Su-Ying Cui

Hypnotic effect of jujubosides from Semen Ziziphi Spinosae

ETHNOPHARMACOLOGICAL SIGNIFICANCE Semen Ziziphi Spinosae, the seed of Ziziphus jujuba Mill. var. spinosa (bunge) Hu ex H.F. Chow has been widely used in treating insomnia and anxiety. AIM OF THE STUDY In this study, we investigated the hypnotic effect of jujubosides, one of the major components (saponin) of Semen Ziziphi Spinosae, in both day and night period. MATERIALS AND METHODS After the administration of jujubosides (9 mg/kg once per day for 3 days), sleep parameters were examined by EEG and EMG analysis in normal rats and the action of jujubosides on pentobarbital-induced sleep assessed by the loss-of righting reflex. RESULTS During daytime (9:00-15:00), jujubosides significantly increased the total sleep and rapid eye movement (REM) sleep without significant influence on non-REM (NREM) sleep. During nighttime (21:00-3:00), jujubosides significantly increased the total sleep and NREM sleep especially the light sleep while showed no significant effect on REM sleep and slow wave sleep (SWS). In pentobarbital-treated mice, jujubosides significantly augmented the hypnotic effect of pentobarbital (45 mg/kg, i.p.), proved by increasing sleep time and this augmentative effect was potentiated by 5-hydroxytryptophan (2mg/kg, i.p.). Furthermore, jujubosides inhibited the para-chlorophenylalanine-induced suppression of pentobarbital-induced hypnosis. CONCLUSIONS These results suggested that the hypnotic effect of jujubosides on normal rats may be influenced by circadian rhythm and the serotonergic system may involve in the hypnotic effect of jujubosides. Jujubosides may be good source of lead compounds for novel hypnotics.

Potentiating effect of spinosin, a C-glycoside flavonoid of Semen Ziziphi spinosae, on pentobarbital-induced sleep may be related to postsynaptic 5-HT1A receptors

Previous results have suggested that spinosin, a C-glycoside flavonoid of Semen Ziziphi spinosae, potentiates pentobarbital-induced sleep via the serotonergic system. The present study investigated whether spinosin potentiates pentobarbital-induced sleep via serotonin-1A (5-hydroxytryptamine, 5-HT(1A)) receptors. The results demonstrated that spinosin significantly augmented pentobarbital (35 mg/kg, i.p.)-induced sleep in rats, reflected by reduced sleep latency and increased total sleep time, non-rapid eye movement (NREM) sleep time, and REM sleep time. With regard to NREM sleep duration, spinosin mainly increased slow-wave sleep (SWS). Additionally, spinosin (15mg/kg, i.g.) significantly antagonized 5-HT(1A) agonist 8-OH-DPAT (0.1mg/kg, i.p.)-induced reductions in total sleep time, NREM sleep, REM sleep, and SWS in pentobarbital-treated rats. These results suggest that spinosin may be an antagonist at postsynaptic 5-HT(1A) receptors because these effects of 8-OH-DPAT were considered to be mediated via postsynaptic 5-HT(1A) receptors. Moreover, co-administration of spinosin and the 5-HT(1A) antagonist 4-iodo-N-{2-[4-(methoxyphenyl)-1-piperazinyl]ethyl}-N-2-pyridinylbenzamide (p-MPPI), at doses that are ineffective when administered alone (spinosin 5mg/kg, p-MPPI 1mg/kg), had significant augmentative effects on pentobarbital-induced sleep, reflected by reduced sleep latency and increased total sleep time, NREM sleep, and REM sleep. In contrast to the attenuating effects of p-MPPI on REM sleep via presynaptic 5-HT(1A) autoreceptors, 15mg/kg spinosin significantly increased REM sleep. These results suggest that the effect of spinosin on REM sleep in pentobarbital-treated rats may be related to postsynaptic 5-HT(1A) receptors.

Extract of Ganoderma lucidum prolongs sleep time in rats.

