Respiration In Rats Research Articles

Disorders Of Mitochondrial Respiration in Rats with Subtotal Cerebral Ischemia Under Conditions of The Use of Modulators of the L-Arginine-No Pathway and Against the Background of The Administration of Omega-3 Polyunsaturated Fatty Acids

The urgency of the problem of cerebrovascular diseases can rightfully be defined as an emergency, requiring the concentration of efforts of specialists. This is due to the fact that cerebrovascular diseases of ischemic origin tend to grow, rejuvenate, are associated with a severe clinical course, high rates of disability and mortality. Omega-3 polyunsaturated fatty acids are involved in the implementation of the basic functions of neurons, such as the transmission of impulses and the functioning of receptors. In this regard, it is of interest to study the morphofunctional features of brain neurons in rats with subtotal cerebral ischemia against the background of the introduction of Omega-3 polyunsaturated fatty acids and L-NAME. There was a significant improvement in the parameters of mitochondrial respiration when using succinate as a substrate in the group of animals treated with Omega-3 PUFAs and even greater activation in the groups of animals SCI + L-NAME + Omega-3 and SCI + L-NAME + L-arginine + Omega-3. When malate/glutamate was used as a substrate in these groups, the same trend in respiration was observed as when succinate was used to activate mitochondrial respiration. However, changes in succinate-dependent respiration were more pronounced.

Muscle Respiration in Rats Is Influenced by the Type and Level of Dietary Fat

Experiments were conducted to elucidate the role of muscle in the enhanced thermogenic response found in rats fed diets enriched with polyunsaturated fatty acids. Isolated soleus muscle respiration and plasma cholesterol and triglyceride concentrations were determined in rats (∼128 g wt, 5 wk age) fed diets (minimum 3 wk) containing coconut oil, beef tallow or safflower oil at 20, 40 or 60% of the total dietary energy in a 3 × 3 factorial design (5–6 rats per treatment). Diet type did not affect plasma cholesterol concentrations but plasma triglycerides were lower (P < 0.01) in rats fed safflower oil-based diets. Greater levels of fat in the diet resulted in higher (P < 0.01) plasma cholesterol concentrations and lower (P < 0.01) plasma triglyceride concentrations. Rats fed coconut oil had lower (P < 0.05) rates of soleus muscle respiration compared with rats fed the other two diets. This lower respiration rate was not related to changes in protein synthesis (cycloheximide-sensitive respiration). However, this change may partially be related to enhanced Na+,K+ transport (ouabain-sensitive respiration). The results indicate that muscle is partially responsible for the enhanced thermogenic response found in rats fed diets enriched with polyunsaturated fatty acids and that enhanced ion transport contributes to this response in muscle.

Mitochondrial respiration in rats during hypothermia resulting from central drug administration.

The ability to induce a hypothermia resembling that of natural torpor would be greatly beneficial in medical and non-medical fields. At present, two procedures based on central nervous pharmacological manipulation have been shown to be effective in bringing core body temperature well below 30°C in the rat, a non-hibernator: the first, based on the inhibition of a key relay in the central thermoregulatory pathway, the other, based on the activation of central adenosine A1 receptors. Although the role of mitochondria in the activation and maintenance of torpor has been extensively studied, no data are available for centrally induced hypothermia in non-hibernators. Thus, in the present work the respiration rate of mitochondria in the liver and in the kidney of rats following the aforementioned hypothermia-inducing treatments was studied. Moreover, to have an internal control, the same parameters were assessed in a well-consolidated model, i.e., mice during fasting-induced torpor. Our results show that state 3 respiration rate, which significantly decreased in the liver of mice, was unchanged in rats. An increase of state 4 respiration rate was observed in both species, although it was not statistically significant in rats under central adenosine stimulation. Also, a significant decrease of the respiratory control ratio was detected in both species. Finally, no effects were detected in kidney mitochondria in both species. Overall, in these hypothermic conditions liver mitochondria of rats remained active and apparently ready to be re-activated to produce energy and warm up the cells. These findings can be interpreted as encouraging in view of the finalization of a translational approach to humans.

