Microinfusion of a corticotrophin-releasing hormone receptor 1 antisense oligodeoxynucleotide into the dorsal hippocampus attenuates stress responses at specific times after stress exposure

Corticotrophin-releasing hormone (CRH) plays a key role in the adjustment of neuroendocrine and behavioural adaptations to stress. Dysregulation in CRH systems has been implicated in a variety of stress-related psychiatric disorders such as post-traumatic stress disorder (PTSD). The present study examined the relationship between stress-induced PTSD-like behavioural response patterns and levels of CRH, CRH receptor (CHR-R)1 and phosphorylated extracellular signal-regulated kinase (pERK1/2) in the rat hippocampus subregions. The effects of pharmacological manipulations on behavioural, physiological and response patterns of brain-derived neurotrophic factor (BDNF) and pERK1/2 expression using a CRH receptor (CRH-R)1-antisense oligodeoxynucleotide (CRH-R1-ASODN) were evaluated. CRH and CRH-R1 mRNA and pERK1/2 protein levels were assessed in the hippocampus subregions 7 days after exposure to predator scent stress (PSS). The effects of CRH-ASODN versus CRH-Scrambled-ODN microinfusion to the dorsal hippocampus either 1 h or 48 h post-exposure on behavioural tests (elevated plus maze and acoustic startle response) were evaluated 7 days later, 14 days after PSS exposure. Localised brain expression of BDNF and ERK1/2 was subsequently assessed. All data were analysed in relation to individual behaviour patterns. A distinct pattern associated with extreme behavioural response (EBR) was revealed in the bioassay of behavioural study subjects, classified according to their individual patterns of behavioural response at 7 days. These EBR individuals displayed significantly higher CRH and CRH-R1 mRNA levels in the CA1 and CA3 areas, mediating down-regulation of pERK1/2 protein levels. Microinfusion of a CRH-R1-ASODN into the dorsal hippocampus 48 h after stress exposure, although not immediately after exposure (1 h), significantly reduced behavioural disruption and was associated with concomitant up-regulation of BDNF and pERK1/2 protein levels compared to CRH-R1-Scrambled -ODN controls. CRH/CRH-R1 is actively involved in the neurobiological response to predator scent stress processes and thus warrants further study as a potential therapeutic avenue for the treatment of anxiety-related disorders.     

顽固性颞叶癫痫患者海马或颞叶BDNF及其受体TrkB的测定

目的检测脑源性神经营养因子(BDNF)及其受体酪氨酸激酶B受体(TrkB)在难治性颞叶癫痫(TLE)患者颞叶和/或海马中的含量,探讨其在癫痫发病机制中的作用。方法选取经手术治疗的82例难治性TLE患者术中切除的海马或颞叶脑组织,用免疫组化方法对BDNF及其受体TrkB含量进行检测,并与11例对照进行比较。结果在难治性TLE患者中,BDNF在颞叶和海马中含量明显增加(分别P<0.05,P<0.01),且海马中含量明显高于颞叶(P<0.01);TrkB在颞叶和海马中含量显著增加(P<0.01),且海马中含量高于颞叶(P<0.05)。结论难治性TLE患者海马和颞叶中BDNF和TrkB含量增高,可能在癫痫发生、发展中起重要作用。     

Differential expression of molecular markers of synaptic plasticity in the hippocampus, prefrontal cortex, and amygdala in response to spatial learning, predator exposure, and stress-induced amnesia

We have studied the effects of spatial learning and predator stress-induced amnesia on the expression of calcium/calmodulin-dependent protein kinase II (CaMKII), brain-derived neurotrophic factor (BDNF) and calcineurin in the hippocampus, basolateral amygdala (BLA), and medial prefrontal cortex (mPFC). Adult male rats were given a single training session in the radial-arm water maze (RAWM) composed of 12 trials followed by a 30-min delay period, during which rats were either returned to their home cages or given inescapable exposure to a cat. Immediately following the 30-min delay period, the rats were given a single test trial in the RAWM to assess their memory for the hidden platform location. Under control (no stress) conditions, rats exhibited intact spatial memory and an increase in phosphorylated CaMKII (p-CaMKII), total CaMKII, and BDNF in dorsal CA1. Under stress conditions, rats exhibited impaired spatial memory and a suppression of all measured markers of molecular plasticity in dorsal CA1. The molecular profiles observed in the BLA, mPFC, and ventral CA1 were markedly different from those observed in dorsal CA1. Stress exposure increased p-CaMKII in the BLA, decreased p-CaMKII in the mPFC, and had no effect on any of the markers of molecular plasticity in ventral CA1. These findings provide novel observations regarding rapidly induced changes in the expression of molecular plasticity in response to spatial learning, predator exposure, and stress-induced amnesia in brainregions involved in different aspects of memory processing.     

