Antidepressant-like effects of the ethanolic extract of Xiaobuxin-Tang, a traditional Chinese herbal prescription in animal models of depression.

BACKGROUND: Xiaobuxin-Tang, a traditional Chinese herbal prescription recorded in a silk scroll unearthed from Mogao Caves of Dunhuang has been indicated that it can remit depressive disorder. The present study was designed to investigate its antidepressant effects in various animal depression models. METHODS: Xiaobuxin-Tang was extracted by 70% alcohol, and then three behavioral despair models and 5-Hydroxytryptophan (HTP)-induced head twitch response model were adopted to assess the antidepressant effects of the ethanolic extract of Xiaobuxin-Tang with the study on spontaneous motor activity. Groups of mice and rats received oral treatment with Xiaobuxin-Tang (150 - 1200 mg/kg) only once acutely in all tests. The duration of immobility was measured during the last 4 minutes of the 6-minutes test period in mice forced swimming test, rats forced swimming test and mice tail suspension test. In 5-HTP-induced head twitch response, the mice were intraperitoneally administered with 120 mg/kg of L-5-HTP, and then the cumulative number of head twitches was counted in 20 minutes. Spontaneous motor activities of mice were recorded automatically in 10 minutes by VIDEOMEX-V image analytic system. RESULTS: The extract at doses of 300 mg/kg (p.o.) and 600 mg/kg (p.o.) significantly decreased the duration of immobility time in a dose dependent manner in mice forced swimming test; also, the extract at dose of 1200 mg/kg (p.o.) significantly decreased the duration of immobility time in rat forced swimming test. Furthermore, the extract at a dose of 600 mg/kg had the same effect in mice tail suspension test. Meanwhile, the extract at the effective doses for behavioral despair models, had no effect on spontaneous motor activity in mice. The extract (300 - 1200 mg/kg, p.o.) also increased the accumulative number of the 5-HTP-induced head twitch response in mice in 20 minutes. CONCLUSION: Our results suggested that the ethanolic extract of Xiaobuxin-Tang exerts antidepressant-like effect.

Anxiolytic effect of agmatine in rats and mice.

In mammalian brain, agmatine is an endogenous neurotransmitter and/or neuromodulator. In this study, the anxiolytic action of agmatine (p.o. or s.c.) was evaluated in three animal behavioral models in mice or rats. In the light-dark transition test, agmatine in a single dose (80 mg/kg, s.c) or repeated administration (20 mg/kg, s.c. or 10 mg/kg, p.o., once a day for 3 days) significantly increased the number of light-dark transitions in mice. Furthermore, treatment with agmatine (20-80 mg/kg, s.c or 10-40 mg/kg, p.o) three times in 24 h significantly increased the number of licks in the Vogel's drinking conflict test in rats. In the social interaction test, agmatine (10-40 mg/kg, p.o, three times in 24 h prior to test) increased the active social interaction of rats. All these results indicate that agmatine exerts a significant anxiolytic effect in both rats and mice.

Inhibition of N-methyl-D-aspartate receptor function appears to be one of the common actions for antidepressants.

In order to explore the possible common action mechanisms of three kinds of classical antidepressants, inhibition of drugs on the N-methyl-D-aspartate (NMDA)-Ca(2)-nitric oxide synthase (NOS) signal pathway was observed. With 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and lactic dehydrogenase (LDH) assay, classical antidepressants, desipramine (1, 10 microM), fluoxetine (0.625-10 microM) or moclobemide (2.5, 10 microM) antagonized NMDA 300 M induced-lesion in PC12 cells. Using fura-2/AM (acetoxymethyl ester) labelling assay, desipramine or fluoxetine at doses 1, 5 microM attenuated the intracellular Ca(2) overload induced by NMDA 200 microM for 24 h in PC12 cells. Meanwhile, using confocal microscope, it was also found that desipramine 5 microM, fluoxetine 2.5 microM or moclobemide 10 microM decreased the NMDA 20 microM induced intracellular Ca(2) overload in primarily cultured rat hippocampal neurons. Furthermore, desipramine (1, 5 microM), fluoxetine (1, 5 microM) or moclobemide (2.5, 10 microM) significantly inhibited NOS activity in NMDA (300 microM) treated PC12 cells for 4h. In summary, we suggest that inhibition on the function of NMDA-Ca(2) -NOS signal pathway appears to be one of the common actions for antidepressants despite their remarkably different structures, which is expected to have great implication for the evaluation and screening in vitro of new antidepressants.

