Gene Expression In Rat Hypothalamus Research Articles

Investigation of brain-derived neurotrophic factor (BDNF) gene expression in hypothalamus of obese rats: Modulation by omega-3 fatty acids

Purpose: The aim of this study was investigating the effect of omega-3 fatty acids (ω-3 FAs) on brain-derived neurotrophic factor (BDNF) gene expression, using in vivo and in vitro models, to unravel the potential mechanisms of polyunsaturated fatty acids use in obesity.Materials and methods: Twenty-nine Sprague-Dawley rats were divided into three groups; lean controls fed normal chow diet for 14 weeks, obese controls fed 60% of their diet as saturated fats for 14 weeks, and ω-3 FAs-treated rats fed 60% saturated fat diet for 14 weeks with concomitant oral administration of 400 mg/kg/day ω-3 FAs, mainly docosahexaenoic acid and EPA, from week 12 to week 14. For the in vitro experiment, hypothalamic cells from six obese rats were cultured in the presence of different concentrations of ω-3 FAs to determine its direct effect on BDNF expression.Results: In vivo results showed that obesity has negative effect on BDNF gene expression in rat hypothalamus that was reversed by administration of ω-3 FAs. Obese rats showed hypercholesterolemia, hypertriglyceridemia, normoinsulinemia, hyperglycemia and hyperleptinemia. Treatment with ω-3 FAs showed significant decrease in serum total cholesterol and TAG. Also serum glucose level and HOMA index were decreased significantly. In vitro results demonstrated the increase in BDNF expression by ω-3 FAs in a dose-dependent manner.Conclusions: Obesity causes down-regulation of BDNF gene expression that can be reversed by ω-3 FAs treatment, making them an interesting treatment approach for obesity and metabolic disease.

Up-regulation of orexigenic and down-regulation of anorexigenic neuropeptide gene expression in rat hypothalamus after partial lipectomy

Leptin down-regulates orexigenic and up-regulates anorexigenic neuropeptide gene expression in hypothalamus. Surgical removal of adipose tissue leads to decrease in circulating leptin concentrations in rats. In the present study, we tested: (a) regulation of neuropeptide gene expression in hypothalamus, (b) food intake, and (c) standard growth rate after removal of adipose tissue in rats. Partial lipectomy caused an approximately 10-fold reduction of subcutaneous, retroperitoneal and epididymal adipose tissue weight (at the end of experiments adipose tissue weight was 1.5±0.9 in lipectomy and 15±3.9g in control rats; statistically significant). Compared to control rats, the animals subjected to lipectomy presented increased food intake, standard growth rate, and decreased serum leptin concentrations (2.6±0.8 vs. 3.7±1.2ng/mL in the controls, statistically significant). These changes were associated with approximately twofold increase in neuropeptide Y, threefold increase in agouti-related peptide (orexigenic neuropeptides) and about 50% decrease in pro-opiomelanocortin and cocaine–amphetamine-regulated transcript peptide (anorexigenic neuropeptides) mRNA levels in the hypothalamus. These results suggest that partial lipectomy, leading to a decrease in circulating leptin concentrations, may exert an effect on hypothalamic orexigenic and anorexigenic neuropeptide gene expression, and consequently modulate food intake and standard growth rate in rats.

Cocaine place conditioning increases pro-opiomelanocortin gene expression in rat hypothalamus

Recent research suggests an involvement of pro-opiomelanocortin (POMC) gene products in modulating cocaine reward and addiction-like behaviors in rodents. In this study, we investigated whether cocaine-induced conditioned place preference (CPP) alters POMC gene expression in the brain or pituitary of rats. Sprague-Dawley rats were conditioned with 4 injections of 0, 10 or 30mg/kg cocaine (i.p.) over 8 days and tested 4 days after the last conditioning session. Another group received the same pattern of cocaine injections without conditioning. POMC mRNA levels in the hypothalamus (including arcuate nucleus), amygdala and anterior pituitary, as well as plasma ACTH and corticosterone levels were measured. Cocaine place conditioning at 10 and 30mg/kg doses increased POMC mRNA levels in a dose-dependent manner in the hypothalamus, with no effect in the amygdala. Cocaine CPP had no effect on POMC mRNA levels in the anterior pituitary or on plasma ACTH or corticosterone levels. In rats that received cocaine at 30mg/kg without conditioning, there was no such effect on hypothalamic POMC mRNA levels. Alteration of POMC gene expression in the hypothalamus is region-specific after cocaine place conditioning, and dose-dependent. The increased POMC gene expression in the hypothalamus suggests that it is involved in the reward/learning process of cocaine-induced conditioning.

