The respective involvement of noradrenaline and its deaminated metabolites in waking and paradoxical sleep: a neuropharmacological model

BiKEGG: a COBRA toolbox extension for bridging the BiGG and KEGG databases

Development of an interface tool between the Biochemical, Genetic and Genomic (BiGG) and KEGG databases is necessary for simultaneous access to the features of both databases. For this purpose, we present the BiKEGG toolbox, an open source COBRA toolbox extension providing a set of functions to infer the reaction correspondences between the KEGG reaction identifiers and those in the BiGG knowledgebase using a combination of manual verification and computational methods. Inferred reaction correspondences using this approach are supported by evidence from the literature, which provides a higher number of reconciled reactions between these two databases compared to the MetaNetX and MetRxn databases. This set of equivalent reactions is then used to automatically superimpose the predicted fluxes using COBRA methods on classical KEGG pathway maps or to create a customized metabolic map based on the KEGG global metabolic pathway, and to find the corresponding reactions in BiGG based on the genome annotation of an organism in the KEGG database. Customized metabolic maps can be created for a set of pathways of interest, for the whole KEGG global map or exclusively for all pathways for which there exists at least one flux carrying reaction. This flexibility in visualization enables BiKEGG to indicate reaction directionality as well as to visualize the reaction fluxes for different static or dynamic conditions in an animated manner. BiKEGG allows the user to export (1) the output visualized metabolic maps to various standard image formats or save them as a video or animated GIF file, and (2) the equivalent reactions for an organism as an Excel spreadsheet.

The antidepressant trans-2-phenylcyclopropylamine protects mice from high-fat-diet-induced obesity

Mice treated with the antidepressant trans-2-phenylcyclopropylamine (2-PCPA) were protected against diet-induced-obesity, and adiposity was reversed in pre-established diet-induced obese mice. Contrary to a recent report that inhibition of lysine-specific demethylase-1 by 2-PCPA results in increased energy expenditure, long-term 2-PCPA treatment had no such effect but its protection against obesity was associated with increased spontaneous locomotor activity, Moreover, pair feeding to assure equal caloric intake in wild type mice as well as in genetic hyperphagic mice (ob/ob) also resulted in weight reduction in 2-PCPA treated mice that correlated with increased activity but no change in energy expenditure. Similarly, short-term intraperitoneal injections of 2-PCPA did not affect food intake but caused a substantial increase in locomotor activity in the light cycle that correlated with increased energy expenditure, whereas activity and energy expenditure were unchanged in the dark cycle. Lastly, 2-PCPA was also effective in reducing obesity in genetic UCP1 null mice. These data suggest that 2-PCPA can reduce obesity by decreasing food intake in the long term while increasing activity in the short-term. However, the protective and weight loss effects of 2-PCPA are independent of UCP1-regulated thermogenesis or basal energy expenditure.

Changes in the serotonergic system during the sleep-wake cycle: simultaneous polygraphic and voltammetric recordings in hypothalamus using a telemetry system

Changes in the serotonergic system in the posterior hypothalamus of freely moving rats were related to sleep and wakefulness using in vivo voltammetry (with carbon fiber microelectrodes) and polygraphic recordings. By using an optoelectronic telemetry system for the voltammetric signals, electrical cross-talk between the two settings was avoided and simultaneous neurochemical and electro-physiological recordings could be made so that a detailed time course of events could be obtained. Extracellular levels of the serotonin metabolite, 5-hydroxy-indoleacetic acid, measured every 2 min, increased with wakefulness and decreased with sleep: levels were significantly lower during desynchronized sleep than slow wave sleep. In vivo voltammetry associated with the optoelectronic telemetry system appears to be a useful tool for studying the relationship between neurochemical changes and electrophysiological events.

Extraneuronal noradrenaline in the prefrontal cortex of morphine-dependent rats: tolerance and withdrawal mechanisms

The changes in extracellular concentrations of noradrenaline (NA) in the prefrontal cortex of morphine-dependent rats were studied by microdialysis following an acute morphine challenge and during naloxone-precipitated withdrawal. Animals were implanted with morphine- or placebo-containing pellets for 5 days. In control rats a challenge dose of morphine (5 mg/kg s.c.) induced a maximum decrease in NA output of about 45% of pre-drug levels. In contrast, morphine challenge had no effect on extraneuronal NA concentrations in morphine-implanted animals. In control animals, naloxone (2 mg/kg i.p.) produced no behavioral effect nor changed NA levels. However, in morphine-dependent animals naloxone suddenly increased extraneuronal NA by 175% of baseline dialysate levels in the first sample after the injection and precipitated a morphine-withdrawal symptomatology that paralleled the changes in NA output. Thus, chronic morphine treatment in rats results in the development of tolerance to the acute inhibitory effect of morphine on extraneuronal NA and is associated with a stimulation of prefrontocortical NA output during naloxone-precipitated withdrawal.

