Tyr-Trp administration facilitates brain norepinephrine metabolism and ameliorates a short-term memory deficit in a mouse model of Alzheimer's disease.

The physiological actions of orally ingested peptides on the brain remain poorly understood. This study examined the effects of 39 orally administered synthetic Tyr-containing dipeptides on the enhancement of brain norepinephrine metabolism in mice by comparing the concentration of 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG). Although Tyr-Tyr administration increased blood and cerebral cortex (Cx) Tyr concentrations the most, Tyr-Trp increased Cx MHPG concentration the most. The oral administration of Tyr-Trp ameliorated a short-term memory deficit of a mouse model of cognitive dysfunction induced by amyloid beta peptide 25-35. Gene expression profiling of mouse brain using a microarray indicated that Tyr-Trp administration led to a wide variety of changes in mRNA levels, including the upregulation of genes encoding molecules involved in catecholamine metabolism. A comparative metabolome analysis of the Cx of mice given Tyr-Trp or Tyr-Tyr demonstrated that Tyr-Trp administration yielded higher concentrations of Trp and kynurenine pathway metabolites than Tyr-Tyr administration, as well as higher L-dopa levels, which is the initial product of catecholamine metabolism. Catecholamines were not significantly increased in the Cx of the Tyr-Tyr group compared with the Tyr-Trp group, despite a marked increase in Tyr. Presumably, Tyr-Trp administration enhances catecholamine synthesis and metabolism via the upregulation of genes involved in Tyr and Trp metabolism as well as metabolites of Tyr and Trp. These findings strongly suggest that orally ingested Tyr-Trp modulates the brain metabolome involved in catecholamine metabolism and contributes to higher brain function.

Measurement of plasma norepinephrine and 3,4-dihydroxyphenylglycol: method development for a translational research study.

OBJECTIVE: Norepinephrine (NE), a sympathetic neurotransmitter, is often measured in plasma as an index of sympathetic activity. To better understand NE dynamics, it is important to measure its principal metabolite, 3,4-dihydroxyphenylglycol (DHPG), concurrently. Our aim was to present a method, developed in the course of a translational research study, to measure NE and DHPG in human plasma using high performance liquid chromatography with electrochemical detection (HPLC-ED). RESULTS: After pre-purifying plasma samples by alumina extraction, we used HPLC-ED to separate and quantify NE and DHPG. In order to remove uric acid, which co-eluted with DHPG, a sodium bicarbonate wash was added to the alumina extraction procedure, and we oxidized the column eluates followed by reduction because catechols are reversibly oxidized whereas uric acid is irreversibly oxidized. Average recoveries of plasma NE and DHPG were 35.3 ± 1.0% and 16.3 ± 1.1%, respectively, and there was no detectable uric acid. Our estimated detection limits for NE and DHPG were approximately 85 pg/mL (0.5 pmol/mL) and 165 pg/mL (0.9 pmol/mL), respectively. The measurement of NE and DHPG in human plasma has wide applicability; thus, we describe a method to quantify plasma NE and DHPG in a laboratory setting as a useful tool for translational and clinical research.

Low baseline salivary 3-methoxy-4-hydroxyphenylglycol (MHPG) in drug-naïve patients with short-illness-duration first episode major depressive disorder.

BACKGROUND: Central noradrenergic dysfunction with autonomic nervous system dysregulation are reported in major depressive disorder (MDD). Salivary 3-methoxy-4-hydroxyphenylglycol (sMHPG) is indicative of central noradrenergic activity. Studies on MHPG in bodily fluids are inconsistent and scarce data is available regarding baseline sMHPG concentration in MDD. METHODS: The basal, non-stimulated sMHPG concentration was studied in this cross-sectional case-control study on 20 non-late-life adult, short-illness-duration first-episode, treatment-naïve MDD patients and in 20 age- and sex-matched healthy controls. Depressed patients showed a score in the Hamilton rating scale for depression (HAMD-17) higher than 20. RESULTS: The baseline sMHPG concentration was significantly lower in depressed individuals as compared to controls (p=0.025). In post hoc analysis significantly lower sMHPG was present in melancholic MDD (p=0.009) as related to controls whereas no difference was seen between non-melancholic MDD patients and controls. The concentration of sMHPG was not significantly correlated neither with duration nor the severity of depressive symptoms as measured by the total HAMD-17 score. LIMITATIONS: The current study is limited by its cross-sectional design and small sample size. CONCLUSION: Low baseline sMHPG concentration was found in MDD. The study provides no support for elevated sMHPG in drug-naïve patients with short-illness-duration first episode MDD. Taken into account the physiology of sMHPG secretion the study results corroborate with the evidence for decreased central noradrenergic activity in MDD when sMHPG is considered indicative of central noradrenergic function.

