Sulfide-induced perturbations of the neuronal mechanisms controlling breathing in rats

1995 ◽  
Vol 78 (2) ◽  
pp. 433-440 ◽  
Author(s):  
J. J. Greer ◽  
R. J. Reiffenstein ◽  
A. F. Almeida ◽  
J. E. Carter
Keyword(s):  
Respiratory Rhythm ◽  
Intraperitoneal Administration ◽  
Experimental Models ◽  
Neonatal Rat ◽  
Ventrolateral Medulla ◽  
Neonatal Rats ◽  
Breathing Patterns ◽  
Adult Rats

The effects of sulfide on neonatal rat respiration were studied. Two in vitro experimental models were utilized: the isolated brain stem-spinal cord preparation and the medullary slice preparation containing respiratory rhythm-generating regions from neonatal rats. Plethysmographic measurements of the effects of sulfide on the breathing patterns of unanesthetized neonatal rats were also made to compare the sensitivities of neonatal and adult rats to sulfide toxicity. In vitro, sulfide acted at sites within the ventrolateral medulla to depress the frequency of respiratory rhythmic discharge by approximately 50–60%. However, the neuronal network underlying respiratory rhythmogenesis continued to function in the presence of concentrations of sulfide far beyond those deemed to be lethal in vivo. Intraperitoneal administration of sulfide caused a dose-dependent decrease in the frequency and amplitude of breathing of neonatal rats of all ages (0–19 days postnatal), although the sensitivity to sulfide increased with age. We hypothesize that the rapid suppression of breathing caused by sulfide is due to changes in neuronal excitability within respiratory rhythm-generating centers rather than, as previously hypothesized, to perturbations of cellular oxidative metabolism.

Sulfated cholecystokinin octapeptide in the rat: pontomedullary distribution and modulation of the respiratory pattern

1999 ◽  
Vol 77 (7) ◽  
pp. 490-504 ◽  
Author(s):  
Howard H Ellenberger ◽  
Frank M Smith
Keyword(s):  
Respiratory Rhythm ◽  
Mean Amplitude ◽  
Neonatal Rat ◽  
Respiratory Pattern ◽  
Reticular Nucleus ◽  
Adult Rats ◽  
Cholecystokinin Octapeptide ◽  
Ventral Respiratory Group

We performed anatomical and physiological studies to determine the site and actions of sulfated cholecystokinin octapeptide (CCK8-S) on breathing. Peptide locations were determined by combined immunodetection of CCK8-S- containing synaptic varicosities and retrograde labeling of medullary neurons projecting to the ventral respiratory group. Retrogradely labeled neurons and CCK8-S immunolabeled varicosities overlapped within the nuclei of the solitary tract, ventral respiratory group, and the Kölliker-Fuse nucleus. Additional CCK8-S immunoreactive terminals were located in the rostroventrolateral medullary reticular nucleus, lateral paragigantocellular reticular nucleus, and the caudal pontine reticular nucleus. The respiratory effects of CCK8-S, which binds to CCKA and CCKB receptors, were examined by intravenous injection in adult rats and by bath application in the in vitro neonatal rat brainstem - spinal cord preparation. CCK8-S produced an increase in the mean amplitude of diaphragmatic electromyogram (EMG) of 28 ± 35% (SD) and a decrease in mean respiratory interval of 13 ± 4% in vivo. In vitro, CCK8-S significantly increased inspiratory duration and decreased respiratory interval, primarily by shortening expiratory duration. CCK8-unsulfated, a specific agonist for CCKB receptors, did not produce these effects. CCK8-S effects in the in vitro preparation were partially blocked by the CCK receptor antagonist lorglumide (final bath concentration 600 nM). These results suggest that CCK8-S modulates the respiratory rhythm via CCKA receptors within one or more medullary or pontine respiratory groups in both neonatal and adult rats.Key words: neuropeptide, ventral respiratory group, medulla, pons, respiratory network.

scholarly journals Maturation of the Mammalian Respiratory System

1999 ◽  
Vol 79 (2) ◽  
pp. 325-360 ◽  
Author(s):  
Gérard Hilaire ◽  
Bernard Duron
Keyword(s):  
Respiratory Activity ◽  
Respiratory Rhythm ◽  
Ventrolateral Medulla ◽  
Pacemaker Neurons ◽  
Inhibitory Processes ◽  
Respiratory Rhythmogenesis ◽  
Respiratory Network ◽  
Network Functions

