Interleukin 1alpha alters hippocampal serotonin and norepinephrine release during open-field behavior in Sprague-Dawley animals: differences from the Fawn-Hooded animal model of depression

Detection of two biogenic amine neurotransmitters, serotonin (5-HT) and norepinephrine (NE) within the CA1 region of the hippocampus (HPC) of behaving male laboratory animals (Rattus norvegicus), was performed with miniature carbon sensors (BRODERICK PROBES) and in vivo semidifferential microvoltammetry after acute administration of the soluble immune factor, human recombinant, interleukin (IL) 1alpha (10 and 100 ng/kg i.p.). Two animal models were compared, i.e., (a) the Sprague-Dawley (SD) model, a strain neither biochemically nor immune-challenged and (b) the Fawn-Hooded (FH) model, a biochemically (5-HT-deficient) and immune-challenged animal. Open-field behaviors, locomotion (ambulations) and stereotypy (fine movements of sniffing and grooming) were monitored with infrared photobeams while 5-HT and NE were selectively and separately detected within seconds in real time. Subchronic studies were performed in the same animals 24 h later at which time no further drug was administered. Results from acute treatment studies showed that IL-1alpha altered HPC monoamines and behavior viz-a-viz habituation values (baseline) in the SD strain differently from those in the FH strain as follows: (1) although 5-HT release was significantly increased within CA1 region of HPC in both SD and FH strains (P<.0001), the extent of the HPC 5-HT increase in the 5-HT-deficient FH strain was significantly less than that of the SD strain at both doses (P<.0001). The subchronic studies showed that 5-HT release within the HPC in the SD strain significantly increased (135%) over drug treatment values (P<.001), whereas HPC 5-HT release in the FH strain remained the same as that seen in the acute drug treatment studies; the difference between strains for the subchronic study was also statistically significant (P<.01). (2) IL-1alpha significantly decreased HPC NE release in the SD strain (P<.0004) while IL-1alpha decreased HPC NE release in the FH strain only at the 10-ng/kg dose (P<.001); at the 100-ng/kg dose in the FH strain, NE rebounded towards baseline and increased 15% above baseline reaching statistical significance (P<.05). Subchronic studies in the SD strain showed a further decreased NE signal to 38% below baseline (P<.0001), whereas subchronic studies in the FH strain showed a significant increase in NE release (P<.02). The difference between strains in the subchronic NE studies was significant (P<.001). (3) Ambulations were increased after IL-1alpha administration in acute studies in both the SD and the FH strains, but the increase did not reach statistical significance, whereas in the subchronic studies, both strains exhibited significant increases as revealed by post hoc analyses (P<.05). There was a statistically significant difference between strains in acute studies (P<.001), whereas no significant differences between models were seen in ambulation behavior in subchronic studies. (4) Fine movements increased over baseline after IL-1alpha administration in both animal models in acute studies, however, results did not reach statistical significance, likely due to the episodic effect of IL-1alpha on movement behavior in both the SD and the FH strains. However, the SD strain showed a significant increase in fine movement behavior during the subchronic studies (P<.02). Significant differences in fine movements between animal models were not observed either acutely or in subchronic studies. In summary, the data show that immune modulation by IL-1alpha affects HPC neurochemistry and behavior in SD versus FH animal models differently and/or to different degrees. The data show that while the FH animal model is subsensitive to 5-HT agonists, 5-HT function can be stimulated. Comparison of genetically diverse animal models provides a reliable means to identify and discern cytokine-induced depressive versus stressor properties. Selective sensor technology provides a powerful tool as movement behavior is monitored and interpreted as a function of monoamine neurotransmission.     

Both oxidative stress-dependent and independent effects of amyloid β protein are detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay has been widely used for evaluating amyloid β protein (Aβ) toxicity. However, the potency of Aβ in inhibiting cellular MTT reduction and the underlying mechanism have been reported with some discrepancies among researchers. To understand what makes such discrepancies, the effect of Aβ detected by MTT reduction assay was re-examined in detail by using cultured rat hippocampal neurons. Micromolar concentrations (>10 μM) of Aβ caused a decrease in cell viability, which resulted in a decrease in MTT reduction per well regardless of assay time. The micromolar Aβ-induced decrease of cellular MTT reduction was significantly attenuated by antioxidants (catalase, propyl gallate or Trolox). On the other hand, nanomolar Aβ did not affect cellular MTT reduction activity at an initial stage of assay (<1 h), and decreased the total production of MTT formazan by accelerating the exocytosis of MTT formazan when MTT assay was performed for a longer time (>2 h). The assay time-dependent, nanomolar Aβ-induced decrease of cellular MTT reduction was not at all affected by antioxidants. Furthermore, subtoxic concentration of H₂O₂ failed to mimic the effect of nanomolar Aβ on MTT reduction. These results indicate that micromolar Aβ-induced, oxidative cell death is detected by MTT assay regardless of assay time, whereas nanomolar Aβ-induced acceleration of MTT formazan exocytosis is not mediated by oxidative stress and detected only when MTT assay is performed for a longer time. The time of MTT assay should be properly chosen depending on the purpose of the study.     

