Effect of emulsified isoflurane on cognitive function in rats

PURPOSE: Recent studies have suggested that exercise training and caloric restriction have beneficial effects on brain function, including the improvements of cognitive function by the promotion of brain-derived neurotrophic factor (BDNF) expression in the hippocampus. In addition, the level of oxidative stress might be involved in the mechanism to explain these effects. The purpose of this study was to investigate the synergy effects between 12-week low-intensity exercise training and caloric restriction on BDNF expression and the level of oxidative stress in rat hippocampus. METHODS: Twenty-six, 7 week-old male Wistar rats were randomly divided into the following 4 groups: 1) sedentary control (Con, n=7); 2) exercise (Ex, n=6); 3) caloric restriction (CR, n=7); and 4) exercise training and caloric restriction (ExCR, n=6). Ex and ExCR underwent treadmill running at 10 m/min, 5° slope, 30 min/day, 5 days/week. Although Con and Ex were fed ad libitum over time, CR and ExCR consumed 40 % less food compared with Con. Forty-eight hours after the termination of the 12-week intervention, rats were sacrificed and the hippocampus was quickly dissected for measurement of BDNF and 4-hydroxy-2-nonenal (4-HNE) contents, and serum total antioxidant capacity (TAC) were also assessed. RESULTS: 4-HNE contents in Ex and CR were significantly increased compared with Con (p<0.05, respectively). However, these elevation was not observed in ExCR. On the other hand, no changes were observed in the alteration of serum TAC among 4 groups. Hippocampal BDNF contents was significantly increased in Ex compared with Con (p<0.05), whereas the exercise-induced elevation in BDNF was completely suppressed by a combination with caloric restriction. Furthermore, we found a significant relationship between hippocampal BDNF and 4-HNE contents (p<0.05), suggesting the hypothesis that oxidative stress is essential for the expression of BDNF in the hippocampus. CONCLUSION: Our findings indicate that optimal stimulus of oxidative stress induced by low-intensity exercise training contributes to BDNF expression in hippocampus. However, it is conceivable that exercise training combined with caloric restriction might not have a synergy effect on hippocampal BDNF expression.

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are two major members of the neurotrophin family. Using immunohistochemistry and in situ hybridization histochemistry, we examined the effect of L5 spinal nerve ligation (SPNL), a neuropathic pain model, on the expression of BDNF in the uninjured L4 dorsal root ganglion (DRG). After L5 SPNL, both immunoreactivity for BDNF and the hybridization intensity for BDNF mRNA increased mainly in the small- and medium-sized neurons. The percentage of BDNF mRNA-expressing neurons increased in the ipsilateral L4 DRG compared with the contralateral DRG from the third to 28th day after ligation. A significantly greater number of BDNF-immunoreactive neurons were observed in the ipsilateral L4 DRG than contralateral side 14 d after ligation. To test the contribution of BDNF to the thermal hyperalgesia produced in this model, we intrathecally injected anti-BDNF antibody at third day after ligation. This treatment clearly attenuated thermal hyperalgesia for a few hours. Almost all BDNF mRNA-expressing neurons coexpressed trkA, a high-affinity NGF receptor, mRNA. The percentage of BDNF mRNA-expressing cells of trkA cells significantly increased in the ipsilateral L4 DRG 14 d after ligation. Furthermore, we examined the contribution of NGF on this phenotypic change using ELISA, Northern blot analysis, and anti-NGF antibody. NGF content in the ipsilateral L4 DRG linearly increased and reached a statistical significant level 14 d after L5 SPNL. Moreover, at this time point, the increase in NGF mRNA was observed in the ipsilateral L5 DRG and sciatic nerve, but not in the ipsilateral L4 DRG or L4 spinal nerve. Local application of anti-NGF antibody to the L4 spinal nerve beside the L5 spinal nerve-ligation site prevented the development of thermal hyperalgesia for 5 d after ligation. Our data suggest that BDNF, which increased in the uninjured L4 DRG neurons, acts as a sensory neuromodulator in the dorsal horn and contributes to thermal hyperalgesia in this neuropathic pain model. The contribution of locally synthesized NGF to thermal hyperalgesia was also demonstrated. These dynamic alterations in the expression and content of BDNF and NGF in the uninjured DRG neurons might be involved in the pathomechanisms of neuropathic pain.

Memory is an important cognitive function in humans. Exercise and environmental enrichment (EE) exposure have positive effects on memory function via improved neurogenesis through expression of growth factors such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF). Exercise and environmental enrichment have independently been shown to increase BDNF and NGF, but the effect of the combination of these treatments has not been widely studied. This experimental study aims to analyse the effect of aerobic exercise, EE exposure, and combination of aerobic exercise and EE exposure on memory function. This study used twenty 7-month old male Wistar rats that were given treatment for 8 weeks. Memory function was tested using forced alternation Y-maze. Hippocampal expression of BDNF and NGF were also assessed. The results showed the combination group has highest performance in memory function test and also the highest level of hippocampal BDNF and NGF (P&lt;0.05). It can be concluded that the combination of aerobic exercise and continuous EE exposure produces the best results for memory function through higher levels of hippocampal BDNF and NGF in adult rats.

