DSIP/DSIP-P and circadian motor activity of rats under continuous light

Daily intravenous injection of 30 nmol/kg DSIP (delta sleep-inducing peptide) in rats under constant illumination produced marked changes of their motor activity as compared to saline controls. Similar marked but distinctly different effects on the circadian pattern of locomotor behavior partially abolished by constant illumination were also obtained after repeated administration of 0.1 nmol/kg DSIP-P (the phosphorylated analogue of DSIP) which enhanced overall motor activity. In both instances the results additionally differed from those reported for a normal 12 hr light:dark cycle. The present results support the hypothesis that DSIP might primarily act by influencing circadian rhythmicity.     

The effect of delta sleep-inducing peptide on the convulsive activity in corasol kindling

The influence of intraperitoneal delta-sleep inducing peptide (DSIP) injection (100 micrograms/kg) on the epileptic activity was investigated in the experiments on Wistar rats and (CBA X C57B1/6)F1 mice. The model of chronically developing epileptic activity--the model of pharmacological kindling--was created by daily repeated corasole injections in subconvulsive doses (30 mg/kg). It has been shown that DSIP injection delayed the manifestation of generalized seizures during kindling, led to the suppression of seizure activity and reduced the mortality rate of animals that developed kindled seizures. The antiepileptic effect of DSIP was observed throughout the period of 5 minutes to 24 hours after the injection. Naloxone (2.5 mg/kg) did not change the antiepileptic effect of DSIP.     

Tolerance to d-amphetamine: behavioral specificity.

In a Y-maze exploratory task mice tend to enter that compartment which was least recently visited (spontaneous alternation). Low doses of d-amphetamine (1.0 mg/kg) reduce alternation to chance levels, while high doses (10.0 mg/kg) result in animals successively visiting only two compartments of the Y-maze (perseveration). Following daily d-amphetamine injection (1.0 or 10.0 mg/kg) over a 30 day period tolerance to the d-amphetamine induced perseveration was observed; however, chronic amphetamine treatment did not modify the locomotor stimulating effects of d-amphetamine or the reduction of alternation to chance levels produced by low doses of the drug. It was hypothesized that tolerance to d-amphetamine occurs exclusively to behaviors mediated by norepinephrine.     

Role of medial prefrontal cortex dopamine in age differences in response to amphetamine in rats: Locomotor activity after intra-mPFC injections of dopaminergic ligands

Changes in medial prefrontal cortex (mPFC) dopamine receptor expression and in mPFC projections to the nucleus accumbens in adolescence suggest that there may be age differences in the regulation of drug‐related behavior by the mPFC. The age‐specific role of prelimbic D1 dopamine receptors on amphetamine‐induced locomotor activity was investigated. In experiment 1, rats aged postnatal day 30 (P30), P45, and P75, corresponding to early and late adolescence and adulthood, were given an injection of D1 and D2 antagonists into the prelimbic mPFC before a systemic injection of 1.5 mg/kg of amphetamine and locomotor activity was recorded. In experiment 2, effects of intra‐prelimbic injections of a D1 agonist and antagonist on locomotor activity produced by a lower dose (0.5 mg/kg) of amphetamine were investigated. D2 receptor antagonist did not alter amphetamine‐induced activity, whereas the D1 receptor antagonist reduced activity produced by 1.5 mg/kg of amphetamine more in P30 than in P45 and P75 rats. In addition, D1 agonist enhanced the locomotor activating effects of 0.5 mg/kg of amphetamine in adolescent rats and decreased activity in adult rats. These results suggest that insufficient activation of mPFC D1 receptors may underlie the reduced activity at the low dose of amphetamine in early adolescent compared to adult rats. © 2011 Wiley Periodicals, Inc. Develop Neurobiol, 2012     

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.’     

