Increased Brain-derived Neurotrophic Factor mRNA Research Articles

Brain-derived Neurotrophic Factor-Tropomyosin-related Kinase B Signaling Contributes to Activity-dependent Changes in Synaptic Proteins

The ability of synapses to undergo changes in structure and function in response to alterations of neuronal activity is an essential property of neural circuits. One way that this is achieved is through global changes in the molecular composition of the synapse; however, it is not clear how these changes are coupled to the dynamics of neuronal activity. Here we found that, in cultured rat cortical neurons, bidirectional changes of neuronal activity led to corresponding alterations in the expression of brain-derived neurotrophic factor (BDNF) and phosphorylation of its receptor tropomyosin-related kinase B (TrkB), as well as in the level of synaptic proteins. Exogenous BDNF reversed changes in synaptic proteins induced by chronic activity blockade, while inhibiting Trk kinase activity or depleting endogenous BDNF abolished the concentration changes induced by chronic activity elevation. Both tetrodotoxin and bicuculline had significant, but opposite, effects on synaptic protein ubiquitination in a time-dependent manner. Furthermore, exogenous BDNF was sufficient to increase ubiquitination of synaptic proteins, whereas scavenging endogenous BDNF or inhibiting Trk kinase activity prevented the ubiquitination of synaptic proteins induced by chronic elevation of neuronal activity. Inhibiting the proteasome or blocking protein polyubiquitination mimicked the effect of tetrodotoxin on the levels of synaptic proteins and canceled the effects of BDNF. Our study indicates that BDNF-TrkB signaling acts upstream of the ubiquitin proteasome system, linking neuronal activity to protein turnover at the synapse.

Differential regional expression of brain-derived neurotrophic factor following olfactory fear learning

We examined brain-derived neurotrophic factor (BDNF) mRNA expression across the olfactory system following fear conditioning. Mice received 10 pairings of odor with footshock or equivalent unpaired odors and shocks. We found increased BDNF mRNA in animals receiving paired footshocks in the multiple regions examined including the posterior piriform cortex (PPC) and basolateral amygdala (BLA). This was in contrast to the unpaired and odor-alone treatments, where BDNF mRNA was increased in the olfactory bulb (OB) and anterior piriform cortex (APC) only, but not the higher olfactory areas. We propose that odor exposure increases expression of BDNF in the OB and APC while the PPC and BLA increase BDNF mRNA only when associative learning occurs.

Central κ-opioid receptor-mediated antidepressant-like effects of nor-Binaltorphimine: Behavioral and BDNF mRNA expression studies

κ-opioid receptor antagonists such as nor-Binaltorphimine (nor-BNI) have been shown to produce antidepressant-like behavioral effects in animal models of depression. The aim of this study was to investigate further the duration of centrally administered nor-BNI-induced antidepressant-like actions measured by both behavior and brain-derived neurotrophic factor (BDNF) gene expression. In addition, antagonist studies were conducted to determine the role of opioid receptor subtypes and the time course of nor-BNI's pharmacological actions. Antidepressant-like behavioral effects were measured by decreased immobility in the rat forced swim test and BDNF mRNA expression was determined by in situ hybridization. Centrally administered nor-BNI (20 μg, i.c.v.) decreased immobility and increased BDNF mRNA expression in the hippocampus on day 1, not on days 3–14, post-administration. Systemic administration of selective μ-, δ- and κ-opioid receptor antagonists did not block nor-BNI-induced antidepressant-like effects. In contrast, i.c.v. administration of nor-BNI 7 or 14 days earlier significantly blocked subsequent nor-BNI-induced decreased immobility and upregulation of BDNF mRNA expression. Although the duration of nor-BNI's antidepressant-like effects did not synchronize with that of its κ-opioid receptor antagonist effects, this study is the first to show that centrally administered nor-BNI, like most clinically used antidepressants, can upregulate BDNF mRNA expression in the rat hippocampus. These findings further demonstrate that central κ-opioid receptor mediates antidepressant-like effects of nor-BNI measured by both behavior and BDNF gene expression.