Ethanol exposure enhances cell death in the developing cerebral cortex: role of brain-derived neurotrophic factor and its signaling pathways

Exposure to ethanol during fetal development induces brain damage, causing cell loss in several brain areas and affecting synaptic connections. Because neurotrophin signaling plays an important role in neuronal survival and differentiation, we have investigated the effect of ethanol exposure on cell death in the developing cerebral cortex and whether this effect correlates with alterations in brain-derived neurotrophic factor (BDNF) levels, expression of its receptors, TrkB, and its signaling. We report that chronic ethanol intake during gestation and lactation enhances natural cell death and induces cell necrosis, decreases BDNF levels, and increases the ratio of the truncated to full-length TrkB mRNA receptors during postnatal developing cerebral cortex. Furthermore, we provide evidence that during brain development BDNF activates the extracellular signal-regulated kinases (ERK1 and ERK2) and the phosphoinoside-3-kinase (PI-3-K/Akt) pathways. However, BDNF-induced cell signaling throughout the above-mentioned survival pathways is significantly reduced by ethanol exposure. These findings suggest that ethanol-induced alterations in BDNF availability and in its receptor function might impair intracellular signaling pathways involved in cell survival, growth, and differentiation, leading to enhanced natural cell death during cerebral cortex development.     

The development of behavioral and endocrine abnormalities in rats after repeated exposure to direct and indirect stress

The present study compared the effects of direct and indirect stress on the behavior and hypothalamic-pituitary-adrenal axis of rats. Animals were placed in a two compartment box. In one compartment the direct stressed rat was subjected to electric foot shocks randomly applied for 10 minutes (0.5 mA of 1 s duration). In the adjacent compartment, the indirect stressed rats witnessed the application of these electric foot shocks. Our data showed substantial behavioral changes in the open field test, but limited effects in the elevated plus maze. The findings suggested that single and repeated stress exposure may have different consequences, that the effects of stress exposure may develop over time and persist for an extended period, and that both direct and indirect stressed rats displayed a hyposensitive HPA axis following acute restraint stress. Overall our observations moderately indicate direct exposure to elicit behavioral changes, and both direct and indirect exposure to stress to result in aberrations within the neuroendocrine system. With additional development our stress models may be considered for studying the complex interrelationship between an external stressor, and the experience of the organism.     

The role of genetic variability in the SLC6A4, BDNF and GABRA6 genes in anxiety-related traits

Arias B, Aguilera M, Moya J, Sáiz PA, Villa H, Ibáñez MI, García‐Portillo MP, Bobes J, Ortet G, Fañanás L. The role of genetic variability in the SLC6A4, BDNF and GABRA6 genes in anxiety‐related traits. Objective: The aims of this study were to test the individual association of the serotonin transporter gene (SLC6A4), the brain‐derived neurotrophic factor gene (BDNF) and the GABA_Aα₆ receptor subunit gene (GABRA6) with anxiety‐related traits and to explore putative gene–gene interactions in a Spanish healthy sample. Method: A sample of 937 individuals from the general population completed the Temperament and Character Inventory questionnaire to explore Harm Avoidance (HA) dimension; a subsample of 553 individuals also filled in the Big Five Questionnaire to explore the Neuroticism dimension. The whole sample was genotyped for the 5‐HTTLPR polymorphism (SLC6A4 gene), the Val66Met polymorphism (BDNF gene) and the T1521C polymorphism (GABRA6 gene). Results: Homozygous individuals for the T allele of the T1512C polymorphism presented slightly higher scores for HA than C allele carriers (F = 2.96, P = 0.019). In addition, there was a significant gene–gene interaction on HA between the 5‐HTTLPR and Val66Met polymorphisms (F = 3.4, P = 0.009). Conclusion: GABRA6 emerges as a candidate gene involved in the variability of HA. The effect of a significant gene–gene interaction between the SLC6A4 and BDNF genes on HA could explain part of the genetic basis underlying anxiety‐related traits.     

Transforming growth factor-beta1 enhances expression of brain-derived neurotrophic factor and its receptor, TrkB, in neurons cultured from rat cerebral cortex.

The effects of transforming growth factor (TGF)-beta1 on expression of brain-derived neurotrophic factor (BDNF) and its high-affinity receptor, TrkB, in neurons cultured from the cerebral cortex of 18-day-old embryonic rats were examined. BDNF mRNA was significantly increased from 24-48 hr after the TGF-beta1 treatment over 20 ng/ml. Accumulation of BDNF protein in the culture medium was also potentiated by TGF-beta1, although the intracellular content of BDNF was nearly unchanged. The enhancement of BDNF mRNA expression was suppressed by the co-presence of decorin, a small TGF-beta-binding proteoglycan that inhibits the biological activities of TGF-betas. mRNA expression of full-length TrkB, the bioactive high-affinity receptor for BDNF, was also upregulated after treatment with TGF-beta1. These observations suggest that: 1) TGF-beta1 potentiates BDNF/TrkB autocrine or local paracrine system; and 2) the neurotrophic activity of TGF-beta1 is partly responsible for the BDNF induced by TGF-beta1 itself. To test this latter possibility, we examined the neuronal survival activity of TGF-beta1 with or without K252a, a selective inhibitor of Trk family tyrosine kinases. TGF-beta1 significantly enhanced neuronal survival, but the co-presence of K252a completely suppressed the activity, demonstrating the involvement of Trk receptor signaling in TGF-beta1-mediated neuronal survival in cultured rat cortical neurons. These results seem to be in line with recent findings by other investigators that some neurotrophic factors including BDNF require TGF-betas as a cofactor to exert their neurotrophic activities.