Brain-derived Neurotrophic Factor Pretreatment Research Articles

Brain-derived neurotrophic factor protects serotonergic neurons against 3,4-methylenedioxymethamphetamine (“Ecstasy”) induced cytoskeletal damage

3,4-Methylenedioxymethamphetamine (MDMA, “Ecstasy”) use has been linked to persistent alterations of the brain serotonergic (5-HT) system in animal and human studies, but the molecular underpinnings are still unclear. Cytoskeletal structures such as neurofilament light chain (NfL) are promising markers of drug-induced brain toxicity and may be involved in MDMA neurotoxicity. The brain-derived neurotrophic factor (BDNF) promotes the growth and sprouting of 5-HT neurons and its differential response to MDMA administration was suggested to mediate dose- and region-dependent 5-HT damage by MDMA. However, the role of BDNF pre-treatment in preventing MDMA neurotoxicity and the potential effects of MDMA on NfL are still elusive. Therefore, a differentiated 5-HT neuronal cell line obtained from rat raphe nucleus (RN46A) was treated in vitro with either MDMA, BDNF, MDMA + BDNF, or vehicle. Cell viability (measured by MTT) and intracellular NfL levels (immunocytochemistry assay) were reduced by MDMA, but partially rescued by BDNF co-treatment. Our findings confirmed that BDNF levels can influence MDMA-induced 5-HT damage, and support BDNF to be a crucial target for neuroprotective interventions of the 5-HT system. We also provide evidence on the sensitivity of NfL to MDMA neurotoxicity, with potential implications for in-vivo monitoring of drug-induced neurotoxicity.

Impact of Bifrontal Home-Based Transcranial Direct Current Stimulation in Pain Catastrophizing and Disability due to Pain in Fibromyalgia: A Randomized, Double-Blind Sham-Controlled Study

This randomized, double-blind trial tested the hypothesis that 20 sessions of home-based anodal(a)-transcranial direct current stimulation (tDCS) (2mA for 20 minutes) bifrontal, with anodal on the left dorsolateral prefrontal cortex (l-DLPFC) would be better than sham-(s)-tDCS to reduce scores on Pain Catastrophizing Scale and disability-related to pain assessed by the Profile of Chronic Pain: Screen (primary outcomes). Secondary outcomes were depressive symptoms, sleep quality, heat pain threshold , heat pain tolerance , and serum brain-derived-neurotrophic-factor (BDNF). Forty-eight women with fibromyalgia, 30 to 65 years-old were randomized into 2:1 groups [a-tDCS (n = 32) or s-tDCS (n = 16)]. Post hoc analysis revealed that a-tDCS reduced the Pain Catastrophizing Scale total scores by 51.38% compared to 26.96% in s-tDCS, and a-tDCS reduced Profile of Chronic Pain: Screen total scores by 31.43% compared to 19.15% in s-tDCS. The a-tDCS improved depressive symptoms, sleep quality and increased the heat pain tolerance. The delta-value in the serum BDNF (mean post treatment end minus pretreatment) was conversely correlated with the a-tDCS effect in pain catastrophizing. In contrast, the a-tDCS impact on reducing the disability-related to pain at the treatment end was positively associated with a reduction in the serum BDNF and improvement of depressive symptoms, sleep quality and pain catastrophizing symptoms. PerspectiveHome-based bifrontal tDCS with a-tDCS on the l-DLPFC are associated with a moderate effect size (ES) in the following outcomes: 1) Decreased rumination and magnification of pain catastrophizing. 2) Improved the disability for daily activities due to fibromyalgia symptoms. Overall, these findings support the feasibility of self-applied home-based tDCS on DLPFC to improve fibromyalgia symptoms.

Co-administration of ethanol and nicotine heightens sensitivity to ethanol reward within the nucleus accumbens (NAc) shell and increasing NAc shell BDNF is sufficient to enhance ethanol reward in naïve Wistar rats.