Sleep disorders and anxiety as symptom profiles of sympathoadrenal system hyperactivity in major depression

Recently, it has been reported that major depression is accompanied by an increased sympathoadrenal system (SAS) activity. In order to study the psychopathological correlates of SAS activity in depression, the authors measured the 24 h urinary excretion of catecholamines (CA), i.e., noradrenaline (NE), adrenaline (E), dopamine (DA) and the NE/E metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) in 80 unipolar depressed subjects. The excretion of these indices of SAS activity have been studied in relation to the depressive items of the Structured Clinical Interview for DSM-III (SCID) and the Hamilton Depression Rating Scale (HDRS). There were significant positive correlations between the SCID item sleep disorders and the HDRS item middle insomnia, on the one hand, and NE, E and DA excretion, on the other. The MHPG excretion in 24 h urine was significantly and negatively related to somatic anxiety and hypochondriasis. It is suggested that these intertwined relationships between increased CA turnover, sleep discontinuity and anxiety may reflect the occurrence of a hyperarousal state in some major depressives that may be regarded as a coping response to various putative noxious stimuli.

Sleep-inducing function of noradrenergic fibers in the medial preoptic area

The aim of the investigation was to find out the role of noradrenergic (NE) terminals of the medial preoptic area (mPOA), in the regulation of sleep-wakefulness. Studies were conducted on free-moving adult male rats with chronically implanted cannulae in the mPOA. Sleep-wakefulness was assessed on the basis of EEG, EMG, and EOG recordings along with behavioral observations. Lesioning of catecholamine terminals (with 6-hydroxydopamine) in the mPOA produced an increase in quiet wakefulness. Prevention of NE fiber destruction, by pretreating the rats with imipramine, prevented this effect. This demonstrated that the increased quiet wakefulness produced by 6-OHDA was the result of NE fiber destruction. Changes in sleep-wakefulness were also assessed after microinjection of NE into the mPOA, in normal and ventral noradrenergic bundle (VNA)-lesioned rats. NE administration induced sleep in VNA-lesioned rats, and arousal in normal rats. The findings suggest that the NE terminals in the mPOA, projecting via VNA, play a role in the induction of sleep.

Characterization of hippocampal norepinephrine release as measured by microdialysis perfusion: pharmacological and behavioral studies

The release of endogenous norepinephrine in hippocampus was studied in freely moving rats with microdialysis perfusion. Using a loop-style dialysis probe, the basal amount of norepinephrine collected in 15-min fractions averaged 12 pg/25 microliters. Correcting for recovery (21%), the concentration of norepinephrine in the extracellular fluid of hippocampus under resting conditions was estimated to be approximately 14 nM. The alpha 2 adrenoceptor antagonist yohimbine (5.0 mg/kg, i.p.) increased norepinephrine efflux to 230% of basal levels. Clonidine (0.3 mg/kg, i.p.), an alpha 2 adrenoceptor agonist, decreased norepinephrine efflux to 56% of baseline. Addition of the reuptake blocker desipramine (1.0 microM) to the perfusate had no significant effect on norepinephrine efflux. However, increasing the K+ concentration of the perfusate to 30 mM increased norepinephrine efflux to 196% of baseline, and this effect was increased nearly two-fold by the addition of desipramine to the perfusate (364% of baseline). Restraint stress and intermittent tailshock increased norepinephrine efflux to 213% and 234% of baseline, respectively. The results suggest that microdialysis is a useful way to study norepinephrine release in hippocampus and they permit several conclusions to be drawn. First, the data obtained with systemic administration of alpha 2 adrenoceptor drugs emphasize the fact that a variety of regulatory mechanisms exist that may affect transmitter levels in the extracellular fluid. Second, the ratio of extracellular to intracellular norepinephrine in hippocampal tissue is considerably higher than that reported for dopamine in striatum. Coupled with the small effect of norepinephrine uptake blockade, this suggests that nerve terminal density is an important factor in determining the concentration of catecholamines in the extracellular fluid.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of some monoamine oxidase inhibitors on the sleep-wakefulness cycle of the cat

