The involvement of AMPA-ERK1/2-BDNF pathway in the mechanism of new antidepressant action of prokinetic meranzin hydrate.

It was recently discovered that ketamine can relieve depression in a matter of hours through an action on α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. This is much more rapid than the several weeks required for the available antidepressants to show therapeutic efficacy. However, ketamine has negative side effects. The aim of this study was to determine whether the natural prokinetic drug meranzin hydrate (MH) has a fast-acting antidepressant effect mediated by AMPA receptors. By means of in vivo and in vitro experiments, we found that (1) treatment of rats with MH at 9 mg/kg decreased immobility time in a forced swimming test (FST), as did the popular antidepressant fluoxetine and the AMPA receptor positive modulator aniracetam. Pretreatment of rats with NBQX (10 mg/kg), an antagonist of AMPA receptors, blocked this effect of MH. (2) MH increased number of crossings of forced swimming rats in the open field test. (3) FST enhanced hippocampal ERK1/2, p-ERK1/2 and BDNF expression levels. MH (9 mg/kg) treatment further up-regulated hippocampal p-ERK1/2 and BDNF expression levels, and this effect was prevented by NBQX. (4) MH-increased BDNF expression corresponded with MH-decreased immobility time in the FST. (5) In vitro experiments, we found that incubation of rats hippocampus slices with MH (10, 20 µM respectively) increased concentrations of BDNF and p-ERK1/2. This effect of MH (20 µM) were prevented by NBQX. In conclusion, in animals subjected to acute stress, the natural prokinetic drug MH produced a rapid effect mediated by AMPA receptors and involving BDNF modulation through the ERK1/2 pathway.

Effect of tribulus terrestris saponins on behavior and neuroendocrine in chronic mild stress depression rats.

OBJECTIVE: To observe the effect of tribulus terrestris saponins (TTS) on behavior and neuroendocrine of chronic mild stress (CMS) depression rats. METHODS: Thirty male Sprague-Dawley rats were randomly allocated to six groups: vehicle group, CMS group, CMS + fluoxetine group and CMS + TTS of low-dosage (0.375 g/kg), medium-dosage (0.75 g/kg) and high-dosage (2.25 g/kg) groups. All rats except the vehicle group singly housed and exposed an unpredicted sequence of mild stressors. The behavior of rats was detected by open-field test (OFT) and sucrose preference test (SPT). The concentration of corticotropin-releasing factor (CRF) and adrenocorticotropic hormone (ACTH) in serum of the rats were detected by radioimmunoassay. The concentration of cortisol (CORT) in serum was detected by enzyme immunoassay. RESULTS: CMS procedure not only significantly decreased the scores of crossing, rears and grooming in OFT and the sucrose preference in SPT (all P < 0.01), but also markedly increased serum CRH and CORT levels (both P < 0.05). Treatment with TTS (0.75 and 2.25 g/kg) could significantly prevent all of these abnormalities induced by CMS (P < 0.05, P < 0.01). CONCLUSION: CMS can affect rat behavior and neuroendocrine and cause depression. TTS has the antagonism on CMS and produce antidepressive effects.

Enhanced antitumoral efficacy and immune response following conditionally replicative adenovirus containing constitutive HSF1 delivery to rodent tumors.

BACKGROUND: Oncolytic adenoviruses are promising as anticancer agents but have limited clinical responses. Our previous study showed that heat shock transcription factor 1 (HSF1) overexpression could increase the anti-tumor efficacy of E1B55kD deleted oncolytic adenovirus through increasing the viral burst. Due to the important roles of heat shock proteins (HSPs) in eliciting innate and adaptive immunity, we reasoned that besides increasing the viral burst, HSF1 may also play a role in increasing tumor specific immune response. METHODS: In the present study, intra-dermal murine models of melanoma (B16) and colorectal carcinoma (CT26) were treated with E1B55kD deleted oncolytic adenovirus Adel55 or Adel55 incorporated with cHSF1, HSF1i, HSP70, or HSP90 by intra-tumoral injection. Tumors were surgically excised 72 h post injection and animals were analyzed for tumor resistance and survival rate. RESULTS: Approximately 95% of animals in the Adel55-cHSF1 treated group showed sustained resistance upon re-challenge with autologous tumor cells, but not in PBS, Adel55, or Adel55-HSF1i treated groups. Only 50-65% animals in the Adel55-HSP70 and Adel55-HSP90 treated group showed tumor resistance. Tumor resistance was associated with development of tumor type specific cellular immune responses. Adel55-cHSF1 treatment also showed higher efficacy in diminishing progression of the secondary tumor focus than Adel55-HSP70 or Adel55-HSP90 treatment. CONCLUSIONS: Besides by increasing its burst in tumor cells, cHSF1 could also augment the potential of E1B55kD deleted oncolytic adenovirus by increasing the tumor-specific immune response, which is beneficial to prevent tumor recurrence. cHSF1 is a better gene for neoadjuvant immunotherapy than other heat shock protein genes.

