Yuan-Li Huang

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.

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.

Tetrandrine, an alkaloid from S. tetrandra exhibits anti-hypertensive and sleep-enhancing effects in SHR via different mechanisms

BACKGROUND Sleep disorders have been found to be associated with hypertension in both cross-sectional and longitudinal epidemiological studies. Tetrandrine, a major component of Stephania tetrandra, is well known as an antihypertensive agent. The anti-hypertension mechanism mainly relies on its L-type calcium channel blocking property. In the previous study, tetrandrine revealed both anti-hypertension and hypnotic effects in spontaneously hypertensive rats (SHRs). PURPOSE This study aims to elucidate whether the antihypertensive mechanism of tetrandrine in SHRs is relevant to its hypnotic effect. DESIGN/METHODS Sleep-wake behavior of the SHRs was detected by electroencephalography (EEG) and electromyography (EMG) recordings. Blood pressure was measured by noninvasive blood pressure tail cuff test. Immunohistochemistry was performed to evaluate the noradrenergic neuronal activity. The level of norepinephrine (NE) was detected by HPLC-ECD. RESULTS Amlodipine (100mg/kg, i.g.), the well-known L-type Ca2+ channel blockers (CCBs) exhibited remarkable antihypertensive activities in SHRs, but did not show effects on sleep of SHRs. Tetrandrine (30 and 60mg/kg/day, i.g.) significantly suppressed blood pressure of SHRs. Meanwhile, tetrandrine (60mg/kg/day, i.g.) remarkably increased non-rapid eye movement sleep (NREMS) time, bouts and mean duration. The hypnotic effect of tetrandrine was potentiated by prazosin (0.5mg/kg, i.p.) but attenuated by yohimbine (2mg/kg, i.p.). Administration of tetrandrine (60mg/kg/day, i.g.) not only significantly decreased c-Fos positive ratio of noradrenergic neurons in the locus coeruleus (LC), but also significantly decrease NE in the endogenous sleep-wake regulating pathways including LC, hypothalamus and ventrolateral preoptic nucleus (VLPO). CONCLUSION In spite of a good potency in blocking L-type Ca2+ channel, the hypnotic effects of tetrandrine may be related to its suppressing effects on the noradrenergic system other than to block calcium channels. As a multi-targets drug, tetrandrine might be favorable to the hypertension patients who suffered poor sleep.

Phosphorylation of CaMKII in the rat dorsal raphe nucleus plays an important role in sleep-wake regulation.

The Ca2+ modulation in the dorsal raphe nucleus (DRN) plays an important role in sleep–wake regulation. Calmodulin‐dependent kinase II (CaMKII) is an important signal‐transducing molecule that is activated by Ca2+. This study investigated the effects of intracellular Ca2+/CaMKII signaling in the DRN on sleep–wake states in rats. Maximum and minimum CaMKII phosphorylation was detected at Zeitgeber time 21 (ZT 21; wakefulness state) and ZT 3 (sleep state), respectively, across the light–dark rhythm in the DRN in rats. Six‐hour sleep deprivation significantly reduced CaMKII phosphorylation in the DRN. Microinjection of the CAMKII activation inhibitor KN‐93 (5 or 10 nmol) into the DRN suppressed wakefulness and enhanced rapid‐eye‐movement sleep (REMS) and non‐REM sleep (NREMS). Application of a high dose of KN‐93 (10 nmol) increased slow‐wave sleep (SWS) time, SWS bouts, the mean duration of SWS, the percentage of SWS relative to total sleep, and delta power density during NREMS. Microinjection of CaCl2 (50 nmol) in the DRN increased CaMKII phosphorylation and decreased NREMS, SWS, and REMS. KN‐93 abolished the inhibitory effects of CaCl2 on NREMS, SWS, and REMS. These data indicate a novel wake‐promoting and sleep‐suppressing role for the Ca2+/CaMKII signaling pathway in DRN neurons.

PKC in rat dorsal raphe nucleus plays a key role in sleep-wake regulation.