Objective To investigate the effect of repetitive transcranial magnetic stimulation (rTMS) on the depressive like behaviors and expression of brain derived neurotrophic factor (BDNF), IL-1β and NF-κB of hippocampal in chronic unpredictable mild stress (CUMS) rats. Methods Thirty-two adult male rats were randomly divided into four groups (n=8): Control group, Control+ rTMS group, CUMS group and CUMS+ rTMS group. The sucrose preference test, forced swim test and open field test were used to evaluate depressive like behaviors for each groups. In addition, the expression of BDNF, NF-κB and IL-1β in hippo were detected by western blot and ELISA after behavioral test, respectively. Results 1.The effects of rTMS on depressive like behaviors of CUMS rats: in the sucrose preference test, the sucrose preference rate of CUMS rats (0.67±0.06) was significantly lower than Control group (0.91±0.04), which was higher in the CUMS+ rTMS group (0.83±0.08). In the forced swim test, the immobility time of CUMS group ((26.88±11.33)s) was longer than Control group ((15.22±6.75)s) and CUMS+ rTMS group ((18.41±6.95)s). In the open field test, both the total distance traveled and number of central area entry times of CUMS group((849.165±769.01)cm, (7.42±5.68)) were significantly shorter ((6224.81±1403.2)cm) and smaller (22.86±3.72) than Control group, and those of the CUMS+ rTMS were longer ((4105.57±1516.92)cm) and larger (21.25±3.45). All the behavioral results were statistically significant (P 0.05). 2. The effects of rTMS on the hippocampal expressions of BDNF, NF-κB and IL-1β in CUMS rats: compared with Control group, the hippocampal expression of BDNF in CUMS rats was significantly decreased, while the expressions of NF-κB and IL-1β in the hippocampus were significantly increased (P<0.05). Compared with CUMS group, the hippocampa expression of BDNF in the CUMS+ rTMS group was increased, and the expressions of NF-κB and IL-1β in the hippocampus was significantly decreased (P<0.05). There are no expressions of BDNF, NF-κB and IL-1β between Control group and Control+ rTMS group had no differences. Conclusion rTMS increased the expression of BDNF, reduced the production of NF-κB and IL-1β, and alleviated depressive like behaviors in CUMS rats. Key words: Repetitive transcranial magnetic stimulation; BDNF; NF-κB; IL-1β; Rats

The antidepressants, reboxetine and citalopram, were used in conjunction with voluntary physical exercise (wheel running) in order to assess the contribution of noradrenergic and serotonergic activation to enhancements in hippocampal brain-derived neurotrophic factor (BDNF) expression resulting from antidepressant treatment and exercise. Reboxetine (40 mg/kg/day), citalopram (10 mg/kg/day), voluntary physical activity, and the combination of antidepressants with exercise were applied to rats for a range of treatment intervals (2 to 14 days). Hippocampal BDNF transcription levels (full-length BDNF, as well as exons I-IV) were then assessed via in situ hybridization. Reboxetine treatment led to a rapid (evident at 2 days) enhancement in BDNF transcription in several hippocampal regions. This increase was also observed when reboxetine treatment was combined with voluntary physical activity for 2 weeks. Treatment with citalopram led to an increase in BDNF mRNA in only one hippocampal region (CA2) after short-term (2 days) treatment, and when combined with exercise, increased BDNF mRNA in the CA4 and dentate gyrus after 2 weeks. As reported in previous studies, voluntary physical activity enhanced BDNF transcription in several hippocampal areas, both on its own and in combination with antidepressant treatments. Examination of the levels of individual BDNF transcript variants influenced by each of these antidepressants revealed distinct patterns of expression in response to the various treatments, and showed that exercise-plus-antidepressant produced significant changes where antidepressant alone failed. Overall, treatment with the norephinephrine-selective antidepressant, reboxetine, in combination with exercise, led to both rapid and sustained increases in hippocampal BDNF mRNA expression. The serotonergic agent, citalopram, appeared to require longer treatment intervals in order to influence BDNF expression positively.

