Plasminogen activator inhibitor-2 (PAI-2) mRNA is localized in the accumbens nucleus of the mouse brain and is induced in specific brain sites after kainate excitation

Plasminogen activator inhibitor-2 (PAI-2) specifically inhibits plasminogen activators, extracellular fibrinolytic serine proteases that are also implicated in brain plasticity and toxicity. Primarily localized intracellularly, PAI-2 is thought to also counteract apoptosis mediated by a currently undefined intracellular protease. Here we localized PAI-2 mRNA through in situ hybridization in brain cryosections derived from normal adult mice or after kainate excitation. We found that in the normal brain PAI-2 mRNA was confined to an area within the accumbens nucleus shell. After kainate was injected (i.p.), PAI-2 mRNA was substantially and rapidly (within 2 h) induced in neuron-like cells primarily in layers II–III of the neocortex; the cingulate, piriform, entorhinal and perirhinal cortices; the olfactory bulb, nucleus and tubercle; in the accumbens nucleus, shell and core; throughout the caudate putamen and the amygdaloid complex; in the CA1 and CA3 areas of the hippocampus, and in the parasubiculum. These findings suggest that PAI-2 could play a role in the accumbens nucleus as well as in activity-related events associated with olfactory, striatal, and limbic structures.     

Cellular Localization of Transforming Growth Factor-α mRNA in Rat Forebrain

Abstract: The cellular localization of transforming growth factor-α (TGFa) mRNA in juvenile and adult rat forebrain was examined using in situ hybridization with a ³⁵S-labeled cRNA probe. TGFα cRNA-labeled neuronal perikarya were distributed across many forebrain regions including the olfactory bulb, caudate-putamen, nucleus accumbens, olfactory tubercle, ventral pallidum, amygdala, hippocam-pal stratum granulosum and CA3 stratum pyramidale, and piriform, entorhinal, and retrosplenial cortices. TGFα cRNA-hybridizing cells were also localized to several thalamic nuclei and to the suprachiasmatic, dorsomedial, and ventromedial nuclei of the hypothalamus. In addition, labeled cells were present in regions of white matter including the corpus callosum, anterior commissure, internal and external capsules, optic tract, and lateral olfactory tract. Thus, both neurons and glia appear to synthesize TGFα in normal brain. Hybridization densities were greater in neuronal fields at 2 weeks of age compared with the adult, suggesting a role for TGFα in the development of several forebrain systems. Our results demonstrating the prominent and widespread expression of TGFα mRNA in forebrain, combined with the extremely low abundance of epidermal growth factor mRNA in brain, support the argument that TGFα is the principal endogenous ligand for the epidermal growth factor receptor in normal brain.     

Alterations of BDNF and trkB mRNA Expression in the 6-Hydroxydopamine-Induced Model of Preclinical Stages of Parkinson’s Disease: An Influence of Chronic Pramipexole in Rats

Our recent study has indicated that a moderate lesion of the mesostriatal and mesolimbic pathways in rats, modelling preclinical stages of Parkinson’s disease, induces a depressive-like behaviour which is reversed by chronic treatment with pramipexole. The purpose of the present study was to examine the role of brain derived neurotrophic factor (BDNF) signalling in the aforementioned model of depression. Therefore, we investigated the influence of 6-hydoxydopamine (6-OHDA) administration into the ventral region of the caudate-putamen on mRNA levels of BDNF and tropomyosin-related kinase B (trkB) receptor. The BDNF and trkB mRNA levels were determined in the nigrostriatal and limbic structures by in situ hybridization 2 weeks after the operation. Pramipexole (1 mg/kg sc twice a day) and imipramine (10 mg/kg ip once a day) were injected for 2 weeks. The lesion lowered the BDNF and trkB mRNA levels in the hippocampus [CA1, CA3 and dentate gyrus (DG)] and amygdala (basolateral/lateral) as well as the BDNF mRNA content in the habenula (medial/lateral). The lesion did not influence BDNF and trkB expression in the caudate-putamen, substantia nigra, nucleus accumbens (shell and core) and ventral tegmental area (VTA). Chronic imipramine reversed the lesion-induced decreases in BDNF mRNA in the DG. Chronic pramipexole increased BDNF mRNA, but decreased trkB mRNA in the VTA in lesioned rats. Furthermore, it reduced BDNF and trkB mRNA expression in the shell and core of the nucleus accumbens, BDNF mRNA in the amygdala and trkB mRNA in the caudate-putamen in these animals. The present study indicates that both the 6-OHDA-induced dopaminergic lesion and chronic pramipexole influence BDNF signalling in limbic structures, which may be related to their pro-depressive and antidepressant activity in rats, respectively.     