Refeeding after prolonged food restriction differentially affects hypothalamic and adipose tissue leptin gene expression

Rat adipose tissue is the principal site of leptin synthesis, however, leptin gene expression has been demonstrated in many rat tissues. Some data indicate that leptin produced by human brain and adipose tissue could cooperate in the regulation of food intake. In this case the regulation of leptin gene expression in hypothalamus and in adipose tissue should be coordinately regulated. Food restriction is often undertaken by many humans trying to lose body weight. Thus, the current study was aimed to analyze whether leptin gene expression in rat hypothalamus and in adipose tissue is regulated synchronously by prolonged food restriction and prolonged food restriction/refeeding. We demonstrate here that although leptin gene is expressed at very low level in rat hypothalamus, its expression in hypothalamus was down-regulated by prolonged food restriction similarly as in the white adipose tissue. Refeeding after prolonged food restriction caused both an increase of leptin gene expression in white adipose tissue and the increase in serum leptin concentration. In contrast, no significant effect of prolonged food restriction/refeeding on hypothalamic leptin gene expression was observed. The reduction of leptin gene expression in both hypothalamus and white adipose tissue by prolonged food restriction was associated with a significant increase of NPY gene (a target of leptin signaling) expression in hypothalamus. Refeeding after prolonged food restriction caused the decrease of NPY gene expression in hypothalamus, however NPY mRNA level remained higher than in controls. The results presented in this paper indicate that prolonged food restriction/refeeding differentially affects leptin gene expression in adipose tissue and in hypothalamus. Moreover, obtained data suggest that in rats leptin synthesized in hypothalamus exerts marginal effect on NPY gene expression and on serum leptin concentration.

Cadmium-induced changes in Per 1 and Per 2 gene expression in rat hypothalamus and anterior pituitary: Effect of melatonin

Chronic cadmium (Cd) administration affects the circadian release of pituitary hormones in rats. To assess whether Cd modifies expression of two major clock genes, period (Per) 1 and Per 2, in the hypothalamic–pituitary unit and to what extent the changes could be prevented by melatonin, rats were exposed to CdCl 2 (5 ppm in drinking water) with or without melatonin (3 μg/mL drinking water) for 1 month and were killed at two time intervals, i.e. a the beginning of the rest span (09:00 h) and at the middle of the activity span (01:00 h). Hypothalamic and pituitary mRNA levels encoding Per 1 and Per 2 were measured by real-time PCR analysis. Cd treatment decreased expression of hypothalamic Per 1 gene at both time intervals, of hypothalamic Per 2 gene at 01:00 h, and of adenohypophysial Per 1 and Per 2 genes at 09:00 h. Melatonin administration counteracted most of the effects of Cd and augmented hypothalamic Per 2, and adenohypophysial Per 1 and Per 2 gene expression. The results indicate that Cd administered chronically in the drinking water to rats affected expression of clock genes in the hypothalamic–pituitary unit, an effect prevented by melatonin.