3,4-Dihydroxyphenylglycol (DHPG): an important phenolic compound present in natural table olives.

The presence of 3,4-dihydroxyphenylglycol (DHPG) was studied in 32 samples and 10 different cultivars of natural table olives, using an accurate method to avoid wrong quantification. Hydroxytyrosol (HT), tyrosol, and verbascoside were also quantified, as these four compounds comprise the majority of the chromatographic profile. Analyses were carried out by HPLC-DAD-UV after extraction of all phenolics, and hydroxytyrosol was the major component in nearly all samples. High levels of DHPG (up to 368 mg/kg of dry weight) were found in the pulp of natural black olives independent of cultivar and processing method, similar to its concentration in the brine in almost all of the samples. The presented data for this antioxidant indicate that natural table olives are a rich source of DHPG and hydroxytyrosol, compounds with interesting nutritional and antioxidant properties.

Synergistic effects of psychological and immune stressors on inflammatory cytokine and sickness responses in humans.

Activation of the innate immune system is commonly accompanied by a set of behavioural, psychological and physiological changes known as 'sickness behaviour'. In animals, infection-related sickness symptoms are significantly increased by exposure to psychosocial stress, suggesting that psychological and immune stressors may operate through similar pathways to induce sickness. We used a double-blind, randomised, placebo-controlled design to examine the effect of acute psychological stress on immune and subjective mood responses to typhoid vaccination in 59 men. Volunteers were assigned to one of four experimental conditions in which they were either injected with typhoid vaccine or saline placebo, and then either rested or completed two challenging behavioural tasks. Typhoid vaccine induced a significant rise in participants' serum levels of interleukin-6 (IL-6) and this response was significantly larger in the stress versus rest conditions. Negative mood increased immediately post-tasks, an effect also more pronounced in the vaccine/stress condition. In the vaccine/stress group, participants with larger IL-6 responses had heightened systolic blood pressure responses to tasks and elevated post-stress salivary levels of the noradrenaline metabolite 3-methoxy-phenyl glycol (MHPG) and cortisol. Our findings suggest that, as seen in animals, psychological and immune stressors may act synergistically to promote inflammation and sickness behaviour in humans.

Effect of short-term exposure to whole body vibration in humans: relationship between wakefulness level and vibration frequencies.

The purpose of this study was to clarify the influence of different vibration frequencies on wakefulness level. Subjects were 7 healthy male university students aged 21.9+/-1.6 years (mean). All students were non-smokers. Three exposure conditions were used (10 Hz vibration, 20 Hz vibration, and no vibration). Whole-body vertical vibration was applied to subjects sitting on a car passenger seat using a whole-body vibration shaker (CV-300, Akashi) at a single frequency (10 or 20 Hz) at an acceleration level of 0.3 ms(-2) r.m.s. for 24 min. The objective wakefulness level based on EEGs was evaluated in terms of the alpha attenuation coefficient (AAC) obtained by the Alpha Attenuation Test (AAT). As parameters of psychological stress, salivary 3-methoxy-4-hydroxyphenylglycol (MHPG) and homovanillic acid (HVA) were used. The subjective wakefulness level was evaluated using a questionnaire based on the Kwansei Gakuin Sleepiness Scale (KSS), which is a scale developed for the Japanese based on the Stanford Sleepiness Scale (SSS). The KSS score, representing the subjective wakefulness level, decreased after the exposure irrespective of the exposure condition, but the decrease was not significant. The AAC, representing the objective wakefulness level, significantly decreased only after vibration exposure (10 Hz/20 Hz) but did not differ between the two vibration frequencies. No significant changes were observed after exposure to whole-body vibration in MHPG or HVA as parameters of vibration-related stress. The AAC decreased after exposure to whole-body vibration (10 Hz/20 Hz), suggesting a decrease in the wakefulness level. However, no differences were observed in the influence of the two different vibration frequencies test.