In this review, the maturational changes occurring in the mammalian respiratory network from fetal to adult ages are analyzed. Most of the data presented were obtained on rodents using in vitro approaches. In gestational day 18 (E18) fetuses, this network functions but is not yet able to sustain a stable respiratory activity, and most of the neonatal modulatory processes are not yet efficient. Respiratory motoneurons undergo relatively little cell death, and even if not yet fully mature at E18, they are capable of firing sustained bursts of potentials. Endogenous serotonin exerts a potent facilitation on the network and appears to be necessary for the respiratory rhythm to be expressed. In E20 fetuses and neonates, the respiratory activity has become quite stable. Inhibitory processes are not yet necessary for respiratory rhythmogenesis, and the rostral ventrolateral medulla (RVLM) contains inspiratory bursting pacemaker neurons that seem to constitute the kernel of the network. The activity of the network depends on CO2 and pH levels, via cholinergic relays, as well as being modulated at both the RVLM and motoneuronal levels by endogenous serotonin, substance P, and catecholamine mechanisms. In adults, the inhibitory processes become more important, but the RVLM is still a crucial area. The neonatal modulatory processes are likely to continue during adulthood, but they are difficult to investigate in vivo. In conclusion, 1) serotonin, which greatly facilitates the activity of the respiratory network at all developmental ages, may at least partly define its maturation; 2) the RVLM bursting pacemaker neurons may be the kernel of the network from E20 to adulthood, but their existence and their role in vivo need to be further confirmed in both neonatal and adult mammals.

Coverslip hypoxia: a novel method for studying cardiac myocyte hypoxia and ischemia in vitro

2004 ◽  
Vol 287 (4) ◽  
pp. H1801-H1812 ◽  
Author(s):  
Kelly R. Pitts ◽  
Christopher F. Toombs
Keyword(s):  
Metabolic Activity ◽  
Cardiac Myocyte ◽  
Experimental Models ◽  
Membrane Dynamics ◽  
Neonatal Rat ◽  
Simple Method ◽  
Glass Coverslip ◽  
Media Volume

In vitro experimental models designed to study the effects of hypoxia and ischemia typically employ oxygen-depleted media and/or hypoxic chambers. These approaches, however, allow for metabolites to diffuse away into a large volume and may not replicate the high local concentrations that occur in ischemic myocardium in vivo. We describe herein a novel and simple method for creating regional hypoxic and ischemic conditions in neonatal rat cardiac myocyte monolayers. This method consists of creating a localized diffusion barrier by placing a glass coverslip over a portion of the monolayer. The coverslip restricts covered myocytes to a thin film of media while leaving uncovered myocytes free to access the surrounding bulk media volume. Myocytes under the coverslip undergo marked morphology changes over time as assessed by video microscopy. Fluorescence microscopy shows that these changes are accompanied by alterations in mitochondrial membrane potential and plasma membrane dynamics and eventually result in myocyte death. We also show that the metabolic activity of myocytes drives cell necrosis under the coverslip. In addition, the intracellular pH of synchronously contracting myocytes under the coverslip drops rapidly, which further implicates metabolic activity in regulating cell death under the coverslip. In contrast with existing models of hypoxia/ischemia, this technique provides a simple and effective way to create hypoxic/ischemic conditions in vitro. Moreover, we conclude that myocyte death is hastened by the combination of hypoxia, metabolites, and acidosis and is facilitated by a reduction in media volume, which may better represent ischemic conditions in vivo.

Growth hormone (GH) autofeedback action in the neonatal rat: involvement of GH-releasing hormone and somatostatin

1990 ◽  
Vol 124 (2) ◽  
pp. 199-205 ◽  
Author(s):  
S. G. Cella ◽  
V. De Gennaro Colonna ◽  
V. Locatelli ◽  
V. Moiraghi ◽  
S. Loche ◽  
...  
Keyword(s):  
Body Weight ◽  
Inhibitory Effect ◽  
Postnatal Period ◽  
Neonatal Rat ◽  
Gh Treatment ◽  
Adult Rats ◽  
Releasing Hormone ◽  
Term Administration