Expression and localization of the iron-siderophore binding protein lipocalin 2 in the normal rat brain and after kainate-induced excitotoxicity

Lipocalin 2 (LCN2) is produced by mammalian hosts to bind bacterial siderophore and sequester free iron as part of an innate immune response, and could also play a role in tissue iron homeostasis, but thus far, little is known about its expression in the CNS. The present study was carried out to study the expression of the lipocalin in the normal rat brain and after neuronal injury induced by kainate (KA). Low levels of LCN2 mRNA and protein expression were detected in most regions of the normal brain except the olfactory bulb, brainstem and cerebellum. KA lesions resulted in damage to the hippocampus, leading to an early increase at three days and a sustained elevation in LCN2 mRNA level of 16-fold, and protein expression at 80-fold in the lesioned tissue compared to controls at 2 weeks post-KA injection. The sustained elevation in mRNA expression was not detected among other lipocalins surveyed using real-time RT-PCR - apoD, PGDS, Rbp4 and LCN5. Single and double immunostaining confirmed that LCN2 is present in astrocytes in the olfactory bulb, brainstem and cerebellum of the normal brain, and reactive astrocytes in the KA-lesioned hippocampus. In conclusion, the present study showed LCN2 to be present in select brain regions, and is upregulated in astrocytes after neuronal injury induced by kainate. We postulate that, as in the periphery, LCN2 may have a role in iron transport or trafficking in the CNS.     

Localization of corticoliberin receptors in the rat brain

Using the in situ hybridization, a distribution of corticotropin-releasing hormone (CRH) receptors CRH-1 and CRH-2 in the rat brain has been studied. Brain levels of CRH-1 mRNA were higher than the those of CRH-2 mRNA. Most intensive CRH-1 gene expression was observed in the forebrain, including neocortex, archicortex, paleocortex and cerebellar cortex. In addition, significant CRH-1 mRNA expression was detected in the red nucleus, pontine nucleus, cochlear nucleus and reticular tegmental nucleus. CRH-2 mRNA was intensively expressed in the olfactory structures, corticomedial amygdala, CA1-CA4 of hippocampus, ventramedial hypothalamus and several modullar nuclei. Moderate CRH-2 mRNA level were seen in the dorsomedial neostriatum. The findings indicate that within the brain two types of CRH receptors are widely expressed. A distinct pattern of CRH-1 and CRH-2 expression in the brain appears to underline the functional specifics of the CRH actions in brain structures.     

Unique properties of mesoprefrontal neurons within a dual mesocorticolimbic dopamine system

The mesocorticolimbic dopamine system is essential for cognitive and emotive brain functions and is thus an important target in major brain diseases like schizophrenia, drug addiction, and attention deficit hyperactivity disorder. However, the cellular basis for the diversity in behavioral functions and associated dopamine-release pattern within the mesocorticolimbic system has remained unclear. Here, we report the identification of a type of dopaminergic neuron within the mesocorticolimbic dopamine system with unconventional fast-firing properties and small DAT/TH mRNA expression ratios that selectively projects to prefrontal cortex and nucleus accumbens core and medial shell as well as to basolateral amygdala. In contrast, well-described conventional slow-firing dopamine midbrain neurons only project to the lateral shell of the nucleus accumbens and the dorsolateral striatum. Among this dual dopamine midbrain system defined in this study by converging anatomical, electrophysiological, and molecular properties, mesoprefrontal dopaminergic neurons are unique, as only they do not possess functional somatodendritic Girk2-coupled dopamine D2 autoreceptors.     

