enkephalin--leucine-2-alanine and Disease-Models--Animal

Meeting the metabolic demands of donor livers using normothermic ex vivo liver perfusion (NEVLP) preservation technology is challenging. The delta opioid agonist [D-Ala2, D-Leu5] enkephalin (DADLE) has been reported to decrease the metabolic demand in models of ischemia and cold preservation. We evaluated the therapeutic potential of DADLE by investigating its ability to protect against oxidative stress and hepatic injury during normothermic perfusion.. Primary rat hepatocytes were used in an in vitro model of oxidative stress to determine the minimum dose of DADLE needed to induce protection and the mechanisms associated with protection. NEVLP was then used to induce injury in rat livers and determine the effectiveness of DADLE in preventing liver injury.. In hepatocytes, DADLE was protective against oxidative stress and led to a decrease in phosphorylation of JNK and p38. Naltrindole, a δ-opioid receptor antagonist, blocked this effect. DADLE also activated the PI3K/Akt signaling pathway, and PI3K/Akt inhibition decreased the protective effects of DADLE treatment. In addition, DADLE treatment during NEVLP resulted in lower perfusate alanine aminotransferase and tissue malondialdehyde and better tissue adenosine triphosphate and glutathione. Furthermore, perfusion with DADLE compared with perfusate alone preserved tissue architecture.. DADLE confers protection against oxidative stress in hepatocytes and during NEVLP. These data suggest that the mechanism of protection involved the prevention of mitochondrial dysfunction by opioid receptor signaling and subsequent increased expression of prosurvival/antiapoptotic signaling pathways. Altogether, data suggest that opioid receptor agonism may serve as therapeutic target for improved liver protection during NEVLP.

Topics: Allografts; Animals; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; Hepatocytes; Humans; Liver; Male; Mitochondria; Organ Preservation Solutions; Oxidative Stress; Perfusion; Primary Cell Culture; Rats; Receptors, Opioid, delta; Reperfusion Injury; Tissue and Organ Harvesting

Hepatic ischemia/reperfusion (I/R) injury is a common pathophysiological process that occurs following liver surgery, which is associated with oxidative stress, and can cause acute liver injury and lead to liver failure. Recently, the development of drugs for the prevention of hepatic I/R injury has garnered interest in the field of liver protection research. Previous studies have demonstrated that [D‑Ala2, D‑Leu5]‑Enkephalin (DADLE) exerts protective effects against hepatic I/R injury. To further clarify the specific mechanism underlying the effects of DADLE on hepatic I/R injury, the present study aimed to observe the effects of various doses of DADLE on hepatic I/R injury in mice. The results indicated that DADLE, at a concentration of 5 mg/kg, significantly reduced the levels of alanine aminotransferase and aspartate aminotransferase in the serum, and the levels of malondialdehyde in the liver homogenate. Conversely, the levels of glutathione, catalase and superoxide dismutase in the liver homogenate were increased. In addition, DADLE was able to promote nuclear factor, erythroid 2 like 2 (Nrf2) nuclear translocation and upregulate the expression of heme oxygenase (HO)‑1, which is a factor downstream of Nrf2, thus improving hepatic I/R injury in mice. In conclusion, the present study demonstrated that DADLE was able to significantly improve hepatic I/R injury in mice, and the specific mechanism may be associated with the Nrf2/HO‑1 signaling pathway.

Topics: Animals; Aspartate Aminotransferases; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; Heme Oxygenase-1; Liver; Liver Diseases; Male; Malondialdehyde; Membrane Proteins; Mice; Mice, Inbred C57BL; NF-E2-Related Factor 2; Oxidative Stress; Reperfusion Injury; Signal Transduction; Superoxide Dismutase; Up-Regulation

