Molecular Brain Research最新文献

It is firmly established that the onset of maternal behavior in the female rat is stimulated by a combination of hormones that include prolactin (PRL), estradiol (E₂), and progesterone (P₄). Specifically, nulliparous rats display short latencies to respond to foster young when primed with Silastic capsules filled with P₄ and E₂ and then administered PRL centrally to the medial preoptic area (MPOA), an area integrally involved in the expression of maternal behavior in this species. PRL or P₄ treatments alone are ineffective in stimulating the expression of maternal care. Since the actions of PRL in the MPOA appear to be mediated by PRL receptors, it was of interest to determine whether and how treatment with P₄ and E₂ together or separately might alter mRNA expression of the long form of the PRL receptor (PRL-R_L) in the MPOA. Using in situ hybridization histochemistry (ISHH), mRNA expression of the PRL-R_L was measured in the MPOA of ovariectomized, nulliparous rats treated with various combinations of P₄ and E₂. Treatment of animals with P₄ alone for 10 days or with P₄ followed by E₂ for 1 or 4 days resulted in reductions in PRL receptor mRNA expression in the MPOA when compared with the expression in animals treated with E₂ alone or blank capsules. The actions of P₄ on mRNA expression of the PRL-R_L were more pronounced in the dorsal MPOA. Circulating PRL levels collected at the time of sacrifice were elevated in all groups treated with E₂, but no association between PRL levels and receptor mRNA expression within the MPOA was evident. These findings indicate that the dorsal MPOA may be one site of progesterone's action in facilitating prolactin-mediated maternal behavior.

This study examined the hypothesis that the high prevalence of white matter injury in premature infants is associated with increased expression of calcium-permeable forms of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtype of glutamate receptors in pre-myelinating white matter. We characterized expression of subunits of the AMPA, and for reference, the N-methyl-d-aspartate (NMDA), glutamate receptors at 0.5, 0.65, 0.85, and term gestation in the ovine fetal white matter and cerebral cortex. There was a low expression of the critical calcium-impermeable AMPA receptor GluR2 subunit in subcortical white matter both absolutely and relative to other AMPA subunits throughout gestation. In contrast, GluR2 subunit mRNA expression fell in the cerebral cortex with increasing gestation whereas protein expression increased. These findings suggest a vulnerability of subcortical white matter to AMPA receptor-mediated calcium toxicity throughout the second half of gestation. Thus, the hypothesis that AMPA receptor-mediated glutamate toxicity contributes to brain damage in premature infants needs to be revised.

α₁-Adrenoreceptors (AR), of which three subtypes exist (α_1A-, α_1B- and α_1D-AR) are G-protein-coupled receptors that mediate the actions of norepinephrine and epinephrine both peripherally and centrally. In the CNS, α₁-ARs are found in the hippocampus where animal studies have shown the ability of α₁-AR agents to modulate long-term potentiation and memory; however, the precise distribution of α₁-AR expression and its subtypes in the human brain is unknown making functional comparisons difficult. In the human hippocampus, ³H-prazosin (α₁-AR antagonist) labels only the dentate gyrus (molecular, granule and polymorphic layers) and the stratum lucidum of the CA3 homogenously. Human α_1A-AR mRNA in the hippocampus is observed only in the dentate gyrus granule cell layer, while α_1D-AR mRNA expression is observed only in the pyramidal cell layers of CA1, CA2 and CA3, regions where ³H-prazosin did not bind. α_1B-AR mRNA is not expressed at detectable levels in the human hippocampus. These results confirm a difference in hippocampal α₁-AR localization between rat and humans and further describe a difference in the localization of the α_1A- and α_1D-AR mRNA subtype between rats and humans.

The purpose of this study is to determine if calcium/calmodulin-dependent protein kinase-II (CaMKII) plays a role in neuronal cell death and if inhibition of this kinase affords some neuroprotection in the RGC-5 retinal ganglion cell line. The RGC-5 cells were treated with glutamate at various concentrations for increasing increments of time. Cytotoxicity was assayed by measuring the lactate dehydrogenase (LDH) leakage from non-viable cells and TUNEL assays. The involvement of caspase-3, Bcl-2 and caspase-8 in glutamate-induced cytotoxicity was determined by immunoblots and/or real time RT-PCR. In addition, the autocamtide-2-related inhibitory peptide (AIP), a specific inhibitor of CaMKII, was used to determine the involvement of CaMKII in glutamate-induced RGC-5 cell death. Application of increasing concentrations of glutamate to RGC-5 cells caused a dose-dependent increase in the level of cell death after 24 h. There was a glutamate-stimulated increase in the expression of caspase-8 and caspase-3 and a corresponding decrease in Bcl-2. The active fragment of caspase-3 increased in glutamate-treated cells. An early transient increase in the expression of CaMKIIα_B gene and a corresponding CaMKIIα nuclear translocation was found in glutamate-treated cells. Treatment with AIP blocked the activation of caspase-3 and protected RGC from glutamate-mediated cell death but did not alter the glutamate-enhanced expression levels of caspase-8 or caspase-3. This report shows the likely involvement of a transcript of the CaMKIIα gene in the cytotoxicity response of RGC-5 cells similar to previous reports in the neural retina. AIP is shown to be a neuroprotectant for RGC-5 cells as was reported for the neural retina.