Effect of Chaihu Shugan San and its components on expression of ERK1/2 mRNA in the hippocampus of rats with chronic mild unpredicted stress depression.

OBJECTIVE: To explore the antidepressant effect and mechanism of Chaihu Shugan San (CHSGS) composition, a compound traditional Chinese herb medicine and its components. METHODS: Rats were randomly divided into 6 groups: normal control group, model control group, a CHSGS group, a component I group, a component II group and a fluoxetine control group. The depression model was replicated by chronic unpredictable mild stress and single house for 28 d. Behavioral scores of the rats were detected by Open-field test and sucrose solution consumption test, and ERK1/2 mRNA expression in the hippocampus tissue was assayed by real-time fluorescent quantitative PCR. RESULTS: ERK1/2 mRNA expression was down-regulated in the depression model group compared with the normal control group (P<0.01). Compared with the model group, ERK1/2 mRNA expression in the CHSGS group and fluoxetine group was both up-regulated (P<0.05 or P<0.01); and only ERK1 mRNA expression in the component I group was up-regulated (P<0.05). No significant difference existed between the component II group and the model group (P>0.05). CONCLUSION: Isolated-living condition and chronic mild unpredictable stress can down-regulate the expression of ERK1/2 mRNA in the hippocampus tissue. CHSGS may exert an antidepressant effect through increasing the expression of ERK1/2 mRNA in the hippocampus, component I may play an important role in its antidepression effect, while compatibility of the use of component II can enhance the antidepressant efficacy.

[Relationship between symptom stratification and syndrome differentiation of traditional Chinese medicine for depressive episode].

On the basis of medical literature review and clinical research experience, the authors analyzed the reasons for low recognition rate of depression and poor progress of traditional Chinese medicine (TCM) differentiation of depression in this paper and put forward that depressive episode symptoms and the corresponding common terminology classification of Chinese and Western medicine should be the breakthrough points. Through symptom stratification and combination, as well as distinguishing between primary and secondary symptoms, the comprehensive integrative medicine clinical assessment of depression was explored so as to further obtain expert consensus and provide a methodology reference for the TCM differentiation of depression and the research of etiology and pathogenesis.

[Effects of Chaihu Shugan San on behavior and plasma levels of corticotropin releasing hormone and adrenocorticotropic hormone of rats with chronic mild unpredicted stress depression].

OBJECTIVE: To investigate the effects of Chaihu Shugan San (CHSGS), a compound traditional Chinese herbal medicine, on behavior and plasma levels of corticotropin releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) of rats with chronic mild unpredicted stress depression. METHODS: Forty male Sprague-Dawley rats were randomly divided into 4 groups: normal control group, untreated group, fluoxetine group and CHSGS group. Except the normal control group, rats were singly housed and exposed to an unpredicted sequence of mild stressor for continuous 4 weeks to induce depression. Since the fifteenth day, rats were intragastrically administered with equal volume agents respectively for 2 weeks [normal saline for the normal control group and the untreated group, fluoxetine (1.8 mg/kg) for the fluoxetine group and CHSGS (5.9 g/kg) for the CHSGS group]. Behavioral scores of rats were detected by open-field test and sucrose preference test, and the plasma levels of CRH and ACTH in different groups were detected by radioimmunoassay. RESULTS: Compared with the normal control group, body weights of the rats in the untreated group were significantly decreased. Scores of crossing, rears and grooming in open-field test were reduced significantly. Pure water consumption in sucrose preference test was increased significantly. The levels of plasma CRH and ACTH were significantly increased. The depressive behaviors of the rats were improved significantly and the levels of plasma CRH and ACTH were obviously reduced in the CHSGS group. CONCLUSION: Chronic mild unpredicted mild stress can affect the neuroendocrine and behavior and cause depression in rats. CHSGS can regulate HPA hyperactivity of rats caused by chronic stress and has antidepressive effects.

