Increase In Norepinephrine Concentration Research Articles

Role of Ammonia and Nitric Oxide in the Decrease in Plasma Prolactin Levels in Prehepatic Portal Hypertensive Male Rats

Objectives: Since very little is known about neuroendocrine changes that occur in portal-systemic hepatic encephalopathy, we studied plasma prolactin (PRL) levels and the involvement of hyperammonemia, nitric oxide (NO) and dopaminergic and adrenergic systems in the control of this hormone secretion in a male rat model of prehepatic portal hypertension (PH). Methods: We conducted in vivo studies to determine plasma ammonia and PRL levels. Dopamine (DA), dihydroxyphenylacetic acid (DOPAC), epinephrine and norepinephrine content in medial basal hypothalamus (MBH) and anterior pituitary (AP) were measured. In addition, NO synthase (NOS) activity and protein expression were evaluated in APs. In in vitro studies, the APs from intact rats were incubated with different doses of ammonia and PRL secretion was determined. In ex vivo studies, the APs from normal and PH rats were incubated in the presence of ammonia and/or a NOS inhibitor, N^G-nitro-L-arginine-methyl ester (L-NAME) and PRL secretion was determined. Results: PH rats had a significant increase in plasma ammonia levels (p < 0.001) and a decrease in plasma PRL levels (p < 0.05). Neither DA nor DOPAC content or DOPAC/DA ratios were modified in both MBH and APs; however, we observed a significant increase in norepinephrine content in both MBH and AP (p < 0.001 and p < 0.05, respectively) and a significant increase in epinephrine in APs (p < 0.001). Moreover, PH produced an increase in NOS activity (p < 0.01) and NOS protein expression (p < 0.0001) in APs. The ammonia (100 µM) significantly reduced PRL secretion from APs in vitro (p < 0.05). The presence of L-NAME, an inhibitor of NOS, abrogated the inhibitory effect of ammonia on PRL secretion from APs from control and PH rats. Conclusions: We found that plasma PRL levels were decreased in PH rats probably due to the high ammonia levels. The central noradrenergic system could also mediate this decrease. Also, the increase in NOS activity and/or content in AP induced NO production that directly inhibited PRL secretion from the AP, without the participation of the dopaminergic system.

The Effect of Streptozotocin‐Induced Diabetes on the Rat Seminal Vesicle

In the streptozotocin (STZ)-diabetic rat major increases in noradrenaline concentration and content of the seminal vesicles were evident as early as 7 weeks following induction of hyperglycemia and returned toward normal after 34 weeks of hyperglycemia. There were significant reductions in the concentration and content of dopamine at 19-42 weeks of diabetes, and small occasionally significant reductions in the content of serotonin and adrenaline, particularly around 19-26 weeks after STZ treatment. The uptake of tritiated noradrenaline in the diabetics was increased at 12 weeks compared to the controls, and decreased to control levels with increasing age. Release of tritiated noradrenline was increased in response to electrical field stimulation and high potassium solutions, and raising calcium concentration caused increased release at rest and during electrical stimulation. Immunohistochemical demonstration of tyrosine hydroxylase was increased during the period when the noradrenaline concentration and content were elevated. It is concluded that there are significant changes in the sympathetic innervation of the seminal vesicle during the course of STZ diabetes, and that alterations in the reuptake, release, and synthesis of the neurotransmitter noradrenaline may contribute to changes in the concentration of the amine in the tissue. It is possible that the changes observed are related to the remodeling and regrowth of sympathetic nerve endings damaged in the early stages of hyperglycemia. These changes may also contribute to disorders of ejaculation in diabetes.