The influence of some monoamine oxidase inhibitors (phenelzine, transamin [tranylcypromine], nialamide) on the structure of the sleep-wakefulness cycle of the cat was studied. It was shown that these monoamine oxidase inhibitors elicit and increase in slow-wave sleep in the sleep-wakefulness cycle due to complete suppression of paradoxical sleep and significant decrease in wakefulness. After the cessation of the action of the monoamine oxidase inhibitors, a selective rebound of wakefulness is observed against the background of complete or partial absence of paradoxical sleep. The gives grounds for the hypothesis that during partial deprivation of wakefulness under the influence of monoamine oxidase inhibitors an intensification occurs on the accumulation of specific need for this physiological state, the satisfaction of which is accomplished as the result of its rebound in the post-deprivational cycle, i.e., after the termination of the EEG of the synchronizing effect of the monoamine oxidase inhibitors.

Comparison of effects of desipramine and amitriptyline on EEG sleep of depressed patients

Despite their widespread use, there are few data concerning the effects of tricyclic antidepressants on EEG sleep in depression. The present study documented the effects of desipramine (DMI, n = 17) and amitriptyline (AT, n = 16) upon EEG sleep in hospitalized depressed patients as part of a double-blind protocol involving 28 days of active treatment. Compared to placebo, patients receiving DMI showed somewhat worsened sleep continuity, particularly after 1 week of administration when the dose was 150 mg/day. On the other hand, sleep architecture and REM measures showed a rapid suppression of REM sleep, and then partial tolerance for this effect was observed with continued administration of DMI for 3 weeks. DMI was a more potent suppressor of REM sleep, while AT was more sedative. Based on these differences in effects upon EEG sleep, a discriminant function was derived and resulted in a correct classification of 87.5% of AT cases and 76.5% of DMI cases. These results are discussed in terms of the differences in pharmacological profiles for uptake blockade and anticholinergic potency for these two compounds.

Biochemical pharmacology of paradoxical sleep

The role of noradrenergic cells in the regulation of paradoxical sleep is still controversial, and experimental data have given rise to contradictory interpretations. Early investigations focused primarily on chemical neurotransmissions. However, the process of information transmission between cells involves many other factors, and the cell surface is an important site for transduction of messages into modifications of the activity of postsynaptic cells. alpha-adrenoceptors are believed to play an important role in the control of wakefulness and paradoxical sleep. Experimental evidence suggests that physiological modulation of receptor sensitivity, possibly by specific neuro-modulators, may be a key mechanism in synaptic transmission. In the investigation of the mechanisms involved in paradoxical sleep regulation, lesions of the locus coeruleus have given equivocal results. Collateral inhibition, probably mediated by alpha 2-adrenoceptors, appears to be a powerful mechanism. The exact temporal relationship between noradrenergic cell activation and paradoxical sleep production is not established, but 5-HT appears to be involved. Differences between paradoxical sleep and waking may be related to a physiological modulation of alpha 2-adrenoceptor sensitivity.

Catecholamines and the sleep-wake cycle. I. EEG and behavioral arousal

The exact role of catecholamines (CA) on the sleep-wake cycle is still controversial. Critical analysis of lesion studies tends to suggest a neuromodulatory role for both dopamine (DA) and norepinephrine (NE) on EEG and behavioral arousal. Support for this view is provided by pharmacological studies in which catecholaminergic systems are activated or inhibited. Taken together they show that disturbances in the dynamic balance between neurochemical systems may alter the conditions for wake-triggering mechanisms to express at optimal levels. Large electrolytic or neurotoxic lesions which affect noradrenergic and dopaminergic structures are associated with marked and prolonged EEG changes and decreased behavioral arousal, respectively. In contrast, specific and circumscribed damage restricted to these systems is followed by a transient decrease in waking activity. Thus, results observed after large central lesions are most probably related to destruction of non-catecholaminergic neurons. Inhibition of brain CA synthesis causes behavioral sedation and a decrease in waking activity. Selective pharmacological stimulation of presynaptic alpha-adrenergic (alpha 2) receptors tends to decrease waking, while opposite effects result from alpha 2-receptor blockade. Drugs with agonistic activity at postsynaptic alpha-adrenergic (alpha 1) sites increase EEG desynchronization, but specific blockade of alpha 1-receptor does not result in marked decreases of waking EEG. In contrast, treatments which simultaneously block NE and DA receptors significantly affect waking. Beta-adrenergic receptor blockers show no conclusive effects on waking or sleep. Selective DA-receptor agonists induce biphasic effects, with low doses decreasing and large doses increasing cortical desynchronization and motility. Opposite effects are observed in laboratory animals after injection of specific DA-receptor blockers.

