Anders Tingström

Increased neurogenesis in a model of electroconvulsive therapy

BACKGROUND Electroconvulsive therapy (ECT) is a widely used and efficient treatment modality in psychiatry, although the basis for its therapeutic effect is still unknown. Past research has shown seizure activity to be a regulator of neurogenesis in the adult brain. This study examines the effect of a single and multiple electroconvulsive seizures on neurogenesis in the rat dentate gyrus. METHODS Rats were given either a single or a series of 10 electroconvulsive seizures. At different times after the seizures, a marker of proliferating cells, Bromodeoxyuridine (BrdU), was administered to the animals. Subsequently, newborn cells positive for BrdU were counted in the dentate gyrus. Double staining with a neuron-specific marker indicated that the newborn cells displayed a neuronal phenotype. RESULTS A single electroconvulsive seizure significantly increased the number of new born cells in the dentate gyrus. These cells survived for at least 3 months. A series of seizures further increased neurogenesis, indicating a dose-dependent mechanism. CONCLUSIONS We propose that generation of new neurons in the hippocampus may be an important neurobiologic element underlying the clinical effects of electroconvulsive seizures.

Hippocampal cytogenesis correlates to escitalopram-mediated recovery in a chronic mild stress rat model of depression

From clinical studies it is known that recurrent depressive episodes associate with a reduced hippocampal volume. Conversely, preclinical studies have shown that chronic antidepressant treatment increases hippocampal neurogenesis. Consequently, it has been suggested that a deficit in hippocampal neurogenesis is implicated in the pathophysiology of depression. To study a potential correlation between recovery and hippocampal cytogenesis, we established the chronic mild stress (CMS) rat model of depression. When rats are subjected to CMS, several depressive symptoms develop, including the major symptom anhedonia. Rats were exposed to stress for 2 weeks and subsequently to stress in combination with antidepressant treatment for 4 consecutive weeks. The behavioral deficit measured in anhedonic animals is a reduced intake of a sucrose solution. Prior to perfusion animals were injected with bromodeoxyuridine (BrdU), a marker of proliferating cells. Brains were sectioned horizontally and newborn cells positive for BrdU were counted in the dentate gyrus and tracked in a dorsoventral direction.CMS significantly decreased sucrose consumption and cytogenesis in the ventral part of the hippocampal formation. During exposure to the antidepressant escitalopram, given as intraperitoneally dosages of either 5 or 10 mg/kg/day, animals distributed in a bimodal fashion into a group, which recovered (increase in sucrose consumption), and a subgroup, which refracted treatment (no increase in sucrose consumption). Chronic treatment with escitalopram reversed the CMS-induced decrease in cytogenesis in the dentate gyrus of the ventral hippocampal formation, but in recovered animals only. Our data show a correlation between recovery from anhedonia, as measured by cessation of behavioral deficits in the CMS model, and an increase in cytogenesis in the dentate gyrus of the ventral hippocampal formation.

Beta 1 integrin-mediated collagen gel contraction is stimulated by PDGF.

The attachment of primary rat hepatocytes and fibroblasts to collagen type I is mediated by non-RGD-dependent beta 1 integrin matrix receptors. In this report we describe a novel 96-well microtiter plate assay for the quantification of fibroblast-mediated contraction of floating collagen type I gels. Fetal calf serum and platelet-derived growth factor (PDGF), but not transforming growth factor-beta 1, stimulated primary rat heart fibroblasts and normal human diploid fibroblasts (AG 1518) to contract collagen gels to less than 10% of the initial gel volume within a 24-h incubation period. Rabbit polyclonal antibodies directed to the rat hepatocyte integrin beta 1-chain inhibited the PDGF-stimulated collagen gel contraction. The inhibitory activity on contraction of the anti-beta 1 integrin IgG could be overcome by adding higher doses of PDGF. The contraction process was not blocked by anti-fibronectin IgG nor by synthetic peptides containing the tripeptide Arg-Gly-Asp (RGD), in concentrations that readily blocked fibroblast attachment to fibronectin-coated planar substrates. Autologous fibronectin or control peptides containing the tripeptide Arg-Gly-Glu were without effect. Immunofluorescence microscopy on fibroblasts grown within collagen gels revealed a punctate distribution of the beta 1 integrin and a lack of detectable levels of endogenously produced fibronectin. Collectively these data suggest a role for integrin collagen receptors with affinity for collagen fibers, distinct from the previously described RGD-dependent fibronectin receptors, in the fibronectin-independent PDGF-stimulated collagen gel contraction process.

