101
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Mishiro-Sato E, Sasaki K, Matsuo T, Kageyama H, Yamaguchi H, Date Y, Matsubara M, Ishizu T, Yoshizawa-Kumagaye K, Satomi Y, Takao T, Shioda S, Nakazato M, Minamino N. Distribution of neuroendocrine regulatory peptide-1 and -2, and proteolytic processing of their precursor VGF protein in the rat. J Neurochem 2010; 114:1097-106. [PMID: 20524965 DOI: 10.1111/j.1471-4159.2010.06827.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Neuroendocrine regulatory peptide (NERP)-1 and NERP-2 are biologically active peptides recently discovered by peptidomic analysis. NERPs are processed out from the 594-residue VGF protein which contains many prohormone convertase cleavage motifs. VGF-deficient mice exhibit a hypermetabolic and infertile phenotype, for which VGF protein-derived peptides including NERPs are presumably responsible. To provide a solid basis for elucidating physiological roles of NERPs, we investigated rat VGF protein processing by chromatographic and mass spectrometric analysis, and immunoblotting, using antibodies against NERPs and the VGF protein C-terminus (VGF-C). Cellular and tissue distribution of immunoreactive (ir) NERPs were also analyzed in the rat. Both ir-NERP-1 and ir-NERP-2, which occur abundantly in the CNS and pituitary, moderately in the gastrointestinal (GI) tract, were mainly localized in neuronal structures. Major endogenous forms of ir-NERPs in the brain and GI tract were identified as NERP-1, NERP-2, and big NERP-2 (NERP-1 + NERP-2), with NERP-1 and big NERP-2 being predominant. Regarding ir-VGF-C peptides, VGF[588-617], VGF[556-617], and VGF[509-617] were found to be major forms. Immunoblotting with the NERP-2 and VGF-C antibodies revealed processing intermediates of 10-37 kDa. Taken together, we deduce that VGF protein is primarily cleaved at 10 sites through the processing pathway common to the brain and GI tract.
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Affiliation(s)
- Emi Mishiro-Sato
- Department of Molecular Pharmacology, National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka, Japan
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102
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Greenwood BN, Strong PV, Fleshner M. Lesions of the basolateral amygdala reverse the long-lasting interference with shuttle box escape produced by uncontrollable stress. Behav Brain Res 2010; 211:71-6. [PMID: 20226213 DOI: 10.1016/j.bbr.2010.03.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Revised: 03/02/2010] [Accepted: 03/03/2010] [Indexed: 10/19/2022]
Abstract
Exposure to an uncontrollable, but not a controllable, stressor produces a constellation of behaviors called learned helplessness. In rodents, uncontrollable stress interferes with the ability to learn to escape from escapable shocks delivered in a shuttle box. The stress-induced shuttle box escape deficit is a common screening tool for potential antidepressant strategies. Inconsistencies in the literature exist regarding the time-course of, and mechanisms underlying, stress-induced escape deficits. When no common cues are shared between the stressor and testing environment, the escape deficit is short lived and independent of conditioned freezing. In contrast, when stress and testing occur in the same or similar environments, the escape deficit is very long lasting. The current studies address the hypothesis that the long-lived escape deficit produced by uncontrollable stress is dependent upon conditioned fear and the basolateral amygdala (BLA). Rats received bilateral excitotoxic lesions of the BLA 2 weeks following uncontrollable foot shocks. One week after surgery, rats were tested for conditioned freezing and escape behavior in the same shuttle boxes in which prior foot shocks were delivered. Stressed rats with sham lesions displayed robust conditioned freezing and failed to escape during shuttle box testing. Lesions of the BLA eliminated conditioned freezing and completely restored stressed rats' ability to perform the escape contingency. These data indicate that the long-lived stress-induced escape deficit produced under conditions in which the stressor and testing environments share common cues is dependent upon conditioned freezing elicited by the BLA. Results have important implications for the mechanisms underlying learned helplessness phenomena.
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Affiliation(s)
- Benjamin N Greenwood
- Department of Integrative Physiology and The Center for Neuroscience, University of Colorado-Boulder, Campus Box 354, Boulder, CO 80309, United States.