Antidepressant-like effect of agmatine and its possible mechanism.

In mammalian brain, agmatine is an endogenous neurotransmitter and/or neuromodulator, which is considered as an endogenous ligand for imidazoline receptors. In this study, the antidepressant-like action of agmatine administered p.o. or s.c. was evaluated in three behavioral models in mice or rats. Agmatine at doses 40 and 80 mg/kg (p.o.) reduced immobility time in the tail suspension test and forced swim test in mice or at dose 20 mg/kg (s.c.) in the forced swim test. Agmatine also reduced immobility time at 10 mg/kg (p.o.) or at 1.25, 2.5 and 5 mg/kg (s.c.) in the forced swim test in rats. These results firstly indicated that agmatine possessed an antidepressant-like action. With 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and lactic dehydrogenase (LDH) assay, 1, 10 and 100 microM agmatine or a classical antidepressant, 2.5 and 10 microM desipramine, protected PC12 cells from the lesion induced by 300 microM N-methyl-D-aspartate (NMDA) treatment for 24 h. Using high-performance liquid chromatography with electrochemical detection (HPLC-ECD), it was found that the levels of monoamines including norepinephrine, epinephrine, dopamine or 5-hydroxytryptamine (5-HT) in PC12 cells decreased after the treatment with 200 microM NMDA for 24 h, while in the presence of 1 and 10 microM agmatine or 1 and 5 microM desipramine, the levels of norepinephrine, epinephrine or dopamine were elevated significantly while 5-HT did not change. Moreover, norepinephrine, 5-HT or dopamine had the same cytoprotective effect as agmatine at doses 0.1, 1 and 10 microM. In the fura-2/AM (acetoxymethyl ester) labeling assay, 1 and 10 microM agmatine, 1 and 5 microM desipramine or monoamines norepinephrine, 5-HT at doses 0.1 and 1 microM attenuated the intracellular Ca(2+) overloading induced by 200 microM NMDA treatment for 24 h in PC12 cells. In summary, we firstly demonstrated that agmatine has an antidepressant-like effect in mice and rats. A classical antidepressant, desipramine, as well as agmatine or monoamines protect the PC12 cells from the lesion induced by NMDA treatment. Agmatine reverses the NMDA-induced intracellular Ca(2+) overloading and the decrease of monoamines (including norepinephrine, epinephrine or dopamine) contents in PC12 cells, indicating that agmatine's antidepressant-like action may be related to its modulation of NMDA receptor activity and/or reversal of the decrease of monoamine contents and Ca(2+) overloading induced by NMDA.

Up-regulation of microtubule-associated protein 4 and drebrin A mRNA expression by antidepressants in rat hippocampus following chronic stress.

We used the differential display-polymerase chain reaction (DD-PCR) protocol to identify genes related to antidepressant effects. Rats were subjected to different kinds of stress for 20 days, and then the antidepressants desipramine and fluoxetine were administered (10 mg/kg per day, i.p.) for 20 days. DD-PCR was performed and differentially expressed cDNAs were further confirmed by dot-blot hybridization. cDNA homology analysis revealed that desipramine up-regulated the expression of microtubule-associated protein 4 (MAP-4) mRNA and fluoxetine up-regulated the expression of drebrin A mRNA in the rat hippocampus compared with the chronically stressed group. This result suggests that MAP-4 and drebrin may be involved in the antidepressant like effects of desipramine and fluoxetine.

Inhibition of the oligosaccharides extracted from Morinda officinalis, a Chinese traditional herbal medicine, on the corticosterone induced apoptosis in PC12 cells.

The mechanisms of the antidepressant action of the oligosaccharides (P(6)) extracted from Morinda Officinalis were studied. By flow cytometry analysis, treatment of PC12 cells with corticosterone (Cort) induced apoptosis in a concentration and time dependent manner. The highest percentage of apoptotic cells accumulated to 27.85 +/- 9.2% following pretreatment with Cort 10 microM for 5 d. In agarose gel electrophoresis of DNA, the sample obtained from PC12 cells pretreated with Cort 10 microM for 5 d showed a typical ladder pattern suggesting that Cort increased the DNA fragmentation significantly. Furthermore, the ultrastructure of Cort-treated cells displayed typical apoptosis-like morphological changes including fragmented chromatin accumulation to the inside of nucleolus membrane with a shape like crescent moon or ring, nuclear fragmentation or apoptotic body. In the presence of P(6), or tricyclic antidepressant desipramine (DIM), the apoptosis induced by Cort in the three measurements above was significantly inhibited. These results indicate that DIM or P(6) antagonize the apoptosis induced by Cort in PC12 cells, which may be one of the cellular mechanisms of their antidepressant effects.