The use of hypercapnic conditions to assess opioid-induced respiratory depression in rats

IntroductionWhole-body plethysmography (WBP) in unrestrained, non-anesthetized rodents is a preclinical method to assess the respiratory depressant effects of opioids, the leading cause of opioid overdose death in humans. However, low baseline respiration rates under normocapnic conditions (i.e., “floor” effect) can render the measurement of respiratory decreases challenging. We assessed hypercapnia-induced increases in respiration as a strategy to assess opioid-induced decreases in respiration in rats. MethodsWBP was used to assess respiration frequency, tidal volume and minute volume in the presence of normocapnic and hypercapnic (8% CO2) conditions in rats during the rat diurnal period of the light cycle. The mu-opioid receptor agonist fentanyl was administered intravenously, and the hot plate test was used to assess acute antinociception. Results and discussionHypercapnia-induced increases in respiratory parameters (frequency, minute volume, and tidal volume) were decreased by fentanyl at doses that did not decrease the same parameters under the normocapnic conditions. These findings show that hypercapnia increases sensitivity to respiratory depressant effects of fentanyl, as compared with assessments during the rat diurnal period when activity and breathing rate are generally low, i.e., there is a floor effect. The current approach is highly sensitive to opioid-induced respiratory depression, and therefore provides a useful method for assessment in a pre-clinical setting.

Fatty Acid Oxidation and Mitochondrial Morphology Changes as Key Modulators of the Affinity for ADP in Rat Heart Mitochondria.

Fatty acids are the main respiratory substrates important for cardiac function, and their oxidation is altered during various chronic disorders. We investigated the mechanism of fatty acid–oxidation-induced changes and their relations with mitochondrial morphology and ADP/ATP carrier conformation on the kinetics of the regulation of mitochondrial respiration in rat skinned cardiac fibers. Saturated and unsaturated, activated and not activated, long and medium chain, fatty acids similarly decreased the apparent KmADP. Addition of 5% dextran T-70 to mimic the oncotic pressure of the cellular cytoplasm markedly increased the low apparent KmADP value of mitochondria in cardiac fibers respiring on palmitoyl-l-carnitine or octanoyl-l-carnitine, but did not affect the high apparent KmADP of mitochondria respiring on pyruvate and malate. Electron microscopy revealed that palmitoyl-l-carnitine oxidation-induced changes in the mitochondrial ultrastructure (preventable by dextran) are similar to those induced by carboxyatractyloside. Our data suggest that a fatty acid oxidation-induced conformational change of the adenosine diphosphate (ADP)/adenosine triphosphate (ATP) carrier (M-state to C-state, condensed to orthodox mitochondria) may affect the oxidative phosphorylation affinity for ADP.

Antagonistic Effects of Tetramethylpyrazine on Hypoxic Respiratory Depression in Rats.

Objective Tetramethylpyrazine (TMP) is an alkaloid extracted from the root and stem of the traditional Chinese herbal medicine called Chuanxiong. The present study aims to study the effects of TMP on hypoxic respiratory depression in rats. Materials and methods. The effects of TMP on respiratory responses of rats induced by hypoxia were observed by diaphragm electromyogram (EMG) recording. The effects of TMP on the protein expression of FOS and acid sensing ion channel1a (ASIC1a) in the brainstem induced by hypoxia were investigated by immunohistochemistry. Results The respiration of rats was first excited and then depressed during hypoxia treatment, while TMP pretreatment could significantly antagonize the respiratory depression induced by hypoxia (P < 0.01). Hypoxia obviously induced the protein expression of FOS (P < 0.01) and ASIC1a(P < 0.05) in the brainstem, which can be also significantly inhibited by TMP pretreatment. Conclusions TMP has protective effects on hypoxic respiratory depression, and the mechanisms might be concerned with its downregulation of FOS and ASIC1a in the brainstem induced by hypoxia.

Participation of GABAB Receptors of Parafacial Respiratory Group in the Regulation of Respiration in Rats.