Studies suggest a tight relationship between protein kinase C (PKC) and circadian clock. However, the role of PKC in sleep-wake regulation remains unclear. The present study was conducted to investigate the role of PKC signaling in sleep-wake regulation in the rat. Our results showed that the phosphorylation level of PKC in dorsal raphe nucleus (DRN) was decreased after 6h sleep deprivation, while no alterations were found in ventrolateral preoptic nucleus (VLPO) or locus coeruleus (LC). Microinjection of a pan-PKC inhibitor, chelerythrine chloride (CHEL, 5 or 10nmol), into DRN of freely moving rats promoted non rapid eye movement sleep (NREMS) without influences on rapid eye movement sleep (REMS). Especially, CHEL application at 5nmol increased light sleep (LS) time while CHEL application at 10nmol increased slow wave sleep (SWS) time and percentage. On the other hand, microinjection of CaCl2 into DRN not only increased the phosphorylation level of PKC, but also reduced NREMS time, especially SWS time and percentage. While CHEL abolished the inhibitory effect of CaCl2 on NREMS and SWS. These data provide the first direct evidence that inhibition of intracellular PKC signaling in DRN could increase NREMS time including SWS time and percentage, while activation of PKC could suppress NREMS and reduce SWS time and percentage. These novel findings further our understanding of the basic cellular and molecular mechanisms of sleep-wake regulation.

Involvement of adrenoceptors, dopamine receptors and AMPA receptors in antidepressant-like action of 7- O -ethylfangchinoline in mice

Aim:7-O-ethylfangchinoline (YH-200) is a bisbenzylisoquinoline derivative. The aim of this study was to investigate the antidepressant-like action and underlying mechanisms of YH-200 in mice.Methods:Mice were treated with YH-200 (15, 30, and 60 mg/kg, ig) or tetrandrine (30 and 60 mg/kg, ig) before conducting forced swimming test (FST), tail suspension test (TST), or open field test (OFT).Results:YH-200 (60 mg/kg) significantly decreased the immobility time in both FST and TST, and prolonged the latency to immobility in FST. YH-200 (60 mg/kg) was more potent than the natural bisbenzylisoquinoline alkaloid tetrandrine (60 mg/kg) in FST. Pretreatment with α1-adrenoceptor antagonist prazosin (1 mg/kg), β-adrenoceptor antagonist propranolol (2 mg/kg), dopamine D1/D5 receptor antagonist SCH23390 (0.05 mg/kg), dopamine D2/D3 receptor antagonist haloperidol (0.2 mg/kg) or AMPA receptor antagonist NBQX (10 mg/kg) prevented the antidepressant-like action of YH-200 (60 mg/kg) in FST. In contrast, pretreatment with α2 adrenoceptor antagonist yohimbine (1 mg/kg) augmented the antidepressant-like action of YH-200 (30 mg/kg) in FST. Chronic administration of YH-200 (30 and 60 mg/kg for 14 d) did not produce drug tolerance; instead its antidepressant-like action was strengthened. Chronic administration of YH-200 did not affect the body weight of mice compared to control mice.Conclusion:YH-200 exerts its antidepressant-like action in mice via acting at multi-targets, including α1, α2 and β-adrenoceptors, D1/D5 and D2 /D3 receptors, as well as AMPA receptors.

Sleep patterns deteriorate over time in chronic corticosterone-treated rats

Repeated corticosterone (CORT) injections reliably produce depressive-like behavior in rodents. Our previous study showed that sleep parameters were altered in rats after daily injections of CORT for 7 days, and sleep disturbances appeared to be correlated with depressive-like behavior. The aim of the present study was to investigate time-dependent correlations between changes in sleep parameters and the formation of depressive-like behavior in rats after more prolonged treatment with CORT. Rats received daily injections of CORT (40 mg/kg, s.c.) for 7, 14, or 21 days. Electroencephalographic recordings were performed to study sleep parameters. The sucrose preference test and forced swim test were performed to evaluate depressive-like behavior. Western blot was used to detect protein levels. Our results showed that 7-day CORT treatment resulted in no significant depressive-like behavior or changes in rapid-eye-movement (REM) sleep. However, the duration of non-REM sleep significantly decreased, tyrosine hydroxylase (TH) levels significantly increased, and glucocorticoid receptor (GR) expression decreased in the locus coeruleus. Treatment with CORT for 14 and 21 days increased depressive-like behavior, enhanced REM sleep, shortened REM sleep latency, decreased TH and GR levels, and increased the levels of the chaperone FK506 binding protein 51 (FKBP51) in the locus coeruleus. These results indicate that the development of depression after chronic CORT treatment may be related to the formation of sleep disorders. Abnormalities of REM sleep may be a characteristic of sleep in models of depression that is induced by chronic CORT administration in rats. The noradrenergic system and GR pathway in the locus coeruleus may be involved in the formation of depression concomitant with sleep disturbances.