ABSTRACT It is known that in adult rats, GH by itself and by promoting secretion of the somatomedins acts at the level of the hypothalamus to trigger release of somatostatin and decrease output of GH-releasing hormone (GHRH), thereby inhibiting further secretion of GH. To assess whether these mechanisms are already operative in the early postnatal period, we have evaluated the effect of short-term administration of GH in 10-day-old rats. Twice-daily s.c. administration of 25 μg human GH/rat, from days 5 to 9 of life, significantly reduced pituitary content of GH, decreased hypothalamic levels of GHRH mRNA and abolished the in-vivo GH response to a challenge dose of GHRH (20 ng/100 g body weight, s.c.). GHRH (20 ng/100 g body weight, twice daily, s.c.) given concomitantly with the GH treatment, completely counteracted the inhibitory effect of the latter on pituitary content of GH and restored to normal the in-vivo GH response to the GHRH challenge. These data indicate that impaired secretion of GHRH is involved in the inhibitory effect elicited by GH treatment in infant rats. However, concomitant involvement of hypothalamic somatostatin as a result of GH treatment cannot be ruled out. In fact, pituitaries from rats pretreated with GH responded in the same manner as pituitaries from control rats to the GHRH challenge in vitro. Journal of Endocrinology (1990) 124, 199–205

Effect of cholinergic agonists on bulbospinal C1 neurons in rats

1997 ◽  
Vol 272 (1) ◽  
pp. R249-R258 ◽  
Author(s):  
D. Huangfu ◽  
M. Schreihofer ◽  
P. G. Guyenet
Keyword(s):  
Brain Slices ◽  
Reversal Potential ◽  
Input Resistance ◽  
Neonatal Rat ◽  
Ventrolateral Medulla ◽  
Cholinergic Agonists ◽  
Inward Currents ◽  
Tone Generation

Cholinergic inputs to the rostral ventrolateral medulla (RVLM) may contribute to sympathetic tone generation. The present study analyzes the response of RVLM neurons to cholinergic agonists. In chloralose-anesthetized rats iontophoresis of carbachol excited RVLM sympathoexcitatory neurons (+69% from resting level of 11.9 +/- 2 spikes/s; n = 28). This effect was reduced 85% by iontophoresis of methylatropine and abolished by intravenous scopolamine. Iontophoresis of nicotine or hexamethonium was ineffective. In contrast, most RVLM respiratory units were inhibited by carbachol. Whole cell recordings of bulbospinal RVLM neurons were made in neonatal rat brain slices (54 cells, 24 C1 adrenergic neurons). In current-clamp recordings (without tetrodotoxin) carbachol produced depolarization, increased postsynaptic potential frequency, and decreased input resistance. In voltage-clamp recording (-50 to -60 mV; 1 microM tetrodotoxin) carbachol produced inward current [50% effective concentration (EC50): 10 +/- 1 microM; 12.6 +/- 2 pA at 30 microM; n = 16] that persisted in low Ca2+/high Mg2+ (n = 6). Muscarine (30 microM) caused smaller inward currents (2.6 +/- 0.6 pA; n = 16). The carbachol-induced current was reduced 46% by 5 microM methylatropine (n = 15) and 84% by 200 microM hexamethonium (n = 9). The current was linear as a function of the holding potential (extrapolated reversal potential: -22 +/- 2 mV). In conclusion, carbachol exerts both pre- and postsynaptic effects on C1 and other putative sympathoexcitatory RVLM neurons. In vitro the postsynaptic effect of carbachol has a mixed nicotinic and muscarinic pharmacology. In vivo, iontophoretically applied carbachol produces muscarinic excitation of barosensitive RVLM neurons.

scholarly journals Some Biochemical and Histological Effects of 2-Chloroethanol in Rats

1992 ◽  
Vol 1 (3) ◽  
pp. 37-56 ◽  
Author(s):  
Leonard Friedman ◽  
John Scalera ◽  
James E. Keys ◽  
Edmund L. Peters ◽  
Dennis W. Gaines ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Rna Synthesis ◽  
Liver Lipid ◽  
Intraperitoneal Administration ◽  
Female Rats ◽  
Male Rats ◽  
Liver Protein ◽  
Adult Rats