Alcohol use disorder most commonly presents as a polydrug disorder where greater than 85% are estimated to smoke. EtOH and nicotine (NIC) co-abuse or exposure results in unique neuroadaptations that are linked to behaviors that promote drug use. The current experiments aimed to identify neuroadaptations within the mesolimbic pathway produced by concurrent EtOH and NIC exposure. The experiments used four overall groups of male Wistar rats consisting of vehicle, EtOH or NIC alone, and EtOH+NIC. Drug exposure through direct infusion into the posterior ventral tegmental area (pVTA) stimulated release of glutamate and dopamine in the nucleus accumbens (NAc) shell, which was quantified through high-performance liquid chromatography. Additionally, brain-derived neurotrophic factor (BDNF) protein levels were measured via enzyme-linked immunosorbent assay (ELISA). A second experiment investigated the effects of drug pretreatment within the pVTA on the reinforcing properties of EtOH within the NAc shell through intracranial self-administration (ICSA). The concluding experiment evaluated the effect of NAc shell pretreatment with BDNF on EtOH reward utilizing ICSA within that region. The data indicated that only EtOH+NIC administration into the pVTA simultaneously increased glutamate, dopamine, and BDNF in the NAc shell. Moreover, only pVTA pretreatment with EtOH+NIC enhanced the reinforcing properties of EtOH in the NAc shell. BDNF pretreatment in the NAc shell was also sufficient to enhance the reinforcing properties of EtOH in the NAc shell. The collected data suggest that concurrent EtOH+NIC exposure results in a distinct neurochemical response and neuroadaptations within the mesolimbic pathway that alter EtOH reward.

Brain-derived neurotrophic factor reduces inflammation and hippocampal apoptosis in experimental Streptococcus pneumoniae meningitis

BackgroundStreptococcus pneumoniae meningitis is a serious inflammatory disease of the central nervous system (CNS) and is associated with high morbidity and mortality rates. The inflammatory processes initiated by recognition of bacterial components contribute to apoptosis in the hippocampal dentate gyrus. Brain-derived neurotrophic factor (BDNF) has long been recommended for the treatment of CNS diseases due to its powerful neuro-survival properties, as well as its recently reported anti-inflammatory and anti-apoptotic effects in vitro and in vivo.MethodsIn this study, we investigated the effects of BDNF-related signaling on the inflammatory response and hippocampal apoptosis in experimental models of pneumococcal meningitis. Pretreatment with exogenous BDNF or the tropomyosin-receptor kinase B (TrkB) inhibitor k252a was performed to assess the activation or inhibition of the BDNF/TrkB-signaling axis prior to intracisternal infection with live S. pneumoniae. At 24 h post-infection, rats were assessed for clinical severity and sacrificed to harvest the brains. Paraffin-embedded brain sections underwent hematoxylin and eosin staining to evaluate pathological severity, and cytokine and chemokine levels in the hippocampus and cortex were evaluated by enzyme-linked immunosorbent assay. Additionally, apoptotic neurons were detected in the hippocampal dentate gyrus by terminal deoxynucleotidyl transferase dUTP-nick-end labeling, key molecules associated with the related signaling pathway were analyzed by real-time polymerase chain reaction and western blot, and the DNA-binding activity of nuclear factor kappa B (NF-κB) was measured by electrophoretic mobility shift assay.ResultsRats administered BDNF exhibited reduced clinical impairment, pathological severity, and hippocampal apoptosis. Furthermore, BDNF pretreatment suppressed the expression of inflammatory factors, including tumor necrosis factor α, interleukin (IL)-1β, and IL-6, and increased the expression of the anti-inflammatory factor IL-10. Moreover, BDNF pretreatment increased TrkB expression, activated downstream phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling, and inhibited the myeloid differentiation primary response gene 88 (MyD88)/NF-κB-signaling pathway.ConclusionsThese data suggested that BDNF administration exerted anti-inflammatory and anti-apoptotic effects on an experimental pneumococcal meningitis model via modulation of MyD88/NF-κB- and PI3K/AKT-signaling pathways. Our results indicated that treatment with exogenous BDNF might constitute a potential therapeutic strategy for the treatment of bacterial meningitis.