Valproate and delta-sleep peptide display high efficacy against metaphit-induced audiogenic seizure in rats

The effects of valproate (VPA) and delta sleep-inducing peptide (DSIP) on metaphit-induced generalized, audiogenic seizure in adult rat males were compared. The animals were i.p. injected with: (1) Saline; (2) metaphit (mp, 10 mg kg(-1)); 3. metaphit (10 mg kg(-1)) and 8 h later with DSIP (0.1, 0.2, 0.4 or 1.0 mg kg(-1)), 4. metaphit (10 mg kg(-1)) and 8 h later with VPA (50, 75 or 100 mg kg(-1)); 5. DSIP alone (1.0 mg kg(-1)) and 6. VPA, alone (100 mg kg(-1)). The rats were exposed to sound stimulation at hourly intervals and the behavior and EEG were analyzed. The EEG signals in metaphit rats appeared as a sleep-like pattern and spike-wave complexes with increased power spectra. Valproate and DSIP reduced the incidence of seizure and prolonged duration of latency in a dose-dependent manner. ED50 of valproate in the 1st hour after administration was 63.19 mg kg(-1) and that of DSIP 3.19 mg kg(-1) four hours after injection. This suggests that VPA, reached a peak of action immediately after the application, while DSIP had a prolonged action, mildly reducing, but not abolishing metaphit seizure. None of the applied VPA and DSIP doses eliminated the metaphit-provoked EEG signs of epileptiform activity.     

Dexamethasone induces biphasic effect on morphine hypermotility in mice: a dose-related phenomenon

The present study examined interaction between dexamethasone (DEX) and morphine on the locomotor activity in groups of mice by using the activity cage test. Morphine administration (30-75-150 mg/kg, ip) induced a dose-related increase of the locomotor activity of mice, whereas DEX per se (0.1-1.0-10 mg/kg, ip) did not modify the activity of control mice. Pretreatment of mice with DEX 0.1 mg did not alter the hyperactivity produced by the three doses of morphine. In contrast, DEX administered at 1.0 mg reduced the morphine effects on locomotor activity, whereas DEX at 10 mg potentiated the morphine hypermotility. Our results suggest that DEX may play an important regulatory role on the central effects of morphine through a differential modulation of brain excitability systems.     

The effects of delta agonists on locomotor activity in habituated and non-habituated rats

The effects of the delta agonists SNC80 and deltorphin II on ambulation and rearing activity were measured in habituated and non-habituated rats. SNC80 (30, 100, 200, 400 nmol, i.c.v.) and deltorphin II (3, 15, 30, 60 nmol, i.c.v.) induced similar, dose-dependent biphasic locomotor effects in non-habituated subjects. An initial decrease in exploratory activity was associated with anxiogenic signs such as pilo-erection, freezing behaviour and pupil dilation for each drug. Pre-treatment with the delta antagonist naltrindole (10 nmol, i.c.v.) inhibited the depressant effect, but not the subsequent stimulant effect, on locomotor activity in response to 30 nmol deltorphin II in this assay (P<0.05). In habituated rats, deltorphin II (0.03, 0.1, 0.3, 3 nmol, i.c.v.) caused significant, naltrindole-reversible increases in locomotor activity (P<0.05 for all doses) at 1,000-fold lower doses than those required for a similar response to SNC80 (10, 30, 100, 300 nmol, i.c.v.). Pharmacokinetic studies suggest that these compounds penetrate the brain to similar extents following i.c.v. injection. The substantial potency difference between deltorphin II and SNC80 in stimulating locomotor activity in habituated rats suggests pharmacological heterogeneity for these delta opioid receptor agonists.     

The ethanol-induced open-field activity in rodents treated with isethionic acid, a central metabolite of taurine.

The effect of isethionic acid, a central metabolite of taurine, on ethanol-induced locomotor activity was investigated in rodents. Ten minutes following an (i.p.) simultaneous administration of ethanol (0.0, 1.5, 2.0, 2.5, 3.0, 3.5 g/kg) and isethionic acid (0.0, 22.5, 45.0, 90.0, 180.0 mg/kg), mice were placed in the open-field chambers and locomotor activity was measured during a ten-minute testing period. A significant interaction was found between isethionic acid and ethanol. Isethionic acid pre-treated mice (45.0, 90.0 and 180.0 mg/kg) showed a higher locomotor activity than the saline group at 2.5 and 3 g/kg of ethanol. In a second study, isethionic acid (45 mg/kg) and ethanol (1 g/kg) were simultaneously injected to rats. Ten minutes after the two treatments, rats were placed in the open-field chamber for a 30-minute period. The depressant effects that ethanol produced on rat locomotion were amplified by the same dose of isethionic acid as it affected ethanol-induced locomotion in mice (45 mg/kg). However, isethionic acid did not change the spontaneous locomotion at any of the doses tested in mice or rats. Since no differences in blood ethanol levels were detected in both mice and rats, the interaction between isethionic acid's action and ethanol-related locomotion does not seem to be due to different rates of absorption of ethanol or any other pharmacokinetic process related to ethanol levels. The current study displayed that isethionic acid, administered intraperitoneally, behaves in a similar way to its immediate precursor, taurine, by amplifying ethanol-induction of the locomotor activity.     