Brain-derived neurotrophic factor gene variation influences cerebrospinal fluid 3-methoxy-4-hydroxyphenylglycol concentrations in healthy volunteers.

Brain-derived neurotrophic factor (BDNF) has been shown to influence monoamine transmitter synthesis, metabolism and release. We investigated possible relationships between four BDNF gene polymorphisms and cerebrospinal fluid (CSF) concentrations of 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) in healthy volunteers (n = 132). All BDNF polymorphisms (270 C/T, -633 T/A, Val66Met, and 11757 G/C) were associated with MHPG (P < 0.02), but not with 5-HIAA and HVA concentrations. At a second clinical investigation 8-20 years after CSF sampling 30% of the subjects had experienced various psychiatric disorders. Development of a psychiatric disorder was predicted by low 5-HIAA concentrations (P = 0.01). The results suggest that BDNF gene variation participates in regulation of norepinephrine turnover rates in the central nervous system of human subjects.

The effects of depressive symptoms on cardiovascular and catecholamine responses to the induction of depressive mood.

We examined the effects of depressive symptoms on cardiovascular and catecholamine responses to the induction of different mood states. Fifty-five healthy men and women (mean age 23.4 +/- 3 years) were recruited. Depressive symptoms were evaluated using the Center for Epidemiological Studies Depression Scale (CES-D) and participants were classified into high depressive (CES-D*16) or low depressive symptoms (CES-D < 16) groups. Following a baseline period, participants were required to complete two separate speech tasks where they were asked to recall life events that made them feel angry or depressed. The tasks were separated by a 30-min recovery period and the order was randomised between participants using a counterbalanced design. Cardiovascular function was monitored continuously using a Finometer device and saliva was collected for the assessment of 3-methoxy-phenylglycol (MHPG, the major metabolite of norephinephrine). Blood pressure (BP), heart rate, and total peripheral resistance (TPR) were significantly increased in response to both tasks (p = .001). Averaged over conditions, higher diastolic BP and higher MHPG levels were observed in high depressive symptoms participants. MHPG levels did not change in response to mood induction in the low depressive symptoms group. However, the high depression symptoms group showed significantly higher levels of MHPG during recovery from the depressed mood induction task and increased levels immediately after the anger induction task. These findings suggest depressive symptoms are associated with heightened central adrenergic activation during negative mood induction, but that the time course of responses is dependent on the type of emotion elicited.

Clinical catecholamine neurochemistry: a legacy of Julius Axelrod.

1. Discoveries, insights, and concepts that Julius Axelrod introduced about the disposition and metabolism of catecholamines provided the scientific basis and spurred the development of clinical catecholamine neurochemistry. 2. Here, we provide examples of this aspect of Axelrod's scientific legacy.

Nicotine potentiates imipramine-induced effects on catecholamine metabolism: possible relation to antidepressant activity.