BDNF Pretreatment of Human Embryonic-Derived Neural Stem Cells Improves Cell Survival and Functional Recovery after Transplantation in Hypoxic–Ischemic Stroke

Intra-arterial neural stem cell (NSC) therapy has the potential to improve long-term outcomes after stroke. Here we evaluate if pretreatment of NSCs with brain-derived neurotrophic factor (BDNF) prior to transplantation improves cell engraftment and functional recovery following hypoxic-ischemic (HI) stroke. Human embryonic-derived NSCs with or without BDNF pretreatment (1 h, 100 ng/ml) were transplanted 3 days after HI stroke. Functional recovery was assessed using the horizontal ladder test. Cell engraftment was evaluated using bioluminescence imaging (BLI) and histological counts of SC121(+) cells. Fluoro-Jade C (FJC) and NeuN stains were used to evaluate neuroprotection. The effect of BDNF on NSCs was analyzed using a migration assay, immunocytochemistry, Luminex proteomic assay, and RT-qPCR.BLI analysis demonstrated significantly higher photon flux in the BDNF-treated NSC group compared to untreated NSC (p = 0.049) and control groups (p = 0.0021) at 1 week after transplantation. Immunohistochemistry confirmed increased transplanted cell survival in the cortex (p = 0.0126) and hippocampus (p = 0.0098) of animals injected with BDNF-treated NSCs compared to untreated NSCs. Behavioral testing revealed that the BDNF-treated NSC group demonstrated increased sensorimotor recovery compared to the untreated NSC and control groups (p < 0.001) over the 1-month period (p < 0.001) following transplantation. A significant improvement in performance was found in the BDNF-treated NSC group compared to the control group at 14, 21, and 28 (p < 0.05) days after transplantation. The cortex and hippocampus of the BDNF-treated NSC group had significantly more SC121(+) NSCs (p = 0.0125, p = 0.0098), fewer FJC(+) neurons (p = 0.0370, p = 0.0285), and a higher percentage of NeuN(+) expression (p = 0.0354) in the cortex compared to the untreated NSC group. BDNF treatment of NSCs resulted in significantly greater migration to SDF-1, secretion of M-CSF, VEGF, and expression of CXCR4, VCAM-1, Thrombospondins 1 and 2, and BDNF. BDNF pretreatment of NSCs results in higher initial NSC engraftment and survival, increased neuroprotection, and greater functional recovery when compared to untreated NSCs.

The influence of BDNF on human umbilical cord blood stem/progenitor cells: Implications for stem cell-based therapy of neurodegenerative disorders

Umbilical cord blood (UCB)-derived stem/progenitor cells (SPCs) have demonstrated the potential to improve neurologic function in different experimental models. SPCs can survive after transplantation in the neural microenvironment and indu ce neuroprotection, endogenous neurogenesis by secreting a broad repertoire of trophic and immunomodulatory cytokines. In this study, the influence of brain-derived neurotrophic factor (BDNF) pre-treatment was comprehensively evaluated in a UCB-derived lineage-negative (Lin−) SPC population. UCB-derived Lin− cells were evaluated with respect to the expression of (i) neuronal markers using immunofluorescence staining and (ii) specific (TrkB) receptors for BDNF using flow cytometry. Next, after BDNF pre-treatment, Lin− cells were extensively assessed with respect to apoptosis using Western blotting and proliferation via BrdU incorporation. Furthermore, NT-3 expression levels in Lin− cells using RQ PCR and antioxidative enzyme activities were assessed. We demonstrated neuronal markers as well as TrkB expression in Lin− cells and the activation of the TrkB receptor by BDNF. BDNF pre-treatment diminished apoptosis in Lin− cells and influenced the proliferation of these cells. We observed significant changes in antioxidants as well as in the increased expression of NT-3 in Lin− cells following BDNF exposure. Complex global miRNA and mRNA profiling analyses using microarray technology and GSEA revealed the differential regulation of genes involved in the proliferation, gene expression, biosynthetic processes, translation, and protein targeting. Our results support the hypothesis that pre-treatment of stem/progenitor cells could be beneficial and may be used as an auxiliary strategy for improving the properties of SPCs.

Brain-Derived Neurotrophic Factor Contributes to Colonic Hypermotility in a Chronic Stress Rat Model.