The respiratory effects of microinjections of baclofen and 2-hydroxysaclofen into the parafacial respiratory group were studied in experiments on rats. It was shown that activation of GABAB receptors of the parafacial respiratory group suppressed external respiration due to a decrease in the tidal volume and inspiratory flow rate. In parallel, we observed a decrease in the amplitude and an increase in the duration of inspiratory bursts of the diaphragm. Injection of GABAB receptor blocker into the parafacial respiratory group increased pulmonary ventilation due to an increase in volumetric parameters of the inspiratory phase. This effect was accompanied by prolongation of expiration and lengthening of the intervals between the inspiratory bursts of the diaphragm. These results suggest that GABAB receptors of the parafacial respiratory group are an important element of the central mechanisms regulating the volumetric respiratory parameters and are involved in the regulation of the phases of the respiratory cycle.

Role of GABAA Receptors of Parafacial Respiratory Group in Control of Respiration in Rats.

The role of GABAergic inhibition in the regulation of activity of the parafacial respiratory group was studied on narcotized mature rats. Microinjections of GABAA agonist muscimol into the parafacial respiratory group inhibited external respiration and bioelectrical activity of the diaphragmatic muscle resulting in diminished tidal volume and decreased respiration rate accompanied by prolonged inspiration, expiration, and intervals between the inspiratory bursts in the phrenic electromyogram. In contrast, microinjections of GABAA antagonist bicuculline into this group stimulated respiration and markedly increased its volumetric parameters. In addition, blockade of GABAA receptors affected the expiratory phase and interburst intervals in the phrenic electromyogram, but produced no effect on respiration rate. These findings attested to contribution of GABAA-mediated inhibition into the performance of parafacial respiratory group. The study revealed different roles of GABAA receptors in modulation of the mechanisms of respiration rate control in mature rats and formation of inspiratory motor outputs originating from the parafacial respiratory group.

Effects of Systemic Hypercapnia and Orexin on Gastric Motility and Respiration in Rats

The theory of pneumogastric ventilation predicts that systemic hypercapnia causes a primary pulmonary hypercapnic ventilatory response (HCVR) that is supplemented by a secondary gastric ventilatory response that work together to remove excess CO2 from the body. Gastric ventilation consumes arterialized CO2 during increased production and secretion of gastric acid. In the stomach lumen, CO2 is reconstituted and “ventilated” out through the esophagus, mixed in the oropharynx with pulmonary gas and “exhaled”. Activation of gastric ventilation occurs during CO2 retention in a hypercapnic environment or with alveolar hypoventilation such as COPD. Both pulmonary and gastric ventilatory responses are integrated and coordinated at the level of the caudal solitary complex (cSC), mediated in large part by the vagus nerve (Dean, 2011, Resp Physiol Neurobiol 175(2): 189–209). Central chemoreceptors in the cSC or stimulated by both CO2/H+ and orexin. Likewise, CO2/H+ and orexin stimulate pulmonary ventilation and gastric acid secretion. In fact, hypercapnia causes an increase in production of orexin, which helps maintain the HCVR during wakefulness (Nattie et al, 2010, J Appl Physiol 89: 153–162). Consistent with the theory of pneumogastric ventilation, we found that hypercapnia causes an acute decrease in gastric pH. We do not know, however, how hypercapnia affects gastric motility. Accordingly, we implanted male Sprague‐Dawley rats with the DSI 4‐ET Telemetry unit to measure ECG, respiratory rate via diaphragmatic EMG (dEMG), and gastric EMG (gEMG) to measure gastric motility. Following recovery from surgery, we then subjected them to step‐wise increases in ambient CO2 (30 min/step) starting with air, 5% CO2 in air, 10% CO2 in air, and recovery in air. We also tested the effects of orexin on gastric motility during normocapnia using a lateral tail vein IV injection of orexin‐A. Histamine was used as a positive control for gastric motility. Our findings show that in air, gEMG activity occurs roughly every 15 seconds with bursts lasting 3–4 seconds. Graded hypercapnia caused a graded decrease in the amplitude of periodic gEMG bursts (5% CO2) that stopped completely in 10% CO2. Recovery in air rapidly returns gEMG activity to normal. As expected, dEMG increased with increasing CO2. Similarly, orexin‐A causes an immediate decrease in gEMG activity. We postulate that CO2 activates cSC neurons causing vagally‐mediated relaxation of gastric smooth muscle and increase in gastric acid production to ventilate gastric CO2 during systemic hypercapnia.Support or Funding InformationONR N000141310405 &amp; N000141612537