INDUCTION OF B-TYPE RECEPTORS FOR PLATELET-DERIVED GROWTH FACTOR IN VASCULAR INFLAMMATION: POSSIBLE IMPLICATIONS FOR DEVELOPMENT OF VASCULAR PROLIFERATIVE LESIONS

Expression of B-type receptors for platelet-derived growth factor (PDGF) in frozen sections of blood vessels from tissues affected by abnormal vascular cell proliferation was investigated by immunohistochemical techniques and compared with expression of these receptors in blood vessels of normal tissues. Receptors were not expressed, or expressed at low levels, in vessels of normal tissues. In contrast, a pronounced expression of PDGF B-type receptors was seen on vascular smooth muscle cells in atherosclerotic plaques, rejected kidneys, and chronic synovitis. These observations suggest induction of PDGF B-type receptors on vascular smooth muscle cells in inflamed tissues, which would render such cells responsive to growth stimulation by PDGF released from captured platelets, or produced locally (eg, by inflammatory cells or smooth muscle cells). Autocrine or paracrine stimulation of cell growth caused by the effect of PDGF on cells with induced receptors may be important in the formation of the proliferative lesions found in atherosclerosis and in certain forms of chronic inflammation.

Electroconvulsive seizures increase hippocampal neurogenesis after chronic corticosterone treatment.

Major depression is often associated with elevated glucocorticoid levels. High levels of glucocorticoids reduce neurogenesis in the adult rat hippocampus. Electroconvulsive seizures (ECS) can enhance neurogenesis, and we investigated the effects of ECS in rats where glucocorticoid levels were elevated in order to mimic conditions seen in depression. Rats given injections of corticosterone or vehicle for 21 days were at the end of this period treated with either a single or five daily ECSs. Proliferating cells were labelled with bromodeoxyuridine (BrdU). After 3 weeks, BrdU‐positive cells in the dentate gyrus were quantified and analyzed for co‐labelling with the neuronal marker neuron‐specific nuclear protein (NeuN). In corticosterone‐treated rats, neurogenesis was decreased by 75%. This was counteracted by a single ECS. Multiple ECS further increased neurogenesis and no significant differences in BrdU/NeuN positive cells were detected between corticosterone‐ and vehicle‐treated rats given five ECS. Approximately 80% of the cells within the granule cell layer and 10% of the hilar cells were double‐labelled with BrdU and NeuN.

Platelet-derived growth factor promotes survival of rat and human mesencephalic dopaminergic neurons in culture

SummaryThe effect of two isoforms of platelet-derived growth factor (PDGF), PDGF-AA and PDGF-BB, was tested on dissociated cell cultures of ventral mesencephalon from rat and human embryos. PDGF-BB but not PDGF-AA reduced the progressive loss of tyrosine hydroxylase- (TH)-positive neurons in rat and human cell cultures. The mean number of TH-positive cells in the PDGF-BB-treated rat culture was 64% and 106% higher than in the control cultures after 7 and 10 days in vitro, respectively. Corresponding figures for human TH-positive neurons were 90% and 145%. The influence of PDGF-BB was specific for TH-positive neurons and not a general trophic effect, since no change of either total cell number or metabolic activity was found. In PDGF-BB-treated cultures of human but not rat tissue the TH-positive neurons had longer neurites than observed in control or PDGF-AA-treated cultures. These data indicate that PDGF-BB may act as a trophic factor for mesencephalic dopaminergic neurons and suggest that administration of PDGF-BB could ameliorate degeneration and possibly promote axonal sprouting of these neurons in vivo.

Electroconvulsive seizures induce proliferation of NG2-expressing glial cells in adult rat amygdala.

BACKGROUND Volumetric changes and glial pathology have been reported in the amygdala in patients with major depressive disorder. Here we report an analysis of glial cell proliferation in response to electroconvulsive seizures (ECS), clinically used for the treatment of severe depression. METHODS Male Wistar rats were subjected to five ECS-treatments and then injected with bromodeoxyuridine (BrdU) to detect cell proliferation in the amygdala. The animals were transcardially perfused either 12 hours or 3 weeks after the last BrdU injection. Tissue sections were double-stained for BrdU and the cell-type markers NG2, OX-42, RIP, S-100beta, Doublecortin, or NeuN. RESULTS Electroconvulsive seizures dramatically increased the proliferation of amygdala cells expressing the oligodendrocyte progenitor marker NG2. Bromodeoxyuridine-labeled NG2-expressing cells were still present after 3 weeks of survival, and a small proportion of the proliferating cells had differentiated into mature oligodendrocytes. CONCLUSIONS Major depression has been associated with a reduction of glial cells. Our results show that ECS, an antidepressant treatment, significantly increases the number of NG2+ glial cells and mature oligodendrocytes in the adult rat amygdala.