The distribution of a dopamine D2 receptor mRNA in rat brain

Based on the recently reported sequence of a dopamine D2 receptor cloned from rat brain, we prepared a series of cDNA probes to determine the distribution of mRNA encoding this receptor. Within the forebrain, D2 receptor mRNA is abundant in the caudate-putamen, accumbens nucleus and olfactory tubercle. Moderate to low levels of mRNA are observed in the medial habenular nucleus, diagonal band, lateral septal nucleus, claustrum, dorsal endopiriform nucleus, and entorhinal cortex. In the mesencephalon, D2 receptor mRNA is abundant within the substantia nigra, pars compacta, and the ventral tegmental area. Comparison of the distribution of the mRNA and ligand binding indicates that both presynaptic and postsynaptic D2 receptors of the nigrostriatal, mesolimbic and mesocortical pathways are derived from the same mRNA.     

Repeated cocaine administration alters the expression of genes in corticolimbic circuitry after a 3-week withdrawal: a DNA macroarray study

Addiction to psychostimulants elicits behavioral and biochemical changes that are assumed to be mediated by alterations of gene expression in the brain. The changes in gene expression after 3 weeks of withdrawal from chronic cocaine treatment were evaluated in the nucleus accumbens core and shell, dorsal prefrontal cortex and caudate using a complementary DNA (cDNA) array. The level of mRNA encoded by several genes was identified as being up- or down-regulated in repeated cocaine versus saline subjects. The results from the cDNA array were subsequently confirmed at the protein level with immunoblotting. Of particular interest, parallel up-regulation in protein and mRNA was found for the adenosine A1 receptor in the accumbens core, neuroglycan C in the accumbens shell, and the GluR5 glutamate receptor subtype in dorsal prefrontal cortex. However, there was an increase in TrkB protein in the nucleus accumbens core of cocaine-treated rats without a corresponding alteration in mRNA. These changes of gene expression in corticolimbic circuitry may contribute to the psychostimulant-induced behavioral changes associated with addiction.     

Effects of endogenous glutamate on extracellular concentrations of taurine in striatum and nucleus accumbens of the awake rat: Involvement of NMDA and AMPA/kainate receptors

Summary. Using microdialysis, the effects of endogenous glutamate on extracellular concentrations of taurine in striatum and nucleus accumbens of the awake rat were investigated. The glutamate uptake inhibitor L-trans-pyrrolidine-2,4-dicarboxylic acid (PDC) was used to increase the extracellular concentration of glutamate. PDC (1, 2 and 4 mM) produced a dose-related increase of extracellular concentrations of glutamate and taurine in striatum and nucleus accumbens. Increases of extracellular taurine were significantly correlated with increases of extracellular glutamate, but not with PDC doses, which suggests that endogenous glutamate produced the observed increases of extracellular taurine in striatum and nucleus accumbens. The role of ionotropic glutamate receptors on the increases of taurine was also studied. In striatum, perfusion of the antagonists of NMDA and AMPA/kainate glutamate receptors attenuated the increases of extracellular taurine. AMPA/kainate, but not NMDA receptors, also reduced the increases of extracellular taurine in nucleus accumbens. These results suggest that glutamate-taurine interactions exist in striatum and nucleus accumbens of the awake rat. Received March 5, 1999/Accepted September 22, 1999     

大鼠脑内代谢型谷氨酸受体5亚型(mGluR5)定位分布的免疫细胞化学研究

本研究用免疫细胞化学技术观察了大鼠脑内参与兴奋性突触传递的代谢型谷氨酸受体5亚型(mGluR5)的精确定位分布.mGluR5阳性浓染的神经元胞体和纤维密集地分布于大脑皮质浅层、嗅球、伏核、尾壳核、前脑基底部、隔区、苍白球、腹侧苍白球、海马CA1和CA2区、下丘中央核、被盖背侧核和三叉神经脊束核尾侧亚核浅层;淡染而稀疏的mGluR5阳性神经元胞体和纤维见于屏状核、终纹床核、杏仁中央核、丘脑部分核团、上丘浅灰质层、外侧丘系背侧核和延髓中央灰质.     

Expression of dihydropyridine-sensitive brain calcium channels in the rat central nervous system.

