State In Rodents Research Articles

Effects of NPY and the specific Y1 receptor agonist [D-His(26)]-NPY on the deficit in brain reward function and somatic signs associated with nicotine withdrawal in rats.

Tobacco addiction is a chronic disorder that is characterized by dysphoria upon smoking cessation and relapse after periods of abstinence. Previous research suggests that Neuropeptide Y (NPY) and Y1 receptor agonists attenuate negative affective states and somatic withdrawal signs. The aim of the present experiments was to investigate the effects of NPY and the specific Y1 receptor agonist [D-His(26)]-NPY on the deficit in brain reward function and somatic signs associated with nicotine withdrawal in rats. The intracranial self-stimulation procedure was used to assess the effects of nicotine withdrawal on brain reward function as this procedure can provide a quantitative measure of emotional states in rodents. Elevations in brain reward thresholds are indicative of a deficit in brain reward function. In the first experiment, NPY did not prevent the elevations in brain reward thresholds associated with precipitated nicotine withdrawal and elevated the brain reward thresholds of the saline-treated control rats. Similar to NPY, [D-His(26)]-NPY did not prevent the elevations in brain reward thresholds associated with precipitated nicotine withdrawal and elevated the brain reward thresholds of the saline-treated control rats. Neither NPY nor [D-His(26)]-NPY affected the response latencies. In a separate experiment, it was demonstrated that the specific Y1 receptor antagonist BIBP-3226 prevented the NPY-induced elevations in brain reward thresholds. NPY attenuated the overall somatic signs associated with precipitated nicotine withdrawal. [D-His(26)]-NPY did not affect the overall somatic signs associated with precipitated nicotine withdrawal, but decreased the number of abdominal constrictions. Both NPY and [D-His(26)]-NPY attenuated the overall somatic signs associated with spontaneous nicotine withdrawal. These findings indicate that NPY and [D-His(26)]-NPY attenuate somatic nicotine withdrawal signs, but do not prevent the deficit in brain reward function associated with precipitated nicotine withdrawal. In addition, NPY decreases the sensitivity to rewarding electrical stimuli via an Y1 dependent mechanism.

Quantification of physiological adaptations during altered loading states in rodents

Muscle unloading due to space travel, bed rest, or immobilization leads to many physiological adaptations at the whole‐body, tissue, and cellular levels. Specifically, hindlimb suspension unloading (HSU) has been devised as a highly effective technique to simulate the effects of microgravity that lead to muscle atrophy, as well as metabolic and endocrine changes. To quantify metabolic adaptations at various levels, we administered a single bolus of “doubly‐labeled” water (Bederman et al, 2006) to determine: (a) energy expenditure and body composition (whole‐body level); (b) turnover rates of tissue‐specific lipids and proteins from the labeling patterns of protein‐bound alanine and triglyceride‐bound glycerol, rates of de novo lipogenesis, (tissue and cellular level); and (c) labeling patterns of pathway specific metabolites (cellular level). Here, we present the application of this novel methodology in a model of muscle disuse. After three weeks of HSU, rats demonstrated changes at the whole body level (elevated VO2 and VCO2 (lower RQ) and leaner body composition). We report on the changes in fuel selection and rates of tissue remodeling using biochemical fluxes of proteins and lipids. Our work provides the experimental basis for multiscale modeling of the metabolic adaptations to altered loading states.

Hydrogen sulphide and its therapeutic potential

Hydrogen sulphide (H2S) is increasingly being recognized as an important signalling molecule in the cardiovascular and nervous systems. The production of H2S from L-cysteine is catalysed primarily by two enzymes, cystathionine gamma-lyase and cystathionine beta-synthase. Evidence is accumulating to demonstrate that inhibitors of H2S production or therapeutic H2S donor compounds exert significant effects in various animal models of inflammation, reperfusion injury and circulatory shock. H2S can also induce a reversible state of hypothermia and suspended-animation-like state in rodents. This article overviews the physiology and biochemistry of H2S, summarizes the effects of H2S inhibitors or H2S donors in animal models of disease and outlines the potential options for the therapeutic exploitation of H2S.