Effects of intraventricularly administered serotonin, noradrenaline, dopamine and metaraminol on the reserpine-induced spikes recorded from the medial nucleus trapezoides in rabbits

Effects of intraventricularly administered serotonin (5HT), noradrenaline (NA), dopamine (DA) and metaraminol on the reserpine-induced spikes recorded from the medial nucleus Trapezoides (Trap. m.) in rabbits were investigated. 5HT (30, 50 micrograms) produced marked decreases in the amplitude and discharge rate of the spikes 3 to 5 min after intraventricular administration. NA (30, 50 micrograms) also produced similar effects to those of 5HT, but DA at the same dosage produced no significant changes in the amplitude and discharge rate of spikes. Metaraminol, a metabolite of alpha-methyl-m-tyrosine, produced gradual and long-lasting, potent suppression of spikes. Ninety min later, spikes were completely suppressed, and no recovery was observed within 6 hours after intraventricular administration. These results indicate that NA has a similar suppressing action to that of 5HT on the generation of the reserpine-induced spikes.

Biphasic effect of chlorpromazine on rat paradoxical sleep: a study of dose-related mechanisms

The experiments reported here investigated the effect of chlorpromazine (CPZ) alone or after inhibition of catecholamine (CA) synthesis on paradoxical sleep (PS) in the rat. The dose--response curve for CPZ was biphasic with enhancement of PS after low doses, and depression of PS after higher doses. In contrast, low doses of CPZ after inhibition of CA synthesis markedly decreased PS. This decrease was greater after tyrosine hydroxylase inhibition than after dopamine-beta-hydroxylase inhibition. These results support the view that low doses of CPZ produce increased activity in brain CA synapses, and that both dopamine and noradrenaline participate in the control of PS in the rat.

Effects of locus coeruleus lesions upon cerebral monoamine content, sleep-wakefulness states and the response to amphetamine in the cat

The purpose of the present study was to investigate the effects of complete lesions of the noradrenaline locus coeruleus neurons upon wakefulness and paradoxical sleep. Radiofrequency lesions of the nucleus were performed in 8 chronically implanted cats which were continuously recorded with an EEG for 5 days prior to and 21 days following the lesions, when they were sacrificed. In 3 of these animals amphetamine (2 mg/kg) was administered on one control day and on the 10th day post-lesion. Following sacrifice, monoamine content was assayed in discrete brain regions, and the lesion was examined in Nissl-stained sections of the pons. (1) The majority (x 69%) of the locus coeruleus was bilaterally destroyed by the lesions which only minimally exceeded the boundaries of the nucleus within the dorsolateral pontine tegmentum. Noradrenaline was depleted by a mean of 85% in the paleo- and neocortex and by a mean of 60% in the thalamus and midbrain. (2) EEG activation reappeared within 12-48 h following the lesion and represented a normal percentage of recording time on the 3rd and subsequent days post-lesion. The behavioral arousal and long-lasting EEG activation produced by amphetamine was qualitatively and quantitatively the same pre- and post-lesion. (3) Despite alteration of certain components, paradoxical sleep reappeared within 48 h and recovered to normal amounts by the second week post-lesion. Muscle atonia was permanently absent in 7 animals. Ponto-geniculo-occipital (PGO) spiking was acutely redistributed across all states and chronically reduced in frequency (by a mean of 50%) within paradoxical sleep. These results indicate that the noradrenaline locus coeruleus neurons are not necessary for the tonic maintenance of EEG activation that occurs in normal wakefulness and in amphetamine-produced arousal. Furthermore, these neurons are not necessary for the occurrence of paradoxical sleep, although they may be involved in modulation of PGO spiking.

Norepinephrine-containing neurons: changes in spontaneous discharge patterns during sleeping and waking

Norepinephrine-containing neurons of the locus coeruleus of the cat were recorded with microelectrodes during unrestrained sleeping and waking. The recorded neurons were subsequently defined by combined fluorescence histochemistry of catecholamines and production of microlesions at recording sites. These pontine units show homogeneous changes in discharge patterns with respect to sleep stages, firing slowly during drowsy periods and slow wave sleep and firing in rapid bursts during paradoxical sleep. These data provide a direct correlation between the activity of defined catecholamine-containing neurons and the spontaneous occurrence of sleep stages.