c-fos Gene expression during emotional stress in rats: blocking by delta sleep-inducing peptide

An emotional stress induces an obvious immediate early gene c-fos expression in the brain limbic structures in the rats predisposed to emotional stress. Administration of the delta-sleep-inducing peptide (DSIP) was shown to inhibit the c-fos expression. It led to an obvious inhibition of the c-fos expression in paraventricular nuclei of the hypothalamus, medial and lateral parts of the septum of rats predisposed to emotional stress. This mechanism seems to play an important role in the DSIP anti-stress effects.     

Delta sleep inducing peptide (DSIP): effect on respiration activity in rat brain mitochondria and stress protective potency under experimental hypoxia

Neuromodulatory delta sleep inducing peptide (DSIP) seems to be implicated in the attenuation of stress-induced pathological metabolic disturbances in various animal species and human beings. Mitochondria, as cell organelles, are considered especially sensitive to stress conditions. In this work, the influence of DSIP and Deltaran((R))-a recently developed product based upon DSIP-on processes of oxidative phosphorylation and ATP production in rat brain mitochondria and rat brain homogenates was studied. A polarographic measurement of oxygen consumption was applied to evaluate the impact of DSIP on maximal rates of mitochondrial respiration and coupling of respiration to ATP production. We provide evidence that DSIP affected the efficiency of oxidative phosphorylation on isolated rat brain mitochondria. This peptide significantly increased the rate of phosphorylated respiration V3, while the rate of uncoupled respiration V(DNP) remaining unchanged. It enhanced the respiratory control ratio RCR and the rate of ADP phosphorylation. DSIP and Deltaran exhibited the same action in rat brain homogenates. We also examined the influence of DSIP under hypoxia when mitochondrial respiratory activity is altered. In rats subjected to hypoxia, we detected a significant stress-mediated reduction of V3 and ADP/t values. Pretreatment of rats with DSIP at the dose of 120 microgram/kg (i.p.) prior to their subjection to hypoxia completely inhibited hypoxia-induced reduction of mitochondrial respiratory activity. The revealed capacity of DSIP to enhance the efficiency of oxidative phosphorylation found in vitro experiments could contribute to understanding pronounced stress protective and antioxidant action of this peptide in vivo.     

Demonstration of delta sleep inducing peptide in a strain of human small cell lung cancer by immunocytology]

The "delta sleep inducing peptide" (DSIP) is a regulatory peptide localized in the brain, the hypophysis and some endocrine cells of the gut. The present immunological study, performed with a monoclonal antibody to DSIP, provides evidence for the presence of DSIP-like immunoreactivity (DSIP-LI) in a strain of small cell carcinoma. The specificity of the immunoreaction was assessed by the tests using heterologous antigen known to be secreted by these cells. The DSIP could play a role in the course of this disease.     

Effects of delta-sleep-inducing peptide during ischemic injury of the rat brain

An anti-ischemic effect of the delta-sleep-inducing peptide (DSIP) was found in rats. The DSIP effect was more obvious than that of the MK-801. The data obtained is discussed considering a possible use of the DSIP for brain stroke prophylaxis.     

Delta sleep-inducing peptide (DSIP)-like material is absorbed by the gastrointestinal tract of the neonatal rat

Entry of delta sleep-inducing peptide (DSIP) into the circulation from the gastrointestinal (GI) tract was studied in unweaned rat pups. The pups were fed an analog of DSIP (N-Tyr-DSIP) or 125I-N-Tyr-DSIP and blood samples collected. Significant increases in plasma DSIP-like immunoreactivity occurred after the feeding of 100 ωg/animal of N-Tyr-DSIP but not after vehicle (normal saline) or 1 ωg/animal. Column chromatography showed this immunoreactivity to coelute with intact DSIP and des-Trp¹- DSIP. A small but statistically significant increase of immunoreactivity occurred in the plasma of pups whose nursing mothers were injected with N-Tyr-DSIP but not in those whose mothers were injected with saline. Radioactivity appeared in both the brain and blood of 1–2 and 10 day old rat pups fed 125I-N-Tyr-DSIP. Although only a small amount of the radioactivity in plasma co-eluted with intact 1251I-N-Tyr-DSIP on column chromatography, almost all of the radioactivity in brain did, suggesting that the radioactivity in the brain represented crossing of the blood-brain-barrier by the peptide and not just contamination by blood. The results cannot be explained by either regurgitation of intestinal contents, or by stimulation of endogenous peptide. They show that a DSIP peptide administered orally can be absorbed through the GI tract into the systemic circulation.     