Effect of rubiscolin,a delta opioid peptide derived from Rubisco,on memory consolidation

Rubiscolin-6 (YPLDLF) is a delta selective opioid peptide isolated from the enzymatic digests of ribulose bisphosphate carboxylase/oxygenase (Rubisco) from spinach leaves. In a step-through type passive avoidance test in ddY mice, rubiscolin-6 enhanced memory consolidation at doses of 3nmol/mouse after intracerebroventricular administration, and at 100mg/kg after oral administration. These doses are smaller than the optimal doses for an analgesic effect. The memory enhancing effect of rubiscolin-6 was blocked by pretreatment with the delta antagonist naltrindole, suggesting the involvement of the delta opioid receptor.     

The delta sleep-inducing peptide as a factor enhancing the content of substance P in the hypothalamus and the resistance of rats to emotional stress]

The influence of the delta-sleep inducing peptide (DSIP, 60 and 120 nmol/kg, intraperitoneally) on the content of substance P (SP) in rats hypothalamus was studied on males of August line. DSIP administration significantly increased the mean SP content in the hypothalamus and also its content in animals, stable and predisposed to emotional stress. Daily DSIP administration before putting the rats in conditions of stress increased the SP content in the hypothalamus decreased at the emotional stress. Preliminary single DSIP administration to the animals subjected to stress also increased the SP content. Single DSIP administration in a dose of 60 nmol/kg sharply reduced classical stress manifestations, such as hypertrophy of adrenals and thymus involution.     

A comparison of the self-stimulation reaction and of conditioned place preference with fenamine administration in rats]

The reinforcing properties of different doses of amphetamine (1 and 5 mg/kg) were examined using two variants of self-stimulation reaction (in the Skinner box and locomotor self-stimulation in a shuttle box) and place preference test. Amphetamine in dose of 1 mg/kg increased the frequency of self-stimulation in the Skinner box and prolonged the time of rat staying in active zone of a shuttle box to a greater degree than 5 mg/kg of the drug. On the contrary, the aversive phase of self-stimulation, determined by a coefficient of "disagreement", grew higher after 5 mg/kg amphetamine than following 1 mg/kg. The study of effects by place preference test revealed the other regularity: the most positive reinforcing properties possessed the drug in a dose of 5 mg/kg. Thus, there are dissociation between the two doses of amphetamine (1 and 5 mg/kg) in their action on different physiological conditioned responses. The mechanisms of this dissociation are discussed.     

Influence of substance P on the behavioral changes induced by haloperidol in rats

Locomotor activity and grooming behavior of rats were recorded for a period of 30 min following intraventricular injections of substance P(SP) in doses of 0.60 and 2.50 microgram/rat. The lower dose of the peptide significantly increased locomotion for 10 min and time spent grooming for 25 min. The effects of the same two doses of SP on the hypokinesia induced by various pharmacological treatments modifying catecholaminergic systems were then examined. SP did not affect the behavioral depression produced by alpha-methyl-para-tyrosine (250 mg/kg), FLA-63 (25 mg/kg) and phenoxybenzamine (20 mg/kg). However, SP, in dose of 0.60 microgram/rat, systematically reversed the decrease in locomotor activity induced by a relatively small dose of haloperidol, 0.1 mg/kg. The dame dose of the peptide significantly counteracted the rigidity but not the hypokinesia and catalepsy resulting from the previous administration of a higher dose of haloperidol, 3 mg/kg. The results support the hypothesis that SP may exert direct or indirect function in motor behavior, possible via a modulatory action on brain dopaminergic systems.     