The vesicular monoamine transporter-2 (VMAT2) sequesters monoamine neurotransmitters into vesicles and prevents neurotoxicity. Human or monkey striatum generated three VMAT2 immunoreactive proteins of ∼75 kDa, ∼52–55 kDa, and ∼45 kDa. The ∼55-kDa band is considered the unglycosylated native protein. Deglycosylation of the VMAT2 from striatum or human VMAT2 expressed in HEK293 cells yielded a ∼45-kDa, but not a 55-kDa immunoreactive band. We investigated this apparent mismatch between observed molecular size and predicted size.

A dramatic example of neuronal and physiological plasticity in adult mammals occurs during the transition from a non-maternal to a maternal, lactating state. In this study, we compared gene expression within a large continuous region of the CNS involved in maternal behaviors (hypothalamus, preoptic regions, and nucleus accumbens) between lactating (L) (postpartum Day 7) and randomly cycling virgin (V) outbred mice. Using high-density oligonucleotide arrays representing 11,904 genes, two statistical algorithms were used to identify significant differences in gene expression: robust multiarray (P < 0.001) (n = 92 genes) and significance analysis of microarrays using a 10% false discover rate (n = 114 genes). 27 common genes were identified as significant using both techniques. A subset of genes (n = 5) were selected and examined by real-time PCR. Our findings were consistent with previous published work. For example, neuropeptide Y (NPY) and proenkephalin were elevated in L mice, whereas POMC was decreased. Increased levels of NPY Y2 receptor and polo-like kinase and decreased levels of endothelin receptor type b in L mice are examples of novel gene expression changes not previously identified. Expression differences occurred in broad classes. Together, our findings provide possible new material on gene expression changes that may support maternal behaviors. The advantages and drawbacks of sampling large CNS regions using arrays are discussed.

Nicotine is known to induce the release of multiple neurotransmitters, including glutamate and dopamine, through activation of nicotinic receptors. Gene expression in the N-methyl-d-aspartate postsynaptic density (NMDA-PSD), as well as other functional groups, was compared in postmortem hippocampus of schizophrenic and nonmentally ill smokers and nonsmokers utilizing a microarray and quantitative RT-PCR approach. The expression of 277 genes was significantly changed between all smokers and nonsmokers. Specific gene groups, most notably genes expressed in the NMDA-PSD, were prevalent among these transcripts. Analysis of the interaction between smoking and schizophrenia identified several genes in the NMDA-PSD that were differentially affected by smoking in patients. The present findings suggest that smoking may differentially modulate glutamatergic function in schizophrenic patients and control subjects. The biological mechanisms underlying chronic tobacco use are likely to differ substantially between these two groups.

Selective serotonin reuptake inhibitors (SSRIs) are widely used for the treatment of depressive mood disorders and well known to inhibit the reuptake of neurotransmitter serotonin into nerve terminals. Thus, it seems conceivable that these drugs may induce the outflow of serotonin from the synapse as a consequence of inhibiting the reuptake, resulting in the stimulation of glial cells surrounding nerve terminals. On this hypothesis, the effect of serotonin on steroid 5α-reductase type 1 (5α-R) gene expression in rat C6 glioma cells was examined as one of the in vitro model experiments for investigating the indirect influence of SSRIs on glial cells. Serotonin elevated 5α-R mRNA and protein levels through the stimulation of serotonin 5-HT_2A receptors, and also elevated Egr-1 mRNA and protein levels prior to 5α-R gene expression in the glioma cells. Furthermore, serotonin failed to significantly increase 5α-R mRNA levels in the cells preloaded with the antisense oligodeoxynucleotide targeted on Egr-1 gene. These results indicate that serotonin may stimulate 5α-R gene expression via transcription factor Egr-1 in glial cells, thus suggesting that serotonin flowing out of the serotonergic synapse may be implicated in SSRI-induced changes in neurosteroid metabolism in brain.

Epileptic seizures cause severe and long-lasting events on the architecture of the brain, including neuronal cell death, accompanied neurogenesis, reactive gliosis, and mossy fiber sprouting. However, it remains uncertain whether these functional and anatomical alterations are associated with the development of hyperexcitability, or as inhibitory processes. Neurotrophic factors are probable mediators of these pathophysiological events. The present study was designed to clarify the role of various neurotrophic factors on the pilocarpine model of seizures. At 4 h following pilocarpine-induced seizures, expression of NGF, BDNF, HB-EGF, and FGF-2 increased only in the mice manifesting tonic–clonic convulsions and not in mice without seizures. NT-3 expression decreased in pilocarpine-treated mice experiencing seizures, tonic–clonic or not, compared to mice with no seizures. Neuronal cell damage, which was evident by Fluoro-Jade B staining, was observed within 24 h in the mice exhibiting tonic–clonic seizures, followed by an increase in the number of BrdU-positive cells and glial cells, which were evident after 2 days. None of these pathophysiological changes occurred in the mice which showed no seizures, although they were injected with pilocarpine, nor in the activated epilepsy-prone EL mice, which experienced repeated severe seizures. Together, these results suggest that neuronal damage occurring in the brain of the mice manifesting tonic–clonic seizures is accompanied by neurogenesis. This sequence of events may be regulated through changes in expression of neurotrophic factors such as NGF, BDNF, HB-FGF, and NT-3.