Differential effects of classical and atypical antipsychotic drugs on rotenone-induced neurotoxicity in PC12 cells

Although classical and atypical antipsychotics may have different effects against neurotoxicity, the underlying mechanisms remain to be elucidated. In the present study, we compared the atypical agents, risperidone (RIP), olanzapine (OLZ), and quetiapine (QTP), with the classical agent haloperidol (HAL) in reducing cytotoxicity induced by rotenone, a mitochondrial complex I inhibitor, in PC12 cells. We also determined whether there were differential effects of RIP and HAL on the expression of brain-derived neurotrophic factor (BDNF), signal transducers and activators of transcription-3 (STAT-3), and the immediate early gene c-fos, as well as intracellular levels of calcium. Exposure to 6 μM rotenone for 24 h resulted in a significant decrease in cell viability and apoptotic alteration. The rotenone-induced cytotoxicity was dose-dependently worsened by pretreatment with HAL, but significantly improved by the aforementioned atypical agents at low doses. Real-time PCR analysis revealed that HAL pretreatment significantly increased BDNF mRNA expression but did not alter c-fos and STAT-3 expression compared to rotenone-exposed cells. Unlike HAL, RIP pretreatment produced a significant elevation of all the three substance mRNA expression and the expression intensity was 2.6- to 4.6-fold greater than HAL. Pretreatment with RIP, but not HAL, also effectively prevented an elevation of intracellular levels of calcium provoked by rotenone. These results suggest that the protective effects of atypical antipsychotics are associated with a greater capacity to enhance pro-cell survival factors, therapeutic biomarker expression, and blockade of calcium influx. This may provide an alternative for explaining therapeutic advantages of atypical agents observed in clinical use.

S18986: A positive modulator of AMPA-receptors enhances ( S)-AMPA-mediated BDNF mRNA and protein expression in rat primary cortical neuronal cultures

The present study describes the effect of ( S)-2,3-dihydro-[3,4]cyclopentano-1,2,4-benzothiadiazine-1,1-dioxide (S18986), a positive allosteric modulator of the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors, on ( S)-AMPA-mediated increases in brain-derived neurotrophic factor (BDNF) mRNA and protein expression in rat primary cortical neuronal cultures. ( S)-AMPA (0.01–300 μM) induced a concentration-dependent increase in BDNF mRNA and protein expression (EC 50 = 7 μM) with maximal increases (50-fold) compared to untreated cultures observed between 5 and 12 h, whereas for cellular protein levels, maximal expression was detected at 24 h. S18986 alone (≤ 300 μM) failed to increase basal BDNF expression. However, S18986 (300 μM) in the presence of increasing concentrations of ( S)-AMPA maximally enhanced AMPA-induced expression of BDNF mRNA and protein levels (3–5-fold). S18986 (100–300 μM) potentiated BDNF mRNA induced by 3 μM ( S)-AMPA (2–3-fold). Under similar conditions, the AMPA allosteric modulator cyclothiazide induced a potent stimulation of ( S)-AMPA-mediated BDNF expression (40-fold; EC 50 = 18 μM), whereas IDRA-21 was inactive. Kinetic studies indicated that S18986 (300 μM) in the presence of 3 μM ( S)-AMPA was capable of enhancing BDNF mRNA levels for up to 25 h, compared to 3 μM ( S)-AMPA alone. On the other hand, S18986 only partially enhanced kainate-mediated expression of BDNF mRNA, but failed to significantly enhance N-methyl- d-aspartate-stimulated BDNF expression levels. In support of these observations, the competitive AMPA receptor antagonist NBQX (1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide) but not the selective NMDA-receptor antagonist, (+)-MK-801 [(5R,10 S)-(+)-5-methyl-10,11-dihydro-5 H-dibenzo[ a, d]cyclohepten-5,10-imine], abrogated S18986-induced effects on BDNF expression. S18986-mediated enhancement of ( S)-AMPA-evoked BDNF protein expression was markedly attenuated in Ca 2+-free culture conditions. Furthermore, from a series of kinase inhibitors only the Calmodulin–Kinase II/IV inhibitor (KN-62, 25 μM) significantly inhibited (− 85%, P < 0.001) AMPA + S18986 stimulated expression of BDNF mRNA. The present study supports the observations that AMPA receptor allosteric modulators can enhance the expression of BDNF mRNA and protein expression via the AMPA receptor in cultured primary neurones. Consequently, the long-term elevation of endogenous BDNF expression by pharmacological intervention with this class of compounds represents a potentially promising therapeutic approach for behavioural disorders implicating cognitive deficits.