Interaction of Delta Sleep-inducing Peptide and Valproate on Metaphit Audiogenic Seizure Model in Rats

Effects of valproate (VPA), a conventional antiepileptic drug and natural delta sleep-inducing peptide (DSIP) on metaphit (1-[1-(3-isothiocyanatophenyl)-cyclohexyl]-piperidine)-induced audiogenic reflex epilepsy were studied. For the purpose of the study, valproate in the doses of 50 or 75 mg/kg and DSIP (1.0 mg/kg) was i.p. injected either alone or in combination to adult Wistar male rats with fully developed metaphit seizures after eight audiogenic testing. The animals were stimulated using an electric bell (100 ± 3 dB and 5–8 kHz, for 60 s) 60 min after metaphit injection and afterwards at hourly intervals during the experiment. For EEG recording and power spectra analysis, three gold-plated screws were implanted into the scull. In EEGs of metaphit-treated animals polyspikes, spike-wave complexes and sleep-like patterns were recorded, while the power spectra were increased. Combined treatment of metaphit-induced seizures with valproate and DSIP was more effective than drugs alone especially during 4 h after administration. None of the applied dose combinations eliminated the EEG signs of metaphit-provoked epileptiform activity. Taken together, the results of the present study suggest that the combinations of valproate and DSIP should be considered as beneficial polytherapy in metaphit model of epilepsy.     

Physiological and behavioral effects of amphetamine in BACE1−/− mice

β‐Site APP‐cleaving Enzyme 1 (BACE1) is a protease that has been linked to schizophrenia, a severe mental illness that is potentially characterized by enhanced dopamine (DA) release in the striatum. Here, we used acute amphetamine administration to stimulate neuronal activity and investigated the neurophysiological and locomotor‐activity response in BACE1‐deficient (BACE1^?/?) mice. We measured locomotor activity at baseline and after treatment with amphetamine (3.2 and 10 mg/kg). While baseline locomotor activity did not vary between groups, BACE1^?/? mice exhibited reduced sensitivity to the locomotor‐enhancing effects of amphetamine. Using high‐performance liquid chromatography (HPLC) to measure DA and DA metabolites in the striatum, we found no significant differences in BACE1^?/? compared with wild‐type mice. To determine if DA neuron excitability is altered in BACE1^?/? mice, we performed patch‐clamp electrophysiology in putative DA neurons from brain slices that contained the substantia nigra. Pacemaker firing rate was slightly increased in slices from BACE1^?/? mice. We next measured G protein‐coupled potassium currents produced by activation of D2 autoreceptors, which strongly inhibit firing of these neurons. The maximal amplitude and decay times of D2 autoreceptor currents were not altered in BACE1^?/? mice, indicating no change in D2 autoreceptor‐sensitivity and DA transporter‐mediated reuptake. However, amphetamine (30 µm )‐induced potassium currents produced by efflux of DA were enhanced in BACE1^?/? mice, perhaps indicating increased vesicular DA content in the midbrain. This suggests a plausible mechanism to explain the decreased sensitivity to amphetamine‐induced locomotion, and provides evidence that decreased availability of BACE1 can produce persistent adaptations in the dopaminergic system.     

Effect of fluoxetine and metergoline on amphetamine-induced rise in plasma corticosterone

The effect of the serotonin reuptake inhibitor, fluoxetine, and the serotonin antagonist, metergoline, on the rise in plasma corticosterone induced by amphetamine was studied in the conscious, unrestrained rat. Fluoxetine (2.5 mg/kg) did not affect plasma corticosterone. However, this dose of fluoxetine when administered two hours prior to amphetamine (0.1 or 0.5 mg/kg) significantly potentiated the amphetamine-induced rise in plasma corticosterone. Fluoxetine had no effect on the response induced by the highest dose of amphetamine (1.0 mg/kg) utilized in the study. In contrast, metergoline produced a dose-dependent increase in plasma corticosterone over the range 0.1 – 5.0 mg/kg. This response reached maximum 30 minutes after drug administration and had a duration of approximately 120 minutes. Pretreatment of animals with metergoline (5.0 mg/kg) three hours before the administration of amphetamine (1.0 mg/kg) resulted in a significant decrease in the corticosterone rise induced by amphetamine. Lower doses of metergoline were ineffective in reducing the amphetamine-induced response. These observations support the hypothesis that the amphetamine-induced rise in plasma corticosterone is due, in part, to stimulation of serotonergic neurons.     