EFFECT OF CURCUMIN ON MITOCHONDRIAL FUNCTION OF CARDIOMYOCYTES WITH DOXORUBICIN-INDUCED OXIDATIVE STRESS

We studied the effect of curcumin on the cardiomyocytes viability, processes of oxidative phosphorylation in the mitochondria of cardiomyocytes, their pro- and antioxidant balance in doxorubicin-induced oxidative stress. It has been revealed that administration of doxorubicin to rats led to a significant increase in the secondary products of lipid peroxidation (TBARS) in mitochondria by 21 and H(2)0(2) by 76%, reduction of the enzymatic activity of mitochondrial Mn-SOD by 14% and intensified catalase activity by 80% compared with the control. After combined use of doxorubicin and curcumin the content of TBARS and H(2)0(2) increased by 14 and 26%, respectively, the enzymatic activity of catalase decreased by 28%, and mitochondrial Mn-SOD activity intensified by 9%. During the incubation with doxorubicin, the number of live cells decreased by 30.4% and the number of necrotic cells increased by 30.4% relative to control. Coadministration of doxorubicin and curcumin led to augmented cell viability by 8%, while the number of necrotic cells reduced by 8% compared with the use of doxorubicin only. In assessing the parameters of mitochondrial respiration in rats that received injections of doxorubicin active breathing index (V(3)) fell by 43.8%, the oxidation rate of the contingency of phosphorylation (V(3)/V(4)(ATp)) decreased by 47% and phosphorylation efficiency index (ADP/O) also declined by 31.7% respectively compared with the control. The combined use of doxorubicin and curcumin improved the indicators of mitochondrial respiration compared to using only doxorubicin: V(3) raised by 25%, V(3)/V(4)(ATP)by 18% and ADP/O by 12% respectively.

The Responses of Tissues from the Brain, Heart, Kidney, and Liver to Resuscitation following Prolonged Cardiac Arrest by Examining Mitochondrial Respiration in Rats.

Cardiac arrest induces whole-body ischemia, which causes damage to multiple organs. Understanding how each organ responds to ischemia/reperfusion is important to develop better resuscitation strategies. Because direct measurement of organ function is not practicable in most animal models, we attempt to use mitochondrial respiration to test efficacy of resuscitation on the brain, heart, kidney, and liver following prolonged cardiac arrest. Male Sprague-Dawley rats are subjected to asphyxia-induced cardiac arrest for 30 min or 45 min, or 30 min cardiac arrest followed by 60 min cardiopulmonary bypass resuscitation. Mitochondria are isolated from brain, heart, kidney, and liver tissues and examined for respiration activity. Following cardiac arrest, a time-dependent decrease in state-3 respiration is observed in mitochondria from all four tissues. Following 60 min resuscitation, the respiration activity of brain mitochondria varies greatly in different animals. The activity after resuscitation remains the same in heart mitochondria and significantly increases in kidney and liver mitochondria. The result shows that inhibition of state-3 respiration is a good marker to evaluate the efficacy of resuscitation for each organ. The resulting state-3 respiration of brain and heart mitochondria following resuscitation reenforces the need for developing better strategies to resuscitate these critical organs following prolonged cardiac arrest.

Characteristics of external respiration of rats in acute hypercapnic hypoxia and its correction by new metal-complex antihypoxant

Changes of external respiration parameters have been studied in experimental rats after oral introduction of new selenium-containing metal-complex substance πQ1983 in dose 100 mg/kg before and under action of acute hypercapnic hypoxia (AH+Hc). A substance for comparison was metabolic antihypoxant amthizole administered in similar way and dosage. The substances were introduced 90 min before (incubation period) placement of animals into hypoxic chambers with 1.0 L free volume. During each experiment as well as during AH+Hc a respiration curve called pneumobarogramm (PBG) was recorded continually. It has been established that the substance πQ1983 decreases parameters of lungs ventilation in the rats. According to PBG dynamics, rats protected by the substance demonstrated a high resistance level to the aroused acute hypoxia with hypercapnia, that expressed by weakening of early reactions from respiratory system under hypercapnia action, twice longer life span of animals in hypoxic experiment, and by rising of possibility to withstand low oxygen concentration. It has been proved that the substance πQ1983 significantly surpass a substance for comparison amthizole in both antihypoxic activity and influence on external respiration parameters.