Running exercise- and antidepressant-induced increases in growth and survival-associated signaling molecules are IGF-dependent

It is known that physical exercise increases hippocampal brain-derived neurotrophic factor (BDNF) mRNA and protein, as well as the expression of several pro-survival signaling proteins and that many of these effects depend on the uptake of peripheral insulin-like growth factor-1 (IGF-1) into the CNS. Because treatment with antidepressants has similar effects upon neurotrophin expression, we investigated whether antidepressant-induced BDNF changes also depend on IGF-1 uptake, as well as whether IGF-1 plays a role in the exercise/antidepressant-induced expression of molecules associated with plasticity/growth (GAP-43, SCG-10) and the intracellular activation of molecules associated with neuronal survival (Akt, ERK1/2). We evaluated the effects of a well known monoamine oxidase inhibitor, tranylcypromine, on BDNF mRNA and protein levels and phospho-Akt and phospho-ERK1/2 immunoreactivity, both with and without systemic blockade of IGF-1 uptake through the use of an antiserum raised against IGF-1. Anti-IGF-1 reversed the increase in BDNF mRNA and protein elicited by exercise as well as tranylcypromine. Exercise also significantly enhanced transcription of axon growth protein, GAP-43, an effect that was also evidenced to be IGF-1-dependent. The combination of exercise-plus-tranylcypromine also increased several cell survival signaling measures, but the BDNF changes associated with the combination treatment appeared to be independent of IGF-1 uptake. Together, these results indicate that the uptake of peripheral IGF-1 in the CNS is essential for antidepressant- as well as exercise-induced enhancement in hippocampal BDNF expression and thus, enhanced hippocampal neuronal survival and plasticity.

Expression of brain derived neurotrophic factor, activity-regulated cytoskeleton protein mRNA, and enhancement of adult hippocampal neurogenesis in rats after sub-chronic and chronic treatment with the triple monoamine re-uptake inhibitor tesofensine

The changes of gene expression resulting from long-term exposure to monoamine antidepressant drugs in experimental animals are key to understanding the mechanisms of action of this class of drugs in man. Many of these genes and their products are either relevant biomarkers or directly involved in structural changes that are perhaps necessary for the antidepressant effect. Tesofensine is a novel triple monoamine reuptake inhibitor that acts to increase noradrenaline, serotonin, and dopamine neurotransmission. This study was undertaken to examine the effect of sub-chronic (5 days) and chronic (14 days) administration of Tesofensine on the expression of brain derived neurotrophic factor ( BDNF) and activity-regulated cytoskeleton protein ( Arc) in the rat hippocampus. Furthermore, hippocampi from the same animals were used to investigate the effect on cell proliferation by means of Ki-67- and NeuroD-immunoreactivity. We find that chronic, but not sub-chronic treatment with Tesofensine increases BDNF mRNA in the CA3 region of the hippocampus (35%), and Arc mRNA in the CA1 of the hippocampus (65%). Furthermore, the number of Ki-67- and neuroD-positive cells increased after chronic, but not sub-chronic treatment. This study shows that Tesofensine enhances hippocampal gene expression and new cell formation indicative for an antidepressant potential of this novel drug substance.