Antioxidant response and oxidative damage in brain cortex after high dose of pilocarpine

Pilocarpine is a cholinergic agonist capable to induce seizures and an epilepticus-like state in rodents. This status epilepticus (SE) is an useful animal model to study the development and understanding of the neuropathology, behavioural and electroencephalographic alterations of human temporal lobe epilepsy. It has been suggested a relationship between SE and reactive oxygen species (ROS) that can result in seizure-induced neurodegeneration. The aim of this study was to evaluate the existence of oxidative damage and the changes in the antioxidant system in cortex after administration of a high pilocarpine dose. Rats were injected with pilocarpine (350 mg/kg i.p.) or with saline as control and 2 h after the animals were sacrificed. Malondialdehyde (MDA) levels, as marker of lipid peroxidation, significantly increased (64%) after pilocarpine treatment evidencing oxidative damage. Antioxidant enzyme activities – catalase (CAT), glutathione peroxidase (GP) and superoxide dismutase (SOD) – significantly increased in response to pilocarpine (28%, 28% and 21%, respectively). GP and Mn-SOD gene expression were induced by pilocarpine treatment. Vitamin E concentration in brain cortex decreased (15%) as result of pilocarpine administration. In conclusion, the high dose of pilocarpine, used in the present study, induces oxidative damage and increases antioxidant enzyme activities and expression in brain cortex. Moreover, increased lipid peroxidation produces the consumption of Vitamin E.

Antioxidant response analysis in the brain after pilocarpine treatments

Cholinergic and gabaergic systems play an important role generating electroencephalographic activity and regulating vigilance states. Pilocarpine is a cholinergic agonist commonly used to induce seizures and an epilepticus-like state in rodents. A relationship between status epilepticus and reactive oxygen species has been also suggested which could result in seizure-induced neurodegeneration. The aim of this study was to evaluate the existence of oxidative damage as well as the antioxidant enzyme response in cortex and hippocampus after the administration of an intraperitoneal (350 mg/kg) and an intracerebroventricular (360 μg, 1 μl) pilocarpine injection in rats. The GABA agonist muscimol (1 mg/kg, i.p.), with described neuroprotective properties, was used as a negative control. Only systemic pilocarpine induced oxidative damage. Malondialdehyde levels, as a marker of lipid peroxidation (LP), increased in both regions (55–56%). Catalase (52–80%) and superoxide dismutase (53–60%) activities also rose in both regions but glutathione peroxidase activity only increased in cortex (45%). Glutathione reductase and caspase-3 activity did not change. In conclusion, systemic pilocarpine produced oxidative brain damage, whereas local pilocarpine brain injection had no effects. Moreover, the enzymatic determinations performed in this study are a good tool to study brain injury in pharmacological manipulations such as the ones used in short recording EEG studies.

Molecular events in kidney ageing

Ageing of the kidney is a problem of clinical and basic interest. The problem of renal dysfunction and end-stage renal disease is a major burden on the health system, and old donor age is a major limitation on the use of donor organs and on survival of transplanted kidneys. Moreover, stresses linked to nephropathies, postoperative stress, inflammation and allograft rejection can lead to premature senescence of renal cells thus accelerating organ atrophy. Age-related and disease or stress-related nephron loss could reflect both the limited ability of epithelial cells to repair and replicate in the face of environmental stresses, and limitations on the number of cell replications caused by telomere shortening. Therefore, elucidating cellular senescence mechanisms is relevant to kidney diseases and kidney transplantation. Recent findings suggest additive effects of replicative and environmental stress-induced senescence in cellular and organ ageing. In particular, ATM/p53/p21 and Ras/p38/p16 pathways have been shown to co-contribute to the overall cellular senescence, which is caused by extrinsic and intrinsic stimuli. Moreover, the role of epigenetic factors, including protein acylation/deacetylation, chromatin remodeling or caloric restriction, is the focus of recent studies on ageing and senescence. Despite significant progress, cellular senescence is still better understood in vitro than in vivo. So far, p16 remains the best marker of chronological age in the kidney, and can be considered as an indicator of premature senescence caused by stresses or disease. The beneficial effects of caloric restriction on organ ageing and the role of histone acetylation in pathologic states in rodents are of considerable interest, and deserve future studies.