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103
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Calabrese F, Molteni R, Cattaneo A, Macchi F, Racagni G, Gennarelli M, Ellenbroek BA, Riva MA. Long-Term Duloxetine Treatment Normalizes Altered Brain-Derived Neurotrophic Factor Expression in Serotonin Transporter Knockout Rats through the Modulation of Specific Neurotrophin Isoforms. Mol Pharmacol 2010; 77:846-53. [DOI: 10.1124/mol.109.063081] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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104
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Alpha2-adrenoceptor blockade accelerates the neurogenic, neurotrophic, and behavioral effects of chronic antidepressant treatment. J Neurosci 2010; 30:1096-109. [PMID: 20089918 DOI: 10.1523/jneurosci.2309-09.2010] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Slow-onset adaptive changes that arise from sustained antidepressant treatment, such as enhanced adult hippocampal neurogenesis and increased trophic factor expression, play a key role in the behavioral effects of antidepressants. alpha(2)-Adrenoceptors contribute to the modulation of mood and are potential targets for the development of faster acting antidepressants. We investigated the influence of alpha(2)-adrenoceptors on adult hippocampal neurogenesis. Our results indicate that alpha(2)-adrenoceptor agonists, clonidine and guanabenz, decrease adult hippocampal neurogenesis through a selective effect on the proliferation, but not the survival or differentiation, of progenitors. These effects persist in dopamine beta-hydroxylase knock-out (Dbh(-/-)) mice lacking norepinephrine, supporting a role for alpha(2)-heteroceptors on progenitor cells, rather than alpha(2)-autoreceptors on noradrenergic neurons that inhibit norepinephrine release. Adult hippocampal progenitors in vitro express all the alpha(2)-adrenoceptor subtypes, and decreased neurosphere frequency and BrdU incorporation indicate direct effects of alpha(2)-adrenoceptor stimulation on progenitors. Furthermore, coadministration of the alpha(2)-adrenoceptor antagonist yohimbine with the antidepressant imipramine significantly accelerates effects on hippocampal progenitor proliferation, the morphological maturation of newborn neurons, and the increase in expression of brain derived neurotrophic factor and vascular endothelial growth factor implicated in the neurogenic and behavioral effects of antidepressants. Finally, short-duration (7 d) yohimbine and imipramine treatment results in robust behavioral responses in the novelty suppressed feeding test, which normally requires 3 weeks of treatment with classical antidepressants. Our results demonstrate that alpha(2)-adrenoceptors, expressed by progenitor cells, decrease adult hippocampal neurogenesis, while their blockade speeds up antidepressant action, highlighting their importance as targets for faster acting antidepressants.
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105
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Calabrese F, Molteni R, Racagni G, Riva MA. Neuronal plasticity: a link between stress and mood disorders. Psychoneuroendocrinology 2009; 34 Suppl 1:S208-16. [PMID: 19541429 DOI: 10.1016/j.psyneuen.2009.05.014] [Citation(s) in RCA: 220] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Revised: 05/22/2009] [Accepted: 05/23/2009] [Indexed: 01/19/2023]
Abstract
Although stress represents the major environmental element of susceptibility for mood disorders, the relationship between stress and disease remains to be fully established. In the present article we review the evidence in support for a role of neuronal plasticity, and in particular of neurotrophic factors. Even though decreased levels of norepinephrine and serotonin may underlie depressive symptoms, compelling evidence now suggests that mood disorders are characterized by reduced neuronal plasticity, which can be brought about by exposure to stress at different stages of life. Indeed the expression of neurotrophic molecules, such as the neurotrophin BDNF, is reduced in depressed subjects as well as in experimental animals exposed to adverse experience at early stages of life or at adulthood. These changes show an anatomical specificity and might be sustained by epigenetic mechanisms. Pharmacological intervention may normalize such defects and improve neuronal function through the modulation of the same factors that are defective in depression. Several studies have demonstrated that chronic, but not acute, antidepressant treatment increases the expression of BDNF and may enhance its localization at synaptic level. Antidepressant treatment can normalize deficits in neurotrophin expression produced by chronic stress paradigms, but may also alter the modulation of BDNF under acute stressful conditions. In summary, there is good agreement in considering neuronal plasticity, and the expression of key proteins such as the neurotrophin BDNF, as a central player for the effects of stress on brain function and its implication for psychopathology. Accordingly, effective treatments should not limit their effects to the control of neurotransmitter and hormonal dysfunctions, but should be able to normalize defective mechanisms that sustain the impairment of neuronal plasticity.
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Affiliation(s)
- Francesca Calabrese
- Center of Neuropharmacology, Department of Pharmacological Sciences, University of Milan, Via Balzaretti 9, 20133 Milan, Italy
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106
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Witkin JM, Li X. New approaches to the pharmacological management of major depressive disorder. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2009; 57:347-79. [PMID: 20230766 DOI: 10.1016/s1054-3589(08)57009-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Despite effective and safe therapies for major depressive disorder (MDD), the current arsenal of antidepressant therapies does not fully satisfy the needs of patients or physicians. Many patients are only partial responders or are treatment resistant and side effects interfere with compliance. The majority of antidepressants directly affect monoamine neurotransmission within the central nervous system. Moving beyond this mechanism has been a challenge because of the lack of knowledge about the underlying etiology and pathophysiology of MDD. Provided in this report is a review of some of the major new advances in MDD research that suggest the possibility of novel and improved future therapeutic options. Emphasis is placed on studies of unipolar, but not bipolar, depression. New therapies include dual and triple monoamine uptake inhibitors, non-conventional antidepressants such as tianeptine, and a number of augmentation strategies. In addition, studies are underway on a number of mechanisms of action that might yield the next therapeutic advance. These include agents that interact with endocannabiniod systems, examination of natural products, and compounds that influence neuropeptide systems such as galanin and melanin-concentrating hormone, and growth and neurotrophic factors. Epigenetic mechanisms involving histone modification are also being explored. An area of intensive investigation is glutamate neurotransmission. Data support the hypothesis that NMDA receptor antagonists are effective in MDD individuals resistant to conventional therapies. The potential of metabotropic glutamate receptors as novel targets is also discussed. Accumulating evidence supports the idea that amplification of AMPA receptor function is a critical link in the transduction processes involved antidepressant effects.