ETHNOPHARMACOLOGICAL RELEVANCE Ganoderma lucidum (Ling Zhi) is a basidiomycete white-rot macrofungus that has been used as a tranquilizing agent (i.e., An-Shen effect) for the treatment of restlessness, insomnia, and palpitation in China for hundreds of years. AIM OF THE STUDY The present study aimed to investigate whether Ganoderma lucidum extract (GLE) influences the sleep of freely moving rats and the potential mechanism. MATERIALS AND METHODS Ganoderma lucidum extract was extracted from fruiting bodies of Ganoderma lucidum. Rats were treated with GLE orally for 3 days, and on the third day, electroencephalographic and electromyographic recordings were made for 6h from 9:00 p.m. to 3:00 a.m. in freely moving rats. Sleep parameters were analyzed using SleepSign software. Tumor necrosis factor-α (TNF-α) levels were measured using the enzyme-linked immunosorbent assay. RESULTS Three-day administration of GLE significantly increased total sleep time and non-rapid eye movement (NREM) sleep time at a dose of 80 mg/kg (i.g.) without influencing slow-wave sleep or REM sleep in freely moving rats. TNF-α levels were significantly increased concomitantly in serum, the hypothalamus, and dorsal raphe nucleus. The hypnotic effect of GLE (80 mg/kg, i.g.) was significantly inhibited by intracerebroventricular injection of TNF-α antibody (2.5 μg/rat). Co-administration of GLE (40 mg/kg, i.g.) and TNF-α (12.5 ng/rat, i.c.v.), both at ineffective doses, revealed an additive hypnotic effect. CONCLUSION These results suggest that GLE has hypnotic effects in freely moving rats. The mechanism by which the extract promoted sleep remains unclear, but this effect appears to be primarily related to the modulation of cytokines such as TNF-α. Furthermore, these data at least partially support the ethnomedical use of Ganoderma lucidum.

Correlations between depression behaviors and sleep parameters after repeated corticosterone injections in rats

Aim:Disrupted sleep may be a prodromal symptom or a predictor of depressive disorders. In this study we investigated the relationship between depression symptoms and disrupted sleep using a novel model of stress-mimicked sleep disorders in rats.Methods:SD rats were injected with corticosterone (10, 20 or 40 mg/kg, sc) or vehicle for 7 d. Their sleep-wake behavior was monitored through implanted EEG and EMG electrodes. Their depressive behaviors were assessed using forced swim test, open field test and sucrose preference test.Results:The corticosterone-treated rats showed significantly reduced sleep time, disinhibition of rapid-eye-movement (REM) sleep and altered power spectra during non-REM sleep. All depressive behavioral tests did not show significant difference across the groups. However, individual correlation analysis revealed statistically significance: the immobility time (despair) was negatively correlated with REM sleep latency, slow wave sleep (SWS) time ratio, SWS bouts and delta power density, and it was positively correlated with REM sleep bouts and beta power density. Meanwhile, sucrose preference (anhedonia) was positively correlated with total sleep time and light sleep bouts, and it was negatively correlated with the REM sleep time ratio.Conclusion:In stress-mimicked rats, sleep disturbances are a predictor of depressive disorders, and certain symptoms of depression may be related to the disruption of several specific sleep parameters.

Tetrandrine, an antihypertensive alkaloid, improves the sleep state of spontaneously hypertensive rats (SHRs).

ETHNOPHARMACOLOGICAL RELEVANCE Radix of Stephania tetrandrae S. Moore has been used since antiquity in China as an antirheumatic, antihypertension, analgesic and antipyretic agent. Tetrandrine is the major component of Stephania tetrandrae. This study aims to evaluate the antihypertensive and hypnotic effect of tetrandrine on spontaneously hypertensive rats (SHR) and the possible mechanisms. MATERIALS AND METHODS Electroencephalography (EEG) and electromyography (EMG) were recorded in freely moving rats and the sleep parameters were analyzed with SleepSign software. The levels of serotonin (5-HT), norepinephrine (NE), dopamine (DA) and their metabolites were examined to investigate the underlying mechanisms by using HPLC-ECD. Blood pressure was measured by noninvasive blood pressure tail cuff test. RESULTS Tetrandrine (100mg/kg, i.g.) significantly suppressed blood pressure of SHR rats day by day during three days treatment. Meanwhile, tetrandrine remarkably improved the sleep efficiency by increasing total sleep time, rapid eye movement (REM) sleep and non-REM (NREM) sleep (including deep sleep and light sleep) time from the first day. Three days treatment of tetrandrine induced 5-HT concentration decrease in DRN, 5-HIAA concentration increase in LC and 5-HIAA/5-HT ratio increase in VTA and LC. In contrast, no changes in NE and DA concentrations in the DRN, VTA and LC occurred in SHR after tetrandrine treatment. These results indicate that modulation of 5-HT, its metabolite 5-HIAA and the 5-HIAA/5-HT ratio in DRN, VTA and LC are likely the mechanism of antihypertensive and hypnotic effects of tetrandrine at least in part. CONCLUSION This is the first observation that tetrandrine possesses both anti-hypertension and hypnotic effects in SHR and suggested that tetrandrine may be useful for the treatment of hypertension patients who accompanied with short sleep time and poor sleep efficiency.