We have localized dihydropyridine (DHP-sensitive calcium channels in rat brain by in situ hybridization and immunohistochemistry. The mRNA for the dihydropyridine-sensitive calcium channel alpha 1 subunit (DHPR-B) is prominently localized in neuronal cells in the olfactory bulb, dentate gyrus, hippocampus, arcuate nucleus, paraventricular nucleus, ventromedial nucleus, cerebral cortex, superior colliculus and the cerebellar Purkinje cell layer. Strong expression of DHPR-B mRNA was also found in the pituitary and pineal glands. DHP-sensitive calcium channel alpha 1 subunit distribution has also been examined immunohistochemically with polyclonal antibodies raised against synthetic peptides specific for the DHPR-B alpha 1 subunit protein. The results from immunohistochemistry were in good agreement with those from in situ hybridization. Thus, regional distribution and localization of DHPR-B mRNA and alpha 1 subunit protein in rat brain suggest that this type of DHP-sensitive brain calcium channel may play an important role in excitation-secretion coupling functions in the neuroendocrine system.     

Selective Increase in Dopamine Utilization in the Shell Subdivision of the Nucleus Accumbens by the Benzodiazepine Inverse Agonist FG 7142

Abstract: We examined the effects of the benzodiazepine inverse agonist FG 7142 on dopamine metabolism in the core and shell subdivisions of the nucleus accumbens. FG 7142 (15 mg/kg i.p.) or vehicle was administered to adult male rats 30 min before they were killed. Selected brain regions, including samples from the whole nucleus accumbens as well as core and shell subdivisions, were collected and assayed for tissue concentrations of dopamine and its major metabolite, 3,4-dihydroxyphenylacetic acid. Consistent with previous reports, FG 7142 administration increased dopamine utilization in the medial prefrontal cortex but not the whole nucleus accumbens. Examination of subdivisions revealed that FG 7142 produced increased dopamine utilization in the shell subdivision of the nucleus accumbens. No effect of FG 7142 on dopamine utilization in the core region of the nucleus accumbens was observed. These data are discussed in terms of in vivo microdialysis studies reporting increased dopamine release in the nucleus accumbens after FG 7142 administration.     

Identification of a noradrenaline-rich subdivision of the human nucleus accumbens

The nucleus accumbens, situated at the junction between rostral pre-commissural caudate and putamen, is now considered to be critically involved in rewarding and motivational functions mediated by the neurotransmitter dopamine. However, in the human, the precise anatomical boundaries of this nucleus are still undetermined and controversy exists as to the extent to which nucleus accumbens activity is controlled by noradrenaline, a related neurotransmitter now much neglected (in favor of dopamine) by the scientific community. Here we resolve the question of noradrenaline in the human nucleus accumbens and identify, in autopsied brain of normal subjects, a small subdivision of the caudomedial portion of this nucleus that selectively contains strikingly high levels of noradrenaline and thus represents the only area in human brain having equally high levels of both noradrenaline and dopamine. The presence of very high, localized noradrenaline concentrations in the caudomedial nucleus accumbens implies a special biological role for this neurotransmitter in human brain motivational processes.     

Heterogeneity of D2 dopamine receptors in different brain regions.

The binding of [3H]spiperone has been examined in membranes derived from different regions of bovine brain. In caudate nucleus, nucleus accumbens, olfactory tubercle and putamen binding is to D2 dopamine and 5HT2 serotonin receptors, whereas in cingulate cortex only serotonin 5HT2 receptor binding can be detected. D2 dopamine receptors were examined in detail in caudate nucleus, olfactory tubercle and putamen using [3H]spiperone binding in the presence of 0.3 microM-mianserin (to block 5HT2 serotonin receptors). No evidence for heterogeneity among D2 dopamine receptors either between brain regions or within a brain region was found from the displacements of [3H]spiperone binding by a range of antagonists, including dibenzazepines and substituted benzamides. Regulation of agonist binding by guanine nucleotides did, however, differ between regions. In caudate nucleus a population of agonist binding sites appeared resistant to guanine nucleotide regulation, whereas this was not the case in olfactory tubercle and putamen.     