Brain-derived neurotrophic factor (BDNF) has prokinetic effects on gut motility and is increased in the colonic mucosa of irritable bowel syndrome. We aimed to investigate the possible involvement of BDNF in stress-induced colonic hypermotility. Male Wistar rats were exposed to daily 1-h water avoidance stress (WAS) or sham WAS for 10 consecutive days. The presence of BDNF and substance P (SP) in the colonic mucosa was determined using enzyme immunoassay kits. Immunohistochemistry and western blotting were performed to assess the expression of BDNF and its receptor, TrkB. The contractions of muscle strips were studied in an organ bath system. Repeated WAS increased the fecal pellet expulsion and spontaneous contractile activities of the colonic muscle strips. Both BDNF and SP in the colonic mucosa were elevated following WAS. Immunohistochemistry revealed the presence of BDNF and TrkB in the mucosa and myenteric plexus. BDNF and TrkB were both up-regulated in colon devoid of mucosa and submucosa from the stressed rats compared with the control. BDNF pretreatment caused an enhancement of the SP-induced contraction of the circular muscle (CM) strips. TrkB antibody significantly inhibited the contraction of the colonic muscle strips and attenuated the excitatory effects of SP on contractions of the CM strips. Repeated WAS increased the contractile activities of the CM strips induced by SP after BDNF pretreatment, and this effect was reversed by TrkB antibody. The colonic hypermotility induced by repeated WAS may be associated with the increased expression of endogenous BDNF and TrkB. BDNF may have potential clinical therapeutic use in modulating gut motility.

BDNF Pretreatment Attenuates Morphine-Induced Learning and Memory Impairment in Rats

Article type: Original Article Background: It has been known that Brain-Derived Neurotrophic Factor (BDNF) is involved in neural survival and long term memory (LTM). Here we hypothesized that BDNF as a potent neurotrophic factor might modulate amnestic effect induced by morphine. Objectives: The aim of this study was to examine whether infusion of exogenous BDNF in the CA1 regions of the dorsal hippocampi could ameliorate memory impairment induced by morphine. Materials and Methods: Forty rats were divided into 5 groups for dose response study of morphine (2.5, 5, 7.5 and 10 mg/kg morphine, and saline, intraperitoneal) on memory retention. For second part of the experiment 24 animals were divided into three groups: (morphine +BDNF, morphine + saline and saline + saline). Two weeks after stereotaxic surgery, animals received 0.5 μl bilateral infusion of either saline or BDNF (5 μg/rat) intrahippocampally, 30 minutes before morphine treatment (7.5 mg/kg, i.p.). Step-through inhibitory avoidance task has been used to examine retrieval of memory formation, 1.5 and 24 h after the training. Results: The results showed that systemic administration of 7.5 and 10 mg/kg morphine compared with saline immediately after the training impairs longterm retention of memory for passive avoidance task in rats tested 24 hours later (p < 0.01). Surprisingly intra-CA1 microinjection of BDNF 30 minutes prior to injection of morphine significantly prevented amnesia (p < 0.001). Conclusions: These findings suggested that increase the level of BDNF in the CA1 region of the hippocampus during 30 minutes time window before morphine administration might modulate morphine-induced amnesia.

Microfluidic Investigation of BDNF‐Enhanced Neural Stem Cell Chemotaxis in CXCL12 Gradients

In vivo studies have suggested that gradients of CXCL12 (aka stromal cell-derived factor 1α) may be critical for neural stem cell (NSC) migration during brain development and neural tissue regeneration. However, traditional in vitro chemotaxis tools are limited by unstable concentration gradients and the inability to decouple cell migration directionality and speed. These limitations have restricted the reproducible and quantitative analysis of neuronal migration, which is required for mechanism-based studies. Using a microfluidic gradient generator, nestin and Sox-2 positive human embryonic NSC chemotaxis is quantified within a linear and stable CXCL12 gradient. While untreated NSCs are not able to chemotax within CXCL12 gradients, pre-treatment of the cells with brain-derived neurotrophic factor (BDNF) results in significant chemotactic, directional migration. BDNF pre-treatment has no effect on cell migration speed, which averages about 1 μm min(-1). Quantitative analysis determines that CXCL12 concentrations above 9.0 nM are above the minimum activation threshold, while concentrations below 14.7 nM are below the saturation threshold. Interestingly, although inhibitor studies with AMD 3100 revealed that CXCL12 chemotaxis requires receptor CXCR4 activation, BDNF pre-treatment is found to have no profound effects on the mRNA levels or surface presentation of CXCR4 or the putative CXCR7 scavenger receptor. The microfluidic study of NSC migration within stable chemokine concentration profiles provides quantitative analysis as well as new insight into the migratory mechanism underlying BDNF-induced chemotaxis towards CXCL12.