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Affiliation(s)
- Jeffrey M Witkin
- Neuroscience Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285, USA
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107
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Proteomic analysis uncovers novel actions of the neurosecretory protein VGF in nociceptive processing. J Neurosci 2009; 29:13377-88. [PMID: 19846725 DOI: 10.1523/jneurosci.1127-09.2009] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Peripheral tissue injury is associated with changes in protein expression in sensory neurons that may contribute to abnormal nociceptive processing. We used cultured dorsal root ganglion (DRG) neurons as a model of axotomized neurons to investigate early changes in protein expression after nerve injury. Comparing protein levels immediately after DRG dissociation and 24 h later by proteomic differential expression analysis, we found a substantial increase in the levels of the neurotrophin-inducible protein VGF (nonacronymic), a putative neuropeptide precursor. In a rodent model of nerve injury, VGF levels were increased within 24 h in both injured and uninjured DRG neurons, and the increase persisted for at least 7 d. VGF was also upregulated 24 h after hindpaw inflammation. To determine whether peptides derived from proteolytic processing of VGF participate in nociceptive signaling, we examined the spinal effects of AQEE-30 and LQEQ-19, potential proteolytic products shown previously to be bioactive. Each peptide evoked dose-dependent thermal hyperalgesia that required activation of the mitogen-activated protein kinase p38. In addition, LQEQ-19 induced p38 phosphorylation in spinal microglia when injected intrathecally and in the BV-2 microglial cell line when applied in vitro. In summary, our results demonstrate rapid upregulation of VGF in sensory neurons after nerve injury and inflammation and activation of microglial p38 by VGF peptides. Therefore, VGF peptides released from sensory neurons may participate in activation of spinal microglia after peripheral tissue injury.
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108
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Lee S, Kim DH, Yoon SH, Ryu JH. Sub-chronic administration of rimonabant causes loss of antidepressive activity and decreases doublecortin immunoreactivity in the mouse hippocampus. Neurosci Lett 2009; 467:111-6. [PMID: 19819298 DOI: 10.1016/j.neulet.2009.10.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Revised: 09/22/2009] [Accepted: 10/05/2009] [Indexed: 10/20/2022]
Abstract
Rimonabant is a cannabinoid receptor 1 antagonist, and is used to treat anorexia and obesity. However, it has been suggested that rimonabant may act as a depressant. In the present study, we investigated the depressive effects of rimonabant using behavioral and biochemical methods. A single treatment with rimonabant (10mg/kg, p.o.) reduced immobility duration in the forced swimming test (FST) to a level similar to that observed for the tricyclic antidepressant, imipramine (15mg/kg, i.p.). However, mice treated with rimonabant for 2 weeks did not show any significant reductions in immobility duration versus vehicle-treated controls. To investigate why the antidepressant effect of rimonabant disappeared after extended treatment, we carried out 5-bromo-2-deoxyuridine (BrdU) and doublecortin (DCX) immunohistochemistry assay. Numbers of BrdU-immunoreactive cells were not significantly changed after administering rimonabant (10mg/kg, p.o.) for 2 weeks in the hippocampal dentate gyrus (DG), but interestingly, numbers of DCX-immunopositive cells in the DG were significantly reduced after 2 weeks of rimonabant treatment at doses of 1 or 10mg/(kgday) compared with vehicle-treated controls (P<0.05). These results suggest that sub-chronic treatments with rimonabant inhibit cell proliferation in DG, and that a lack of antidepressive activity may be related to a reduction in cell proliferation in this region.
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Affiliation(s)
- Seungjoo Lee
- Department of Life and Nanopharmaceutical Sciences, College of Pharmacy, Kyung Hee University, Hoeki-dong, Dongdaemoon-Ku, Seoul 130-701, Republic of Korea
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109
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Li YF, Huang Y, Amsdell SL, Xiao L, O'Donnell JM, Zhang HT. Antidepressant- and anxiolytic-like effects of the phosphodiesterase-4 inhibitor rolipram on behavior depend on cyclic AMP response element binding protein-mediated neurogenesis in the hippocampus. Neuropsychopharmacology 2009; 34:2404-19. [PMID: 19516250 PMCID: PMC2743762 DOI: 10.1038/npp.2009.66] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Inhibition of phosphodiesterase-4 (PDE4), an enzyme that catalyzes the hydrolysis of cyclic AMP (cAMP), increases phosphorylation of the cAMP response element binding protein (pCREB) and hippocampal neurogenesis, and produces antidepressant-like effects on behavior; however, causal links among these actions have not been established. In this study, chronic administration of rolipram (0.31-1.25 mg/kg, 16-23 days) produced antidepressant- and anxiolytic-like effects on behavior in mice. It also increased cAMP and pCREB levels in the hippocampus and prefrontal cortex, but increased Sox2, a marker for mitotic progenitor cells, only in the hippocampus. Chronic rolipram treatment also increased hippocampal neurogenesis, as evidenced by increased bromodeoxyuridine (BrdU)-positive cells in the hippocampal dentate gyrus. Methylazoxymethanol (MAM), which is toxic to proliferating cells, reversed rolipram-induced increases in BrdU-positive cells and pCREB in the hippocampus and partially blocked its behavioral effects. Approximately 84% of BrdU-positive cells became newborn neurons, 93% of which co-expressed pCREB; these proportions were not altered by rolipram or MAM, either alone or in combination. Finally, 3 weeks after the end of the MAM treatment, when neurogenesis was no longer inhibited, rolipram again increased hippocampal pCREB and its antidepressant- and anxiolytic-like effects were restored. Overall, these results suggest that rolipram produces its effects on behavior in a manner that at least partially depends on its neurogenic action in the hippocampus, targeting mitotic progenitor cells rather than newborn or mature neurons; cAMP/CREB signaling in hippocampal newborn neurons is critical for neurogenesis and contributes to the behavioral effects of rolipram.
