Search

Neuronal circuits in the brain help to control feeding behavior and systemic metabolism in response to afferent nutrient and hormonal signals. Although astrocytes have historically been assumed to have little relevance for such neuroendocrine control, we investigated whether lipid uptake via lipoprotein lipase (LPL) in astrocytes is required to centrally regulate energy homeostasis. Ex vivo studies with hypothalamus-derived astrocytes showed that LPL expression is upregulated by oleic acid, whereas it is decreased in response to palmitic acid or triglycerides. Likewise, astrocytic LPL deletion reduced the accumulation of lipid droplets in those glial cells. Consecutive in vivo studies showed that postnatal ablation of LPL in glial fibrillary acidic protein-expressing astrocytes induced exaggerated body weight gain and glucose intolerance in mice exposed to a high-fat diet. Intriguingly, astrocytic LPL deficiency also triggered increased ceramide content in the hypothalamus, which may contribute to hypothalamic insulin resistance. We conclude that hypothalamic LPL functions in astrocytes to ensure appropriately balanced nutrient sensing, ceramide distribution, body weight regulation, and glucose metabolism. [ABSTRACT FROM AUTHOR]

Background: Studies of major depressive disorder (MDD) in postmortem brain tissue report pathology in the serotonin system. Hypothesis: Length density of axons expressing SERT is decreased in the orbitofrontal cortex (ORB) in MDD. Methods: ORB from 18 subjects with MDD and age-matched controls were fixed, sectioned and SERT antibody was used to immunohistochemically label the transporter. The total 3-D length density of SERT-IR axons in ORB layer VI was estimated using Stereo Investigator. Results: Age of subjects with MDD was negatively correlated with SERT fiber length (r=0.609, p<0.001). The SERT fiber length was significantly increased in younger MDD subjects vs. age-matched controls (p<0.01) and a trend for decrease in older MDD subjects. Conclusion: This effect of age on SERT fiber length in MDD is consistent with the effect of age on density of pyramidal neurons in ORB. Pyramidal neurons in deep ORB project indirectly to the dorsal raphe, where there is other evidence of serotonergic pathology in MDD. Pertinence: Overall age-related decrease in the length density of SERT-IR fibers and trend for a decrease in the length density of SERT-IR fibers in older subjects with MDD support reported frontal white matter lesions in older MDD subjects. [ABSTRACT FROM AUTHOR]

In the present study, we investigated the influence of repeated treatment with fluoxetine (FLU, 5 or 10 mg/kg) and amantadine (AMA, 10 mg/kg), given separately or jointly (twice daily for 14 day), at the mRNA level (the Northern blot) in the hippocampus and cerebral cortex. The experiment was carried out on male Wistar rats. The tissue for biochemical assays was dissected 24 h after the last dose of drug. We also studied the effect of repeated treatment with FLU and AMA on the action of 5-hydroksytryptamine (5-HT)(1A)- and 5-HT(2) receptor agonists (+/-)-8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) and (+/-)-1-(4-iodo-2,5-dimethoxy-phenyl)-2-aminopropane ((+/-)DOI), respectively, in behavioral tests. The obtained results showed that FLU (10 mg/kg) in the hippocampus, and FLU (5 and 10 mg/kg) and AMA(10 mg/kg) in the cerebral cortex, significantly elevated BDNF mRNA levels. Joint administration of FLU (5 or 10 mg/kg) and AMA(10 mg/kg) induced a more substantial increase in BDNF gene expression in the cerebral cortex (but not in the hippocampus), and inhibited the behavioral syndrome induced by 8-OH-DPAT or (+/-)DOI (compared to treatment with either drug alone). The obtained results suggest that the enhancement of BDNF gene expression may be essential for the therapeutic effect of the co-administration of FLU and AMA in drug-resistant depressed patients, and that among other mechanisms, 5-HT(1A) and 5-HT(2) receptors may play some role in this effect.