Authenticity, depression, and deep brain stimulation

In 2005 the journal Neuron published Mayberg et al.’s (2005) pioneering study on deep brain stimulation (DBS) targeting treatment-refractory major depressive disorder (MDD). Since then a handful of studies, in total encompassing little over 50 patients, have been published (Aouizerate et al., 2005; Jimenez et al., 2005; Mayberg et al., 2005; Kuhn et al., 2007; Lozano et al., 2008; Neimat et al., 2008; Schlaepfer et al., 2008; Malone et al., 2009; Bewernick et al., 2010; Sartorius et al., 2010) and larger trials are underway (Bell et al., 2009). A common ethical concern voiced when DBS is used for a psychiatric disorder such as MDD is that the stimulation specifically targets cognition, mood, and behavior; elements which are closely linked to the patients personality. Obviously, this holds true also for other antidepressants such as psychotherapy and medication. Apart from that these standard therapies have been of no avail for the patients considered for MDD DBS, one could still ask whether their potential to alter cognition, mood, and behavior, differ - with regard to ethical concerns - from that of DBS. Further, the relevant ethical concern is arguably not what functions the stimulation are intended to alter, as in psychiatric indications, but rather what functions that could be altered by DBS. Unintended alterations of cognition, mood and behaviour could occur as a consequence of both psychiatric and motoric DBS. Thus, potential alterations of personality seem, apart from the historical stigma connected with the former, to be relevant for most DBS indications. A lot of work remains to be done before a comprehensive analysis of these concerns could be presented. Our contribution is to introduce one question relevant to the intersection of DBS, MDD, and the notion(s) of authenticity.

Environmental enrichment, exercise and corticosterone affect endothelial cell proliferation in adult rat hippocampus and prefrontal cortex

Stress and environmental enrichment have opposing effects on cerebral cellular plasticity. Stress-induced disturbances in neuronal and glial plasticity have been implicated in the pathophysiology of affective disorders. Patients with depression often show volume reductions in specific brain regions. The mechanisms behind these changes are not well understood, but animal studies have indicated that increased levels of glucocorticoids and stress have negative impact on the neuronal and glial cell populations. On the contrary, enriched environment and physical activity have positive effects. In this study we have examined the effect of corticosterone (CORT), environmental enrichment (EE) and running on angiogenesis in hippocampus and prefrontal cortex (PFC). We demonstrate a dramatic inhibition in endothelial cell proliferation in these brain regions in CORT-treated rats. Environmental enrichment had the opposite effect and stimulated endothelial cell proliferation both in the hippocampus and in the PFC. Running had a stimulatory effect in hippocampus, but not in the PFC. We suggest that the angiostatic effect of CORT demonstrated in this study might be paralleled in human subjects exposed to high levels of stress hormones for prolonged periods of time. Raised cortisol levels in depressed or old patients could, by reducing endothelial cell formation/turnover, lead to rarefaction and aging of the vascular bed, and as a result, neuronal function could be impaired. It is tempting to speculate that a physically and intellectually active life may protect against stress-induced vascular changes. Therapeutic agents also targeting the cerebral vasculature could consequently constitute a new tool in the combat of stress-related disorders.

Electroconvulsive seizures induce angiogenesis in adult rat hippocampus

BACKGROUND Electroconvulsive seizure (ECS)-treatment, a model for electroconvulsive therapy (ECT) has been shown to induce proliferation of endothelial cells in the dentate gyrus (DG) of adult rats. Here we quantified the net angiogenic response after chronic ECS-treatment in the molecular layer (ML) of the dentate gyrus. Patients undergoing ECT are routinely oxygenated to prevent hypoxia, a known inducer of angiogenesis. Therefore we also examined the effect of oxygenation on ECS-induced proliferation of endothelial cells. METHODS Total endothelial cell numbers and vessel length were estimated utilizing design based stereological analysis methods. Endothelial cell proliferation in the DG after ECS with or without oxygenation was assessed using bromodeoxyuridine. RESULTS The total number of endothelial cells and total vessel length was increased. Oxygenation did not abolish the ECS-induced proliferation of endothelial cells in the DG. CONCLUSIONS ECS-treatment induces a dramatic increase in endothelial cell proliferation leading to a 30% increase in the total number of endothelial cells. The increase in cell number resulted in a 16% increase in vessel length. These findings raise the possibility that similar vascular growth is induced by clinically administered ECT.