Following our behavioral studies demonstrating augmentation of imipramine action by concomitant administration of nicotine, we investigated the effects of one or 14 days of treatment (twice daily) with imipramine and nicotine on dopamine metabolism in various brain areas of rat and noradrenaline in the brain stem. In addition, we evaluated the responses of this metabolism to apomorphine challenge in the rat. Generally, chronic treatment of imipramine and nicotine produced opposite effects to acute administration. As revealed by HPLC, dopamine metabolism in the nucleus accumbens was slightly decreased after 14 days of treatment with imipramine, and co-administration of nicotine resulted in a significant and much more pronounced depression of dopamine metabolism in all investigated dopaminergic structures. Such biochemical effects suggested the development of a compensatory mechanism related with hypersensitivity of dopamine D(2) receptors in the mesolimbic and nigrostriatal system. Chronic administration of imipramine produced an opposite effect to the acute one in the brain stem noradrenergic system, like it was observed in dopaminergic structures. Significant inhibition of noradrenaline metabolism after acute administration of imipramine may be explained by its inhibitory effect on noradrenaline reuptake process. In contrast, chronic imipramine administration had no effect on noradrenaline metabolism what indicated the development of subsensitivity of (2)-adrenoceptors in the brain stem responsible for the rate of noradrenaline metabolism. Apomorphine alone decreased metabolism of both catecholamine, dopamine and noradrenaline through activation of dopamine D(2) receptors which are located also on noradrenergic neurons. The biochemical response to apomorphine in terms of dopamine metabolism was not changed by chronic administration of the investigated drugs but noradrenaline metabolism in the brain stem was strongly attenuated after a combined treatment of imipramine and nicotine. The present data demonstrate facilitation and potentiation of biochemical antidepressant-like effects of imipramine by nicotine co-treatment. We suggest that nicotine may potentiate the antidepressant-like effects of imipramine by promoting some plastic changes in the brain within dopamine and noradrenaline system considerably more strongly than imipramine alone.

[Assessment of mental condition by saliva level of 3-methoxy-4-hydroxyphenylglycol].

There is substantial evidence that the anxiety state in human is associated with a high level of 3-methoxy-4-hydroxyphenylglycol (MHPG), noradrenaline metabolite, in the plasma, urine and cerebrospinal fluid. Moreover, the plasma level of MHPG in some patients with depression has been reported to be lower than that in normal controls. Recently, the saliva level of MHPG was well correlated with a level of plasma and CSF. Social dysfunction score of General Health Questionnaire (GHQ-28) was negatively correlated with the saliva level of MHPG in normal volunteers (n = 270, r = -0.213, p < 0.001). Lowered baseline saliva MHPG level was associated with the poor performance on a continuous task requiring effortful attention. These data indicate that reduced saliva MHPG in general population would reflect a depressive state. The saliva level of MHPG at first visit to a hospital in patients with anxiety disorder was significantly higher than that of control individuals and was reduced by alprazolam treatment for 1 week. Thus, a saliva MHPG would be a useful marker to assess some mental states in psychiatric patients as well as the general population.

Las investigaciones biológicas del suicidio. Aspectos históricos / Biological studies in suicide. Historical features

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Involvement of the noradrenergic system in performance on a continuous task requiring effortful attention.

To determine the effects of noradrenergic neuronal activity on performance in continuous tasks requiring effortful attention, the performance of 23 male students in the Uchida-Kraepelin test (UKT) was examined. The UKT requires continuous arithmetic addition of single-digit figures for 25 min. The relationship of performance with saliva levels of 3-methoxy-4-hydroxyphenylglycol (sMHPG) was analyzed. Saliva samples were taken before, during and after test performance, and sMHPG levels determined by gas chromatography-mass spectrometry. There was no significant change in mean sMHPG as a result of test performance. However, when initial effort was calculated, defined as number of items completed during the 1st min subtracted from the average completed per minute in the 1st and the 2nd halves (blocks) of the test, significant correlations with sMHPG (p = 0.0002 for the 1st block and p < 0.0001 for the 2nd block) were found. Thus the data indicate that noradrenergic neuronal activity affects the performance on continuous tasks requiring effortful attention.

Extraneuronal enzymatic degradation of myocardial interstitial norepinephrine in the ischemic region.

