Glial pathology in an animal model of depression: reversal of stress-induced cellular, metabolic and behavioral deficits by the glutamate-modulating drug riluzole.

Growing evidence indicates that glia pathology and amino-acid neurotransmitter system abnormalities contribute to the pathophysiology and possibly the pathogenesis of major depressive disorder. This study investigates changes in glial function occurring in the rat prefrontal cortex (PFC) after chronic unpredictable stress (CUS), a rodent model of depression. Furthermore, we analyzed the effects of riluzole, a Food and Drug Administration-approved drug for the treatment of amyotrophic laterosclerosis, known to modulate glutamate release and facilate glutamate uptake, on CUS-induced glial dysfunction and depressive-like behaviors. We provide the first experimental evidence that chronic stress impairs cortical glial function. Animals exposed to CUS and showing behavioral deficits in sucrose preference and active avoidance exhibited significant decreases in 13C-acetate metabolism reflecting glial cell metabolism, and glial fibrillary associated protein (GFAP) mRNA expression in the PFC. The cellular, metabolic and behavioral alterations induced by CUS were reversed and/or blocked by chronic treatment with the glutamate-modulating drug riluzole. The beneficial effects of riluzole on CUS-induced anhedonia and helplessness demonstrate the antidepressant action of riluzole in rodents. Riluzole treatment also reversed CUS-induced reductions in glial metabolism and GFAP mRNA expression. Our results are consistent with recent open-label clinical trials showing the drug's effect in mood and anxiety disorders. This study provides further validation of hypothesis that glial dysfunction and disrupted amino-acid neurotransmission contribute to the pathophysiology of depression and that modulation of glutamate metabolism, uptake and/or release represent viable targets for antidepressant drug development.

The differential contributions of the parvocellular and the magnocellular subdivisions of the red nucleus to skilled reaching in the rat.

During the execution of the skilled reaching task, naïve rats bring their elbow to the midline of their body to aim at the food target, perform the arpeggio movement to grasp it and supinate the paw to bring the food to their mouth. Red nucleus lesions in the rat interfere with each of these three movement elements of reaching. On the other hand, lesions to the rubrospinal tract, which originate from the magnocellular subdivision of the red nucleus, only interfere with the arpeggio movement. This latter evidence strongly suggests that impairment in aiming and supinating could be under the control of the parvocellular subdivision of the red nucleus. In order to test this hypothesis, rats were trained on the skilled reaching task and then received either complete lesions of the red nucleus or lesions restricted to its parvo- or magnocellular subdivision. In line with previous data, complete excitotoxic lesions of the red nucleus compromised limb aiming, arpeggio and supination. Lesions restricted to the parvocellular division of the red nucleus abolish supination and interfere with aiming, although the latter result did not reach significance. The results are discussed in terms of the distinct connectivity and functional significance of these two architectonic subdivisions of the red nucleus.

Glucocorticoid response to forced exercise in laboratory house mice (Mus domesticus).

We examined the time course and sex differences of the glucocorticoid response to forced, moderate-intensity treadmill exercise in outbred laboratory house mice. Mice (n = 64 total) were divided into eight groups, each of four males and four females, which were run on a motorized treadmill at 1.0 km/h for either 0, 2, 5, 10, 15, 25, 40, or 60 min. Serum samples were taken immediately after exercise and corticosterone (CORT) concentration was determined by radioimmunoassay. Resting CORT levels ranged between 11.6 and 29.5 ng/mL for both sexes. CORT levels increased with length of exercise and then exhibited a plateau by 25 min in females and by 40 min in males. Females displayed a significantly more rapid increase in serum CORT levels and attained higher maximal CORT levels than males. Females also had significantly larger adrenal glands, both in absolute terms and relative to body mass.

A molecular characterization of the choroid plexus and stress-induced gene regulation.

The role of the choroid plexus (CP) in brain homeostasis is being increasingly recognized and recent studies suggest that the CP has a more important role in physiological and pathological brain functions than currently appreciated. To obtain additional insight on the CP function, we performed a proteomics and transcriptomics characterization employing a combination of high resolution tandem mass spectrometry and gene expression analyses in normal rodent brain. Using multiple protein fractionation approaches, we identified 1400 CP proteins in adult CP. Microarray-based comparison of CP gene expression with the kidney, cortex and hippocampus showed significant overlap between the CP and the kidney. CP gene profiles were validated by in situ hybridization analysis of several target genes including klotho, CLIC 6, OATP 14 and Ezrin. Immunohistochemical analyses were performed for CP and enpendyma detection of several target proteins including cytokeratin, Rab7, klotho, tissue inhibitor of metalloprotease 1 (TIMP1), MMP9 and glial fibrillary acidic protein (GFAP). The molecular functions associated with various proteins of the CP proteome indicate that it is a blood-cerebrospinal fluid (CSF) barrier that exhibits high levels of metabolic activity. We also analyzed the gene expression changes induced by stress, an exacerbating factor for many illnesses, particularly mood disorders. Chronic stress altered the expression of several genes, downregulating 5HT2C, glucocorticoid receptor and the cilia genes IFT88 and smoothened while upregulating 5HT2A, BDNF, TNFα and IL-1b. The data presented here attach additional significance to the emerging importance of CP function in brain health and CNS disease states.

An osmotin-like cryoprotective protein from the bittersweet nightshade Solanum dulcamara.

Cold acclimation in plants is a polygenic phenomenon involving increased expression of several genes. The gene products participate either directly or indirectly towards increasing cold tolerance. Evidence of proteins having a direct effect on cold tolerance is emerging but limited. With isolated protoplasts from warm-grown kale (Brassica oleracea) as a model system, we tested protein fractions from winter bittersweet nightshade, Solanum dulcamara, stems for the presence of proteins that have a cryoprotective effect. Purification of one such fraction resulted in isolation of a 25 kDa protein. N-terminal Edman degradation amino acid sequence analysis showed that it has high homology to osmotin and osmotin-like proteins. When added to warm-grown protoplasts, it increased the cryosurvival of frozen-thawed protoplasts by 24% over untreated or BSA-treated controls at -8 degrees C. A cDNA library which was made in November from stems and leaves of S. dulcamara was successfully screened for the corresponding cDNA clone. The deduced amino acid sequence indicated that the protein consists of 206 amino acid residues including a N-terminal signal sequence and a putative C-terminal propeptide. The mature protein, without the N-terminal signal sequence, was expressed in Escherichia coli. The partially purified protein in the supernatant fraction of the culture medium had cryoprotective activity.