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Affiliation(s)
- Yun-Feng Li
- Department of Behavioral Medicine & Psychiatry, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA,Department of Physiology & Pharmacology, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA
| | - Ying Huang
- Department of Behavioral Medicine & Psychiatry, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA,Department of Neurobiology & Anatomy, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA
| | - Simon L. Amsdell
- Department of Behavioral Medicine & Psychiatry, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA,Department of Physiology & Pharmacology, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA
| | - Lan Xiao
- Department of Behavioral Medicine & Psychiatry, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA,Department of Neurobiology & Anatomy, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA
| | - James M. O'Donnell
- Department of Behavioral Medicine & Psychiatry, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA,Department of Neurobiology & Anatomy, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA
| | - Han-Ting Zhang
- Department of Behavioral Medicine & Psychiatry, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA,Department of Physiology & Pharmacology, West Virginia University Health Sciences Center, Morgantown, WV 26506, USA
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110
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Severini C, La Corte G, Improta G, Broccardo M, Agostini S, Petrella C, Sibilia V, Pagani F, Guidobono F, Bulgarelli I, Ferri GL, Brancia C, Rinaldi AM, Levi A, Possenti R. In vitro and in vivo pharmacological role of TLQP-21, a VGF-derived peptide, in the regulation of rat gastric motor functions. Br J Pharmacol 2009; 157:984-93. [PMID: 19466987 DOI: 10.1111/j.1476-5381.2009.00192.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Vgf gene expression has been detected in various endocrine and neuronal cells in the gastrointestinal tract. In this study we investigated the pharmacological activity of different VGF-derived peptides. Among these, TLQP-21, corresponding to the 556-576 fragment of the protein was the unique active peptide, and its pharmacological profile was further studied. EXPERIMENTAL APPROACH The effects of TLQP-21 were examined in vitro by smooth muscle contraction in isolated preparations from the rat gastrointestinal tract and, in vivo, by assessing gastric emptying in rats. Rat stomach tissues were also processed for immunohistochemical and biochemical characterization. KEY RESULTS In rat longitudinal forestomach strips, TLQP-21 (100 nmol x L(-1)-10 micromol x L(-1)) concentration-dependently induced muscle contraction (in female rats, EC(50) = 0.47 micromol.L(-1), E(max): 85.7 +/- 7.9 and in male rats, 0.87 micromol x L(-1), E(max): 33.4 +/- 5.3; n = 8), by release of prostaglandin (PG)E(2) and PGF(2a) from the mucosal layer. This effect was significantly antagonized by indomethacin and selective inhibitors of either cyclooxygenase-1 (S560) or cyclooxygenase-2 (NS398). Immunostaining and biochemical studies confirmed the presence of VGF in the gastric neuronal cells. TLQP-21, injected i.c.v. (2-32 nmol per rat), significantly decreased gastric emptying by about 40%. This effect was significantly (P < 0.05) blocked by i.c.v. injection of indomethacin, suggesting that, also in vivo, this peptide acts in the brain stimulating PG release. CONCLUSIONS AND IMPLICATIONS The present results demonstrate that this VGF-derived peptide plays a central and local role in the regulation of rat gastric motor functions.
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Affiliation(s)
- C Severini
- Institute of Neurobiology and Molecular Medicine, 00143 Rome, Italy.