Progesterone modulates brain-derived neurotrophic factor and choline acetyltransferase in degenerating Wobbler motoneurons

Progesterone (PROG) shows neuroprotective effects in nervous system diseases. The Wobbler mouse, a model of motoneuron degeneration, suffers a mutation of the Vsp154 gene on chromosome 11 leading to motoneuron vacuolation and astrocytosis of the spinal cord. Previous work has demonstrated beneficial effects of PROG in the Wobbler mouse. As an extension of this work, we now studied steroid effects on neuronal brain-derived neurotrophic factor (BDNF) mRNA and protein, on choline acetyltransferase (ChAT) immunoreactivity (IR) and activity in the spinal cord, and on recovery of muscle atrophy. Wobbler mice received implants of PROG pellets (20 mg) at 6 and 10 weeks of age and were killed at 14 weeks. In situ hybridization for BDNF mRNA demonstrated that grain density in large (> 600 μm 2) and medium size (< 600 μm 2) ventral horn neurons was decreased in untreated Wobblers, whereas PROG treatment increased BDNF mRNA in both neuronal types. PROG also induced a subcellular redistribution of BDNF protein, which in controls and steroid-naive Wobblers showed a predominant perinuclear and nucleolar location, whereas after PROG treatment, it was detected in cytoplasmic aggregates. ChAT activity was reduced by 55.3% in muscles of untreated Wobbler mice, whereas a significant increment was obtained after PROG treatment. Wobblers also showed reduced number of ChAT positive motoneurons, but this number was restored to normal by PROG. Finally, the pronounced biceps atrophy of steroid-naive Wobbler mice was slightly but significantly increased by PROG-treatment. Considering the important role played by neurotrophins on neuronal function, changes in BDNF might be part of the PROG activated-pathways to provide neuroprotection and re-establish neurotransmission and neuromuscular function in this degeneration model.

Immobilization Stress Induces BDNF in Rat Submandibular Glands

Brain-derived neurotrophic factor (BDNF) promotes survival and differentiation of the cells of the central and peripheral nervous systems. BDNF has been identified in non-neural tissue, including the heart, lung, platelets, lymphocytes, and lacrimal glands. Immobilization stress modifies BDNF mRNA expression in some organs. The present study examines the effect of immobilization stress on BDNF, and its receptor TrkB, in male rat submandibular glands. Increased BDNF mRNA and protein expression were observed in duct cells as a result of immobilization stress, as demonstrated by real-time PCR, Western blot, immunohistochemistry, and analysis by microdissection. TrkB mRNA was not detected in salivary gland tissue, or oral or esophageal mucosa, by RT-PCR. Rat submandibular gland was thus identified as an organ which expresses BDNF. Furthermore, the results of this study suggest that increased salivary BDNF expression occurs following immobilization stress.

Endogenous opioids upregulate brain‐derived neurotrophic factor mRNA through δ‐ and µ‐opioid receptors independent of antidepressant‐like effects

Systemic administration of delta-opioid receptor (DOR) agonists decreases immobility in the forced swim test (FST) and increases brain-derived neurotrophic factor (BDNF) mRNA expression in rats, indicating that DOR agonists may have antidepressant-like effects. The aim of this study was to investigate the effects of central administration of endogenous opioid peptides on behavior in the FST and on brain BDNF mRNA expression in rats. Effects of endogenous opioids were compared with those produced by intracerebroventricular administration of a selective non-peptidic DOR agonist (+)BW373U86. Antidepressant-like effects were measured by decreased immobility in the FST. BDNF mRNA expression was determined by in situ hybridization. Centrally administered (+)BW373U86 decreased immobility and increased BDNF mRNA expression in the frontal cortex through a DOR-mediated mechanism, because these effects were blocked by the DOR antagonist naltrindole, but not by the micro-opioid receptor (MOR) antagonist naltrexone (NTX) or the kappa-opioid receptor antagonist nor-binaltorphimine. Of all the endogenous opioids tested, only leu- and met-enkephalin produced behavioral effects like those of (+)BW373U86 in the FST. Unlike (+)BW373U86, the enkephalins upregulated BDNF mRNA expression in the hippocampus through DOR- and MOR-mediated mechanisms. beta-Endorphin, endomorphin-1 and endomorphin-2 significantly increased BDNF mRNA levels in the frontal cortex, hippocampus and amygdala without reducing immobility; and most of these effects were reversed by NTX. This study is the first to provide evidence that endogenous opioids can upregulate BDNF mRNA expression through the DOR and MOR, and that leu- and met-enkephalin have similar pharmacological profiles to synthetic DOR agonists in producing antidepressant-like effects.

