes and asymmetric synapses in normal and PD-like conditions in experimental and human PD. Our results unravel a dramatic regulation of striatal astrocytosis supporting the hypothesis of a key role in (dys) regulating corticostriatal transmission. Astrocytes and their various properties might thus represent a therapeutic target in PD.

Acute morphine treatments alleviate tremor in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated monkeys

Parkinson’s disease (PD) is a chronic and progressive neurodegenerative disorder associated with decreased striatal dopamine levels. Morphine has been found to elevate dopamine levels, which indicates a potential therapeutic effect in PD treatment that has not been investigated previously. To evaluate this hypothesis, an investigation of the acute effects of morphine on PD symptoms was carried out in male rhesus PD monkeys that had been induced with MPTP. All MPTP induced monkeys displayed progressive and irreversible PD motor symptoms. The behavioral response of these animals to morphine and L-Dopa were quantified with the Kurlan scale. It was found that L-Dopa alleviated bradykinesia, but did not significantly improve tremor. In contrast, acute morphine alleviated tremor significantly. These results suggested that, compared to L-Dopa, morphine has different therapeutic effects in PD therapy and may act through different biological mechanisms to alleviate PD symptoms.

Endogenous morphine-6-glucuronide (M6G) is present in the plasma of patients: validation of a specific anti-M6G antibody for clinical and basic research

Endogenous morphine and its derivatives (morphine-6-glucuronide [M6G]; morphine-3-glucuronide [M3G]) are formed by mammalian cells from dopamine. Changes in the concentrations of endogenous morphine have been demonstrated in several pathologies (sepsis, Parkinson's disease, etc.), and they might be relevant as pathological markers. While endogenous morphine levels are detectable using enzyme-linked immunosorbant assay (ELISA), mass spectrometry (MS) analysis was, so far, the only approach to detect and quantify M6G. This study describes the preparation of a specific anti-M6G rabbit polyclonal antibody and its validation. The specificity of this antibody was assessed against 30 morphine-related compounds. Then, a M6G-specific ELISA-assay was tested to quantify M6G in the plasma of healthy donors, morphine-treated, and critically ill patients. The antibody raised against M6G displays a strong affinity for M6G, codeine-6-glucuronide, and morphine-3-6-glucuronide, whereas only weak cross-reactivities were observed for the other compounds. Both M6G-ELISA and LC-MS/MS approaches revealed the absence of M6G in the plasma of healthy donors (controls, n = 8). In all positive donors treated with morphine-patch (n = 5), M6G was detected using both M6G-ELISA and LC-MS/MS analysis. Finally, in a study on critically ill patients with circulating endogenous morphine (n = 26), LC-MS/MS analysis revealed that 73% of the positive-patients (19 of 26), corresponding to high M6G-levels in M6G-ELISA, contained M6G. In conclusion, we show that endogenous M6G can be found at higher levels than morphine in the blood of morphine-naive patients. With respect to the interest of measuring endogenous M6G in pathologies, we provide evidences that our ELISA procedure represents a powerful tool as it can easily and specifically detect endogenous M6G levels.

The pharmacology of L-DOPA-induced dyskinesia in Parkinson's disease

L-3,4-Dihydroxyphenylalanine (L-DOPA) remains the most effective symptomatic treatment of Parkinson's disease (PD). However, long-term administration of L-DOPA is marred by the emergence of abnormal involuntary movements, i.e., L-DOPA-induced dyskinesia (LID). Years of intensive research have yielded significant progress in the quest to elucidate the mechanisms leading to the development and expression of dyskinesia and maintenance of the dyskinetic state, but the search for a complete understanding is still ongoing. Herein, we summarize the current knowledge of the pharmacology of LID in PD. Specifically, we review evidence gathered from postmortem and pharmacological studies, both preclinical and clinical, and discuss the involvement of dopaminergic and nondopaminergic systems, including glutamatergic, opioid, serotonergic, γ-aminobutyric acid (GABA)-ergic, adenosine, cannabinoid, adrenergic, histaminergic, and cholinergic systems. Moreover, we discuss changes occurring in transcription factors, intracellular signaling, and gene expression in the dyskinetic phenotype. Inasmuch as a multitude of neurotransmitters and receptors play a role in the etiology of dyskinesia, we propose that to optimally alleviate this motor complication, it may be necessary to develop combined treatment approaches that will target simultaneously more than one neurotransmitter system. This could be achieved via three ways as follows: 1) by developing compounds that will interact simultaneously to a multitude of receptors with the required agonist/antagonist effect at each target, 2) by targeting intracellular signaling cascades where the signals mediated by multiple receptors converge, and/or 3) to regulate gene expression in a manner that has effects on signaling by multiple pathways.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).

Good mass spectrometry and its place in good science

The mass spectrometry community has expanded as instruments became more powerful, user-friendly, affordable and readily available. This opens up opportunities for novice users to perform high impact research, using highly advanced instrumentation. This introductory tutorial is targeted at the novice user working in a research setting. It aims to offer the benefit of other people's experiences and to help newcomers avoid known pitfalls and problematic issues. It discusses some of the essential features of sound analytical chemistry and highlights the need to use validated analytical methods that provide high quality results along with a measure of their uncertainty. Examples are used to illustrate potential pitfalls and their consequences.

Rat CYP2D2, not 2D1, is functionally conserved with human CYP2D6 in endogenous morphine formation

The assumption that CYP2D1 is the corresponding rat cytochrome to human CYP2D6 has been revisited using recombinant proteins in direct enzyme assays. CYP2D1 and 2D2 were incubated with known CYP2D6 substrates, the three morphine precursors thebaine, codeine and (R)-reticuline. Mass spectrometric analysis showed that rat CYP2D2, not 2D1, catalyzed the 3-O-demethylation reaction of thebaine and codeine. In addition, CYP2D2 incubated with (R)-reticuline generated four products corytuberine, pallidine, salutaridine and isoboldine while rat CYP2D1 was completely inactive. This intramolecular phenol-coupling reaction follows the same mechanism as observed for CYP2D6. Michaelis-Menten kinetic parameters revealed high catalytic efficiencies for rat CYP2D2. These findings suggest a critical evaluation of other commonly accepted, however untested, CYP2D1 substrates.