Efficacy and Safety of a Formulated Herbal Granula, Jiu Wei Zhen Xin, for Generalized Anxiety Disorder: A Meta-Analysis.

BACKGROUND: The traditional Chinese medicine formula Jiu Wei Zhen Xin Granula (JWZXG) is prescribed to treat generalized anxiety disorder (GAD) in China. This study was to assess the efficacy and safety of JWZXG in patients with GAD. METHOD: Data were pooled from 14 randomized controlled trials involving the assessment of mean changes of Hamilton Anxiety Rating Scale (HAMA) total scores, response rates, adverse event rates, quality, publication bias, and risk of bias. RESULTS: Pooled analysis showed no significant difference in response rate (risk ratio 1.01, 95% CI [0.93-1.08]; Z test = 0.17, P = 0.86) and no significant difference between JWZXG group and azapirones group (RR 0.69, 95% CI [0.45, 1.06]; Z test = 1.69, P = 0.09) in rate of adverse events. Though no difference exists between JWZXG group and azapirones group in HAMA total score from baseline, JWZXG group was inferior to selective serotonin reuptake inhibitors (SSRIs) group (WMD -0.93, 95% CI [-1.64, -0.23]; Z test = 2.6, P = 0.009) which had more adverse events than JWZXG group (RR 0.64, 95% CI [0.46, 0.89]; Z test = 2.63, P = 0.009). CONCLUSIONS: This meta-analysis preliminarily suggests that JWZXG is as effective as azapirones, though having the same possibility of suffering AEs. JWZXG was inferior to SSRIs but causes fewer AEs in the treatment of GAD.

Study on the interrelationship between 5-HTTLPR/G-protein beta3 subunit (C825T) polymorphisms and depressive disorder.

OBJECTIVE: To assess whether the promoter region of the serotonin transporter gene (5-HTTLPR) and G-protein beta3-subunit (GNbeta3 C825T) polymorphisms are associated with depressive disorder and explore the genetic mechanism concerning the pathogenesis of this disorder. METHODS: The genotypes were determined with polymerase chain reaction and allele-specific restriction enzyme analysis. Patients suffering from depression (n=184) and sex and age-matched controls (n=158) were compared in this study. RESULTS: The frequencies of 5-HTTLPR SS and GNbeta3 825TT genotypes and 5-HTTLPR S and GNbeta3 825T alleles in patients suffering from depression were significantly higher than those in the controls (P<0.01). Combined genotype analysis showed that individuals with both 5-HTTLPR S and GNbeta3 825T alleles (odds ratio=3.25, P=0.002) had a risk of depressive disorder higher than those with 5-HTTLPR S (odds ratio=1.817, P=0.01) or GNbeta3 825T alleles (odds ratio=2.214, P=0.001) alone. CONCLUSIONS: These results indicated that the etiology of depressive disorder is associated with 5-HTTLPR and GNbeta3 C825T polymorphisms. Our data also suggests that an interaction effect may exist between the 5-HTTLPR S allele and GNbeta3 825T allele in increasing the risk of depressive disorder.

Clinical experience in treatment of Amanita mushroom poisoning with Glossy Ganoderma Decoction and routine Western medicines.

OBJECTIVE: To assess the effects of treatment of Amanita mushroom poisoning with Glossy anoderma Decoction (, GGD). METHODS: Twelve patients with acute Amanita mushroom poisoning received conventional treatment (penicillin and reduced glutathione) combined with oral administration of GGD (treated group), which was prepared out of 200 g Glossy ganoderma decocted in water to 600 mL, and 200 ml was given once, three times a day for 7 successive days; while conventional treatment alone was given to the other 11 patients assigned to the control group. The therapeutic efficacy and changes in serum levels of total bilirubin (TBil), bile acids (BA), alanine transaminase (ALT), and aspartate transaminase (AST) activities in the two groups were compared. RESULTS: The cured-markedly effective rate in the treated group was more significant than that in the control group (P<0.01). Elevation in TBil, BA, ALT, and AST activities were observed in both groups 3 days after poisoning, which progressively increased thereafter in the control group. In the treated group, they reached their peak on the 3rd day and then declined gradually. The differences between pre-treatment and post-treatment in both groups were obviously significant (P<0.01), so were the differences between the two groups at corresponding time points (P<0.01). CONCLUSION: GGD shows excellent clinical efficacy in the treatment of acute Amanita mushroom poisoning and can reduce mortality significantly.