BDNF mRNA expression is increased in adult rat forebrain after limbic seizures: temporal patterns of induction distinct from NGF

We have localized brain-derived neurotrophic factor (BDNF) mRNA in rat brain and examined its regulation by seizure activity. In situ hybridization of BDNF 35S-cRNA most prominently labeled neurons in hippocampal stratum pyramidale and stratum granulosum, superficial olfactory cortex, pyramidal cell layers of neocortex, amygdala, claustrum, endopiriform nucleus, anterior olfactory nucleus, and ventromedial hypothalamus. Hybridization to BDNF mRNA was markedly increased in all of these regions after lesion-induced recurrent limbic seizures and within dentate gyrus granule cells following one electrically stimulated epileptiform afterdischarge. In contrast to seizure-elicited changes in nerve growth factor (NGF) mRNA expression, increases in BDNF mRNA occur in a greater number of different neuronal populations and develop several hours more rapidly in extrahippocampal loci. These results indicate that regulation by physiological activity may be an intrinsic property of this class of neurotrophic factor but that, in the recurrent seizure paradigm, different mechanisms mediate increased expression of mRNAs for BDNF and NGF outside hippocampus.     

LOCALIZATION OF GABAERGIC, CHOLINERGIC AND AMINERGIC STRUCTURES IN THE MESOLIMBIC SYSTEM

Abstract— The localization of cholinergic, GABAergic and aminergic structures in the 'mesolimbic' system has been discussed from studies on the topographical distribution of choline acetyltransferase, glutamate decarboxylase and aromatic amino acid decarboxylase in normal rat brain and in brains hemitransected at the level of globus pallidus. The structures analysed included nucleus accumbens, olfactory tubercle, septum, medial forebrain bundle, striatum, substantia nigra, ventral tegmental area and nucleus interpeduncularis.
Choline acetyltranferase was highly concentrated in the nucleus interpeduncularis, but it did also exhibit considerable activity in the nucleus accumbens, the olfactory tubercle and the striatum. The activities did not change after hemitransection. Aromatic amino acid decarboxylase was highly concentrated in the ventral tegmental area, but high activities were also found in the striatum, the nucleus accumbens, the olfactory tubercle and the pars compacta of the substantia nigra. The activity decreased in all areas rostral to the hemitransection. Glutamate decarboxylase was highly concentrated in the dopamine innervated regions, moreso in the limbic structures than in the striatum. Much higher activity was found in the substantia nigra than in the ventral tegmental area. After hemitransection the activity in the substantia nigra was decreased whereas in the ventral tegmental area it was unchanged. Our results thus suggest that dopaminergic cells in the ventral tegmental area do not receive GABAergic fibres from the terminal regions of the ascending dopaminergic fibres. In addition, we found a very high concentration of glutamate decarboxylase in a region traversed by the rostral medial forebrain bundle. Here the activity was mainly confined to the paniculate fraction, probably the synaptosomes. This fraction also displayed a very active high affinity uptake of y-aminobutyric acid.     

Involvement of Dopamine D1 and D2 Receptors in the Regulation of Proenkephalin mRNA Abundance in the Striatum and Accumbens of the Rat Brain

The effects of short-term treatment (6 h) with selective D1 or D2 agonists and antagonists on the mRNA for proenkephalin in the medial and anterior aspects of the caudate-putamen and the nucleus accumbens were assessed by in situ hybridization histochemistry. Proenkephalin mRNA abundance was significantly changed in the striatum and accumbens in response to D2 receptor manipulation. D2 blockade with haloperidol or raclopride increased, whereas D2 stimulation with LY-171555 (D2 agonist) decreased, striatal and accumbens proenkephalin mRNA abundance. Antagonism of D1 receptor activity with SCH-23390 significantly decreased proenkephalin mRNA abundance in all brain regions. Concurrent administration of the D1 agonist SKF-38393 prevented the SCH-23390 effect in all brain areas. The data demonstrate that acute treatment with dopaminergic D2 agonists and antagonists affects proenkephalin mRNA abundance in the striatum and accumbens via a D2 receptor mechanism, consistent with the concept that D2 receptor function inhibits the synthesis of the mRNA encoding the enkephalin peptides. Moreover, D1 receptor activity, directly or indirectly, exerts modulatory effects on proenkephalin mRNA abundance in the striatum and nucleus accumbens.