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111
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Chronic intracerebroventricular injection of TLQP-21 prevents high fat diet induced weight gain in fast weight-gaining mice. GENES AND NUTRITION 2009; 4:49-57. [PMID: 19247701 DOI: 10.1007/s12263-009-0110-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Accepted: 01/07/2009] [Indexed: 01/31/2023]
Abstract
The vgf gene regulates energy homeostasis and the VGF-derived peptide TLQP-21 centrally exerts catabolic effects in mice and hamsters. Here, we investigate the effect of chronic intracerebroventricular (icv) injection of TLQP-21 in mice fed high fat diet (HFD). Fast weight-gaining mice injected with the peptide or cerebrospinal fluid were selected for physiological, endocrine, and molecular analysis. TLQP-21 selectively inhibited the increase in body weight and epididymal white adipose tissue (eWAT) weight induced by HFD in control animals despite both groups having a similar degree of hyperphagia. TLQP-21 normalized the increase in leptin and decrease in ghrelin while increasing epinephrine and epinephrine/norepinephrine ratio when compared to values in controls. Finally, HFD-TLQP-21 mice showed a selective increase of eWAT beta3-adrenergic receptor mRNA. Peroxisome-proliferator-activated-receptor-delta and hormone-sensing-lipase mRNA were also upregulated. In conclusion, chronic icv infusion of TLQP-21 prevented the early phase of diet-induced obesity despite overfeeding. These effects were paralleled by activation of catabolic pathways within the eWAT. Our results further support a role for TLQP-21 as a catabolic neuropeptide.
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112
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Abstract
New neurons continue to be produced in adult mammals, including humans, predominantly in the anterior subventricular zone of the lateral ventricle and the subgranular zone of the dentate gyrus. This update focuses on the emerging concept that adult CNS neurogenesis can be regulated by targeting neurotransmitter receptors, which, in turn, drive expression of crucial neurotrophic and growth factors. Such an approach might enable the development of pharmacological treatments that harness the endogenous potential of the CNS to replace lost cells in neurological disorders such as stroke and Alzheimer's and Huntington's diseases. This review samples in vivo studies in adult mammals from 2006 to mid-2008. It also provides some considerations for navigating toward translation to human disorders. Among them are the formidable problems of scaling up production of new neurons within the two "niches" of the brain and delivering sufficient numbers to distant degenerating regions for cell replacement. However, an expedition can only succeed if started.
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Affiliation(s)
- Theo Hagg
- Kentucky Spinal Cord Injury Research Center, Departments of Neurological Surgery and of Pharmacology and Toxicology, University of Louisville, Kentucky, USA.
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113
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Abstract
Gene expression changes in neuropsychiatric and neurodegenerative disorders, and gene responses to therapeutic drugs, provide new ways to identify central nervous system (CNS) targets for drug discovery. This review summarizes gene and pathway targets replicated in expression profiling of human postmortem brain, animal models, and cell culture studies. Analysis of isolated human neurons implicates targets for Alzheimer's disease and the cognitive decline associated with normal aging and mild cognitive impairment. In addition to tau, amyloid-beta precursor protein, and amyloid-beta peptides (Abeta), these targets include all three high-affinity neurotrophin receptors and the fibroblast growth factor (FGF) system, synapse markers, glutamate receptors (GluRs) and transporters, and dopamine (DA) receptors, particularly the D2 subtype. Gene-based candidates for Parkinson's disease (PD) include the ubiquitin-proteosome system, scavengers of reactive oxygen species, brain-derived neurotrophic factor (BDNF), its receptor, TrkB, and downstream target early growth response 1, Nurr-1, and signaling through protein kinase C and RAS pathways. Increasing variability and decreases in brain mRNA production from middle age to old age suggest that cognitive impairments during normal aging may be addressed by drugs that restore antioxidant, DNA repair, and synaptic functions including those of DA to levels of younger adults. Studies in schizophrenia identify robust decreases in genes for GABA function, including glutamic acid decarboxylase, HINT1, glutamate transport and GluRs, BDNF and TrkB, numerous 14-3-3 protein family members, and decreases in genes for CNS synaptic and metabolic functions, particularly glycolysis and ATP generation. Many of these metabolic genes are increased by insulin and muscarinic agonism, both of which are therapeutic in psychosis. Differential genomic signals are relatively sparse in bipolar disorder, but include deficiencies in the expression of 14-3-3 protein members, implicating these chaperone proteins and the neurotransmitter pathways they support as possible drug targets. Brains from persons with major depressive disorder reveal decreased expression for genes in glutamate transport and metabolism, neurotrophic signaling (eg, FGF, BDNF and VGF), and MAP kinase pathways. Increases in these pathways in the brains of animals exposed to electroconvulsive shock and antidepressant treatments identify neurotrophic and angiogenic growth factors and second messenger stimulation as therapeutic approaches for the treatment of depression.
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114
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McHugh PC, Rogers GR, Glubb DM, Allington MD, Hughes M, Joyce PR, Kennedy MA. Downregulation of Ccnd1 and Hes6 in rat hippocampus after chronic exposure to the antidepressant paroxetine. Acta Neuropsychiatr 2008; 20:307-13. [PMID: 25384412 DOI: 10.1111/j.1601-5215.2008.00334.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
OBJECTIVE The mechanism of action of antidepressant drugs is not fully understood. Application of genomic methods enables the identification of biochemical pathways that are regulated by antidepressants, and this may provide novel clues to the molecular and cellular actions of these drugs. The present study examined gene expression profiles in the hippocampus of rats exposed to chronic antidepressant treatment. METHODS Animals were treated for 12 days with the selective serotonin reuptake inhibitor paroxetine; then, hippocampal ribonucleic acid was recovered, and changes in gene expression were assessed by microarray analysis. RESULTS A total of 160 genes that showed differential expression after paroxetine exposure were identified. Using functional relevance and observed fold change as selection criteria, the expression changes in a subset of these genes were confirmed by quantitative polymerase chain reaction. CONCLUSION Of this subset, only two genes, cyclin D1 (Ccnd1) and hairy and enhancer of split 6 (Hes6), showed robust and consistent changes in expression. Both genes were downregulated by paroxetine, and both have been previously implicated in neurogenesis. Further investigation of these two genes may provide new insight into the mechanism of action of antidepressants.