[Mechanism and protective effect of glossy ganoderma decoction on the activities of RNA polymerase in hepatocyte of rabbits with Amanita mushroom poisoning].

OBJECTIVE: To investigate the mechanism of glossy ganoderma decoction in Amanita mushroom poisoning. METHODS: Twenty male New Zealand white rabbits were randomly divided into 4 groups, including a normal control, a model poison group, and 2 treatment groups (different doses of glossy ganoderma decoction). The activities of hepatocyte RNA polymerase were measured by ultraviolet spectrophotometry and liver function were measured. RESULTS: The activities of hepatocyte RNA polymerase of the model group significantly decreased, and those of the 2 treatment groups were significantly higher than those of the model group. There was a dose-dependent manner between the 2 treatment groups ( all Ps<0.01), and the differences of liver function test including total bilirubin (TBIL), direct bilirubin (DB), total bile acid (TBA), and alanine aminotransferase (ALT) in the 4 groups were significant (P<0.01). CONCLUSION: Glossy ganoderma decoction may protect the liver from Amanita mushroom poisoning. Its mechanism may be related to the increase of the activities of hepatocyte RNA polymerase.

[Comparative study on two methods of back propagation network test in TCM syndrome typing of depression].

OBJECTIVE: To compare the effect of the two methods of back propagation network (BPN) test on TCM syndrome typing of depression. METHODS: Test was carried out by two methods as following: (1) Cross train-test method: 1731 patients with depression typed to 5 syndrome types were randomly divided into 2 groups, and they were trained and tested in turn; (2) Round-Robin method: Test was conducted in an altered cycle mode, that is, in a cycle, one out of the 1731 patients were selected to be tested, while the others were trained, the next cycle started when the test on the selected patient was finished and another one for test was selected. In this way, one cycle after the other, until all patients had been tested. RESULT: The total training sensitivity of the two methods was 97.9% and 98.2% respectively, and the total testing sensitivity was 72.7% and 74.2% respectively. CONCLUSION: (1) The five TCM syndrome types of depression could be well differentiated by BPN, which is valuable for TCM syndrome typing in certain extent; (2) The sensitivity of Round-Robin method is slightly higher than that of Cross train-test method, but in comparison between them no remarkable significance was shown.

[Anti-tumor effect and mechanism of Paeonol on the hepatocellular carcinoma cell line Bel-7404].

OBJECTIVE: To investigate the anti-tumor effect of Paeonol (Pae) on the hepatocellular carcinoma cell line Bel-7404 and its molecular mechanisms. METHODS: Hepatocellular carcinoma cell line Bel-7404 was treated by Pae in various concentrations and different time points respectively; and then the cell proliferation was assayed by light microscope, MTT method. DNA agarose gel electrophoresis and TUNEL were used to detect the apoptosis. The expression of PTEN and Akt were examined by RT-PCR and immunocytochemical ABC method. RESULTS: Compared with the control groups Pae obviously increased the inhibitory and apoptosis rate of hepatocellular carcinoma cell line Bel-7404. It also showed a typical apoptotic morphology and DNA depicted a ladder pattern characteristic of the apoptosis, indicating the presence of DNA fragmentation. RT-PCR and immunocytochemical ABC assay showed that Pae could increase the expression of PTEN and decrease the expression of Akt. CONCLUSION: Pae can increase the anti-hepatocellular carcinoma effect, and its mechanism may be the increase of apoptosis-inducing effect which is regulated by phosphatidylinositol-3-kinase.

[Effect of BST on synapse protein SYT and SYN in the hippocampus of chronic stress depression in rats].