Depolarization promotes survival of ciliary ganglion neurons by BDNF-dependent and -independent mechanisms

Membrane activity upregulates brain derived neurotrophic factor (BDNF) expression to coordinately support neuronal survival in many systems. In parasympathetic ciliary ganglion (CG) neurons, activity mimicked by KCl depolarization provides nearly full trophic support. While BDNF has been considered unable to influence CG neuronal survival, we now document its expression during CG development and show that low concentrations do support survival via high-affinity TrkB receptors. Furthermore, a contribution of BDNF to activity-induced trophic support was demonstrated by showing that KCl depolarization increased BDNF mRNA and protein in, and release of BDNF from, CG neuron cultures. Application of anti-BDNF blocking antibody or mitogen activated protein kinase (MAPK) kinase inhibitor, attenuated depolarization-supported survival, implicating canonical BDNF/TrkB signaling. Ca 2+-Calmodulin kinase II (CaMKII) was also required since its inhibition combined with anti-BDNF or MAPK kinase inhibitor abolished or greatly reduced the trophic effects of depolarization. Membrane activity may thus support CG neuronal survival both by stimulating release of BDNF that binds high-affinity TrkB receptors to activate MAPK and by recruiting CaMKII. This mechanism could have relevance late in development in vivo as ganglionic transmission and the effectiveness of BDNF over other growth factors both increase.

Peptidic delta opioid receptor agonists produce antidepressant-like effects in the forced swim test and regulate BDNF mRNA expression in rats

Systemically active, nonpeptidic delta opioid receptor agonists have been shown to produce antidepressant and anxiolytic effects in animal models in rodents. In addition, delta agonists have been shown to increase expression of brain-derived neurotrophic factor (BDNF) mRNA, an effect of some antidepressants, which may be important for the clinical efficacy of antidepressant drugs. The present study examined whether a variety of peptidic delta agonists, DPDPE, JOM-13, a systemically active derivative of DPDPE, deltorphin II, and H-Dmt-Tic-NH-CH 2-Bid could produce convulsions and antidepressant-like effects in the forced swim test. In addition, some of these compounds were examined for their influence on BDNF mRNA expression. All four agonists dose-dependently decreased immobility in the forced swim test, indicating an antidepressant-like effect. Only JOM-13 produced convulsions at doses required for antidepressant-like effects. In addition, DPDPE increased BDNF mRNA expression, as measured by in situ hybridization, in the frontal cortex. The antidepressant-like effect of the agonists in the forced swim test and the increase in BDNF mRNA expression produced by DPDPE were blocked by the delta antagonist naltrindole. Therefore, activation of the delta receptor by centrally administered peptidic agonists and intravenously administered JOM-13 produces behavioral antidepressant-like effects without producing convulsions, and some peptidic agonists can increase BDNF mRNA expression, however, not as consistently as the systemically active nonpeptidic agonists.