Ca2+ modulation in dorsal raphe plays an important role in NREM and REM sleep regulation during pentobarbital hypnosis

Our previous studies indicated that L-type calcium channel blocker diltiazem could potentiate pentobarbital-induced hypnosis through serotonergic system. In view of the important role of dorsal raphe nucleus (DRN) on the sleep regulation and the pharmacological actions of calcium channel blocker, we presumed that Ca(2+) in the DRN may play an important role in sleep regulation in pentobarbital treated rats. Therefore, we investigated whether the Ca(2+) modulation in DRN by the microinjection of L-type Ca(2+) channel antagonist diltiazem, agonist BAY-K-8644, Ca(2+) chelator EGTA and CaCl(2) would alter the sleep parameters in pentobarbital treated rats. Results showed that perfusion of the agents attenuating Ca(2+) function, such as diltiazem (5 or 20 nmol) or EGTA (3 or 6 pmol) into DRN significantly increased pentobarbital (35 mg/kg, i.p.)-induced total sleep (TS), non-rapid eye movement (NREM) sleep and the slow wave sleep (SWS) ratio in NREM sleep. On the contrary, the DRN injection of the agents improving Ca(2+) function, such as BAY-K-8644 (10 nmol) or CaCl(2) (50 or 100 nmol) significantly reduced pentobarbital (35 mg/kg, i.p.)-induced TS, NREM sleep, rapid eye movement (REM) sleep and REM sleep ratio in TS without influence on SWS. These results suggested that the suppression of Ca(2+) function in DRN could increase NREM sleep including SWS, and the elevation of Ca(2+) function could reduce both NREM and REM sleep in pentobarbital treated rats.

Mechanisms Underlying Footshock and Psychological Stress-Induced Abrupt Awakening From Posttraumatic “Nightmares”

Background: Posttraumatic nightmares are a highly prevalent and distressing symptom of posttraumatic stress disorder (PTSD), but have been the subject of limited phenomenological investigations. Methods: We utilized a communication box to establish PTSD symptoms in rats through exposure to footshock stress (FS) and psychological stress (PS). The immunohistochemical test and high-performance liquid chromatography with electrochemical detection were used to detect the activity and monoamine levels in the rats’ arousal systems. Results: Twenty-one days after traumatic stress, 14.17% of FS and 12.5% of PS rats exhibited startled awakening, and the same rats showed hyperfunction of the locus coeruleus/noradrenergic system and hypofunction of the perifornical nucleus/orexinergic system. Changes in serotonin levels in the dorsal raphe nucleus showed opposite trends in the FS and PS rats that were startled awake. No differences were found in other sleep/arousal systems. Conclusion: These results suggest that different clinically therapeutic strategies should be considered to treat different trauma-induced posttraumatic nightmares.

Different neural circuitry is involved in physiological and psychological stress-induced PTSD-like “nightmares” in rats

Posttraumatic nightmares are a core component of posttraumatic stress disorder (PTSD) and mechanistically linked to the development and maintenance of this disorder, but little is known about their mechanism. We utilized a communication box to establish an animal model of physiological stress (foot-shock [FS]) and psychological stress (PS) to mimic the direct suffering and witnessing of traumatic events. Twenty-one days after traumatic stress, some of the experimental animals presented startled awakening (i.e., were startled awake by a supposed “nightmare”) with different electroencephalographic spectra features. Our neuroanatomical results showed that the secondary somatosensory cortex and primary auditory cortex may play an important role in remote traumatic memory retrieval in FS “nightmare” (FSN) rats, whereas the temporal association cortex may play an important role in PS “nightmare” (PSN) rats. The FSN and PSN groups possessed common emotion evocation circuits, including activation of the amygdala and inactivation of the infralimbic prefrontal cortex and ventral anterior cingulate cortex. The decreased activity of the granular and dysgranular insular cortex was only observed in PSN rats. The present results imply that different types of stress may cause PTSD-like “nightmares” in rodents and identified the possible neurocircuitry of memory retrieval and emotion evocation.

Tenuifolin, a saponin derived from Radix Polygalae, exhibits sleep-enhancing effects in mice.