Tissue Oxygenation and Mitochondrial Respiration under Different Modes of Intermittent Hypoxia

We compared the results of five modes of intermittent hypoxia training (IHT) on gastrocnemius muscle Po2 and heart and liver mitochondrial respiration in rats. Minutes of hypoxia, %O2, and recovery minutes on air in each mode were: 1) 5, 12%, 5; 2) 15, 12%, 15; 3) 5, 12%, 15; 4) 5, 7%, 5; and 5) 5, 7%, 15. Mode 1 proved best in that Pmo2 dropped minimally at the end of every hypoxic bout and recovered quickly after each bout. One, 2, and 3 week IHT in mode 1 each increased tissue PO2 in both normoxic and 30 min severe hypoxic (7% O2) tests. Adaptation to IHT in Mode 1 caused the substrate-dependent reorganization of liver and heart mitochondrial energy metabolism favoring NADH-dependent oxidation and improving the efficiency of oxidative phosphorylation. Mitochondrial adaptation occurred after 14 days of IHT in liver tissue, but after 21 days in myocardium, and was preserved during the 3 months following IHT termination. When using Mode 2, positive changes were also registered, but were less pronounced. Other IHT modes provoked negative effects on Pmo2 levels, both during hypoxic periods and reoxygenation. In conclusion, the most effective IHT regimen is 5 min 12% O2 with 5 min breaks, five cycles per day during 2 or 3 weeks depending on the task of IHT.

Disparate purinergic modulation of respiration in rats and mice

Disparate purinergic modulation of respiration in rats and mice

Identification of the Minimal Dose of Na2EDTA Able to Stimulate Respiration in Rats during Hypothermia

Identification of the Minimal Dose of Na2EDTA Able to Stimulate Respiration in Rats during Hypothermia

Acute and chronic treatment with serotonin reuptake inhibitors exert opposite effects on respiration in rats: possible implications for panic disorder

Prompted by the suggested importance of respiration for the pathophysiology of panic disorder, we studied the influence of serotonin reuptake inhibitors (SRIs) as well as other serotonin-modulating compounds on respiration in freely moving rats. The effect on respiration after acute administration of compounds enhancing synaptic levels of serotonin, that is, the serotonin reuptake inhibitors paroxetine and fluoxetine, the serotonin-releasing agents m-chlorophenylpiperazine and d-fenfluramine, and the selective 5-HT1A antagonist WAY-100635, were investigated. All serotonin-releasing substances decreased respiratory rate in unrestrained, awake animals, suggesting the influence of serotonin on respiratory rate under these conditions to be mainly inhibitory. In line with a previous study, rats administered fluoxetine for 23 days or more, on the other hand, displayed an enhanced respiratory rate. The results reinforce the assumption that the effect of subchronic administration of a serotonin reuptake inhibitor on certain serotonin-regulated parameters may be opposite to that obtained after acute administration. We suggest that our observations may be of relevance for the fact that acute administration of SRIs, d-fenfluramine, or m-chlorophenylpiperazine often is anxiogenic in panic disorder patients, and that weeks of administration of an SRI leads to a very effective prevention of panic.

Detection of exhaled sulfide gas: a potential in vivo, continuous monitoring technique for therapeutic sulfide donor compounds