Maternal swimming during pregnancy enhances short-term memory and neurogenesis in the hippocampus of rat pups

In the present study, the effects of maternal swimming during pregnancy on the short-term memory ability, hippocampal neurogenesis, and brain-derived neurotrophic factor (BDNF) mRNA expression of rat pups were investigated. After confirming their pregnancy, the pregnant rats were divided into two groups: the control group and the swimming group. From the 15th day of pregnancy until delivery, pregnant rats were subcutaneously injected with 100 mg/kg of 5-bromo-2′-deoxyuridine (BrdU) once a day at 30 min before the starting of swimming exercise. Pregnant rats in the swimming group were forced to swim for 10 min once a day until delivery. On the 21 days after birth, the rat pups were trained in a step-down avoidance test. The latency time of the step-down avoidance task was determined on the 28 days after birth in order to evaluate the short-term memory ability of pups. On the 29 days after birth, the rat pups' brains were removed, and BrdU immunohistochemistry for the detection of neurogenesis and reverse transcription-polymerase chain reaction (RT-PCR) for the detection of BDNF mRNA expression were then performed. The rat pups born from the maternal rats that performed swimming during pregnancy showed significantly increased BDNF mRNA expression, enhanced hippocampal neurogenesis, and improved short-term memory capability. The present results have clearly shown that maternal swimming by rats during pregnancy enhances the memory of the rats' offspring by increasing neurogenesis. Our present study provides the evidence that maternal exercise during the gestational period may enhance the brain functions of the mothers' offspring.

The role of CaMKII in BDNF-mediated neuroprotection of retinal ganglion cells (RGC-5)

The purpose of the study is to determine if expression or secretion of brain-derived neurotrophic factor (BDNF) in retinal ganglion cells (RGC-5) is mediated by NFκB or Ca2+/calmodulin-dependent protein kinase II (CaMKII). RGC-5 cells were exposed to 1 mM glutamate for various periods of time, in the presence or absence of prospective regulatory molecules. BDNF mRNA and protein expression were assessed with the aid of real-time PCR and immunoblots, respectively, and BDNF secretion was determined by ELISA. The NFκB inhibitor (TLCK and PTD-p65), or a specific CaMKII inhibitor (m-AIP), was used to study association of NFκB or CaMKII with BDNF expression/secretion in RGC-5 cells. Glutamate stimulated a transient increase in BDNF mRNA and protein in RGC-5 cells, and also stimulated an early release of BDNF into the culture media. Neutralizing the BDNF or blocking the TrkB receptor enhanced the glutamate-induced cytotoxicity. NFκB nuclear translocation was revealed in response to glutamate treatment. Application of TLCK or PTD-p65 inhibited the glutamate-induced BDNF expression and secretion. Inhibition of CaMKII by m-AIP did not affect expression but significantly enhanced the release of BDNF from glutamate challenged cells. Our data suggest that glutamate treatment may stimulate expression of BDNF in RGC-5 cells through NFκB activation. A novel mechanism for neuroprotection is proposed for the CaMKII inhibitor, AIP, which appears to protect RGC-5 cells from cytotoxicity by enhancing the release of BDNF from glutamate challenged cells.

Chronic administration of the delta opioid receptor agonist (+)BW373U86 and antidepressants on behavior in the forced swim test and BDNF mRNA expression in rats

Selective delta opioid receptor agonists have been shown to produce antidepressant-like behavioral effects and increase brain-derived neurotrophic factor (BDNF) mRNA expression when given acutely, but the chronic effects of delta agonists have been less well characterized. The present study examined the effects of chronic exposure to the delta agonist (+)BW373U86 (BW) on antidepressant-like behavior in the forced swim test and on BDNF mRNA expression in comparison to chronic treatment with the antidepressants fluoxetine, desipramine, bupropion, and tranylcypromine. Sprague-Dawley rats were treated chronic ally with one of the above treatments and were tested for antidepressant effects in the forced swim test, and assayed for BDNF mRNA expression by in situ hybridization. Acute administration of 10 mg/kg BW produced a significant antidepressant-like effect in the forced swim test, while chronic (8- or 21-day) BW administration did not produce a significant antidepressant-like effect. When 10 mg/kg BW was administered for 8 days, it produced a significant increase in BDNF mRNA expression in the frontal cortex, while having no effect on BDNF expression when given for 21 days. Chronic bupropion and desipramine significantly decreased BDNF expression in the dentate gyrus of the hippocampus, while fluoxetine had no effect in any brain region. Chronic tranylcypromine produced a significant increase in BDNF expression in the CA1 region of the hippocampus. Chronic exposure to BW produces tolerance to most effects, although at differential rates. In addition, increased BDNF mRNA expression does not appear to be a common effect of chronic administration of various antidepressants.