The release of spinal prostaglandin E2 and the effect of nitric oxide synthetase inhibition during strychnine-induced allodynia.

The removal of spinal glycinergic inhibition by intrathecal strychnine produces an allodynia-like state in rodents. Our objective was to measure spinal prostaglandin E2 (PGE2) release during strychnine-allodynia and examine the effects of Nomega-nitro-L-arginine (L-NOARG), an inhibitor of nitric oxide synthetase. Under halothane, rats were fitted with intrathecal and spinal microdialysis catheters, and microelectrodes implanted into the locus coeruleus for measurement of catechol oxidation current (CAOC) using voltammetry. Animals were then administered urethane and treated as follows: 1) baseline control 10 min, intrathecal strychnine (40 microg) 10 min, 10 min of hair deflection, and 2) 10-min control followed by intrathecal strychnine (40 microg) with hair deflection for 60 min. Spinal dialysate samples were collected for PGE2 levels determined by using immunoassay. In separate experiments, the effect of intrathecal strychnine (40 microg) followed by hair deflection was studied in rats pretreated with intrathecal l-NOARG (50 nmol). After intrathecal strychnine, hair deflection significantly increased spinal PGE2 release (619% +/- 143%), locus coeruleus CAOC (181% +/- 6%), and mean arterial pressure (123% +/- 2%) P < 0.05. Pretreatment with intrathecal l-NOARG significantly inhibited strychnine-allodynia. In this model, hair deflection evokes spinal PGE2 release, locus coeruleus activation, and an increase in mean arterial pressure. L-NOARG pretreatment attenuated the locus coeruleus CAOC, a biochemical index of strychnine-allodynia, suggesting a mediator role of nitric oxide. A mediator role of nitric oxide is also implicated, helping to explain the pathophysiology of this allodynic pain.

Hypothalamic adrenergic receptor changes in the metabolic syndrome of genetically obese (ob/ob) mice

The genetically, seasonally, and diet-induced obese, glucose-intolerant states in rodents, including ob/ob mice, have each been associated with elevated hypothalamic levels of norepinephrine (NE). With the use of quantitative autoradiography on brain slices of 6-wk-old obese (ob/ob) and lean mice, the adrenergic receptor populations in several hypothalamic nuclei were examined. The binding of [(125)I]iodocyanopindolol to beta(1)- and beta(2)-adrenergic receptors in ob/ob mice was significantly increased in the paraventricular hypothalamic nucleus (PVN) by 30 and 38%, in the ventromedial hypothalamus (VMH) by 23 and 72%, and in the lateral hypothalamus (LH) by 10 and 15%, respectively, relative to lean controls. The binding of [(125)I]iodo-4-hydroxyphenyl-ethyl-aminomethyl-tetralone to alpha(1)-adrenergic receptors was also significantly increased in the PVN (26%), VMH (67%), and LH (21%) of ob/ob mice. In contrast, the binding of [(125)I]paraiodoclonidine to alpha(2)-adrenergic receptors in ob/ob mice was significantly decreased in the VMH (38%) and the dorsomedial hypothalamus (17%) relative to lean controls. This decrease was evident in the alpha(2A)- but not the alpha(2BC)-receptor subtype. Scatchard analysis confirmed this decreased density of alpha(2)-receptors in ob/ob mice. Together with earlier studies, these changes in hypothalamic adrenergic receptors support a role for increased hypothalamic NE activity in the development of the metabolic syndrome of ob/ob mice.