Sex-differential modulation of visceral pain by brain derived neurotrophic factor (BDNF) in rats

In spite of the fact that brain derived neurotrophic factor (BDNF) has been reported to be implicated in the development of visceral pain, it remains to be determined whether the role of BDNF in pain is gender dependent. The present study investigated the effect of BDNF on visceral pain in different gender rats. A model for visceral pain was established by intraperitoneal (i.p.) injection of acetic acid (AA) into Sprague–Dawley rats: males, females and females with an ovariectomy (OVX). The pain behavior index was assessed by counting the number of abdominal contractions for 60 min after i.p. injection of AA. Anti-BDNF antibody, or BDNF, was administered 1 h before the AA injection to examine the role of BDNF in visceral pain. After the AA injection, the number of abdominal contraction was dramatically increased in all rats but females showed more severe pain behavior than males. The higher sensitivity to AA-induced nocifensive response was attenuated by OVX. Pretreatment with anti-BDNF antibody significantly exacerbated the nocifensive response in males but attenuated it in females. While exogenous BDNF administration did not alter AA injection-induced nocifensive response in females, BDNF pretreatment attenuated the nocifensive response in males but exacerbated it in females with OVX. The present study suggests there is a gender dichotomy in visceral pain induced by AA injection. In addition, the modulation of visceral pain by BDNF is also sex dependent, i.e., BDNF facilitates the visceral pain in female rats but displays an opposite effect in male rats. Our results may have important implications in the management of clinical pain.

Effects of BDNF pretreatment against cerebral ischemia-reperfusion injury in gerbils

Objective To investigate the effects of brain-derived neurotrophic factor (BDNF) pretreatment on neuron apoptosis and the expression of Bcl-2 and Bax protein following global cerebral ischemia-reperfusion (I/R) injury in gerbils. Method Forty-eight mongolian gerbils were randomly divided into six groups in equal number (n = 8): normal control group (group C), ischemia-reperfusion group (group I/R) and four BDNF pretreatment groups according to various lengths of time from BDNF pretreatment to ischemia-reperfusion. The BDNF pretreat-ment was carried out in gerbils with lateral ventricular injection of BDNF 0.5μg 6 h, 12 h,24 h and 48 hours be-fore cerebral ischemia, and those gerbils assigned into PR6, PR12, PR24 and PR48 groups. The global cerebral is-chemia-reperfusion was induced by occlusion of bilateral common carotid arteries for 20 minutes and then the arter-ies were released for 24 hours reperfusion. The confirmation of global cerebra ischemia was evidenced by the ap-pearance of mydriasis and disappearance of light reflex and righting reflex. Twenty-four hours later, all gerbils including those of control group were sacrificed and a piece of tissue was taken from frontal cortex just behind the optic chiasma 1～4 millimeter for making paraffin sections. Neuron apoptosis was identified by using TUNEL and immunohischemistry was used to detect the expression of Bcl-2 and Bax protein in cerebral cortex. The data were analyzed by using analysis of variance. Results There were no apoptotic cells, and expression of Bcl-2 and Bax protein positive cells found in group C. Neuron apoptosis in brain cortex was detected in I/R group and BDNF pre-treatment groups. The indexes of neuron apoptosis in BDNF pretreatment groups were markedly lower than those in group I/R (P < 0.01). Compared with group I/R, the index of expression of Bcl-2 protein positive cells was in-creased significantly in BDNF pretreatment groups (P = 0.005), while the index of expression of Bax protein posi-tive cells were decreased significantly (P < 0.01 in all groups). Among 4 BDNF pretreatment group, the lowest apoptosis index and lowest of expression of Bax protein positive cells were found in PR6 and PR12 BDNF pretreat-ment groups (P = 0.0056 and 0.001, respectively). Conclusions Different time windows of BDNF pretreatment can decrease the neuron apoptosis in different degree, and protect brain against cerebral ischemia-reperfusion injury significantly. Among BDNF pretreatment time windows, pretreatment of 6 hours and 12 hours are the better ones.The mechanism of protection of BDNF pretreatment may be attributed to inducing Bcl-2 protein expressions and in-hibiting Bax protein expressions, and thereby inhibiting neuron apoptosis. Key words: Brain ischemia; Reperfusion; Brain-derived neurotrophic factor; Apoptosis; Apoptotic related-genes