In previous experiments it has been demonstrated that the synthesis of BDNF (brain-derived neurotrophic factor) and NGF in neurons of the hippocampus is regulated by neuronal activity. The glutamate system is predominantly responsible for upregulation and the GABAergic system for downregulation both in vitro and in vivo (Zafra et al., 1990, 1991). The aim of the present study is to examine the extent to which the cholinergic system is also involved in the regulation of NGF and BDNF mRNA and whether the regulatory contribution of the cholinergic system changes during development. Partial transection of the fimbria fornix bundle in the second postnatal week resulted in a reduction of BDNF and NGF mRNA levels in the hippocampus, suggesting that septal cholinergic input is involved in the regulation of hippocampal BDNF and NGF mRNA levels. Because the fimbria fornix bundle also contains fibers other than cholinergic ones, we further evaluated the importance of the cholinergic influence by injecting pilocarpine, a muscarinic agonist. Pilocarpine markedly increased hippocampal BDNF and NGF mRNA levels in both early postnatal and adult rats. In situ hybridization experiments demonstrated that pilocarpine led to an increase in BDNF expression in the CA1-CA4 regions of the hippocampus and in the dentate gyrus. However, pilocarpine increased NGF mRNA only in those neurons of the dentate gyrus and CA1-CA4 regions that also expressed NGF mRNA in the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergic rhinitis (AR) is characterized in part by hyperresponsiveness to nonspecific stimuli, a phenomenon that reflects the fundamental role of nasal neural pathways in chronic airway inflammation. Neurotrophins may serve pivotal roles in mediating hyperresponsiveness in allergic airway disease, although the role of such neurogenic mediators in chronic rhinosinusitis (CRS) is not well understood. This study was designed to examine the expression of two potent neurotrophins, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), in CRS. Inferior turbinate and sinus mucosa were obtained from CRS patients with and without nasal polyps (NPs) and from nonallergic controls. Enzyme-linked immunosorbent assay was used for quantitative determination of tissue concentrations of NGF and BDNF. Ninety-four tissue samples from 48 patients were included. Mean concentration of NGF in sinus mucosa was significantly higher in CRS than controls. CRS without NPs was associated with a 60% increase in sinus NGF over controls (p < 0.05), and CRS with NPs was associated with a 140% increase (p < 0.05). Mean sinus NGF concentration was significantly elevated in allergic subjects compared with controls (p < 0.01). A similar trend was noted in subjects with nonallergic CRS, although this did not reach significance. Mean BDNF concentration was decreased in CRS compared with controls, with the most significant decrease in patients with polyps (p < 0.05). Mean turbinate concentration of both NGF and BDNF were similar in controls and CRS. Increased expression of NGF may contribute to neural hyperresponsiveness in CRS sinus mucosa, particularly those patients with NP and/or allergies. BDNF expression is decreased in CRS sinus mucosa. Alterations in neurogenic inflammation may contribute to the pathophysiology of CRS and provide alternative therapeutic targets.

Objective To investigate the role of hippocampal cyclophilin D (CypD) in sepsis-associated encephalopathy in rats. Methods A total of 36 adult male Sprague-Dawley rats, aged 3-4 months, weighing 300-400 g, were randomly divided into 3 groups (n =12 each) using a random number table: sham operation group (Sham group), sepsis group (S group), and sepsis + CypD inhibitor cyclosporin A group (CsA group). Sepsis was induced by cecal ligation and puncture (CLP). Cyclosporin A 6 mg/kg was injected intraperitoneally at 30 min before CLP in group CsA.All the animals underwent Morris water maze test on 4th day after CLP.The animals were sacrificed after the test, and the hippocampus was isolated for determination of the expression of cytochrome c (Cyt c), CypD, caspase-3, brain-derived neurotrophic factor (BDNF), phosphorylated protein kinase A (p-PKA), and phosphorylated cyclic adenosine monophosphate response element-binding protein (p-CREB). Results Compared with group Sham, the escape latency was significantly prolonged, the space exploration time was shortened, the expression of Cyt c, CypD, caspase-3, p-PKA and p-CREB was up-regulated, and the expression of BDNF was down-regulated in S and CsA groups (P<0.05). Compared with group S, the escape latency was significantly shortened, the space exploration time was prolonged, the expression of Cyt c, CypD, caspase-3, p-PKA and p-CREB was down-regulated, and the expression of BDNF was up-regulated in group CsA (P<0.05). Conclusion Hippocampal CypD may be involved in the pathophysiological mechanism of sepsis-associated encephalopathy, and the downstream mechanism is probably related to promotion of activation of PKA/CREB signaling pathway in rats. Key words: Sepsis; Cyclophilins; Hippocampus; Brain diseases

The ganglioside GQ1b regulates BDNF expression via the NMDA receptor signaling pathway

The adrenal steroid corticosterone has profound effect on the structure and function of the hippocampus. Probably as a result of that, it modulates memory formation. In this review, the question is addressed if the corticosterone effects on memory processes are mediated by alterations in the expression of the neurotrophin Brain-Derived Neurotrophic Factor (BDNF) in the hippocampus. First, studies are described investigating the effect of corticosterone on BDNF expression in the rat hippocampus. It appears that corticosterone suppresses the BDNF expression at the mRNA and protein level in a subfield-specific way. Second, a model for the mechanism of action is proposed. In this model, activated mineralocorticoid and glucocorticoid receptors repress transcriptional activity of the BDNF promoter site-specifically via interaction with other transcription factors. Third, the implications for learning and memory are discussed. Studies show that during water maze training, corticosterone levels rise significantly, but the BDNF expression is not suppressed in any hippocampal subfield. Furthermore, high BDNF expression levels in specific subfields correlate with a good memory performance. Therefore, we suggest that the resistance of the hippocampal BDNF expression to suppression by corticosterone, as seen after water maze training, may contribute to an optimal memory performance.