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Affiliation(s)
- Patrick C McHugh
- 1Department of Pathology, University of Otago, Christchurch, Christchurch, New Zealand
| | - Geraldine R Rogers
- 1Department of Pathology, University of Otago, Christchurch, Christchurch, New Zealand
| | - Dylan M Glubb
- 1Department of Pathology, University of Otago, Christchurch, Christchurch, New Zealand
| | - Melanie D Allington
- 1Department of Pathology, University of Otago, Christchurch, Christchurch, New Zealand
| | - Mark Hughes
- 2Genetics Factors, Riccarton, Christchurch, New Zealand
| | - Peter R Joyce
- 3Department of Psychological Medicine, University of Otago, Christchurch, Christchurch, New Zealand
| | - Martin A Kennedy
- 1Department of Pathology, University of Otago, Christchurch, Christchurch, New Zealand
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115
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Abstract
Unravelling the pathophysiology of depression is a unique challenge. Not only are depressive syndromes heterogeneous and their aetiologies diverse, but symptoms such as guilt and suicidality are impossible to reproduce in animal models. Nevertheless, other symptoms have been accurately modelled, and these, together with clinical data, are providing insight into the neurobiology of depression. Recent studies combining behavioural, molecular and electrophysiological techniques reveal that certain aspects of depression result from maladaptive stress-induced neuroplastic changes in specific neural circuits. They also show that understanding the mechanisms of resilience to stress offers a crucial new dimension for the development of fundamentally novel antidepressant treatments.
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Affiliation(s)
- Vaishnav Krishnan
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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116
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The neurotrophin-inducible gene Vgf regulates hippocampal function and behavior through a brain-derived neurotrophic factor-dependent mechanism. J Neurosci 2008; 28:9857-69. [PMID: 18815270 DOI: 10.1523/jneurosci.3145-08.2008] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
VGF is a neurotrophin-inducible, activity-regulated gene product that is expressed in CNS and PNS neurons, in which it is processed into peptides and secreted. VGF synthesis is stimulated by BDNF, a critical regulator of hippocampal development and function, and two VGF C-terminal peptides increase synaptic activity in cultured hippocampal neurons. To assess VGF function in the hippocampus, we tested heterozygous and homozygous VGF knock-out mice in two different learning tasks, assessed long-term potentiation (LTP) and depression (LTD) in hippocampal slices from VGF mutant mice, and investigated how VGF C-terminal peptides modulate synaptic plasticity. Treatment of rat hippocampal slices with the VGF-derived peptide TLQP62 resulted in transient potentiation through a mechanism that was selectively blocked by the BDNF scavenger TrkB-Fc, the Trk tyrosine kinase inhibitor K252a (100 nm), and tPA STOP, an inhibitor of tissue plasminogen activator (tPA), an enzyme involved in pro-BDNF cleavage to BDNF, but was not blocked by the NMDA receptor antagonist APV, anti-p75(NTR) function-blocking antiserum, or previous tetanic stimulation. Although LTP was normal in slices from VGF knock-out mice, LTD could not be induced, and VGF mutant mice were impaired in hippocampal-dependent spatial learning and contextual fear conditioning tasks. Our studies indicate that the VGF C-terminal peptide TLQP62 modulates hippocampal synaptic transmission through a BDNF-dependent mechanism and that VGF deficiency in mice impacts synaptic plasticity and memory in addition to depressive behavior.
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Thakker-Varia S, Alder J. Neuropeptides in depression: role of VGF. Behav Brain Res 2008; 197:262-78. [PMID: 18983874 DOI: 10.1016/j.bbr.2008.10.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Accepted: 10/05/2008] [Indexed: 12/20/2022]
Abstract
The monoamine hypothesis of depression is increasingly called into question by newer theories that revolve around changes in neuronal plasticity, primarily in the hippocampus, at both the structural and the functional levels. Chronic stress negatively regulates hippocampal function while antidepressants ameliorate the effects of stress on neuronal morphology and activity. Both stress and antidepressants have been shown to affect levels of brain-derived neurotrophic factor (BDNF) whose transcription is dependent on cAMP response element binding protein (CREB). BDNF itself has antidepressant-like actions and can induce transcription of a number of molecules. One class of genes regulated by both BDNF and serotonin (5-HT) are neuropeptides including VGF (non-acryonimic) which has a novel role in depression. Neuropeptides are important modulators of neuronal function but their role in affective disorders is just emerging. Recent studies demonstrate that VGF, which is also a CREB-dependent gene, is upregulated by antidepressant drugs and voluntary exercise and is reduced in animal models of depression. VGF enhances hippocampal synaptic plasticity as well as neurogenesis in the dentate gyrus but the mechanisms of antidepressant-like actions of VGF in behavioral paradigms are not known. We summarize experimental data describing the roles of BDNF, VGF and other neuropeptides in depression and how they may be acting through the generation of new neurons and altered synaptic activity. Understanding the molecular and cellular changes that underlie the actions of neuropeptides and how these adaptations result in antidepressant-like effects will aid in developing drugs that target novel pathways for major depressive disorders.