BACKGROUND Radix Polygalae, the dried root of Polygala tenuifolia, has been extensively used as a traditional Chinese medicine for promoting intelligence and tranquilization. Polygalasaponins extracted from the root of P. tenuifolia possess evident anxiolytic and sedative-hypnotic activities. Previous studies have reported that tenuifolin was a major constituent of polygalasaponins. PURPOSE The currently study aims to investigate the hypnotic effect and possible mechanism of tenuifolin in freely moving mice. DESIGN/METHODS The hypnotic effects of tenuifolin (20, 40 and 80mg/kg, p.o.) were assessed by electroencephalographic (EEG) and electromyographic (EMG) analysis. Double-staining immunohistochemistry test was performed to evaluate the neuronal activity of sleep-wake regulating brain areas. High performance liquid chromatograph- electrochemical detection (HPLC-ECD) and ultrafast liquid chromatography-mass spectrometry (UFLC-MS) were used for the detection of neurotransmitters. Locomotor activity was measured by Open-field Test. RESULTS Tenuifolin at doses of 40 and 80mg/kg (p.o.) significantly prolonged the total sleep time by increasing the amount of non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, associated with the significant increase in the bouts of episodes respectively. After administration of tenuifolin, the cortical EEG power spectral densities during NREM and REM sleep were similar to that of natural sleep (vehicle) and thus compatible with physiological sleep. Double-immunohistochemistry staining test showed that tenuifolin increased the c-Fos positive ratios of GABAergic NREM sleep-promoting neurons in ventrolateral preoptic area (VLPO), cholinergic REM sleep-promoting neurons in laterodorsal tegmental area (LDT) and pontomesencephalic tegmental area (PPT) and decreased the c-Fos positive ratios in wake-promoting neurons (locus coeruleus (LC) and perifornical area (Pef)). Neurotransmitter detections revealed that tenuifolin significantly reduced the noradrenaline (NA) levels in LC, VLPO, PPT and LDT, elevated the GABA levels in VLPO, LC and Pef and increased the acetylcholine (Ach) levels in LDT and PPT. In addition, tenuifolin did not cause any change to locomotor activity. CONCLUSION Taken together, these results provide the first experimental evidence of the significant sleep-enhancing effect of tenuifolin in mice. This effect appears to be mediated, at least in part, by the activation of GABAergic systems and/or by the inhibition of noradrenergic systems. Moreover, this study adds new scientific evidence and highlights the therapeutic potential of the medicinal plant P. tenuifolia in the development of phytomedicines with hypnotic properties.

Diltiazem potentiates pentobarbital-induced hypnosis via 5-HT1A and 5-HT2A/2C receptors: role for dorsal raphe nucleus.

It has been reported that the sedative component of pentobarbital is mediated by GABA receptors in an endogenous sleep pathway and the ventrolateral preoptic area (VLPO)-tuberomammillary nucleus (TMN) or VLPO-dorsal raphe nucleus (DRN) neural circuit is important in the sedative response to pentobarbital. Our previous findings indicated that the VLPO-TMN neuronal circuit may play crucial part in the augmentative effect of diltiazem on pentobarbital sleep and the serotonergic system may be involved. This study was designed to investigate the role of DRN and the serotonergic receptors 5-HT(1A) and 5-HT(2A/2C) in the augmentative effect of diltiazem on pentobarbital-induced hypnosis in rats. The results showed that diltiazem (5mg/kg, i.g.) significantly reversed pentobarbital-induced (35 mg/kg, i.p.) reduction of c-Fos expression in 5-HT neurons of DRNV (at -7.5mm Bregma), DRND, DRNVL and MRN (at -8.0mm Bregma). However it did not influence this reducing effect of pentobarbital on non-5-HT neurons either in DRN or in MRN. Moreover, the effect of diltiazem (1 or 2mg/kg, i.g.) on pentobarbital-induced (35 mg/kg, i.p.) hypnosis was significantly inhibited by 5-HT(1A) agonist 8-OH-DPAT (0.5mg/kg, i.p.) and 5-HT(2A/2C) agonist DOI (0.5mg/kg, i.p.), and potentiated by 5-HT(1A) antagonist p-MPPI (2mg/kg, i.p.) and 5-HT(2A/2C) antagonist ritanserin (2mg/kg, i.p.), respectively. From these results, it should be presumed that the augmentative effect of diltiazem on pentobarbital-induced sleep may be related to 5-HT(1A) and 5-HT(2A/2C) receptors, and DRN may be involved. In addition, it also suggested that the DRN may play a multi-modulating role in sleep-wake regulation rather than being recognized simply as arousal nuclei.