Effects of brain-derived neurotrophic factor pretreatment on oxidative stress and neuron apoptosis following focal cerebral ischemia-reperfusion injury in rats

Objective To investigate the effects of different dose of brain-derived neurotrophic factor (BDNF) pretreatment on oxidative stress and neuron apoptosis following focal cerebral ischemia-reperfusion injuries in rats. Methods Focal cerebral ischemia-reperfusion model was established in rats by reversible left middle cerebral artery occlusion with filament. Left cerebral ischemia was for 2 hours and then with 72 hours reperfusion. BDNF was injected into the lateral ventricle before ischemia for 12 hours. The activities of brain tissue superoxide dismutase (SOD) were measured by the method of xanthine oxidase and the contents of brain tissue malondialdehyde (MDA) were determined by the method of thiobarbituric acid. Neuron apoptosis was identified by TUNEL and immunohischemistry was used to detect the expression of Bci-2 and Bax protein in cerebral cortex. Results Compared with group I/R, the activity of SOD was increased significantly but the content of MDA was decreased significantly in ischemia brain tissue in every BDNF pretreatment group( P<0.05 or P <0.01 ). The index of apoptotic neuron cells and the expression of Bax protein positive cells in BDNF pretreatment groups were decreased significantly ( P <0.01) while the expression of Bcl-2 protein positive cells was increased significantly ( P <0. 01 ) in ischemia brain cortex. In high dose of BDNF pretreatment group, the SOD activity and the expression of Bcl-2 protein were the highest but the content of MDA and the expression of Bax protein and the index of apoptotic neuron ceils were the lowest( P <0. 05 or P <0. 01 ). Conclusions Different dose of BDNF pretreatment could significantly reduce the oxidative stress and neuron apoptosis following focal cerebral ischemia-reperfusion, which has varying degree cerebral protection. The protection may be related to the dose of BDNF pretreatment. The mechanism of protection may be related that BDNF pretreatment can increase the content of endogenous anti- oxidation agents and regulate the different expression of apoptosis-related gene. Key words: Brain-derived neurotrolahic factor/PD; Brain ischemia/Bl; Reperfusion injury; Oxidative stress; Apoptosis; Neuron

Brain-derived neurotrophic factor enhances histamine-induced airway responses and changes levels of exhaled nitric oxide in guinea pigs in vivo

The neurotrophin brain-derived neurotrophic factor (BDNF) occurs in elevated levels during airway inflammation, including asthma and hypoxic lung injury, and has been suggested to be associated with airway hyperresponsiveness in these conditions. The aim of the present study was to examine whether airway responses to histamine challenge and levels of exhaled nitric oxide (NO) in vivo might be altered upon BDNF treatment. Pulmonary resistance, lung compliance, insufflation pressure, and levels of exhaled NO were measured in anaesthetized guinea pigs exposed to BDNF prior to challenge with histamine and with intact or inhibited endogenous NO production. BDNF pretreatment significantly enhanced histamine-evoked increase in pulmonary resistance and insufflation pressure, as well as the decrease in lung compliance. BDNF markedly accentuated the reduction in exhaled NO following histamine challenge. In animals with inhibited endogenous NO production BDNF induced a significantly earlier histamine-evoked increase in airway responses. The present data show that BDNF can induce an augmentation of histamine-evoked airway responses and reduce levels of NO in exhaled air in vivo. Endogenous NO seems to exert a braking action on BDNF-induced enhancement of airway responses and a reduced ability to release NO may be one mechanism for increased airway response during elevated BDNF levels. Taken together this indicates that BDNF may be of importance for airway hyperresponsiveness in vivo. The interaction between BDNF and airway NO formation, and its relation to airway responses, merit further investigation.