Olfactory bulbectomy (OB) is an established animal model of depression that has been investigated mostly in rats. As in human major depression, OB induces behavioral alterations that can be ameliorated by chronic antidepressant treatment. Furthermore, it was shown that OB induces changes of various protein receptor levels in brain areas that are important in antidepressant therapy. In the present study, we investigated the effects of OB and amitriptyline (AMI) treatment on the expression of metabotropic glutamate receptors (mGluR) in the mouse hippocampus using the western blot method. AMI was given for 14 days, in a dose of 10 mg/kg, intraperitoneally. The levels of most subtypes of mGlu receptors, e.g., mGlu1a (mGluR group I), mGlu2/3 (mGluR group II), mGlu4, and mGlu7 (mGluR group III) receptors, were measured. Additionally, immunohistochemical stainings were made in slices of the mouse hippocampus. It was found that OB induced an increase in mGluR1a-immunoreactivity (IR), which was abolished by AMI treatment in the hippocampus. The removal of the olfactory bulbs caused a decrease in the level of mGlu2/3 receptors in the hippocampus, which was reversed after AMI administration. MGluR4-IR was decreased in the hippocampus in all the groups studied. A decrease of mGluR7-IR was observed in the OB group, and the effect was abolished by the administration of AMI. However, decreases in the level of mGlu2/3 and mGlu7 receptors were observed after AMI administration. The results obtained indicate an influence of OB on mGlu receptors levels in the hippocampus, and the OB-induced effect can be reversed by chronic AMI treatment in the case of mGlu1a, mGlu2/3 and mGlu7 receptors.

Treatment with most antidepressants induces expression of the gene coding for brain-derived neurotrophic factor (BDNF) in the hippocampus (and cerebral cortex). Recent data indicate antidepressant-like activity of group I mGlu receptor (mGluR1 and mGluR5) antagonists in animal tests/models. We now report that chronic treatment with 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a selective mGlu5 receptor antagonist, increased hippocampal but reduced cortical BDNF mRNA level (Northern blot). Desipramine, a classic antidepressant, increased BDNF mRNA level in both examined brain regions. This is the first demonstration that an antagonist of mGlu5 receptors, like a majority of well-established antidepressants, induces hippocampal BDNF gene expression. A significance of MPEP ability to reduce cortical BDNF needs further study. Nevertheless, this observation further indicates a potential antidepressant activity of the group I mGlu receptor antagonists in human depression.

The problem of drug-resistant depression indicates a strong need for alternative antidepressant therapies. Recently it was shown that joint administration of imipramine (IMI) and metyrapone (MET), an inhibitor of glucocorticoid synthesis, produced a more potent "antidepressant" effect in the forced swimming test than did treatment with either drug alone. Our studies also showed that co-administration of IMI and MET to drug-resistant, unipolar depressed patients effected a clinical improvement. In addition, recent studies indicated a role of the brain-derived neurotrophic factor (BDNF) in the mechanism of action of antidepressant drugs (ADs). Since the most potent effect of ADs on BDNF gene expression was found after prolonged treatment, in the present research we investigated the influence of repeated treatment with IMI (5 or 10 mg/kg) and MET (50 mg/kg), given separately or jointly (twice daily for 14 day), on the BDNF mRNA level (the Northern blot) in the hippocampus and cerebral cortex. The experiment was carried out on male Wistar rats. The tissue for biochemical assays was collected 24 h after the last dose of IMI and MET. The obtained results showed that in the hippocampus IMI (10 mg/kg) and cerebral cortex IMI (5 mg/kg) and MET (50 mg/kg) significantly elevated the BDNF mRNA level. Joint administration of IMI (10 mg/kg) and MET (50 mg/kg) induced a more potent increase BDNF gene expression in both the examined brain regions (compared to the treatment with either drug alone). Moreover, the obtained results suggested that BDNF may be involved in the mechanism of the synergistic antidepressant effect of IMI and MET in drug-resistant depressed patients.