Effect of hypoxia during early organogenesis on cardiac activity and noradrenergic regulation in the postnatal period

Cardiac activity in rats during the postnatal period was studied in vitro and in vivo after exposure of rat pups to antenatal acute hypobaric hypoxia at the stage of organogenesis (day 9-10 of gestation). Cultured cardiomyocytes from rat pups exposed to antenatal hypoxia were characterized by increased rate of contractions and decreased reactivity to norepinephrine. Heart rate elevation, predominance of sympathetic influences on cardiac activity, and significant increase in norepinephrine concentration in the cerebral cortex were found in freely moving animals exposed to antenatal hypoxia. Our results indicate that hypoxia at the stage of organogenesis modulated cardiac activity during the postnatal period, which manifested at the level of effector structures in the heart and activity of regulatory systems.

Increased extracellular concentrations of norepinephrine in cortex and hippocampus following vagus nerve stimulation in the rat

The vagus nerve is an important source of afferent information about visceral states and it provides input to the locus coeruleus (LC), the major source of norepinephrine (NE) in the brain. It has been suggested that the effects of electrical stimulation of the vagus nerve on learning and memory, mood, seizure suppression, and recovery of function following brain damage are mediated, in part, by the release of brain NE. The hypothesis that left vagus nerve stimulation (VNS) at the cervical level results in increased extracellular NE concentrations in the cortex and hippocampus was tested at four stimulus intensities: 0.0, 0.25, 0.5, and 1.0 mA. Stimulation at 0.0 and 0.25 mA had no effect on NE concentrations, while the 0.5 mA stimulation increased NE concentrations significantly in the hippocampus (23%), but not the cortex. However, 1.0 mA stimulation significantly increased NE concentrations in both the cortex (39%) and hippocampus (28%) bilaterally. The increases in NE were transient and confined to the stimulation periods. VNS did not alter NE concentrations in either structure during the inter-stimulation baseline periods. No differences were observed between NE levels in the initial baseline and the post-stimulation baselines. These findings support the hypothesis that VNS increases extracellular NE concentrations in both the hippocampus and cortex.

Sex‐specific differences in the reactivity of spinotrapezius arterioles to norepinephrine, sodium nitroprusside and 21% superfusate O 2 in male (M) and female (F) Sprague‐Dawley (SD) rats fed a low (LS, 0.4% NaCl) or high salt diet (HS, 4.0% NaCl)

Hartford Avenue (UWM) 8701 Watertown Plank Rd (MCW), Shorewood, Wisconsin, 53211 High salt intake independent of an increase in blood pressure has been implicated as a cause of endothelial dysfunction that is a hallmark of many cardiovascular diseases that are expressed in a sexually dimorphic manner. We investigated sex based differences in the reactivity of arterioles of salt insensitive SD rats (intact male and female) in an in situ preparation of the spinotrapezius muscle to norepinephrine (NE), acetylcholine (ACh), sodium nitroprusside (SNP) and 21% superfusate O2. Arterioles of the HS F were more sensitive to NE than those of the HS M but not of the LS F. The % change in vessel diameter to increasing NE concentration was significantly greater in the arterioles of the LS F than in the LS M or the HS M. The arterioles of the F on a LS diet were more sensitive to SNP than those of the HS F and the LS M. The arterioles of the LS M were more sensitive to SNP than those of the HS M. The arterioles of the HS F constricted significantly more to elevated O2 than those of either the LS F or the HS M. These studies demonstrate that there are sex-based differences in skeletal muscle vascular reactivity and that those differences are influenced by the level of salt intake.

Effect of moderate cold exposure on 24-h energy expenditure: similar response in postobese and nonobese women.

Twenty-four-hour energy expenditure (EE) and substrate oxidation rates were measured two times in eight postobese women and eight matched controls. On one occasion the subjects were exposed to a room temperature of 16 degrees C, on the other to 24 degrees C. Cold exposure elicited a 2% increment in 24-h EE (P < 0.05), with similar response in the two groups. The slight increase in EE was entirely covered by an enhanced carbohydrate oxidation rate. Fasting plasma norepinephrine (NE) increased from 0.74 +/- 0.08 to 1.29 +/- 0.21 nmol/l under cold exposure (P < 0.05), with no group difference. The cold-induced increase in 24-h EE was positively correlated to the increase in NE concentration (r2 = 0.41, P = 0.01). Sleeping EE was found to be 5% lower in the postobese women than in the controls (P = 0.04). The postobese group also had higher 24-h nonprotein respiratory quotient than the control group (P = 0.04), which was due to a 26% lower lipid-to-carbohydrate oxidation ratio. The study demonstrates that the thermogenic response to cold is normal in women susceptible to obesity, but it supports previous reports of a slightly lower basal EE and lower lipid-to-carbohydrate oxidation ratio in postobese subjects.