Effect of cytokines on hypothalamic neuropeptide Y release in vitro

Studies involving altered energy balance states in rodents have demonstrated that hypothalamic neuropeptide Y (NPY) activity is strongly activated in states of negative energy balance, such as periods of dietary restriction or starvation. However, in cancer cachexia, when there is a significant reduction in body weight as a result of appetite loss, leading to loss in fat and lean tissue mass, there is no augmentation in the activity of the hypothalamic NPY system. Therefore, we have examined whether cytokines, interleukin (IL)-1, IL-1β, IL-6, and tumor-necrosis factor-α (TNF-α; cachectin), which are elevated in cancer patients, can attenuate NPY release from hypothalamic slices in vitro. None of the cytokines altered either the basal or stimulated NPY release from the hypothalamic slices. However, we were able to measure a significant reduction in potassium-stimulated NPY release (−60%) by using the nonselective voltage-dependent calcium channel blocker NiCl (30 μM) without any effect on basal release, as a positive control. Therefore, we suggest that the failure to activate the hypothalamic NPY system in states of cancer cachexia cannot be attributed to a cytokine-induced reduction in neurotransmitter release.

Orphanin-FQ: Role as a neuromodulator of mood/anxiety-like states in rodents

Orphanin-FQ: Role as a neuromodulator of mood/anxiety-like states in rodents

Effects of 5-HT 3 receptor antagonists on neuroleptic-induced catalepsy in mice

Typical neuroleptics (e.g. haloperidol) can induce a cataleptic state in rodents by means of striatal DA receptor blockade. It has been shown that drugs which influence central serotonergic (5-HTergic) mechanisms can modify neuroleptic-induced catalepsy, suggesting that dopaminergic transmission is under 5-HTergic modulation. The aim of this study was to examine the effects of bemesetron and granisetron, two selective 5-HT 3 receptor antagonists, on this catalepsy in mice. Catalepsy was induced with haloperidol (1.5 mg/kg, i.p.) and measured at 30-min intervals by means of a bar test. Drugs (or saline, for the controls) were injected i.p. 20 min before haloperidol, with each animal used only once. Bemesetron significantly reduced catalepsy at a dose of 1 mg/kg, whilst 10 mg/kg potentiated the phenomenon and 0.1 mg/kg was found to be without effect. Granisetron inhibited catalepsy at doses of 0.04 and 0.1 mg/kg, while 4 mg/kg of the antagonist significantly increased the duration of catalepsy. These data suggest that 5-HT 3 receptors play a role in neuroleptic-induced catalepsy. Considering the high affinities of both antagonists for 5-HT 3 receptors, it is tempting to speculate that the potentiation of catalepsy by high doses of them is due to non 5-HT 3 receptor mechanisms.

Effects of STZ-induced diabetes and fasting on insulin receptor mRNA expression and insulin receptor gene transcription in rat liver.

Insulinopenic states in rodents are known to cause an increase in the number of hepatic insulin receptors. To determine if this change is related to an abnormality in insulin receptor gene expression, insulin receptor binding, insulin receptor mRNA levels, and insulin receptor gene transcription rates have been measured in livers from rats rendered hypoinsulinemic by STZ administration (65 mg/kg) or fasting. In the two groups of experimental rats, insulin binding to liver plasma membranes was increased (approximately 40 and 25%, respectively) relative to control, normoinsulinemic animals. Northern blot analysis of either total or poly (A)+ RNA from livers of hypo- and normoinsulinemic rats revealed two major insulin receptor mRNA species of 9.5 and 7.5 kbs. In hypoinsulinemic rats, insulin receptor mRNA levels were increased > or = 10-fold, with similar effects on the two mRNA species. The effects of STZ administration and fasting on insulin receptor binding and insulin receptor mRNA levels were fully reversed by insulin treatment or refeeding, respectively. Injection of ACT D, an inhibitor of gene transcription, decreased insulin receptor mRNA levels by > or = 80% in control and diabetic rats and suppressed the overexpression of mRNA seen in diabetic rats. In vitro nuclear transcription assays showed that the rate of transcription of the insulin receptor gene was increased 2-fold in STZ-induced diabetic rats and fasted rats relative to control animals. Taken together, these results suggest that the upregulation of the insulin receptor induced by chronic insulinopenia results, at least in part, from an increase in insulin receptor gene transcription.