OBJECTIVE: To explore the effects of Baisong tablets (BST) on synapse protein synatotagmin (SYT) and synaptophysin (SYN) of hippocampus in chronic stress depression in rats. METHODS: Twenty eight male Sprague-Dawley rats were randomly allocated to 4 groups: a normal control group,a model group,a fluoxetine (FXT) group and a BST group. The normal control rats were fed in a natural environment. Rats of the model, FXT and BST groups were singly housed and given an chronic unpredicted sequence of mild stressors. The distribution and expression differences of SYT and SYN in the hippocampus of rats in different groups were investigated with in situ hybridization and immunoblotting. RESULTS: Expressions of SYT and SYN in the hippocampus of model rats were significantly reduced, compared with that of the normal control (P<0.05); and the expressions of SYT and SYN were significantly increased in the hippocampus of the FXT and BST groups, compared with that of the model group (P<0.05). CONCLUSION: The expressions of SYT and SYN protein and their mRNA decrease in the hippocampus of stress-model rats. BST can up-regulate their expression.

[Effect of chronic stress on PKA and P-CREB expression in hippocampus of rats and the antagonism of antidepressors].

OBJECTIVE: To observe the effect of chronic unpredicted sequence of mild stress on the expression of cAMP-dependent protein kinase A(PKA) and phosphorylated cAMP-responsive element binding protein (P-CREB) in hippocampus of rats and the antagonism of antidepressors (fluoxetine). METHODS: Thirty-six male Sprague Dawley rats were randomly and equally allocated to 3 groups: A normal control group, a model group, and a fluoxetine group. All rats except the control group were singly housed and exposed to an unpredicted sequence of mild stressors. The different distribution and expression of PKA and P-CREB in the hippocampus of rats in different groups were investigated with immunohistochemistry and Westernblot technique. RESULTS: The positive PKA and P-CREB cells in the hippocampus of normal controls were the pyramidal cells and the granule cells. The PKA and P-CREB protein expression levels in the hippocampus of model rats were significantly lower than those of the normal controls (P<0.05). The PKA and P-CREB protein expression levels in the hippocampus of the fluoxetine group were significantly higher than those of the model group (P<0.05). CONCLUSION: Chronic unpredicted mild stress can affect the PKA and P-CREB expression in hippocampus of rats and fluoxetine has antagonism against it.

[Anti-depressive effect of Baisong tablets on the chronic mild unpredicted stress depression in rats].

OBJECTIVE: To investigate the effect of Baisong tablets on the nerve-biochemistry and neuroendocrine of chronic mild unpredicted stress depression in rats. METHODS: Sixty male Sprague-Dawley rats were randomly allocated to 4 groups: a normal control (NC), a model control (MC), a fluoxetine control (FC) and a Baisong tablet treatment group (BST). All rats except the control group were singly housed and exposed to an unpredicted sequence of mild stressor. The levels of serotonin (5-HT), glutamate (Glu) and gama-aminobutyric acid (GABA) of the hippocampus were measured by high-performance liquid chromatography. The concentration of corticotropin releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and cortisol (CORT) in the plasma of the rats were detected by radio-immunity. The CRHmRNA expressions in the hypothalamus and prefrontal cortex were semiquantified by RT-PCR method. The differences of BDNF and TrkB protein expression in CA1 and CA3 pyramidal and dentate gyrus granule cells layers of hippocampus were investigated with immunohistochemistry technique. RESULTS: In comparison with NC group, the levels of 5-HT, and GABA of the hippocampus in MC rats reduced significantly (P<0.01), and the concentration of CRH, ACTH, and CORT of the plasma and the level of Glu of the hippocampus and CRH mRNA expression in the brain increased significantly. Fluoxetine or Baisong could significantly regulate the abnormal changes of all the above. CONCLUSION: Chronic mild unpredicted stress can affect neuroendoerine and cause depression, and Baisong tablet has antagonism against it.

Serotonin transporter and tryptophan hydroxylase gene polymorphisms in Chinese patients with generalized anxiety disorder.