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Affiliation(s)
- Smita Thakker-Varia
- Department of Neuroscience and Cell Biology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, 683 Hoes Lane West, Robert Wood Johnson-School of Public Health 357A, Piscataway, NJ 08854-5635, United States
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Balu DT, Lucki I. Adult hippocampal neurogenesis: regulation, functional implications, and contribution to disease pathology. Neurosci Biobehav Rev 2008; 33:232-52. [PMID: 18786562 DOI: 10.1016/j.neubiorev.2008.08.007] [Citation(s) in RCA: 272] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Revised: 08/13/2008] [Accepted: 08/14/2008] [Indexed: 12/28/2022]
Abstract
It is now well established that the mammalian brain has the capacity to produce new neurons into adulthood. One such region that provides the proper milieu to sustain progenitor cells and is permissive to neuronal fate determination is located in the dentate gyrus of the hippocampus. This review will discuss in detail the complex process of adult hippocampal neurogenesis, including proliferation, differentiation, survival, and incorporation into neuronal networks. The regulation of this phenomenon by a number of factors is described, including neurotransmitter systems, growth factors, paracrine signaling molecules, neuropeptides, transcription factors, endogenous psychotropic systems, sex hormones, stress, and others. This review also addresses the functional significance of adult born hippocampal granule cells with regard to hippocampal circuitry dynamics and behavior. Furthermore, the relevance of perturbations in adult hippocampal neurogenesis to the pathophysiology of various disease states, including depression, schizophrenia, epilepsy, and diabetes are examined. Finally, this review discusses the potential of using hippocampal neurogenesis as a therapeutic target for these disorders.
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Affiliation(s)
- Darrick T Balu
- Department of Pharmacology, University of Pennsylvania, Philadelphia, PA, USA
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Almgren M, Nyengaard JR, Persson B, Lavebratt C. Carbamazepine protects against neuronal hyperplasia and abnormal gene expression in the megencephaly mouse. Neurobiol Dis 2008; 32:364-76. [PMID: 18773962 DOI: 10.1016/j.nbd.2008.07.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Revised: 07/11/2008] [Accepted: 07/29/2008] [Indexed: 11/18/2022] Open
Abstract
Carbamazepine (CBZ) is an anticonvulsant drug used to treat epilepsy and mood disorders. However, it can cause birth defects like reduced head circumference. It was recently shown to protect against brain overgrowth and seizure-induced abnormal plasticity in the megalencephalic mice Kv1.1(mceph/mceph), (mceph/mceph) despite remaining seizures. The mceph/mceph mouse displays two-fold enlarged hippocampus due to more neurons and astrocytes. Using stereology, we found that CBZ normalized the number of neurons and astrocytes in mceph/mceph hippocampus. To characterize CBZ's protective ability on brain growth we studied the gene expression profile of mceph/mceph and wild type hippocampus, with and without CBZ treatment. Microarray analysis revealed transcripts involved in proliferation, differentiation and apoptosis including; NPY, Penk, Vgf, Mlc1, Sstr4, ApoD, Ndn, Aatk, Rgs2 and Gabra5, where Vgf may be of particular interest. The results also support CBZ's effect on synaptic transmission through GABA A receptors, which could promote apoptotic neurodegeneration, affecting cell number.
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Affiliation(s)
- Malin Almgren
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska Hospital L8:00, 171 76 Stockholm, Sweden.
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120
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Yuan TF, Hoff R. Mirror neuron system based therapy for emotional disorders. Med Hypotheses 2008; 71:722-6. [PMID: 18703289 DOI: 10.1016/j.mehy.2008.07.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2008] [Revised: 07/01/2008] [Accepted: 07/02/2008] [Indexed: 01/13/2023]
Abstract
Mirror neuron system (MNS) represents one of the most important discoveries in the area of neuropsychology of past decades. More than 500 papers have been published in this area (PubMed), and the major functions of MNS include action understanding, imitation, empathy, all of which are critical for an individual to be social. Recent studies suggested that MNS can modulate emotion states possibly through the empathy mechanism. Here we propose that MNS-based therapies provide a non-invasive approach in treatments to emotional disorders that were observed in autism patients, post-stroke patients with depression as well as other mood dysregulation conditions.
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Affiliation(s)
- Ti-Fei Yuan
- Department of Anatomy, Li Kai Shing Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Hong Kong.