The effects of 2-chioroethanol (2-CE) on rat tissue following in vitro and in vivo exposure were studied. At concentrations as low as 2.5 mg/ml, protein synthesis in liver slices was inhibited; at concentrations of 25 mg/ml and above, RNA synthesis and respiration were also impaired. Single oral doses of 2-CE to young adult rats at levels of 15-40 mg/kg body weight depressed liver nonprotein sulfhydryl (GSH) concentration and liver protein but not RNA synthesis. Liver lipid was increased by 7 hr after a single oral dose of 30 mg/kg. The time courses and dose-response relationship for GSH depletion and restoration and for protein synthesis inhibition and recovery were similar. The livers of female rats were more sensitive than the livers of male rats to the effects of 2-CE. Protein synthesis was also depressed in kidneys of 2-CE-treated male rats but at higher doses than those needed for this effect to occur in livers of the same animals. Liver polysome disaggregation also occurred after oral 2-CE doses of 20 mg/kg and greater. The effects of 2-CE on ribosome profiles and protein synthesis were at least partially reversed by concurrent intraperitoneal administration of cysteine. The possible relationship of these findings to a role of GSH in protein synthesis is discussed.

scholarly journals Glial TLR4 signaling does not contribute to opioid-induced depression of respiration

2014 ◽  
Vol 117 (8) ◽  
pp. 857-868 ◽  
Author(s):  
Jennifer D. Zwicker ◽  
Yong Zhang ◽  
Jun Ren ◽  
Mark R. Hutchinson ◽  
Kenner C. Rice ◽  
...  
Keyword(s):  
Respiratory Depression ◽  
Respiratory Rhythm ◽  
Opioid Antagonist ◽  
Adult Rats ◽  
Opioid Receptor Agonist ◽  
Bath Application ◽  
The Central Nervous System ◽  
Tlr4 Antagonist

Opioids activate glia in the central nervous system in part by activating the toll-like receptor 4 (TLR4)/myeloid differentiation 2 (MD2) complex. TLR4/MD2-mediated activation of glia by opioids compromises their analgesic actions. Glial activation is also hypothesized as pivotal in opioid-mediated reward and tolerance and as a contributor to opioid-mediated respiratory depression. We tested the contribution of TLR4 to opioid-induced respiratory depression using rhythmically active medullary slices that contain the pre-Bötzinger Complex (preBötC, an important site of respiratory rhythm generation) and adult rats in vivo. Injection with DAMGO (μ-opioid receptor agonist; 50 μM) or bath application of DAMGO (500 nM) or fentanyl (1 μM) slowed frequency recorded from XII nerves to 40%, 40%, or 50% of control, respectively. This DAMGO-mediated frequency inhibition was unaffected by preapplication of lipopolysaccharides from Rhodobacter sphaeroides (a TLR4 antagonist, 2,000 ng/ml) or (+)naloxone (1–10 μM, a TLR4-antagonist). Bath application of (−)naloxone (500 nM; a TLR4 and μ-opioid antagonist), however, rapidly reversed the opioid-mediated frequency decrease. We also compared the opioid-induced respiratory depression in slices in vitro in the absence and presence of bath-applied minocycline (an inhibitor of microglial activation) and in slices prepared from mice injected (ip) 18 h earlier with minocycline or saline. Minocycline had no effect on respiratory depression in vitro. Finally, the respiratory depression evoked in anesthetized rats by tail vein infusion of fentanyl was unaffected by subsequent injection of (+)naloxone, but completely reversed by (−)naloxone. These data indicate that neither activation of microglia in preBötC nor TLR4/MD2-activation contribute to opioid-induced respiratory depression.

scholarly journals Lactobacillus rhamnosusGG Suppresses MeningiticE. coliK1 Penetration across Human Intestinal Epithelial Cells In Vitro and Protects Neonatal Rats against Experimental Hematogenous Meningitis

2009 ◽  
Vol 2009 ◽  
pp. 1-7 ◽  
Author(s):  
Sheng-He Huang ◽  
Lina He ◽  
Yanhong Zhou ◽  
Chun-Hua Wu ◽  
Ambrose Jong
Keyword(s):  
Neonatal Sepsis ◽  
Lactobacillus Rhamnosus ◽  
Inhibitory Effect ◽  
Neonatal Rat ◽  
Control Group ◽  
Dependent Manner ◽  
Neonatal Rats ◽  
E Coli