Physiological variability in brain-derived neurotrophic factor expression predicts dendritic spine density in the mouse dentate gyrus

Ovarian hypofunction is characterized by decay in brain-derived neurotrophic factor (BDNF), a neurotrophin associated with cognitive and memory function. Hormone replacement therapy is the most common treatment to counteract the negative effects of ovarian insufficiency; however, this therapy may increase the odds of endometrial cancer, blood clots, stroke, and breast cancer. Therefore, a safer alternative to synthetic estrogens is needed. One possible candidate may be phytoestrogens. Hibiscus sabdariffa L. (Malvaceae) is a source of natural food colorants; the calyces and leaves of the plant are consumed in drinks and culinary preparations and are recognized for several health benefits related to their high content of anthocyanins. In the present study, we used an ovariectomized rat model to assess the phytoestrogenic effect of H. sabdariffa, and evaluated spatial memory and BDNF expression. Ninety-day-old female Wistar rats were randomly separated into six groups. Rats from four groups were ovariectomized and injected with a physiological dose of estradiol, or given, in drinking water, an extract prepared from calyces of H. sabdariffa at doses of 50 or 100 mg/kg body weight. Both Intact and Sham groups were included as controls. At day 42, short- and long-term memories were assessed by the Barnes maze test, and hippocampal BDNF expression was evaluated by RT-qPCR and Western blot. Ovariectomy significantly decreased memory performance and BDNF expression, compared with controls. However, administration of H. sabdariffa extract reversed the negative effect of ovariectomy on short- and long-term memory parameters and BDNF expression. A stronger effect was observed at a lower dose of the extract. In conclusion, the extract from H. sabdariffa acted as a phytoestrogen in ovariectomized rats, improving spatial memory performance and hippocampal BDNF expression. Based on these promising results, further clinical experimentation is recommended to study the benefits of H. sabdariffa as an alternative hormonal therapy in patients with ovarian hypofunction.

Acute onset by 5-HT 6-receptor activation on rat brain brain-derived neurotrophic factor and activity-regulated cytoskeletal-associated protein mRNA expression

Effects of serotonin depletion on the hippocampal GR/MR and BDNF expression during the stress adaptation

Fetal exposure to inhaled anesthetics, such as isoflurane, may lead to neurodevelopmental impairment in offspring. Yet, the mechanisms of prenatal isoflurane-induced developmental neurotoxicity have not been fully elucidated. Gut microbiota is a pivotal modulator of brain development and functions. While the antibiotic effect of isoflurane has been previously investigated, the relationship between prenatal isoflurane exposure and postnatal gut microbiota, brain biology, and behavior remains unknown. In the present study, we treated pregnant rats with 2% isoflurane for 4h on gestational day 14. Their offspring were tested with novel object recognition task on postnatal day 28 (P28) to assess cognition. Fecal microbiome was assessed using 16S RNA sequencing. We also analyzed hippocampal expression of brain-derived neurotrophic factor (BDNF) in P28 rat brains. To further explore the role of gut microbiota on prenatal isoflurane-induced developmental neurotoxicity, we treated rats with mixed probiotics on P14 for 14days and evaluated novel object recognition and hippocampal expression of BDNF on P28. Results indicate that prenatal exposure to isoflurane significantly decreased novel object recognition (novel object preference ratio: mean difference (MD) - 0.157; 95% confidence interval (CI) - 0.234 to - 0.080, P < 0.001) paralleled by diminished expression of hippocampal BDNF in juvenile rats. Prenatal exposure to isoflurane also significantly altered the diversity and composition of gut microbiota. Treatment with probiotics mitigated these changes in cognition (novel object preference ratio: isoflurane group vs. control group: MD - 0.177; 95% CI - 0.307 to - 0.047, P = 0.006; probiotic group vs. isoflurane group: MD 0.140; 95% CI 0.004 to 0.275, P = 0.042) and BDNF expression. Taken together, our findings suggest that gut dysbiosis may be involved in the pathogenesis of maternal isoflurane exposure-induced postnatal cognitive impairment. To determine the causal relationship between gut microbiota and cognition in prenatal anesthetic-induced developmental neurotoxicity, further studies are needed.