Delta sleep-inducing peptide (DSIP) stimulates LH release in steroid-primed ovariectomized rats

Delta sleep inducing peptide (DSIP) has been shown to increase sleep in various animals and it is found in various parts of the brain including the hypothalamus. While intraventricular administration of DSIP (2 or 10 micrograms) failed to affect LH release in ovariectomized rats, in two separate experiments DSIP (2 or 10; 15 or 30 micrograms) promptly stimulated LH release in ovariectomized estrogen, progesterone-primed rats. However, DSIP (10(-8) or 10(-6)M) had no effect on either basal or luteinizing hormone-releasing hormone-induced in vitro LH release from the hemipituitaries of ovarian steroid-primed rats. These findings are in accord with the hypothesis that DSIP or DSIP-like peptide(s) may activate the hypothalamic neural circuitry responsible for stimulation of LH release reported to occur during sleep.     

Effect of delta sleep-inducing peptide on lipid peroxidation and xanthine oxidase activity in rat tissues during cold stress

I. p. administration of exogenous delta-sleep-inducing peptide (DSIP) decreased the amount of diene conjugates and Schiff bases in the liver and brain in rats. The xanthine oxidase activity, at that, did not change. Cold stress enhanced the xanthine oxidase activity well as the amount of diene conjugates and Schiff bases. Preliminary administration of the delta-sleep-inducing peptide to cold-exposed animals diminished the xanthine oxidase activity and lipid peroxidation in the liver and brain. Protective effects of the DSIP under stress is discussed.     

The Delta-Sleep Inducing Peptide in Cerebral Mechanisms of Emotional Stress

The problem of the anti-stressor effect of the delta-sleep inducing peptide (DSIP) and of its neurophysiological mechanisms of action is considered. Physiological data are exposed that indicate an intraventricular administration of DSIP in rats to results in an increase of resistance to emotional stress, according to behavioral and autonomous reactions, and in a decrease of excitability of the brain structures responsible for protective reaction. Radioimmunological evidence is presented for the resistance of animals to emotional stress to depend on the content in hypothalamus of certain oligopeptides, such as -endorphin, DSIP, and the substance P. It was shown that animals resistant to emotional stress had a higher content of these oligopeptides in hypothalamus than those predisposed to stress. The issue is discussed that the prolonged anti-stressor effects after the DSIP administration are determined by considerable changes of the content of other polypeptides and hormones in hypothalamus and blood, which are involved in the reaction under the effect of DSIP.     

Characterization of Delta-Sleep-Inducing Peptide-Evoked Release of Met-Enkephalin from Brain Synaptosomes in Rats

Delta-sleep-inducing peptide (DSIP) stimulates the release of Met-enkephalin (Met-ENK) from superfused slices of the rodent lower brainstem in vitro. In our present study, DSIP (10(-10)-10(-9) M) induced a significant release of Met-ENK from medullary synaptosomes of rats. This DSIP-evoked release of Met-ENK was Ca2+ dependent and tetrodotoxin (TTX) insensitive. Furthermore, DSIP (10(-11)-10(-9) M) significantly increased 45Ca2+ uptake in medullary synaptosomes. These results demonstrate that DSIP acts directly on the nerve endings of Met-ENK-containing neurons to release this pentapeptide by generating a Ca2+ influx into these neurons. Effects of DSIP on Met-ENK release in other discrete brain regions were also studied. Significant DSIP-evoked Met-ENK release from synaptosomes was observed in the cortex, hypothalamus, and midbrain (at concentrations of 10(-10) and 10(-9) M) and in the hippocampus and thalamus (only at 10(-9) M), but not in the striatum. In the hypothalamus, the release of Leu-enkephalin from its synaptosomes was slightly, but not significantly, enhanced by DSIP (10(-10)-10(-8) M). Our findings demonstrate that DSIP triggered a Ca2+ influx in nerve endings to induce a subsequent release of Met-ENK from neurons in only certain brain regions.     