BACKGROUND: The serotonin transporter (5-HTT) and tryptophan hydroxylase (TPH) gene are important candidate genes for the psychiatric disorders. Many studies of patients with anxiety disorders have found abnormalities of serotonin metabolism and dysfunction of regulation in the transporter itself. In this study, we hypothesize that genetic variation in the 5-HTT and TPH gene may have an effect on the etiology of generalized anxiety disorder (GAD). METHODS: Using a polymerase chain reaction-based technique, the allele and genotype frequencies of three polymorphisms in the serotonin transporter gene (a deletion/insertion polymorphism in the transcriptional control region and a variable number of tandem repeats in intron 2) and TPH gene (A218C in intron 7) were analyzed in 138 patients with GAD and 90 healthy controls. These two groups were matched for ethnic and geographic origin. RESULTS: The frequencies of 5-HTT gene-linked functional polymorphic region (5-HTTLPR) SS (short/short) genotype were significantly higher in GAD patients than in control subjects (68% versus 49%, chi = 12.274, df = 2, P = 0.002), and the frequencies of S (short) allele observed in the GAD patients were higher than those in healthy subjects (79 versus 71%, chi = 4.063, df = 1, P = 0.044). The odds ratio for the SS genotype versus the other two genotypes was 2.33 (95% confidence interval, 1.29-3.86). Similarly, the odds ratio for the S allele versus L allele was 1.56 (95% confidence interval, 1.01-2.41). The genotypic and allelic distribution of 5-HTT VNTR and TPH A218C polymorphisms did not show statistically significant differences between patients and controls. CONCLUSION: Our findings support that the presence of 5-HTTLPR-SS genotype may increase the risk of GAD.

[Thinking on the assessment of clinical therapeutic effectiveness of TCM].

How to assess the therapeutic effectiveness of TCM is the focus of this paper, the trend of study on standard for therapeutic effectiveness assessment and application of standard for disease combined with symptom diagnosis and treatment were described. Taking the study on standard for TCM syndrome of Gan as an example, the basic principle and existing problem in standard formulation were pointed out. The possibility in establishing the therapeutic effectiveness assessment system of TCM by using the quantified scale for therapeutic effectiveness assessment as a tool, i.e., the theoretical design of the scale formation should be in accord with the theories of TCM, and followed with scientific measuring principle, based on the sample investigation to establish the database of quantified scale, to make sure the scale that having corresponding checking process and scoring criteria so as to make the scale meeting the need of reliability and validity. It was also pointed owt that the scale should be used in combination with the standard for syndrome differentiation, thus, the scientific, practical therapeutic effectiveness assessment system of TCM could be built up.

[The effects of Baisong tablet on the behaviors and CRHmRNA expression in the brain of rats following chronic stress].

OBJECTIVE: To investigate the effects of Baisong tablet on the behaviors and CRHmRNA expression in the chronic stress rats. METHOD: Rats were exposed to different ways of chronic stress. Body weight and behaviors were investigated during the whole procedure, the CRHmRNA expressions in the hypothalamus and prefrontal cortex were semiquantified by the RT-PCR method. RESULT: In comparision with the normal group, rats exposed to chronic stress showed decreased body weight and a significant reduction of consumption of sucrose solution, and the duration of immobility during the forced swimming test was increased significantly. The chronic stress rats was in depression of behavior. CRHmRNA expression in the brain of the chronic stress rats was upregulated significantly, while it was downregulated in the groups of Baisong tablet and the group of fluoxetin. CONCLUSION: Baisong tablet has the effect of antidepressant, and it may be related to the effect of the downregulated CRHmRNA expression in brain.

[Effects of baisong tablets on the behavior and levels of norepinephrine and dopamine in the brain of stress rats].

OBJECTIVE: To explore the effects of baisong tablets on the behavior and contents of norepinephrine and dopamine in the brain of stress rats. METHODS: Forty adult Sprague-Dawley male rats were randomly divided into 4 groups: the control group, the depression model group, the baisong tablet group and the fluoxetine group. The depression model was replicated by chronic unpredictable mild stress and single house in 21 days. Ten rats as a group were treated with baisong tablets or fluoxetine hydrochloride. Changes of behaviors were observed by open-field test and the volume of sugar-solution the rat drank in 24 hours. The weight increase was also observed. The levels of norepinephrine and dopamine in the brain in each group were detected with high-pergomance liquid chromatography. RESULTS: Compared with the model group, baisong tablets could improve the depressive behaviors significantly, and increase the levels of norepinephrine and dopamine in the rat brain. CONCLUSION: Baisong tablets can improve the depressive behaviors and increase the levels of 5-hydroxytryptaimne and dopamine in the brain of stress rats.