Skeletal muscle HSP72 and norepinephrine response to static magnetic field in rat

The present work was undertaken in order to investigate the noradrenergic system and skeletal muscle heat shock protein 72 (HSP72) response to static magnetic field (MF) in male rats. At thermoneutrality (25 degrees C), the exposition of rats 1 hour/day for 5 consecutive days to MF of 128 mT (m tesla) induced an increase in norepinephrine content in gastrocnemius muscle (+25%, p < 0.05) but had no effect at 67 mT (+1%, p > 0.05), indicating a stimulatory effect of sub-acute MF exposure on the noradrenergic system activity. Moreover, exposed rats to MF displayed a non-significant increase of HSP72 levels in gastrocnemius muscles (+29%, p > 0.05). The results indicate that noradrenergic systems in rat's gastrocnemius muscles are affected by MF exposure. Interestingly, sub-acute exposure insufficiency increased HSP72 levels in gastrocnemius muscles.

Pro- and anti-apoptotic evidence for cholinergic denervation and hippocampal sympathetic ingrowth in rat dorsal hippocampus

In rat, injection of the specific cholinotoxin, 192 IgG-saporin, into the medial septum results not only in a selective cholinergic denervation of hippocampus, but in an ingrowth of peripheral sympathetic fibers, originating from the superior cervical ganglion, into the hippocampus. A similar process, in which peripheral noradrenergic axons invade hippocampus, may also occur in Alzheimer's disease. Since apoptotic cell death has been demonstrated in the selective neuronal loss found in Alzheimer's disease, the aim of this study was to measure apoptotic protein expression and DNA fragmentation in hippocampal sympathetic ingrowth and cholinergic denervation. Western blot, TdT-mediated dUTP nick end labeling, and oligo ligation techniques were used. Choline acetyltransferase activity and norepinephrine concentrations were also measured. As seen in our previous results, an increase in apoptotic markers was induced by cholinergic denervation alone (medial septum lesion + ganglionectomy), while hippocampal sympathetic ingrowth (medial septum + sham ganglionectomy) reduced or normalized apoptotic effects to control group levels. A decrease in choline acetyltransferase activity was also found in the dorsal hippocampus of hippocampal sympathetic ingrowth and cholinergic denervation groups. An increase in norepinephrine concentration was found in hippocampal sympathetic ingrowth but not in cholinergic denervation group. Results of this study suggest that cholinergic denervation is responsible for most of the proapoptotic responses, while hippocampal sympathetic ingrowth produces a protective effect in the process of programmed cell death in rat dorsal hippocampus. This effect may be a secondary to an altered relationship between norepinephrine–acetylcholine.

Influence of medetomidine on stress-related neurohormonal and metabolic effects caused by butorphanol, fentanyl, and ketamine administration in dogs