OBJECTIVE: Catechol O-methyltransferase (COMT) is believed to exert degradative action at high norepinephrine (NE) levels. Although COMT exists in cardiac tissues, the contribution of cardiac COMT activity to regional NE kinetics, particularly in ischemia-induced NE accumulation, remains unclear. We investigated the role of cardiac COMT in NE kinetics in the ischemic region. METHODS: We implanted a microdialysis probe into the left ventricular myocardium of anesthetized rabbits and induced myocardial ischemia by 60-min coronary artery occlusion. We monitored myocardial interstitial levels of NE and its metabolites in the presence and absence of a COMT inhibitor. We intraperitoneally administered entacapone (10 mg/kg) 120 min before control sampling. RESULTS: In control, entacapone increased interstitial dihydroxyphenylglycol (DHPG, intraneuronal NE metabolite by monoamine oxidase (MAO)) levels and decreased interstitial normetanephrine (NMN, extraneuronal NE metabolite by COMT) and 3-methoxy-4-hydroxyphenylglycol (MHPG, extraneuronal DHPG metabolite by COMT) levels, but did not change interstitial NE levels. Coronary occlusion increased NE levels to 165+/-48 nM at 45-60 min of occlusion. This increase was accompanied by increases in DHPG and NMN levels (11.3+/-1.1 and 9.3+/-1.3 nM at 45-60 min of occlusion). Entacapone augmented the ischemia-induced NE and DHPG responses (333+/-51 and 22.9+/-2.4 nM at 45-60 min of occlusion). In contrast, the ischemia-induced NMN response was suppressed by entacapone (2.0+/-0.4 nM at 45-60 min of occlusion). Reperfusion decreased interstitial NE levels and increased interstitial DHPG and NMN levels. Entacapone suppressed changes in NE and NMN levels, but augmented the increase in dialysate DHPG. CONCLUSION: Myocardial ischemia evoked increases in myocardial interstitial NE and NMN levels. COMT inhibition augmented the increase in NE (substrate of COMT) levels and suppressed the increase in NMN (metabolite by COMT) levels. In the ischemic heart, COMT contributes to the removal of accumulated NE in the myocardium.

Mu opioid modulation of oxytocin secretion in late pregnant and parturient rats. Involvement of noradrenergic neurotransmission.

We have investigated effects of micro- and kappa-opioid agonists and antagonists on plasma oxytocin levels and noradrenaline content in the supraoptic nucleus (SON) and paraventricular nucleus (PVN) of 20-day pregnant rats. beta-Endorphin, oxytocin, estrogen and progesterone profiles in late pregnant and parturient rats were also sought. Stage of estrous cycle was monitored by vaginal smear, and pro-estrous animals were left overnight with male. In the first set of experiments, pregnant rats were monitored and decapitated on days 20 and 21 and after the delivery of second pup. In the second set, 20-day pregnant rats were intracerebroventricularly infused with morphine (50 microg/10 microl), U50,488H (kappa-agonist; 50 microg/10 microl), clocinnamox (micro-antagonist; 50 microg/10 microl) and norbinaltorphimine (kappa-antagonist; 50 microg/10 microl). Controls received saline alone. Serum estrogen and progesterone levels were measured by enzyme immunoassay, and plasma oxytocin and beta-endorphin by radioimmunoassay. Noradrenaline and its metabolite (3,4-dihydroxyphenylglycol) were determined in micropunched hypothalamic nuclei by HPLC-ECD. In parturient rats, oxytocin levels were increased (p < 0.05) and beta-endorphin decreased (p < 0.01) compared to 20-day pregnant animals. Serum progesterone concentrations progressively declined towards parturition (p < 0.001). Clocinnamox raised oxytocin levels (p < 0.01) while U50,488H caused decreases (p < 0.05). Noradrenaline content was elevated by clocinnamox in the SON (p < 0.01) and PVN (p < 0.05) compared to control values. Other agonists and antagonists had no significant effect on the noradrenergic neurotransmission or oxytocin secretion. We suggest that noradrenaline may mediate the inhibitory effects of micro-opioids on oxytocin release. Our findings have also shown that kappa-opioid receptors are not involved in modulation of oxytocin neurons in late pregnant rats.