The purpose of this study was to examine prophylactic efficacy of probiotics in neonatal sepsis and meningitis caused byE. coliK1. The potential inhibitory effect ofLactobacillus rhamnosusGG (LGG) on meningiticE. coliK1 infection was examined by using (i) in vitro inhibition assays with E44 (a CSF isolate from a newborn baby withE. colimeningitis), and (ii) the neonatal rat model ofE. colisepsis and meningitis. The in vitro studies demonstrated that LGG blocked E44 adhesion, invasion, and transcytosis in a dose-dependent manner. A significant reduction in the levels of pathogen colonization,E. colibacteremia, and meningitis was observed in the LGG-treated neonatal rats, as assessed by viable cultures, compared to the levels in the control group. In conclusion, probiotic LGG strongly suppresses meningiticE. colipathogens in vitro and in vivo. The results support the use of probiotic strains such as LGG for prophylaxis of neonatal sepsis and meningitis.

Implantation increases tensile strength and collagen content of self-assembled tendon constructs

2010 ◽  
Vol 108 (4) ◽  
pp. 875-881 ◽  
Author(s):  
Sarah Calve ◽  
Ian F. Lytle ◽  
Karl Grosh ◽  
David L. Brown ◽  
Ellen M. Arruda
Keyword(s):  
Tensile Strength ◽  
Collagen Fiber ◽  
Fiber Diameter ◽  
Collagen Content ◽  
Neonatal Rat ◽  
Adult Rats ◽  
Autologous Cell ◽  
Lower Tensile Strength

Tissue-engineered tendons, derived from an autologous cell source, have the potential to provide an ideal replacement graft that is biologically compatible and has the ability to adapt to the specific mechanical requirements of the in vivo environment. Scaffold-free tendon constructs have been successfully engineered in vitro. However, when compared against native tendons the constructs demonstrate both a lower tensile strength and collagen content. We hypothesized that the in vitro environment lacks certain environmental stimuli and that implantation in vivo would facilitate the maturation of engineered tissues. Using primary Achilles tendon fibroblasts from adult rats, self-organizing constructs were created in vitro. Tendon constructs were implanted subcutaneously into the groins of adult rats for 4 wk, while controls remained in vitro. Implanted constructs increased in stiffness by three orders of magnitude when compared with the in vitro controls (7,500 vs. 22.3 kPa). This increase in tangent modulus correlated with a significant increase in collagen content, as measured by hydroxyproline concentration, from 3.9% for the in vitro controls to 22.7% in the in vivo conditioned group. In addition, collagen fiber diameter increased from 22.0 to 75.4 nm as a result of in vivo implantation. The tensile strength and collagen content of in vivo conditioned constructs were similar to the values determined for neonatal rat tibialis anterior tendons.

Medullary regions for neurogenesis of gasping: noeud vital or noeuds vitals?

1996 ◽  
Vol 81 (5) ◽  
pp. 1865-1877 ◽  
Author(s):  
Walter M. St. John
Keyword(s):  
Mammalian Species ◽  
Respiratory Rhythm ◽  
Rhythmic Activity ◽  
Neonatal Rat ◽  
Rhythm Generation ◽  
Bötzinger Complex ◽  
Per Se ◽  
Respiratory Rhythm Generation

St. John, Walter M. Medullary regions for neurogenesis of gasping: noeud vital or noeuds vitals? J. Appl. Physiol. 81(5): 1865–1877, 1996.—Gasping is a critical mechanism for survival in that it serves as a mechanism for autoresuscitation when eupnea fails. Eupnea and gasping are separable patterns of automatic ventilatory activity in all mammalian species from the day of birth. The neurogenesis of the gasp is dependent on the discharge of neurons in the rostroventral medulla. This gasping center overlaps a region termed “the pre-Bötzinger complex.” Neuronal activities of this complex, characterized in an in vitro brain stem spinal cord preparation of the neonatal rat, have been hypothesized to underlie respiratory rhythm generation. Yet, the rhythmic activity of this in vitro preparation is markedly different from eupnea but identical with gasping in vivo. In eupnea, medullary neuronal activities generating the gasp and the identical rhythm of the in vitro preparation are incorporated into a portion of the pontomedullary circuit defining eupneic ventilatory activity. However, these medullary neuronal activities do not appear critical for the neurogenesis of eupnea, per se.

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