To examine stress-related neurohormonal and metabolic effects of butorphanol, fentanyl, and ketamine administration alone and in combination with medetomidine in dogs. 10 Beagles. 5 dogs received either butorphanol (0.1 mg/kg), fentanyl (0.01 mg/kg), or ketamine (10 mg/kg) IM in a crossover design. Another 5 dogs received either medetomidine (0.02 mg/kg) and butorphanol (0.1 mg/kg), medetomidine and fentanyl (0.01 mg/kg), medetomidine and ketamine (10 mg/kg), or medetomidine and saline (0.9% NaCI) solution (0.1 mL/kg) in a similar design. Blood samples were obtained for 6 hours following the treatments. Norepinephrine, epinephrine, cortisol, glucose, insulin, and nonesterified fatty acid concentrations were determined in plasma. Administration of butorphanol, fentanyl, and ketamine caused neurohormonal and metabolic changes similar to stress, including increased plasma epinephrine, cortisol, and glucose concentrations. The hyperglycemic effect of butorphanol was not significant. Ketamine caused increased norepinephrine concentration. Epinephrine concentration was correlated with glucose concentration in the butorphanol and fentanyl groups but not in the ketamine groups, suggesting an important difference between the mechanisms of the hyperglycemic effects of these drugs. Medetomidine prevented most of these effects except for hyperglycemia. Plasma glucose concentrations were lower in the combined sedation groups than in the medetomidine-saline solution group. Opioids or ketamine used alone may cause changes in stress-related biochemical variables in plasma. Medetomidine prevented or blunted these changes. Combined sedation provided better hormonal and metabolic stability than either component alone. We recommend using medetomidine-butorphanol or medetomidine-ketamine combinations for sedation or anesthesia of systemically healthy dogs.

The effect of central cholinergic and noradrenergic denervation on hippocampal sympathetic ingrowth and apoptosis-like reactivity in the rat

In this study, the effect of intraseptal injection of specific cholinotoxin 192-IgG saporin (SAP) ± intraperitoneal injection of N-[chloroethyl]- N-ethyl-2-bromobenzylamine (DSP-4) (noradrenergic fiber neurotoxin) was examined in rat hippocampus. Medial septal lesions resulted not only in selective cholinergic denervation of hippocampus (Medial septal lesion + ganglionectomy; SAP + Gx) but also in hippocampal sympathetic ingrowth (IG) of adrenergic fibers (Medial septal lesion + sham ganglionectomy; SAP + IG). Saporin-induced septal lesions produced a significant reduction in hippocampal choline acetyltransferase activity in all tested groups (SAP + IG ± DSP-4 and SAP + Gx ± DSP-4), and an increase in noradrenaline concentration in the SAP + IG group. Visualization of noradrenergic fibers by histofluorescence revealed a mixture of fine and thick varicosities in the SAP + IG but only fine fibers in control and SAP + Gx animals. SAP + IG + DSP-4 lesions produced significant reduction in noradrenaline concentration in all groups with a concomitant decrease in visualization of central noradrenergic fibers in dorsal and ventral hippocampus. Treatment of SAP + IG animals with DSP-4 left mostly thick fibers, probably derived from peripheral sympathetic ingrowth. No fluorescence was seen in either the control + DSP-4 or SAP + Gx + DSP-4 animals. Apoptotic-like changes, using in situ oligonucleotide ligation techniques, were also assessed. Proapoptotic changes were seen in the SAP + Gx ± DSP-4 group as compared to CON ± DSP-4 groups. SAP + IG regardless of DSP-4 treatment protected hippocampal cells from apoptotic cell death when compared to positive control and SAP + Gx ± DSP-4 groups. In summary, elevated noradrenaline concentration following specific cholinergic denervation probably reflects compensatory hippocampal ingrowth originating from the peripheral sympathetic system which may be responsible for neuroprotective effects, i.e., antiapoptosis-like effect. Since cholinergic and noradrenergic systems are known to be involved in Alzheimer's disease and related cognitive function, knowing how these neurotransmitters work after specific lesions may be of importance as an animal model of Alzheimer's disease and as a potential target for Alzheimer's disease drug therapies.

Tempol Protects against Ischemic Acute Renal Failure by Inhibiting Renal Noradrenaline Overflow and Endothelin-1 Overproduction