A BDNF infusion into the medial prefrontal cortex suppresses cocaine seeking in rats

The medial prefrontal cortex (mPFC) is critical for reinstatement of cocaine seeking and is the main source of brain-derived neurotrophic factor (BDNF) to striatal regions of the brain relapse circuitry. To test the hypothesis that BDNF in the mPFC regulates cocaine-seeking behavior, rats were trained to press a lever for cocaine infusions (0.2 mg/inf, 2 h/day) paired with light+tone conditioned stimulus (CS) presentations on 10 consecutive days. After the last self-administration session, rats received a single infusion of BDNF (0.75 microg/0.5 microL/side) into the mPFC; this manipulation produced protracted effects on cocaine-seeking behavior (non-reinforced lever pressing). BDNF pretreatment administered after the last session attenuated cocaine seeking 22 h later and, remarkably, it also blocked cocaine-induced suppression of phospho-extracellular-regulated kinase and elevated BDNF immunoreactivity in the nucleus accumbens. The same pretreatment also suppressed cocaine-seeking behavior elicited by response-contingent CS presentations after 6 days of forced abstinence or extinction training, as well as a cocaine challenge injection (10 mg/kg, i.p.) after extinction training. However, BDNF infused into the mPFC had no effect on food-seeking behavior. Furthermore, BDNF infused on the sixth day of abstinence failed to alter responding, suggesting that the regulatory influence of BDNF is time limited. The suppressive effects of BDNF infused into the mPFC on cocaine seeking indicate that BDNF regulates cortical pathways implicated in relapse to drug seeking and that corticostriatal BDNF adaptations during early abstinence diminish compulsive drug seeking.

Cellular levels of TrkB and MAPK in the neuroprotective role of BDNF for embryonic rat cortical neurons against hypoxia in vitro

Intrauterine asphyxia often results in neonatal loss or mental retardation. Brain-derived neurotrophic factor (BDNF) has been shown to be a protective agent against hypoxic damage to neurons. To understand the signaling mechanism underling the neuroprotective function of BDNF and to find therapeutic interventions for intrauterine asphyxia, we utilized an immunofluorescent technique to measure the intracellular levels of tyrosine kinase B (TrkB), phosphorylated TrkB, and the mitogen-activated protein kinase (MAPK) in the rat embryonic cortical neurons cultured in hypoxic conditions with and without BDNF pretreatment. The results showed that the fluorescent intensity of TrkB and phosphorylated TrkB in the cytoplasm and the fluorescent intensity of MARK in both cytoplasma and nucleus of the neurons were significantly increased in the presence of BDNF. The results indicate that the neuroprotective function of BDNF against hypoxia-induced neurotoxicity requires the participation of TrkB and is transduced via the Ras–MAPK signaling pathway.

BDNF Protects against Spatial Memory Deficits Following Neonatal Hypoxia-Ischemia

Hypoxic-ischemic (H-I) brain injury in the human perinatal period often leads to significant long-term neurobehavioral dysfunction in the cognitive and sensory-motor domains. Using a neonatal H-I injury model (unilateral carotid ligation followed by hypoxia) in postnatal day seven rats, previous studies have shown that neurotrophins, such as brain-derived neurotrophic factor (BDNF), can be protective against neural tissue loss. The present study explored potential relationships between neural protective and behavioral protective strategies in this neonatal H-I model by determining if neonatal H-I was associated with behavioral spatial learning and memory deficits and whether the neurotrophin BDNF was protective against both brain injury and spatial learning/memory dysfunction. Postnatal day seven rats received vehicle or BDNF pretreatments (intracerebroventricular injections) followed by H-I or sham treatments and then tested for spatial learning and memory on the simple place task in the Morris water maze from postnatal days 20 to 30, and their brains were histologically analyzed at 4 weeks following treatments. H-I rats with vehicle pretreatment displayed significant tissue loss in the hippocampus (including CA1 neurons), cortex, and striatum, as well as severe spatial memory deficits (e.g., short probe times). BDNF pretreatment resulted in significant protection against both H-I-induced brain tissue losses and spatial memory impairments. These findings indicate that unilateral H-I brain injury in a neonatal rodent model is associated with cognitive deficits, and that BDNF pretreatment is protective against both brain injury and spatial memory impairment.

Evidence that brain-derived neurotrophic factor neuroprotection is linked to its ability to reverse the NMDA-induced inactivation of protein kinase C in cortical neurons.