The cytoprotective effect of inulin-type hexasaccharide extracted from Morinda officinalis on PC12 cells against the lesion induced by corticosterone.

High concentration of corticosterone (Cort) 0.2 mM was incubated with PC12 cells to simulate the lesion state of brain neurons in depressive illness, it was found that the inulin-type oligosaccharides extracted from Morinda officinalis, inulin-type hexasaccharide (IHS) at the doses of 0.625, 1.25 microM or desipramine (DIM) 0.25, 1 microM protected the PC12 cells from the lesion induced by Cort. With Fura-2/AM labeling assay, DIM 0.25, 1 microM or IHS 2.5, 10 microM attenuated the intracellular Ca2+ overloading induced by Cort 0.1 mM for 48 h in PC12 cells. Using RT-PCR, treatment with Cort 0.1 mM for 48 h decreased the nerve growth factor (NGF) mRNA level in PC12 cells, IHS 5, 10 microM reversed this change. In summary, IHS attenuate the intracellular Ca2+ overloading and thereby up-regulate the NGF mRNA expression in Cort-treated PC12 cells, which may be consisted at least part of the cytopretective effect of IHS. These results also extend evidence for our hypothesis that neuroprotective action is one of the common mechanisms for antidepressants.

The effect of Morinda officinalis How, a Chinese traditional medicinal plant, on the DRL 72-s schedule in rats and the forced swimming test in mice.

The present study observed the antidepressant-like action of the medicinal plant Morinda officinalis in the differential reinforcement of low rate 72-s (DRL 72-s) schedule, a behavioral screen selective and sensitive to antidepressant drugs, and the forced swimming test, a well-known animal model of depression. In the DRL 72-s schedule in rats, the plant extract (25-50 mg/kg), similar to clinically effective antidepressant drug desipramine (5-10 mg/kg), significantly reduced response rate and efficiency ratio while at the same time increasing reinforcement rate. In the forced swimming test in mice, the plant extract (50 mg/kg), like the effect of desipramine (20 mg/kg), also elicited a significant reduction in the duration of immobility. A tendency to this phenomenon could be seen at the dose of 100 mg/kg. Meanwhile, the plant extract, in the effective doses for the forced swimming test, had no effects on spontaneous motor activity in mice. These findings provide further support for the conclusion that M. officinalis extract possesses the antidepressant effect.

[Antagonistic effect of aqueous extract of detoxified cottonseeds on corticosterone-induced lesion in cultured PC12 cells].

OBJECTIVE: To study the possible mechanism of aqueous extract of detoxified cottonseeds (CTN-W). METHOD AND RESULT: CTN-W 0.01, 0.03, 0.10, 0.30 mg.mL-1 was incubated directly with the synaptic membrane extracted from the cerebral cortex in rats, and adenylyl cyclase (AC) activity was detected by using radio-immunoassay. RESULT: Showed that CTN-W could activate AC in a dose-dependend manner. After incubation with PC12 cells in the presence of corticosterone 2 x 10(-4)mol.L-1 for 48 h, CTN-W 0.08, 0.4, 2 mg.mL-1 protected PC12 cells from the lesion induced by corticosterone. CONCLUSION: Antidepressant and anxiolytic effects of CTN-W are related with the activation of AC-cAMP pathway in signal transduction system, thus protecting neurons from the lesion. These two aspects maybe partly form the mechanism of CTN-W's action.

Desipramine antagonized corticosterone-induced apoptosis in cultured PC12 cells.

AIM: To study possible action mechanism of a tricyclic antidepressant, desipramine (DIM). METHODS: Cultured PC12 cells were exposed to corticosterone in the absence or presence of DIM for 5 d. Agarose gel electrophoresis, flow cytometry, and electron microscopy were used to detect the apoptosis of PC12 cells. RESULTS: Corticosterone 10 micromol/L treatment for 5 d elicited typical apoptotic biochemical and morphological changes including condensed chromatin shaped like crescent moon, nuclear fragmentation, and DNA degradation. The highest percentage of apoptotic cells accumulated to 28 % +/- 9 %. Agarose gel electrophoresis showed typical DNA ladders pattern. While in the presence of DIM 1 or 5 micromol/L, apoptosis percentage was markedly decreased with lightened DNA ladder and ultrastructure of the cells was improved. CONCLUSION: DIM could antagonize the apoptosis in PC12 cells induced by corticosterone, which may be one of the cellular mechanisms of its antidepressant effect.