The effects of tempol, a superoxide dismutase mimetic, on ischemia/reperfusion-induced acute renal failure (ARF), noradrenaline (NA) overflow and endothelin-1 (ET-1) overproduction in rats were examined. Ischemic ARF was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal functional parameters such as blood urea nitrogen, plasma creatinine concentration, and fractional excretion of sodium, NA concentrations in renal venous plasma, and renal ET-1 contents were determined. Renal function in ARF rats markedly decreased at 1 d after reperfusion. Pre-ischemic treatment with tempol (10, 100 mg/kg, i.v.) dose-dependently attenuated the ischemia/reperfusion-induced renal dysfunction. Histopathological examination of the kidney of ARF rats revealed severe renal damages, such as tubular necrosis, proteinaceous casts in tubuli and medullary congestion, which were also significantly suppressed by the tempol treatment. There was a significant increase in NA concentrations in renal venous plasma after the ischemia/reperfusion, and this increase was markedly suppressed by the treatment with tempol. In addition, tempol treatment significantly attenuated the increment of ET-1 content in the kidney exposed to the ischemia/reperfusion. These findings suggest that tempol improves the post-ischemic renal injury by inhibiting the neural activity of renal sympathetic nerve and ET-1 overproduction.

Nongenomic Actions of Glucocorticosteroids on the Airway Vasculature in Asthma

Inhaled glucocorticosteroids (corticosteroids) continue to be the standard treatment for nonexacerbated asthma because of their anti-inflammatory actions. These include effects on the airway vasculature, which participates in the inflammatory process. Corticosteroids are now known to have genomic as well as nongenomic effects that involve different mechanisms of action. The genomic vascular effects of inhaled corticosteroids include a decrease in airway wall hypervascularity (inhibition of angiogenesis), reversal of the increased airway blood flow, and inhibition of vascular hyperpermeability and leukocyte recruitment. In addition, inhaled corticosteroids decrease airway blood flow acutely (within minutes) and reversibly through a nongenomic action that involves noradrenergic neurotransmission. This effect is likely related to the binding of inhaled corticosteroids to the plasma membrane of and the inhibition of the extraneuronal monoamine transporter on airway vascular smooth muscle cells, thereby increasing norepinephrine concentrations at alpha(1)-adrenoceptors and causing airway vascular smooth muscle contraction and a decrease in airway blood flow. Inasmuch as vascular hyperperfusion is a manifestation of airway inflammation, the acute vasoconstriction could also be considered an anti-inflammatory effect of inhaled corticosteroids.

Antidepressant Activity Requires Norepinephrine

Cryan et al. used mice deficient for the norepinephrine (and epinephrine) biosynthetic enzyme dopamine β-hydroxylase ( Dbh —/— ) to determine that the acute behavioral effects of different classes of antidepressants were dependent on norepinephrine and not only on changes in serotonergic or dopaminergic signaling. Drugs that were not selective but inhibited the reuptake or metabolism of serotonin, dopamine, and norepinephrine were effective in heterozygous littermates, but not in Dbh —/— mice, at decreasing immobility in the tail suspension test, an assay for the acute effects of antidepressant drugs. Two of the three drugs in the serotonin selective reuptake class were not effective in decreasing immobility in the tail suspension test in Dbh —/— mice. Only citalopram, which is the most selective and does not increase norepinephrine concentrations in vivo, was effective in the Dbh —/— mice. Restoration of norepinephrine by administration of the precursor L- threo -3,4-dihydroxyphenylserine (L-DOPS) restored responsiveness to norepinephrine selective reuptake inhibitors and the serotonin selective reuptake inhibitors. Thus, most antidepressants appear to have a requirement for noradrenergic signaling, with the exception of citalopram, which appears to bypass this requirement. J. F. Cryan, O. F. O'Leary, S.-H. Jin, J. C. Friedland, M. Ouyang, B. R. Hirsch, M. E. Page, A. Dalvi, S. A. Thomas, I. Lucki, Norepinephrine-deficient mice lack responses to antidepressant drugs, including serotonin reuptake inhibitors. Proc. Natl. Acad. Sci. U.S.A. 101 , 8186-8191 (2004). [Abstract] [Full Text]

Increased spillover of norepinephrine to the portal vein during CO2‐pneumoperitoneum in pigs