In vivo protective effect of melatonin on cadmium‐induced changes in redox balance and gene expression in rat hypothalamus and anterior pituitary

Cadmium (Cd) is widely used in industrial applications and is an important side contaminant of agricultural products. As an endocrine disruptor, Cd modifies pituitary hormone release. It has been shown that this metal causes oxidative stress in primary cultures of anterior pituitary cells. To examine whether Cd induces redox damage in the hypothalamic-pituitary axis in vivo and to evaluate the efficacy of the antioxidant molecule melatonin to prevent Cd activity, rats were exposed to Cd (5 p.p.m. in drinking water) with or without melatonin (3 microg/mL drinking water) for 1 month. In the anterior pituitary, Cd increased lipid peroxidation and mRNA levels for heme oxygenase-1 (HO-1) at both time intervals tested (09:00 and 01:00 hr, beginning of rest span and middle of activity span, respectively). Melatonin administration prevented the Cd-induced increase in both parameters. In the hypothalamus, Cd affected the levels of mRNA for HO-1 by decreasing it in the evening. Melatonin reduced hypothalamic HO-1 gene expression. Cd treatment augmented gene expression of nitric oxide synthase (NOS)1 and NOS2 in the pituitary whereas melatonin decreased it, impairing the activity of Cd. Exposure to Cd increased the levels of hypothalamic NOS1 mRNA at 09:00 hr and decreased the levels of NOS2 mRNA at 01:00 hr, with melatonin treatment preventing Cd effects. Cd treatment decreased plasma thyroid-stimulating hormone levels at both examined times, while melatonin reversed the effect of Cd at 09:00 hr and partially counteracted the effect at 01:00 hr. There were important variations between day and night in the expression of all the genes tested in both tissues. Melatonin treatment was effective reducing all examined effects of Cd, documenting its effectiveness to protect the rat hypothalamic-pituitary axis from the toxic metal effects.

Neuropeptide Y and lipid increase apolipoprotein AIV gene expression in rat hypothalamus

Apolipoprotein AIV (apo AIV) is a circulating signal released from intestinal cells in response to lipid feeding and contributes to the anorectic effect of a lipid meal. We have demonstrated that apo AIV is also synthesized in the hypothalamus, and that hypothalamic apo AIV gene expression is regulated physiologically. Neuropeptide Y (NPY) is a hypothalamic neuropeptide with broad regulatory actions in the central nervous system. In the present studies, the effects of intracerebroventricular (i.v.t.) administration of NPY and of intraduodenal lipid infusion on hypothalamic apo AIV gene expression were determined using competitive RT-PCR in fasted rats. I.v.t. injection of NPY alone significantly increased apo AIV mRNA levels in the hypothalamus in a dose-dependent manner. Intraduodenal infusion of lipid also stimulated the gene expression of hypothalamic apo AIV, but no further significant increment occurred when i.v.t. injection of NPY was combined with lipid infusion. These results suggest that NPY and lipid may regulate apo AIV gene expression in the rat hypothalamus.

Chronic intracerebroventricular cocaine differentially affects prodynorphin gene expression in rat hypothalamus and caudate-putamen

We investigated the effects of sustained administration of cocaine on the regulation of prodynorphin gene expression in rat brain. Intracerebroventricular (i.c.v.) infusion of cocaine hydrochloride (30 μg/day) for 7 days, by means of osmotic minipumps, elicited a significant 35% decrease of prodynorphin mRNA levels in rat hypothalamus and increase (22%) in caudate-putamen. At the same time and in the same animals, no significant changes were detected in the hippocampus or in the nucleus accumbens. These results indicate that continuously infused cocaine is able to modulate expression of the prodynorphin gene in opposite directions or has no effect on prodynorphin expression, depending on the brain region analysed. Cocaine, as well as opiates, might activate specific neuronal pathways, shared by different classes of drugs of abuse, involving, at least in part, the endogenous opioid system.

Chronic intracerebroventricular cocaine differentially affects prodynorphin gene expression in rat hypothalamus and caudate-putamen.

We investigated the effects of sustained administration of cocaine on the regulation of prodynorphin gene expression in rat brain. Intracerebroventricular (i.c.v.) infusion of cocaine hydrochloride (30 micrograms/day) for 7 days, by means of osmotic minipumps, elicited a significant 35% decrease of prodynorphin mRNA levels in rat hypothalamus and increase (22%) in caudate-putamen. At the same time and in the same animals, no significant changes were detected in the hippocampus or in the nucleus accumbens. These results indicate that continuously infused cocaine is able to modulate expression of the prodynorphin gene in opposite directions or has no effect on prodynorphin expression, depending on the brain region analysed. Cocaine, as well as opiates, might activate specific neuronal pathways, shared by different classes of drugs of abuse, involving, at least in part, the endogenous opioid system.