N-乙酰半胱氨酸对脑缺血诱导信号转导与转录激活子-3的磷酸化及DNA结合活性的影响

目的 研究抗氧化剂N-乙酰半胱氨酸对全脑缺血诱导海马组织信号转导与转录激活子-3(STAT3)的激活及DNA结合活性的影响。方法 采用SD雄性大鼠四动脉结扎(4-VO)全脑缺血模型，以及腹腔注射给药的方法。运用抗磷酸化STAT3抗体做免疫印迹(IB)检测海马核抽提物磷酸化STAT3的变化；以及电泳迁移率改变实验(EMSA)分析核内STAT3 DNA结合活性的变化。结果 全脑缺血不同时间导致核内STAT3磷酸化水平及DNA结合活性的持续增高；缺血前20min腹腔注射抗氧化剂N-乙酰半胱氨酸能明显抑制其增高。结论 全脑缺血所致STAT3的磷酸化水平及DNA结合活性的增高与氧化应激有一定的关系。     

Changes in pyruvate dehydrogenase complex (PDHc) activity and [3H]QNB-receptor binding in rat brain subsequent to intracerebroventricular injection of bromopyruvate

Summary Pyruvate dehydrogenase complex (PDHc), a link between carbohydrate and acetylcholine metabolism, is a regulatory enzyme for glucose and neurotransmitter metabolism in the brain and is reduced in Alzheimer-diseased brain. To study functional consequences of an inhibition of PDHc on muscarinic receptor binding, bromopyruvate, a suicide inhibitor of PDHc, was injected intracerebroventricularly (icv) in rats. Bromopyruvate caused a reduction of PDHc activity in the 3 brain regions examined, however, reaching significance only in the cerebral cortex and the hippocampus and not in the striatum, 24h after injection. 3, 6, and 12 weeks later, there was a normalization or transiently increased activity, respectively, of PDHc in these brain regions. No changes in concentrations of energy-rich phosphates could be demonstrated in the cerebral cortex 12 weeks after brompyruvate injection. The number of muscarinic receptors was significantly reduced in the cerebral cortex 12 weeks after injection. the data indicate that a transient reduction of brain PDHc activity in vivo is associated with a long-lasting reduction in muscarinic cholinergic receptors. Because comparable changes of PDHc and muscarinic receptors are found in dementia of Alzheimer type, the model of bromopyruvate inhibition of PDHc in rats is suggested to be useful for experimental dementia research.     

Nutraceuticals in the treatment of obsessive compulsive disorder (OCD): a review of mechanistic and clinical evidence

Obsessive-Compulsive Disorder (OCD) is a debilitating mental illness which has a significant impact on quality of life. First-line SSRI treatments for OCD typically are of limited benefit to only 40-60% of patients, and are associated with a range of adverse side effects. Current preclinical research investigating nutraceuticals (natural products) for OCD, reveals encouraging novel activity in modulating key pathways suggested to be involved in the pathogenesis of OCD (glutamatergic and serotonergic pathway dysregulation). Emerging clinical evidence also appears to tentatively support certain nutrients and plant-based interventions with known active constituents which modulate these pathways: N-acetlycysteine, myo-inositol, glycine, and milk thistle (Silybum marianum). The serotonin precursor tryptophan is unlikely to be of use in treating OCD while 5-HTP may possibly be a more effective precursor strategy. However, there is currently no clinical evidence to test the efficacy of either of these substances. Currently the balance of clinical evidence does not support the use of St. John's wort (Hypericum perforatum) in OCD. While clinical research in this area is in its infancy, further research into nutraceuticals is warranted in light of the promising preclinical data regarding their mechanisms of action and their favourable side effect profiles in comparison to current SSRI treatments. It is recommended that future clinical trials of nutraceutical treatments for OCD utilize randomized placebo-controlled study designs and considerably larger sample sizes in order to properly test for efficacy.