Chronic treatment with fluoxetine up-regulates cellular BDNF mRNA expression in rat dopaminergic regions

During the last few years several studies have highlighted the possibility that major depression can be characterized by a general reduction in brain plasticity and an increased vulnerability under challenging situations. Such dysfunction may be the consequence of reduced expression and function of proteins important for neuroplasticity such as brain-derived neurotrophic factor (BDNF). On this basis, by using a sensitive non-radioactive in-situ hybridization, we evaluated the effects of a chronic treatment with fluoxetine on BDNF expression within rat dopaminergic regions. In fact, besides the well-established role of the hippocampus, increasing evidence indicates that other brain regions may be involved in the pathophysiology of depression and consequently be relevant for the therapeutic action of antidepressant drugs. Our results indicate that 3 wk of fluoxetine administration up-regulates BDNF mRNA levels selectively within structures belonging to the meso-cortico-limbic pathway. The expression of the neurotrophin is significantly increased in the ventral tegmental area, prefrontal cortex, and shell region of the nucleus accumbens, whereas no changes were detected in the substantia nigra and striatum. Moreover, in agreement with previous studies, fluoxetine increased BDNF mRNA levels in the hippocampus, an effect that was limited to the cell bodies without any change in its dendritic targeting. These data show that chronic treatment with fluoxetine increases BDNF gene expression not only in limbic areas but also in dopaminergic regions, suggesting that such an effect may contribute to improve the function of the dopaminergic system in depressed subjects.

Expression of c- fos and BDNF mRNA in subregions of the prefrontal cortex of male and female rats after acute uncontrollable stress

Women exhibit higher lifetime prevalences of stress-related disorders than men. These disorders have been associated with changes in prefrontal cortex structure and function. Here, we examine the effects of acute inescapable stress, an animal model of behavioral depression and post-traumatic stress disorder, on plasma corticosterone (CORT) and on c- fos mRNA and brain-derived neurotrophic factor (BDNF) mRNA in regions of the prefrontal and frontal cortex in male and cycling female rats. Inescapable stress consisted of 100 1 mA tailshocks, and no-stress controls remained in their home cages. Rats were sacrificed immediately (0 min) or 60 min after termination of the stressor. CORT levels were increased at both 0 and 60 min post-stress termination relative to controls, and the increase was greater in females at both time points. c- fos mRNA expression increased at 0 min in prefrontal cortical regions, but this increase was greater in males than estrus and proestrus females. At 60 min, c- fos mRNA levels were lower than at 0 min in males but not females. No correlations between CORT and c- fos mRNA levels in prefrontal regions were observed in females in the stress groups, but significant correlations were observed in males in several prefrontal regions. BDNF mRNA expression was greater in control females than control males. Inescapable stress increased BDNF mRNA expression at 0 but not 60 min in males, but there was no effect of inescapable stress on BDNF mRNA in females. These results reveal sex differences in inescapable stress-induced gene expression that may have implications for differences in vulnerability to stress-related disorders.