In our prior study, we showed that delta-opioid peptide [D-Ala(2), D-Leu(5)] enkephalin (DADLE), by regional perfusion into the abdominal aorta, could protect the spinal cord against ischemia-reperfusion (I/R) injury caused by aortic occlusion. However, the relative dose-response effects of DADLE still remain unclear. This study investigated whether DADLE has a dose-dependent efficiency on spinal cord I/R injury.. New Zealand White rabbits were randomly divided into one of six groups: normal saline (NS; n = 8), DADLE (D) groups D0.0005 (n = 8), D0.005 (n = 8), D0.05 (n = 8), and D0.5 mg/kg (n = 8), and a sham group (n = 6). In the NS and DADLE groups, spinal cord ischemia was induced by infrarenal aortic occlusion for 30 minutes. During the occlusion, the same volume of NS or DADLE at the indicated doses was infused continuously through a catheter to the distally clamped abdominal aorta. Heart rate, blood pressure, and core temperature were monitored continuously to evaluate the potential adverse effects of DADLE. Neurologic behavioral function was assessed with the Tarlov scale system at 1, 6, 24, 48, and 72 hours after reperfusion. Neuronal injury evaluation in the ventral horn of the gray matter was evaluated by counting the normal motor neurons at 72 hours after reperfusion.. The therapeutic benefits increased at the doses of DADLE from 0.0005 to 0.05 mg/kg and decreased at 0.5 mg/kg, whereas the hemodynamic parameter was suppressed temporarily at the dose of 0.5 mg/kg.. These data revealed that regional administration of DADLE through the abdominal aorta provided dose-dependent protection on spinal cord I/R in rabbits.

Topics: Animals; Aorta, Abdominal; Catheterization, Peripheral; Disease Models, Animal; Dose-Response Relationship, Drug; Enkephalin, Leucine-2-Alanine; Female; Infusions, Intravenous; Ligation; Male; Motor Neurons; Neuroprotective Agents; Rabbits; Regional Blood Flow; Reperfusion Injury; Spinal Cord Ischemia; Time Factors

Previous studies have demonstrated that (D‑Ala2, D‑Leu5)‑enkephalin (DADLE) protects rats from hepatic ischemia/reperfusion (I/R) injury. In the present study, DADLE was also observed to alleviate IR‑induced intestinal epithelial cell injury in rats by inhibiting mitogen‑activated protein kinase kinase 7 (MKK7)‑c‑Jun N‑terminal kinase (JNK) pathway signaling. To investigate the protective effect of DADLE on hypoxia/reoxygenation injury in rat intestinal epithelial cells, rat intestinal epithelial cells were treated with different concentrations of DADLE, following which the cell survival rate was determined using a tetrazolium (MTT) colorimetric assay, and apoptosis was determined using flow cytometry. To confirm whether the protective effect of DADLE was due to its effect on MKK7‑JNK signaling, the phosphorylation levels of MKK7 and JNK were analyzed using western blot analysis following treatment with different concentrations of DADLE. The results demonstrated that, following treatment with DADLE, the survival rate of the rat intestinal cells subjected to I/R‑induced injury increased significantly and the apoptotic rate decreased in a concentration‑dependent manner. In addition, the levels of phosphorylated MKK7 and JNK decreased in a concentration‑dependent manner following treatment with DADLE. Silencing the gene expression of MKK7 using small interfering RNA prior to DADLE treatment resulted in a reduction in the protective effects of DADLE on the rat intestinal epithelial cells subjected to I/R injury. Collectively, the results of the present study demonstrated that the protective effects of DADLE in I/R injury in rat intestinal cells occurred through inhibition of the MKK7‑JNK pathway.

Topics: Animals; Apoptosis Regulatory Proteins; Cell Line; Cell Proliferation; Cell Survival; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; Epithelial Cells; Female; G1 Phase Cell Cycle Checkpoints; Intestines; JNK Mitogen-Activated Protein Kinases; Male; MAP Kinase Kinase 7; MAP Kinase Signaling System; Neuroprotective Agents; Phosphorylation; Rats; Rats, Sprague-Dawley; Reperfusion Injury; RNA Interference; RNA, Small Interfering