Colchicine induces the GAP-43 gene expression in rat hypothalamus.

Injection of colchicine, a mitogen inhibitor, in the dorsal third ventricle induced the expression of the growth associated protein-43 (GAP-43) mRNA in some groups of cells of the adult rat brain. These mRNAs were detected by in situ hybridization histochemistry using an alkaline phosphatase labeled oligonucleotide probe. A substantial up-regulation of GAP-43 mRNA was noticed by the increase of both the number of positive cells and the intensity of the hybridization signal. These changes were observed in the hypothalamic nuclei located near the ventral third ventricle, namely the preoptic area, the supraoptic nucleus, the peri- and the paraventricular nuclei of the hypothalamus, the dorsal subnucleus of the ventromedial nucleus, the arcuate nucleus and the posterior part of the peri-mammillary region. Such abundant GAP-43 mRNA positive cells have not been observed in control adult rat hypothalamus. Since the positive cell number and shape initially suggested that these were neurons or astrocytes, double labeling in situ hybridization using both radioactive (for the detection of GFAP mRNA as a marker of astrocyte) and non-radioactive (for the detection of GAP-43 mRNA) probes was carried out. This demonstrated that these GAP-43 mRNA positive cells were not astrocytes. In addition enhanced GAP-43 mRNA expression was also found in some neuronal component, particularly in neurosecretory magnocells of the pareaventricular and the supraoptic nuclei. This up-regulation was further confirmed by the Northern blot analysis. About five fold increase in GAP-43 mRNA in the colchicine-treated hypothalamic tissue was shown.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminergic pathways regulating vasopressin gene expression in rat hypothalamus from medullary A1-neurons

Aminergic pathways regulating vasopressin gene expression in rat hypothalamus from medullary A1-neurons

Ontogeny of corticotropin releasing hormone gene expression in rat hypothalamus — comparison with somatostatin

Using in situ hybridization histochemistry, corticotropin-releasing hormone gene expression is first detectable in the parvocellular portion of the rat paraventricular nucleus on the 17th fetal day. The prevalence of messenger RNA for corticotropin releasing hormone decreases perinatally, specifically between the 19th and 21st fetal days. By the 4th postnatal day, CRH gene expression is similar to that of the adult rat. Somatostatin messenger-RNA is detectable on the 14th fetal day in the periventricular nucleus. No perinatal hiatus in somatostatin gene expression is evident.

A subset of neurons containing immunoreactive prolactin is a target for estrogen regulation of gene expression in rat hypothalamus.

Cells whose nuclei accumulated 3H-estradiol were identified autoradiographically in fixed, frozen sections of colchicine-treated rat hypothalamus (n = 3 animals). After autoradiogram development, these sections were subjected to immunocytochemistry using rabbit antirat prolactin antiserum and the avidin-biotinylated horseradish peroxidase method. In the hypothalamus, a substantial subset of the neurons containing immunoreactive prolactin accumulated 3H-estradiol in their nuclei: of 3, 642 immunoreactive cells examined, 1,216 had autoradiographically labeled nuclei, or about 33%. The immunoreactive prolactin neurons with autoradiographically labeled nuclei were located in the medial basal hypothalamus intermingled with immunoreactive prolactin neurons whose nuclei were not labeled autoradiographically. Since hypothalamic immunoreactive prolactin neurons have a rich and widely distributed fiber system, the present results suggest that estrogen, acting through a subset of these neurons, can modify directly the neuronal activity of several brain regions which regulate diverse aspects of the reproductive effort. Also, since immunoreactive prolactin and immunoreactive beta-endorphin exist in the same hypothalamic cell population, opioid peptides derived from pro-opiomelanocortin may mediate some effects of estrogen on the neural circuitry regulating reproduction.