Mechanisms of up-regulation of the liver insulin receptor in chronically hypoinsulinemic rats: assessment of receptor endocytosis

Chronic hypoinsulinemic states in rodents are known to cause an increase in the number of insulin receptors at the hepatocyte surface. To assess whether this change results from a reduced endocytosis of the receptors, the effects of streptozotocin treatment and fasting on the number and the subcellular distribution of hepatic insulin receptors have been evaluated in the rat. In streptozotocin-treated rats, insulin receptor number was increased by 25–40% in plasma membrane and total cellular membrane fractions, and by 60–130% in the light Golgi-endosomal (GE) fraction. In contrast, receptor number was unaffected in the intermediate GE fraction and decreased by 25–35% in the heavy GE fraction. Such changes were detectable at 12 h in GE fractions and at 2 days in other subcellular fractions, and lasted for at least 8 days. Streptozotocin treatment also led to a 3- to 4-fold decrease in the insulin content of GE fractions, indicating reduced hormone endocytosis. Fasting for 16 h elicited changes in receptor and ligand concentration in cell fractions comparable to those induced by Streptozotocin. It is concluded that, although endocytosis of hepatic insulin receptors is reduced in chronic hypoinsulinemic states, changes in receptor synthesis and/or degradation also occur in these states.

Endocrine Regulation of Fetal and Postnatal Meat Animal Growth

Evidence is discussed which indicates that nutrient partitioning between muscle and adipose tissue can be altered by growth hormone administration in meat animals. In the limited number of studies conducted with meat animals, growth rate, feed efficiency and carcass composition were improved by growth hormone administration. When insulin was administered to normally growing swine no improvement in growth performance was observed. The mechanisms by which growth hormone affects growth performance are not clear but considerable data from rodent studies exist to indicate that many of the growth promoting effects of this hormone are due to somatomedins. However, few data are available for meat animals to indicate whether the growth promoting effects of growth hormone are mediated by somatomedins. Knowledge about the mechanisms that regulate growth hormone synthesis, secretion and biological action is accumulating. It is apparent that growth hormone administration induces an insulin-resistant state in rodents and meat animals. It is not clear whether chronic growth hormone administration in meat animals induces a growth hormone resistant state. Based on the available information, manipulation of systemic hormone concentrations and(or) tissue sensitivity to hormones involved in growth and differentiation may result in means to manipulate fetal and postnatal growth and development.

Lithium and central monoamine neurotransmitter systems

AbstractLithium salts have been in use in psychiatric medicine for the past three decades, but their mechanism of action is still unknown. Studies using a model of mania to delineate the means by which they exert their therapeutic effect have been hampered by the lack of a suitable animal analogue, although attempts have been made to induce a “manic” state in rodents. For this reason, most investigations of the neurochemical basis of lithium action have used normal animals, and have focused primarily on the monoaminergic neurotransmitters, mainly because of the predominant theory of affective disorders (the “biogenic amine hypothesis”). Data indicate that these neurotransmitter substances are affected by lithium administration, although the findings are not always consistent and it is therefore difficult to determine exactly their role in the antimanic effect of lithium and the pathogenesis of the bipolar affective disorder. While animal studies have confirmed the existence of a “withdrawal” phenomenon, the involvement of biogenic amines or of central Y‐aminobutyric acid (GABA)minergic system in the rapid recurrence of psychotic symptoms soon after cessation of lithium therapy is still equivocal.