The frequency composition of the brain electrical activity in rats after the use of the delta-sleep peptide and its analogs]

Frequency spectra of brain electrograms in the course of 1 h after peripheral and central administration of the delta-sleep peptide (DSIP) or two its analogues were studied in freely moving rats. In autumn series of experiments carried out on 18 animals was revealed the phase action of DSIP being manifested in initial (up to 20 min after the injection) suppression of fast (20-26 Hz) oscillations in electrocorticograms and their augmentation in subsequent intervals. Under the identical conditions analogues of DSIP induced the effects characteristic for different phases of DSIP action. In spring-summer series of experiments carried out in 6 animals was revealed a significant increase of the delta-waves in electrical activity of the Putamen after intraperitoneal injection of DSIP and its first analogue. Under the conditions of intraventricular injection DSIP induced stable augmentation of oscillations in a diapason of 14-16 Hz in the neocortex, and its analogues induced similar changes in a nearby frequency diapason of 9.6-11 Hz.     

Features of regulating delta sleep-inducing peptide by free radical processes in tissue and erythrocyte membranes in intact animals and under stress

In activity the comparative analysis of metabolic effects delta--sleep inducing peptide (DSIP) in tissues and erythrocytes of intact rats and under cold stress is conducted. The regulation effect of DSIP in attitude of free radical processes will be realised through modulation the prooxidant--antioxidant balance: both for intact animal, and at stress. Exogenous DSIP increases the antioxidant system activity in tissues of brain, liver and blood in standard conditions and under cold stress. The anti-stress effect of DSIP is directed as on increase of power endogenic enzymatic antioxidant system activity, specially glutathione peroxidase activity, and not enzymatic of antioxidant protection. The DSIP renders different influence on activity of prooxidant enzymes: for intact animal boosts the myeloperoxidase activity in blood neutrophils, not rendering essential influencing on the xanthine oxidase activity in tissues of brain, liver and activates the myeloperoxidase activity, depresses the xanthine oxidase activity for rats at stress. The membranotropic effect of DSIP in the norm and under stress is connected to increase of stability of protein--lipid interplays. The membranostabilizing effect of DSIP in conditions of stress is characterized decrease of polarity of lipid phase and negative surface charge of erythrocyte membranes, modified in course of lipid peroxidation.     

The effect of the delta-sleep peptide on the adrenaline level in rat tissues under normal conditions and during cold stress

Adrenalin content in the brain, liver and adrenal glands under the effect of cold stress grows by 314, 500 and 56% as compared to the control. A single administration of the delta-sleep inducing peptide (DSIP) in a dose of 12 microgram/100 g to intact animals makes the adrenalin content in the brain higher 1, 3, 6 and 24h after administration; two and three days later the adrenalin content in the brain does not change. The amount of adrenalin in the liver of the same animals increases 1, 3, 6 h and 1, 2, 3 days after DSIP administration. Intraperitoneal administration of DSIP induces an increase of the adrenalin level in the adrenal glands of rats an hour and a day after administration. Two days later the level of adrenaline decreases by 41%; 3, 6 h and 3 days after DSIP administration the content of adrenaline remains unchanged. As a result of the DSIP administration in a dose of 12 micrograms/100 g to the animals in the state of cold stress, the content of adrenalin increases in the rat brain by 129, in the liver--by 300, adrenal glands--by 44% as compared with the control.     

Level of delta sleep-inducing peptide (DSIP) in the brain of rats with different alcoholic motivation

Radioimmunoassay was used to measure the content of delta-sleep-inducing peptide (DSIP) in random-bred albino rats divided into groups according to the duration of ethanol anesthesia and the levels of 15% ethanol consumption under free-choice conditions. The concentration of the neuropeptide was assayed in intact brain, in the cortex of large hemispheres, medulla oblongata, thalamus and striatum. The short-sleeping rats manifested a statistically significant lowering of the DSIP content in intact brain homogenates, in the cortex of large hemispheres and striatum. On the contrary, thirty minutes after a single intraperitoneal injection of ethanol in a dose of 1 g/kg the DSIP content in the medulla oblongata, thalamus and striatum was found to be increased. The raising of the ethanol dose up to 2.5 and 4.5 g/kg was followed by a less significant increase in the neuropeptide content. Prolonged chronic alcoholization under free-choice conditions led after 12 months to the reduced DSIP content in the medulla oblongata, thalamus and striatum. The importance of DSIP for the pathogenesis of experimental alcoholism using rats with different levels of alcoholic motivation is discussed.     