Genetic evidence that cocaine and caffeine stimulate locomotion in mice via different mechanisms

The effects of cocaine and caffeine on motor activity in two mouse strains 129/OlaHsd (129) and C57BL/6J (C57) were compared. The former mice exhibited lower basal motor activity than the latter. Cocaine (3, 10, 30 mg/kg) injected i.p. in habituated C57 mice produced a dose-dependent increase in rearing, motility and locomotion. In 129 mice, little or no stimulation was seen and only with the highest dose of cocaine. In both strains caffeine (3, 15, 30 mg/kg) produced a dose-dependent increase in rearing, motility and locomotion. The effect of caffeine on rearing was greater in C57 than in 129 mice, but motility and locomotion were stimulated approximately to the same degree in both strains. Thus, differences in the sensitivity to caffeine and cocaine between mouse strains provide genetic evidence that these two stimulants probably produce locomotor stimulation via somewhat different mechanisms.     

Behavioral interactions between ethanol and imidazodiazepines with high affinities for benzodiazepine receptors

The intrinsic effects of two imidazodiazepines RO 15-3505 and RO 17-1812 on the behavior of mice in a holeboard test were investigated. The interactions of these two drugs with ethanol were also studied. RO 15-3505 (0.75-6.0 mg/kg) failed to significantly alter either exploratory head-dipping or locomotor activity when administered alone but doses of 0.75 and 1.5 mg/kg reversed the reduction in the number of head-dips caused by ethanol (2 g/kg) and partially reversed ethanol's locomotor stimulant action. In contrast, RO 17-1812 (0.75-6.0 mg/kg) increased locomotor activity when administered alone, and enhanced the reduction in exploration caused by ethanol. Neither RO 15-3505 nor RO 17-1812 altered blood alcohol concentrations suggesting a pharmacodynamic basis for these interactions. The results suggest that in the holeboard test the interactions of imidazodiazepines with ethanol are related to the nature of their interaction with benzodiazepine receptors, inverse agonists antagonising and agonists enhancing ethanol's effects on exploration.     

The effect of amphetamine sensitization on mouse immunoreactivity.

Recent studies indicate a role of the immune system in the behavioral effects of amphetamine in rodents. In the present study we attempted to find a connection between the behavioral changes induced by repeated, intermittent administration of amphetamine and some immunological consequences of sensitization to amphetamine in mice. Male Albino Swiss mice were treated repeatedly (for 5 days) with amphetamine (1 mg/kg, i.p.). On day 9, they received a challenge dose of amphetamine (1 mg/kg). Acute administration of amphetamine increased their locomotor activity by ca. 40%. In animals treated repeatedly with amphetamine, the challenge dose of the psychostimulant induced behavioral sensitization, i.e. the higher locomotor activation as compared with that after its first administration to mice. Immune functions were evaluated by the ability of splenocytes to proliferate and to produce cytokines such as interferon gamma (IFN-gamma), interleukin (IL)-4 and IL-10. Acute amphetamine administration significantly decreased, by ca. 30% and 25%, the proliferation of splenocytes in response to an optimal and a suboptimal dose of concanavalin A (Con A), respectively, and increased their ability to produce IL-4. Chronic intermittent treatment with amphetamine significantly decreased, by ca. 65% and 50%, the proliferative response of T cells to an optimal and a suboptimal dose of Con A, respectively, and diminished by 20% the metabolic activity of splenocytes. The above data showed that both acute and chronic amphetamine administration diminished some aspects of the cell-mediated immunity; nevertheless, immunosuppression was particularly evident in amphetamine-sensitized mice. Our findings seem to indicate possible importance of monitoring and correcting immune changes in the therapy of amphetamine addiction.     

Neuropharmacological actions of panchagavya formulation containing Emblica officinalis Gaerth and Glycyrrhiza glabra Linn in mice

A panchagavya Ayurvedic formulation containing E. officinalis, G. glabra, and cow's ghee was evaluated for its effect on pentobarbital-induced sleeping time, pentylenetetrazol-induced seizures, maximal electroshock-induced seizures, spontaneous motor activity, rota-rod performance (motor coordination) and antagonism to amphetamine in mice. The formulation (300, 500 mg/kg, po) produced a significant prolongation of pentobarbital-induced sleeping time and reduced spontaneous locomotor activity. The formulation also significantly antagonised the amphetamine induced hyper-locomotor activity (500, 750 mg/kg, po) and protected mice against tonic convulsions induced by maximal electroshock (500, 750 mg/kg, po). The formulation slightly prolonged the phases of seizure activity but did not protect mice against lethality induced by pentylenetetrazole. The formulation did not show neurotoxicity. The results suggest that the panchagavya formulation is sedative in nature.