Several lines of evidence indicate that a rapid loss of neuronal protein kinase C (PKC) activity is a characteristic feature of cerebral ischemia and is a necessary step in the NMDA-induced death of cultured neurons. Exposing embryonic day 18 primary rat cortical neurons to 50 microM NMDA or 50 microM glutamate for 10 min caused approximately 80% cell death over the next 24 h, but excitotoxic death was largely averted, i.e., by 70-80%, in cells pretreated with brain-derived neurotrophic factor (BDNF). An 8-h preexposure to BDNF (50-100 ng/ml) maximally protected cortical cells from the effects of NMDA and glutamate, although the transient application of BDNF between 8 and 4 h before NMDA was equally protective. These effects of BDNF were abolished at supralethal, i.e., >100 microM, NMDA concentrations. It is significant that BDNF pretreatment prevented the inactivation of PKC in cortical cells normally seen 30 min to 2 h following lethal NMDA or glutamate exposure. This BDNF effect did not arise from changes in NMDA channel activity because neither whole-cell NMDA current amplitudes nor increases in intracellular free Ca2+ concentration were altered by the 8-h BDNF pretreatment. Furthermore, BDNF offered no neuroprotection to cells treated with the PKC inhibitors staurosporine (10-20 nM), calphostin C (1-2.5 microM), or GF-109203X (100 nM) at the time of NMDA addition. These results underscore the importance of PKC inactivation in glutamate-induced neuronal death. They also suggest that BDNF neuroprotection arises, at least in part, via its ability to block the mechanism by which pathophysiological Ca2+ influx through the NMDA receptor causes membrane PKC inactivation.

Brain derived neurotrophic factor and insulin like growth factor-1 attenuate upregulation of nitric oxide synthase and cell injury following trauma to the spinal cord. An immunohistochemical study in the rat.

The possibility that brain derived neurotrophic factor (BDNF) and insulin like growth factor-1 (IGF) induced neuroprotection is influenced by mechanisms involving nitric oxide was examined in a rat model of focal spinal cord injury. BDNF or IGF-I (0.1 microgram/10 microliters in phosphate buffer saline) was applied topically 30 min before injury on the exposed spinal cord followed by repeated doses of growth factors immediately before and 30 min after injury. Thereafter application of BDNF or IGF was carried out at every 1 h interval until sacrifice. Five hours after injury, the tissue pieces from the T9 segment were processed for nNOS immunostaining, edema and cell injury. Untreated injured rats showed a profound upregulation of nNOS which was most pronounced in the nerve cells of the ipsilateral side. A marked increase in the blood-spinal cord barrier (BSCB) permeability to 125I-albumin, water content and cell injury in these perifocal segments was also found. Pretreatment with BDNF and IGF significantly reduced the upregulation of nNOS in the spinal cord. This effect of the growth factors was most pronounced in the contralateral side. Rats treated with these neurotrophic factors showed much less signs of BSCB damage, edema and cell injury. These results suggest that BDNF and IGF pretreatment is neuroprotective in spinal cord injury and that these neurotrophic factors have the capacity to down regulate nNOS expression following trauma to the spinal cord. Our data provide new experimental evidences which suggest that BDNF and IGF may exert their potential neuroprotective effects probably via regulation of NOS activity.

Down-regulation of phosphatidylinositol response to BDNF and NT-3 in cultures of cortical neurons

The hydrolysis of phosphatidyl 4,5-biphosphate (PI), which is involved in the transduction mechanism of neurotransmitters and growth factors, is stimulated by brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) in primary cultures of fetal brain neurons. In the present study we sought to examine the effect of pretreatment with these factors on their acute stimulation capabilities and, furthermore, to substantiate that the effects of BDNF and NT-3 reflect actions on neurons rather than glial cells. Pretreatment with BNDF and NT-3 for 4 days followed by 1 day without growth factor abolished the effect of an acute stimulation with these factors. The growth factors were mutually effective so that BDNF pretreatment abolished the acute response to NT-3 and vice versa. In contrast, the effects of bFGF (basic fibroblast growth factor, a non-neurotrophin growth factor) also stimulating PI hydrolysis in these culture systems, were not reduced by neurotrophin pretreatment. Pretreatment with K-252b, at concentrations known to inhibit trk receptors, did not alter the acute stimulation of PI hydrolysis induced by the neurotrophins. PI hydrolysis stimulated by BDNF and NT-3 in cultures grown in presence of cytosine arabinoside C, containing > 95% neurons, was higher than in cultures containing non-neuronal cells, indicating that the neurotrophin stimulation occurs in neuronal cells. No stimulatory effect was detected in bFGF treated pure neuronal cultures. The findings suggest that prolonged exposure of responsive neurons to BDNF and NT-3 down-regulates their stimulatory effects on PI hydrolysis.