Elevated intra abdominal pressure (IAP) during CO2-insufflation has been associated with increased catecholamine concentrations in plasma. We have previously indicated that this may be due to a regional increased spillover from the abdominal region. In this experimental study we investigated catecholamine spillover from the drainage area of the portal vein during CO2-pneumoperitoneum. Eight pigs under general anesthesia were investigated before and after CO2-pneumoperitoneum with an IAP of 15 mmHg. Regional spillover of catecholamines was determined by measuring plasma catecholamine concentrations and flow simultaneously. Plasma concentrations of catecholamines were measured from the portal and femoral veins, the pulmonary and carotid arteries. Flow data were collected with laser-Doppler transit time flow probes around the portal and femoral veins. Cardiac output was measured by the thermo-dilution technique. Estimated spillover was calculated by the veno-arterial difference multiplied by flow. We found a significant increase in estimated spillover of norepinephrine from the drainage area of the portal vein from 10 (-1.2, 78) ng x min(-1) to 27 (1.8, 475) ng x min(-1)[median (range)] (P = 0.05), but no change in estimated spillover of norepinephrine from the drainage area of the femoral vein. Plasma concentrations of norepinephrine increased in central venous and arterial blood. There was no significant change in epinephrine concentrations in arterial blood. Estimated norepinephrine spillover from the drainage area of the portal vein increased during CO2-pneumoperitoneum in pigs. This may indicate that the increased norepinephrine concentrations found in arterial plasma reflects a local activation of sympathetic nerves in the region of the portal drainage area.

The development of myocardial insulin resistance in conscious dogs with advanced dilated cardiomyopathy.

The failing heart demonstrates a preference for glucose as its metabolic substrate. Advanced, severe DCM is characterized by depletion of adenosine triphosphate (ATP) stores, which may be a consequence of impaired insulin mediated glucose uptake and oxidation at a time when the myocardium prefers glucose as its substrate. We examined the time course and magnitude of myocardial insulin resistance during the evolution of dilated cardiomyopathy. Thirty-four conscious, chronically instrumented dogs were studied at four stages during the evolution of dilated cardiomyopathy (DCM) induced by rapid RV pacing [control, early, late and advanced severe]. Transmyocardial glucose, lactate, and non-esterified fatty acid (NEFA) concentrations were measured in the fasting state. The cellular insulin signaling cascade and ATP levels were measured on myocardial samples. NEFA and insulin concentrations increased early and progressively in DCM in association with increased norepinephrine concentrations and progressive hemodynamic impairment. In advanced DCM but not earlier stages, myocardial ATP levels were decreased by 34%. There was decreased myocardial glucose uptake evident under both basal (-29 +/- 5%) and insulin stimulated (-32 +/- 4%) conditions in advanced, severe DCM, associated with a 31% reduction in GLUT-4 translocation. Importantly, there were no alterations in proximal steps in insulin signaling, but significant reductions in serine (Ser473) phosphorylation of Akt-1. Advanced, severe DCM is associated with the development of myocardial insulin resistance. There is impaired myocardial glucose uptake and altered myocardial insulin signaling, involving decreased Ser 473 phosphorylation of Akt-1. Myocardial insulin resistance in advanced, severe DCM was also associated with reduced myocardial ATP levels.

Changes of central norepinephrine, beta-endorphin, LEU-enkephalin, peripheral arginine-vasopressin, and angiotensin II levels in acute and chronic phases of sino-aortic denervation in rats.