Method for simultaneous measurement of norepinephrine, 3-methoxy-4-hydroxyphenylglycol and 3,4-dihydroxyphenylglycol by liquid chromatography with electrochemical detection: application in rat cerebral cortex and plasma after lithium chloride treatment.

An assay was developed to quantify norepinephrine (NE) and its metabolites (MHPG and DHPG) by high-performance liquid chromatography with electrochemical detection method (HPLC-ECD) in brain tissue and plasma of rats treated by LiCl. Separation on C(18) column was obtained by a mobile phase consisting of 4.5% methanol in buffer (0.1 M sodium acetate, 0.2 M citric acid) containing 0.2 mM ethylenediaminetetraacetic acid disodium salt (EDTA Na(2)) and 0.4 mM sodium octylsulfate, operated at a flow rate of 0.8 ml/min. A potential of +0.78 V was applied across the working and reference electrodes of the detector. The precision was in the range 2.88-4.35% for NE, 5.94-11.0% for MHPG and 1.97-4.40% for DHPG. Accuracy was 98.8-99.3% for NE, 97.4-100% for MHPG and 96.1-101% for DHPG. The limit of detection was 0.6 ng/ml for NE, 0.5 ng/ml for MHPG and 0.2 ng/ml for DHPG. The linearity is over the range 20-60 ng/ml for NE, 7-23 ng/ml for MHPG and 6-20 ng/ml for DHPG. The assay has been applied successfully to measure simultaneously cortex and plasmas concentrations of these three catecholamines in rats.

Detection of 3-methoxy-4-hydroxyphenylglycol in rabbit skeletal muscle microdialysate.

A high-performance liquid chromatography with electrochemical detection (HPLC-ED) method is described for determination of 3-methoxy-4-hydroxyphenylglycol (MHPG) in microdialysate from the skeletal muscle interstitial space. Using a microdialysis technique, we sampled 30 microl dialysate from the skeletal muscle interstitial space and injected dialysate directly into HPLC-ED system. The control MHPG concentration of dialysate was 213+/-18 pg/ml. The MHPG concentrations were reduced by entacapone (catechol-O-methyltransferase inhibitor, COMT), augmented by local infusion of dihydroxyphenylglycol. This system offers a new possibility for simple, rapid monitoring of MHPG as an index of COMT activity in skeletal muscle.

Monoaminergic changes associated with socially induced sex reversal in the saddleback wrasse.

The process of sex reversal in fishes is socially mediated and requires a total reorganization of the hypothalamo-pituitary-gonadal axis. When the ratio of males to females in a population of saddleback wrasse (Thalassoma dupperrey) is too low, the largest female becomes male over the course of 6 to 8 weeks. This event requires the conversion of external social cues into internal chemical cues. In an attempt to investigate the role monoamines might play in this process, two females were housed together in floating enclosures in order to induce sex reversal in the larger. Brains were sampled at various time points throughout the process of sex reversal. Monoamines were measured in the amygdala, preoptic area, ventral hypothalamus, locus coeruleus and raphe nucleus. Changes were demonstrated in monoamine metabolism for all brain regions examined. The most important changes in monoamine-system activation were seen during the first week of sex reversal. It is during this time that transitional animals undergo behavioral sex reversal. There is an increase in serotonergic activity in the amygdala which is likely related to territorial acquisition. The absence of male aggression results in a less stressful environment for the female and a reduction in serotonergic activity in the preoptic area allowing for an increase in noradrenergic activity potentially triggering the reorganization of the reproductive axis. In the ventral hypothalamus, there is a decrease in noradrenergic and increase in dopaminergic activity associated with this change from female to male. The locus coeruleus shows an increase in noradrenergic activity later in the process of sex reversal which is probably a response to more circulating androgens. In the raphe nucleus, there is a decrease in serotonergic activity at the time of behavioral sex reversal. This decrease in serotonergic activity is linked to the behavioral component of sex reversal. This study suggests that monoamines play a very important role in both behavioral and gonadal sex reversal in the saddleback wrasse, the former under the control of serotonin in the raphe and the latter mediated via serotonergic effects on norepinephrine in the preoptic area.