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Chan JP, Cordeira J, Calderon GA, Iyer LK, Rios M. Depletion of central BDNF in mice impedes terminal differentiation of new granule neurons in the adult hippocampus. Mol Cell Neurosci 2008; 39:372-83. [PMID: 18718867 DOI: 10.1016/j.mcn.2008.07.017] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Revised: 07/08/2008] [Accepted: 07/15/2008] [Indexed: 11/18/2022] Open
Abstract
Granule neurons generated in the adult mammalian hippocampus synaptically integrate to facilitate cognitive function and antidepressant efficacy. Here, we investigated the role of BDNF in facilitating their maturation in vivo. We found that depletion of central BDNF in mice elicited an increase in hippocampal cell proliferation without affecting cell survival or fate specification. However, new mutant neurons failed to fully mature as indicated by their lack of calbindin, reduced dendritic differentiation and an accumulation of calretinin(+) immature neurons in the BDNF mutant dentate gyrus. Furthermore, the facilitating effects of GABA(A) receptor stimulation on neurogenesis were absent in the mutants, suggesting that defects might be due to alterations in GABA signaling. Transcriptional analysis of the mutant hippocampal neurogenic region revealed increases in markers for immature neurons and decreases in neuronal differentiation facilitators. These findings demonstrate that BDNF is required for the terminal differentiation of new neurons in the adult hippocampus.
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Affiliation(s)
- Jason P Chan
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
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Comparison of dorsal root ganglion gene expression in rat models of traumatic and HIV-associated neuropathic pain. Eur J Pain 2008; 13:387-98. [PMID: 18606552 PMCID: PMC2706986 DOI: 10.1016/j.ejpain.2008.05.011] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Revised: 05/02/2008] [Accepted: 05/20/2008] [Indexed: 12/28/2022]
Abstract
To elucidate the mechanisms underlying peripheral neuropathic pain in the context of HIV infection and antiretroviral therapy, we measured gene expression in dorsal root ganglia (DRG) of rats subjected to systemic treatment with the anti-retroviral agent, ddC (Zalcitabine) and concomitant delivery of HIV-gp120 to the rat sciatic nerve. L4 and L5 DRGs were collected at day 14 (time of peak behavioural change) and changes in gene expression were measured using Affymetrix whole genome rat arrays. Conventional analysis of this data set and Gene Set Enrichment Analysis (GSEA) was performed to discover biological processes altered in this model. Transcripts associated with G protein coupled receptor signalling and cell adhesion were enriched in the treated animals, while ribosomal proteins and proteasome pathways were associated with gene down-regulation. To identify genes that are directly relevant to neuropathic mechanical hypersensitivity, as opposed to epiphenomena associated with other aspects of the response to a sciatic nerve lesion, we compared the gp120 + ddC-evoked gene expression with that observed in a model of traumatic neuropathic pain (L5 spinal nerve transection), where hypersensitivity to a static mechanical stimulus is also observed. We identified 39 genes/expressed sequence tags that are differentially expressed in the same direction in both models. Most of these have not previously been implicated in mechanical hypersensitivity and may represent novel targets for therapeutic intervention. As an external control, the RNA expression of three genes was examined by RT-PCR, while the protein levels of two were studied using western blot analysis.
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Abstract
Recent studies have identified adaptations of intracellular signaling pathways and target genes that could contribute or modulate the action of antidepressant drugs, as well as exercise-mediated antidepressant responses. Understanding these adaptations, particularly those changes that are common to diverse antidepressant treatments, is important for the development of more potent and specific treatments of depression. There is growing evidence that growth factors may be important mediators of antidepressant responses. Now, VGF (not an acronym), a neuropeptide that has previously been shown to be involved in maintaining organismal energy balance, as well as in mediating hippocampal synaptic plasticity, may be involved in mediating antidepressant responses. These studies use in vivo approaches to link VGF to the antidepressant-like behavioral effects produced by antidepressant drugs and exercise.
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Abstract
PURPOSE OF REVIEW Failing adult neurogenesis is increasingly considered a factor in the pathogenesis and course of psychiatric disorders. The level of evidence in favor of such hypotheses varies, but disturbed cellular plasticity in the hippocampus may be a common aspect of several neuropsychiatric diseases. RECENT FINDINGS This review covers the literature from mid-2006 to the end of 2007. We discuss studies and theoretical papers dealing with the contribution of adult neurogenesis to dementias and neurodegeneration, major depression, schizophrenia, and alcohol and drug abuse. Of these disorders, most progress has recently been made with schizophrenia for which, in contrast to the other conditions, suggestive genetic evidence exists (e.g. Disc1, Npas3). SUMMARY Failing adult hippocampal neurogenesis may not explain major depression, addiction or schizophrenia, but contributes to the hippocampal aspects of the disease. We propose that the key to a more thorough understanding of this contribution will come from increased knowledge on the functional relevance of new neurons in the hippocampus and better clinical data relating to symptoms possibly related to such function. Research on the molecular basis of adult hippocampal neurogenesis may help to explain how hippocampal aspects of these disorders develop.
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