We and others have demonstrated that impaired arterial baroreceptor reflex (ABR) function is one of the major causes of hypertension-associated end organ damage. The goal of this study was to clarify the potential neuro-humoral mechanisms responsible for impaired ABR-induced end organ damage. The sino-aortic denervated (SAD) rat was used as an animal model of ABR dysfunction. One-week SAD rats were characterized by hypertension, tachycardia, increased norepinephrine content, and decreased beta-endorphin and leu-enkephalin content in hypothalamus and medulla oblongata, and increased plasma levels of arginine-vasopressin. In 18-week SAD rats, the 24-hour average arterial pressure, heart rate, beta-endorphin, and leu-enkephalin content in hypothalamus and medulla oblongata and plasma levels of arginine-vasopressin and angiotensin II were not different from those measured in ABR-intact rats. However, blood pressure variability and angiotensin II content in kidney and left ventricle increased. When exposed to chronic stress, exaggerated changes in arterial pressure, blood pressure variability, the levels of central norepinephrine, beta-endorphin and leu-enkephalin, plasma arginine-vasopressin and angiotensin II, and tissue angiotensin II were found in 18-week SAD rats. These data indicate that a long-term impairment of ABR leads to chronic activation of central noradrenergic neurons and tissue renin-angiotensin system, and that stress induces exaggerated responses of neuro-humoral factors and hemodynamics in SAD rats. Thus, if the present results hold true for humans, one can expect abnormal neurotransmitter/neuromodulator responses to environmental insults in patients with impaired ABR function.

Norepinephrine induces apoptosis in neonatal rat endothelial cells via down-regulation of Bcl-2 and activation of beta-adrenergic and caspase-2 pathways.

Heart failure is associated with increased plasma norepinephrine (NE) and endothelial apoptosis. Recent reports have suggested that endothelial dysfunction is an important target for future therapies of heart failure. However, whether NE can induce endothelial apoptosis and its mechanism remains unknown. Endothelial cells from neonatal rat heart were treated with various concentrations of NE for different durations. Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated nick end-labeling (TUNEL) and DNA fragmentation assays. Caspase activity was measured using specific fluorogenic substrates. Proteins of Bcl-2 family and cytochrome c were assayed by Western blotting. NE induced endothelial apoptosis in a dose- and time-dependent manner. After treatment for 48 h, increasing NE concentration from 5, 10, 50, 100 to 200 microM resulted in 6+/-3%, 14+/-5%, 43+/-4%, 66+/-5%, and 89+/-6% apoptotic cells, respectively. The apoptosis was accompanied by down-regulation of Bcl-2 protein synthesis but not by cytosolic cytochrome c translocation. Caspase-2, -3, -6 and -9 were activated during apoptosis and caspase-2 inhibitor (Z-VDVAD-FMK) and caspase-3 inhibitor (Z-DEVD-FMK) significantly attenuated the apoptosis. Overexpression of Bcl-2 inhibited caspase activity and decreased the apoptosis. Moreover, the NE-mediated apoptotic effect was attenuated by beta- (beta2>beta>beta1) adrenergic antagonists (ICI-118,551>propranolol>atenolol) but was not affected by alpha1- or alpha2-adrenergic antagonists (prazosin or yohimbine). Our study is the first report documenting that NE induces apoptosis in neonatal rat endothelial cells mainly through down-regulation of Bcl-2 protein and activation of the beta-adrenergic (beta2>beta1) and caspase-2 pathways. beta-Adrenergic antagonists and caspases inhibitors may be useful in the prevention and management of NE-mediated endothelial apoptosis during heart failure.

Central adaptation to chronic administration of interleukin-1β (IL-1β) in rats

Interleukin-1β (IL-1β), a cytokine, has been shown to induce a number of central and neuroendocrine effects. Prolonged treatment with IL-1β is associated with adaptive responses in feeding, body temperature and hormone profiles. The purpose of the present study was to see if these effects are accompanied by changes in hypothalamic norepinephrine (NE) and to compare it with the acute effects of IL-1β. Adult male Sprague–Dawley rats were treated (i.p.) with 5 μg of IL-1β once (acute) or daily for 5 consequent days (chronic). The control animals received an injection of the vehicle for IL-1β (0.1% PBS–BSA). Body weight, food intake, and rectal temperature were monitored daily. At the end of treatment, the animals were sacrificed, and specific areas of the hypothalamus were microdissected and analyzed for NE concentrations. Corticosterone levels were measured in the serum. Both acute and chronic IL-1β treatment produced significant changes in a number of parameters. However, there were marked differences between the two treatment regimens. While acute treatment with IL-1β increased NE concentrations in both the paraventricular nucleus and the median eminence (ME), chronic treatment increased NE concentrations only in the ME. A corresponding increase in serum corticosterone levels was observed with acute IL treatment. Chronic treatment with IL-1β decreased body weight, and produced an initial decrease in food intake which returned to control levels by the fourth day of treatment. Chronic IL treatment also produced an initial increase in body temperature that returned to control levels by day 4. These results indicate that the effects of IL-1β on central and neuroendocrine functions are dependent on the duration of the treatment and that the adaptive responses observed in feeding and body temperature after chronic IL treatment are accompanied by similar responses in brain NE.