Entrapment and in vitro release of delta-sleep inducing peptide from polymer hydrogels based on modified polyvinyl alcohol

The aim of this study was to entrap delta-sleep inducing peptide (DSIP) in cross-linked poly(vinyl alcohol)-based hydrogels of different structures and to determine kinetics of the peptide release from these hydrogels using an in vitro model. Isotropic and macroporous hydrogels based on poly(vinyl alcohol) acrylic derivative (Acr-PVA) and also macroporous epoxy groups containing hydrogels synthesized by copolymerization of this macromer and glycidyl methacrylate, have been used in this study. Isotropic hydrogels were prepared at positive temperatures while macroporous ones were obtained by formation in cryo-conditions. The peptide was entrapped into macroporous PVA hydrogels by adding the peptide solution onto preformed matrices, while peptide immobilization on PVA-GMA hydrogels, containing free epoxy groups, was carried out by sorption of peptide from its aqueous solution. In the case of DSIP entrapment into isotropic PVA gel the peptide solution was added into the polymer mixture at hydrogel formation. The kinetics of peptide release from hydrogels was studied by incubating matrices in PBS solution (pH 7.4), in physiological solution (0.9% NaCl) and in water. DSIP concentration in supernatants was determined by reverse-phase HPLC. Incubation of macroporous PVA gels in PBS, 0.9% NaCl, and water for 30 min caused release of 74, 70, and 64% DSIP, respectively, and this processes completed within 3 h. From hydrogel containing epoxy groups the release of neither peptide nor its degradation products was observed even after incubation for 48 h. For freshly prepared isotropic hydrogel the release kinetics was as follows: 27 and 78% DSIP were released within first 30 min and 33 h, relatively. For the lyophilized hydrogel samples the peptide release was 63% after incubation for 30 min, while drying of samples at room temperature for 3 days caused significant peptide loss because of its structure damage.     

Effect of leu-enkephalin and the delta-sleep-inducing peptide, M (DSIP), on endogenous noradrenaline release by brain synaptosomes in the rat

Fluorometry was employed to measure the noradrenaline (NA) content in rat brain synaptosomes depending on the duration of incubation, depolarization effects (40 mM KCl or 1.5 mM ouabain), composition of the synaptosomal fraction and concentration of the peptides. The 10-minute incubation in a potassium medium of a suspension of light synaptosomes was used as an optimal test-system for studying the peptide action. Leu-enkephalin inhibited the depolarization-induced NA release. The effect was abolished by naloxone. The delta-sleep-inducing peptide (DSIP) did not influence the neurotransmitter release at concentrations of 10(-8)-10(-5) M. A mixture of amino acids imitating the amino acid composition of the DSIP influenced spontaneous release of NA. This effect is discussed in connection with the physiological action of the peptide on its intraventricular injection.     

DSIP affects adrenergic stimulation of rat pineal N-acetyltransferase in vivo and in vitro

The natural occurrence, sleep, and extra-sleep effects of delta sleep-inducing peptide (DSIP) have been shown by different laboratories. However, neither an in vitro assay system nor a probable mechanism of action of the peptide have been conclusively demonstrated so far. The recent finding that DSIP influences the nocturnal rise of N-acetyltransferase (NAT) activity in rat pineal led us to investigate a possible effect on pharmacologically induced NAT activity in vivo and in vitro. Stimulation of the enzyme with adrenergic drugs such as isoproterenol and phenylephrine was reduced by DSIP at doses of 150 and 300 μg/kg injected subcutaneously. In vitro, 6, 150 and 300 nM DSIP attenuated isoproterenol stimulation of the enzyme in cultured pineals, whereas 150 nM DSIP effectively reduced stimulation induced by a combination of the two drugs. The peptide alone did not influence NAT activity in vitro, but produced a slight stimulation in vivo. To our knowledge, these results represent the first report of a direct interaction of DSIP with adrenergic transmission. The in vitro system could prove useful for establishing possible mechanism(s) of action of the ‘sleep peptide.’     