Muscarinic receptor activities potentiated by desensitization of nicotinic receptors in rat superior cervical ganglia.

AIM: The influences of desensitized nicotinic acetylcholine receptors (nAChR) on the activities of muscarinic acetylcholine receptors (mAChR) were investigated in single cultured rat superior cervical ganglion. METHODS: Whole-cell patch-clamp techniques were used. RESULTS: An inward current was induced by nicotine 80 micromol/L in the sympathetic neurons and desensitized rapidly after the prolonged exposure to nicotine. An outward current was induced by oxotremorine 100 micromol/L or pilocarpine 100 micromol/L and it showed no desensitization after exposure to its agonists. After nAChR desensitized completely, the current evoked by oxotremorine was increased significantly compared with its control. There were (42 38) % (n=8, P<0.05) and (165 66) % (n=5, P<0.01) increases induced by 100 and 500 micromol/L oxotremorine, respectively. Similar results were also obtained from pilocarpine and the current evoked by 100 micromol/L pilocarpine increased by (66 33) % (n=6, P<0.05) after nAChR desensitization. Once nicotine was removed, nAChR recovered from desensitization gradually and the enhanced mAChR activity also subsided along with it. Furthermore, the facilitatory effect of desensitized nAChR on mAChR activity could be prevented by mecamylamine. CONCLUSION: The activities of mAChR to its agonists were potentiated by the desensitization of nAChR in rat sympathetic neurons

Cytoprotective effect is one of common action pathways for antidepressants.

AIM: To explore the possible common action mechanism of antidepressants. METHODS: The cell viability was detected by MTT assay. The intracellular Ca2+ concentration ([Ca2+]i) was measured by Fura 2-AM fluorescence labeling assay. Using RT-PCR, the mRNA level of nerve growth factor (NGF) was also detected. RESULTS: High concentration of corticosterone (0.2 mmol/L) was incubated with PC12 cells to simulate the lesion state of brain neurons in depressive illness. Three main kinds of antidepressants used in clinic [(1) tricyclic antidepressants (TCAs), such as desipramine (DIM) 0.625-10 micromol/L; (2) selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (FLU) 0.625-10 micromol/L; (3) monoamine oxidase inhibitors (MAOIs), such as moclobemide (MOC) 2.5-40 micromol/L] protected cells from the lesion induced by corticosterone. While antipsychotic drug chlorpromazine or anxiolytic agent diazepam 0.4-50 micromol/L had no such effect. Moreover, DIM 1, 5 micromol/L or FLU 1, 5 micromol/L attenuated the [Ca2+]i overload induced by corticosterone 0.1 mmol/L for 48 h in PC12 cells. Furthermore, treatment with DIM or FLU 10 micromol/L for 48 h elevated the NGF mRNA expression in PC12 cells. CONCLUSION: Despite a remarkable structural diversity, the cytoprotective effect can be viewed as the common action pathway of the antidepressants. Moreover, attenuation of the intracellular Ca2+ overload and elevation of neurotrophic factor (such as NGF) expression is one of the mechanisms of cytoprotective effect of antidepressants.

Moclobemide up-regulates proliferation of hippocampal progenitor cells in chronically stressed mice.

AIM: To explore the action mechanism of antidepressants. METHODS: The PC12 cell proliferation was detected by flow cytometry. The proliferation of hippocampal progenitor cells and level of brain-derived neurotrophic factor (BDNF) were measured by immunohistochemistry. RESULTS: Treatment with N-methylaspartate (NMDA) 600 micromol/L for 3 d significantly decreased the percentage of S-phase in PC12 cells, while in the presence of classical antidepressant, moclobemide (MOC) 2 and 10 micromol/L, the percentage in S-phase increased. Furthermore, the proliferation of progenitor cells in hippocampal dentate gyrus (subgranular zone), as well as the level of BDNF in hippocampus significantly decreased in chronically stressed mice, while chronic administration with MOC 40 mg/kg (ip) up-regulated the progenitor cell proliferation and BDNF level in the same time course. CONCLUSION: Up-regulation of the proliferation of hippocampal progenitor cells is one of the action mechanisms for MOC, which may be closely related to the elevation of BDNF level at the same time. These results also extend evidence for our hypothesis that up-regulation of the hippocampal neurogenesis is one of the common mechanisms for antidepressants.