Neuroendocrine effects of perfluorooctane sulfonate in rats.

Perfluorooctane sulfonate (PFOS) is a degradation product of sulfonyl-based fluorochemicals that are used extensively in industrial and household applications. Humans and wildlife are exposed to this class of compounds from several sources. Toxicity tests in rodents have raised concerns about potential developmental, reproductive, and systemic effects of PFOS. However, the effect of PFOS on the neuroendocrine system has not been investigated thus far. In this study, adult female rats were injected intraperitoneally with 0, 1, or 10 mg PFOS/kg body weight (BW) for 2 weeks. Food and water intake, BW, and estrous cycles were monitored daily. At the end of treatment, PFOS levels in tissues were measured by high-performance liquid chromatography (HPLC) interfaced with electrospray mass spectrometry. Changes in brain monoamines were measured by HPLC with electrochemical detection, and serum corticosterone and leptin were monitored using radioimmunoassay. Treatment with PFOS produced a dose-dependent accumulation of this chemical in various body tissues, including the brain. PFOS exposure decreased food intake and BW in a dose-dependent manner. Treatment with PFOS affected estrous cyclicity and increased serum corticosterone levels while decreasing serum leptin concentrations. PFOS treatment also increased norepinephrine concentrations in the paraventricular nucleus of the hypothalamus. These results indicate that exposure to PFOS can affect the neuroendocrine system in rats.

Corticosterone in drinking water: altered kinetics of a single oral dose of corticosterone and concentrations of plasma sodium, albumin, globulin, and total protein

Effects of chronic exposure to corticosterone in drinking water on corticosterone kinetics, blood chemistry, and concentrations of catecholamines in parts of brain were studied in Long-Evans rats. Rats were randomly grouped into 3 x 2 treatments (n=4), with three treatments of drinking water (tap water, or 2.5% ethanol, or 400 microg/mL of corticosterone in 2.5% ethanol) for 28 days and two treatments of gavage with a single dose of either corn oil or corticosterone 20 mg/kg on day 28. Blood samples were collected at 0, 15, 30, 60, 120, 240, 480, and 720 min after dosing to determine plasma corticosterone concentrations. Blood samples were collected for clinical pathology on day 42. Hippocampus, cerebral cortex, caudate-putamen, and pons were examined to determine concentrations of catecholamines and activities of esterases. Concentrations of plasma corticosterone before gavage of the corticosterone-drinking rats (47.61 +/- 1.13 ng/mL) were lower than the water (418.47 +/- 1.13 ng/mL) or the ethanol rats (383.71 +/- 1.13 ng/mL, P < 0.0001). Plasma corticosterone rose to peak concentrations by 15 min after gavage in all three groups of drinking rats. Corticosterone-drinking rats had concentrations of plasma corticosterone that returned to basal levels slower than water- and ethanol-drinking rats. Plasma sodium and chloride concentrations were lower in the corticosterone-drinking rats than the water-drinking rats (P < 0.01). Plasma albumin, globulin, and total protein were highest in the corticosterone-drinking rats when compared to the other groups of drinking rats (P < 0.001, P < 0.05, and P < 0.001, respectively). Corticosterone in drinking water did not affect activities of brain neurotoxic esterase, carboxylesterase, acetylcholinesterase, or concentrations of monoamines and their metabolites. A single oral dose of corticosterone reduced neurotoxic esterase activity in the cerebral cortex (P < 0.05) and increased norepinephrine concentrations in the hippocampus (P < 0.05).