Influence of delta-sleep-inducing peptide on the activity of proteolytic enzymes in the rat brain under hypokinesia]

Single administration of the delta-sleep-inducing peptide (DSIP) in a dose of 12 micrograms/100 g to intact animals makes the activity of neutral proteinases and cathepsin D higher in the rat brain and blood serum. Hypokinesia of different duration changes activity of neutral and acidic proteinases and induces accessibility of cathepsin D to the cytosol as a result of damage in lysosomal membrane. Injection DSIP induces a decrease A/B of cathepsin D to the control level under 1-h hypokinesia condition and normalizes the neutral proteolytic activity under 6-h hypokinesia condition.     

Oligopeptides in the development of biological motivations

Data are presented, demonstrating the action of a number of oligopeptides on biological motivations of hunger, fear, self-stimulation and on alcohol addiction. In the structure of animals feeding motivation, such oligopeptides take part as beta-lipotropin and its fragments, ACTH, pentagastrin, delta-sleep inducing peptide (DSIP), substance P; in organization of defensive motivation--angiotensin II (AII), DSIP, substance P, bradykinin, beta-endorphin etc.; in organization of self-stimulation--AII, DSIP, bradykinin, ACTH, beta-endorphin etc. It is established that most of the above oligopeptides, injected to the brain lateral ventriculi, inhibit biological motivations, and only some of them have an activating action. On the basis of experiments, a hypothesis is formulated that oligopeptides act as a feedback between the genome of brain neurones and pacemaker cells of motivation centres of the hypothalamus area. Some oligopeptides elaborated by neuronal genomes under the action of dominating motivation, activate--and the other--suppress the activity of motivation hypothalamus centres.     

Delta sleep-inducing peptide (DSIP): a still unresolved riddle

Delta sleep-inducing peptide (DSIP) was isolated from rabbit cerebral venous blood by Schoenenberger-Monnier group from Basel in 1977 and initially regarded as a candidate sleep-promoting factor. However, the link between DSIP and sleep has never been further characterized, in part because of the lack of isolation of the DSIP gene, protein and possible related receptor. Thus the hypothesis regarding DSIP as a sleep factor is extremely poorly documented and still weak. Although DSIP itself presented a focus of study for a number of researchers, its natural occurrence and biological activity still remains obscure. DSIP structure is different from any other known representative of the various peptide families. In this mini-review we hypothesize the existence of a DSIP-like peptide(s) that is responsible (at least partly) for DSIP-like immunoreactivity and DSIP biological activity. This assumption is based on: (i) a highly specific distribution of DSIP-like immunoreactivity in the neurosecretory hypothalamic nuclei of various vertebrate species that are not particularly relevant for sleep regulation, as revealed by the histochemical studies of the Geneva group (Charnay et al.); (ii) a large spectrum of DSIP biological activity revealed by biochemical and physiological studies in vitro; (iii) significant slow-wave sleep (SWS) promoting activity of certain artificial DSIP structural analogues (but not DSIP itself!) in rabbits and rats revealed by our early studies; and (iv) significant SWS-promoting activity of a naturally occurring dermorphin-decapeptide that is structurally similar to DSIP (in five of the nine positions) and the sleep-suppressing effect of its optical isomer, as revealed in rabbits. Potential future studies are outlined, including natural synthesis and release of this DSIP-like peptide and its role in neuroendocrine regulation.     

Delta sleep-inducing peptide (DSIP)-like material exists in peripheral organs of rats in large dissociable forms

The presence of delta sleep-inducing peptide (DSIP) in brain has been shown by radioimmunoassay (RIA) and by immunocytochemistry. We now describe the occurrence of DSIP-like material in the peripheral organs of the rat as measured by RIA. Tissue from 12 areas was extracted with water, and the amounts of immunoreactive material found to be between 86 pg/mg tissue (muscle) and 849 pg/mg (stomach). Recoveries of about 80% of added DSIP were achieved at tissue concentrations of 1 mg/ml or less. This percentage was reduced in liver at higher concentrations. The percentage of small peptide adsorbed by charcoal was greatly increased at lower tissue concentrations in all organs. This effect was significant and linear. Chromatography on columns of Sephadex G-15 and G-25 showed immunoreactive material mostly larger than DSIP. Digestion with trypsin, however, produced small immunoreactive peptides with only a minimal reduction in total immunoreactivity. Thus, DSIP-like material is widespread in peripheral tissues and appears to exist mainly in a large form, probably bound to protein, that can be reduced in size by tryptic digestion and can be dissociated at lower concentrations of tissue to yield small immunoreactive peptides.