IK‐1001 is a parenteral sulfide donor that recently entered human clinical trials. Current methodology to measure blood sulfide involves chemical derivatization or detection via electrodes. Hewe we have established a method to detect sulfide concentrations in exhaled air. Male rats were anesthetized with ketamine and instrumented with intravenous catheters and pneumotachometers. The sampling port of the pneumotachometer was directed to a sulfide gas detector (Interscan, Chatsworth, CA) with a sensitivity range of 5 to 0.05 ppm. IK‐1001 was infused intravenously while the airway was monitored for exhaled sulfide. Exhaled sulfide became detectable with infusions of 0.3 mg/kg/min and higher and the concentration increased in proportion up to 1.2 mg/kg/min. After correction for sample dilution arising from the sampling rate of the sulfide detector (500 mL/min) greatly exceeding minute respiration in rats (145 – 175 mL/min), exhaled sulfide concentration was estimated to range from 0.2 to 14 ppm over the tested infusion rates. Quantification of exhaled gas in comparison to sulfide equivalents administered indicates exhaled sulfide is approximately 0.1 to 2% of the infused dose. We conclude that monitoring exhaled sulfide may be a useful means of detecting and quantifying sulfide exposure during therapy with sulfide donor compounds.

Mechanism of suppression of physiological functions in hypothermia and means for their stimulation without body warming

Cold-suppressed thermoregulatory reactions and respiration in rats in deep hypothermia (rectal body temperature (25-22 degrees C) were shown to be stimulated by injecting disodium ethylenediaminetetraacetic acid (EDTA) solution into the blood stream of cold rats at a dose of 16.5 mg/100 g (0.0045 mmol/100 g). EDTA binds Ca2+ ions in the blood, forming complexes. Increases in cold shivering and pulmonary respiration (by 5 min after the start of administration) coincided with a reduction in the blood Ca2+ concentration by 42-45% of normal. By 15 min after the start of the EDTA injection, the blood Ca2+ concentration returned to the normal level present in cold rats before EDTA treatment. This was accompanied by suppression of cold shivering and pulmonary respiration. Repeated injection of EDTA into the blood stream produced a new drop in blood Ca2+ and repeated stimulation of cold shivering and pulmonary respiration.

Evaluation of the mitochondrial respiration of cardiac myocytes in rats submitted to mechanical bile duct obstruction

The objective of the present study was to evaluate the capacity of the myocardium for energy production by the analysis of mitochondrial respiration in rats with jaundice submitted to bile duct ligature. Sixteen male Wistar rats were divided into 2 Groups: Group SO submitted to nontherapeutic laparotomy (sham operation) and Group IC (icteric group) submitted to bile duct ligature. After 7 days, laparotomy was again performed in all animals for cardiac muscle extraction and analysis. Mitochondrial oxygen consumption was determined by stage 3 velocity and stage 4 velocity. The respiratory control ratio (RCR) was obtained by the ratio of stage 3 to stage 4 velocity. Statistical analysis was performed by the Mann-Whitney test, with the level of significance set at 5% (p<0.05). Statistical analysis revealed a significant drop in oxygen consumption during stage 3 mitochondrial respiration in group IC compared with SO, whereas the values obtained during stage 4 were basically identical for the two groups. Likewise, RCR values exhibited a significant reduction. The cellular respiration of the "jaundiced heart" is depressed. This was demonstrated by the reduced capacity of cardiac mitochondria to consume oxygen and synthesize ATP, supporting the idea of a latent cardiac impairment responsible for the hemodynamic decompensation occurring during cholestasis.

Rapid and Precise Control of Sniffing During Olfactory Discrimination in Rats

Olfactory perception relies on an active sampling process, sniffing, to rapidly deliver odorants from the environment to the olfactory receptors. The respiration cycle strongly patterns the flow of information into the olfactory systems, but the behavioral significance of particular sniffing patterns is not well understood. Here, we monitored the frequency and timing of nasal respiration in rats performing an odor-mixture-discrimination task that allowed us to test subjects near psychophysical limits and to quantify the precise timing of their behavior. We found that respiration frequencies varied widely from 2 to 12 Hz, but odor discrimination was dependent on 6- to 9-Hz sniffing: rats almost always entered and maintained this frequency band during odor sampling and their accuracy on difficult discrimination dropped when they did not. Moreover, the switch from baseline respiration to sniffing occurred not in response to odor delivery but in anticipation of odor sampling and was executed rapidly, almost always within a single cycle. Interestingly, rats also switched from respiration to rapid sniffing in anticipation of reward delivery, but in a distinct frequency band, 9-12 Hz. These results demonstrate the speed and precision of control over respiration and its significance for olfactory behavioral performance.