Estrogen Increases Nociception-Evoked Brain-Derived Neurotrophic Factor Gene Expression in the Female Rat

Chronic pain induces plastic changes in nociceptive sensory pathways, and is often accompanied and exacerbated by depression. Estrogen can influence nociceptive sensory processing, but the molecular mechanisms underlying sex differences in pain remain unclear. Brain-derived neurotrophic factor (BDNF) may orchestrate changes occurring during persistent pain or depression by increasing spinal nociceptive signaling and altering neuronal growth in higher brain structures. This study addressed whether estrogen regulates BDNF gene expression in central systems associated with nociceptive processing and/or affective state, which may in turn influence sex differences in pain sensitivity. Thus, BDNF gene expression was quantified in intact female rats in proestrus and diestrus, and in ovariectomized (OVX) rats with or without 17β-estradiol (E₂) replacement following intraplantar injection of dilute formalin as an inflammatory nociceptive stimulus. Twenty-four hours after formalin injection, central nervous system (CNS) tissues were removed and solution hybridization-nuclease protection assays used to quantify BDNF mRNA levels. Results demonstrated that estrogen replacement increased BDNF mRNA levels in the hippocampus, cortex and spinal cord. Cortical BDNF mRNA levels were significantly decreased by nociception, in the hippocampus this decrease was only evident in estrogen-treated rats. Spinal BDNF expression was robustly increased by nociception. The pain-evoked up-regulation of spinal BDNF gene expression was significantly potentiated by concomitant estrogen treatment. Results demonstrate that BDNF gene expression in certain brain structures is inhibited by inflammatory pain, yet estrogen may enhance central nervous system sensitization associated with sensory processing. Since alterations in BDNF gene expression in higher brain centers may be relevant to cognitive changes that occur in recurrent depression, these results may provide insights into the coincidence of chronic pain and depression.

Erythropoietin protects primary hippocampal neurons increasing the expression of brain‐derived neurotrophic factor

Erythropoietin, the principal regulator of erythroids progenitor cells, also promotes neuronal survival. Using primary cultures of rat hippocampal neurons, we investigated whether erythropoietin could mediate neuroprotection favouring the transcription of brain-derived neurotrophic factor (BDNF). Erythropoietin 2.7 nm reduced by approximately 50% the neuronal death triggered by the prototypic neurotoxicant trimethyltin (TMT) and time-dependently induced BDNF mRNA. This effect resulted in an increased production of biologically active BDNF, which led to a sustained activation of the specific BDNF receptor tyrosine kinase B (TrkB). Reduction of TMT-induced neuronal death by erythropoietin was specifically prevented by a neutralizing anti-BDNF antibody (15 microg/mL), indicating the involvement of this neurotrophin in erythropoietin neuroprotective effect. Intracerebroventricular administration of erythropoietin in mice significantly increases BDNF mRNA expression in brain, supporting the idea of the involvement of this neurotrophin in erythropoietin action within the CNS. BDNF expression in neuronal cells is induced by activation of voltage Ca(2+)-channels and recruitment of Ca(2+)-sensitive transcription factors. Consistently, 2.7 nm erythropoietin increased intracellular Ca(2+) in 5 min and cAMP response element binding protein (CREB) phosphorylation at Ser 133 in 30 min. Both effects were abolished by 1 microm nitrendipine, a selective blocker of L-type voltage Ca(2+)-channels. These data demonstrate that erythropoietin activates the CREB transcription pathway and increases BDNF expression and production, which contributes to erythropoietin mediated neuroprotection.

A single cocaine exposure increases BDNF and D3 receptor expression: implications for drug-conditioning

Environmental stimuli associated with a single cocaine exposure acquire long-lasting motivational properties that are able to induce relapse. We measured Brain-derived neurotrophic factor (BDNF) and dopamine D3 receptor (Drd3) expressions in rat brain regions that have been involved in drug-conditioning. Acute cocaine produced a transient increase in BDNF mRNA in the prefrontal cortex, associated with a long-lasting increase in drd3 mRNA, and a delayed and long-lasting increase in Drd3 protein in the nucleus accumbens. Methamphetamine and morphine, two drugs known to easily induce drug-conditioning, also markedly elevated BDNF mRNA. Nicotine had more limited effects. Abused drugs increase acutely BDNF expression, which leads to subsequent long-lasting elevation of Drd3 in the nucleus accumbens that may facilitate responding to drug-associated stimuli.