The delta opioid peptide [D-Ala2, D-Leu5]enkephalin (DADLE) plays a key role in neuronal protection against both hypoxic and ischemic conditions. However, the cellular mechanisms of action of DADLE under these conditions remain unclear.. Ischemia was simulated with perfusing the brain slices with glucose-free artificial cerebrospinal fluid. Apoptosis was examined using an in situ cell death detection kit and expressed as the percentage of positively labeled neurons relative to total number of neurons. PCR was performed by adding cDNA, 5 pm dNTP, 1 μL Taqase, and primers. PCR products were separated with electrophoresis, stained with ethidium bromide, and visualized under ultraviolet light.. To investigate the potential effects of DADLE in an ex vivo model of cerebral ischemia/reperfusion.. DADLE attenuated lactic dehydrogenase release and neuronal apoptosis in a concentration-dependent manner. The protective effects of DADLE were attenuated by representative selective delta2, but not delta1 opioid antagonists. Treatment with PD98059, a selective inhibitor of ERK kinase (MEK), also blocked the protective effect of DADLE as well as ERK phosphorylation induced by DADLE.. Endogenous opioid peptides could promote cell survival via delta2 opioid receptors, possibly through the downstream MEK-ERK pathway.

Topics: Animals; Apoptosis; Brain Ischemia; Cerebral Cortex; Disease Models, Animal; Dose-Response Relationship, Drug; Enkephalin, Leucine-2-Alanine; In Vitro Techniques; L-Lactate Dehydrogenase; Male; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Receptors, Opioid, delta; Reperfusion Injury

This study is to compare the effect of the δ-opioid receptor agonist, D-Ala(2)-D-Leu(5) enkephalin (DADLE) with normothermic control and therapeutic hypothermia on post resuscitation myocardial function and 72-h survival in a rat model of cardiac arrest and resuscitation.. Ventricular fibrillation (VF) was induced in 15 male Sprague-Dawley rats. After 8 min of untreated VF, cardiopulmonary resuscitation was performed for 8 min before defibrillation. Animals were randomized to three groups of five: (a) normothermia; (b) hypothermia (32 °C); and (c) normothermia with DADLE intravenous infusion (1 mg/kg h(-1)). Hypothermia and drug infusion were started after successful defibrillation. Myocardial functions, including cardiac output (CO), left ventricular ejection fraction (LVEF), and myocardial performance index (MPI) were measured echocardiographically together with duration of survival.. The 72-h survival was significantly greater in the hypothermic group than in both DADLE and normothermic group (p = 0.02). However, the survival time of the DADLE treated animals was significantly longer than that of the normothermia group (51.8 ± 18.9 vs 18.8 ± 10.1h, p < 0.01). DADLE group showed significantly better CO (PR 60 min, p = 0.049), better LVEF (PR 60 min, p = 0.044; PR 240 min, p < 0.001) and lower MPI (PR 60 min, p = 0.043; PR 240 min, p = 0.045) than normothermic group. Hypothermia group also showed significantly better CO (PR 60m in, p = 0.044; PR 240 min, p = 0.007), better LVEF (PR 60 min, p = 0.001; PR 240 min, p < 0.001) and lower MPI (PR 60 min, p = 0.003; PR 240 min, p = 0.012) than the normothermic group.. DADLE attenuated post resuscitation myocardial dysfunction and increased short term survival time. However, the 72-h survival in the DADLE group was less than that in the hypothermia group.

Topics: Animals; Cardiopulmonary Resuscitation; Disease Models, Animal; Echocardiography; Enkephalin, Leucine-2-Alanine; Heart; Hypothermia, Induced; Infusions, Intravenous; Male; Rats; Rats, Sprague-Dawley; Receptors, Opioid, delta; Stroke Volume

Sepsis is the major cause of death in intensive care units, despite enormous efforts in the development of antimicrobial therapies. Sepsis is mediated by early [e.g., tumor necrosis factor (TNF)-α and interleukin (IL)-1β] and late [e.g., high-mobility group box 1 protein (HMGB1)] proinflammatory cytokines. HMGB1, which is secreted into extracellular milieu by activated macrophages or passively released by destroyed macrophages, stimulates intensive inflammatory responses. D-Ala2-D-Leu5-enkephalin (DADLE), a synthetic δ-opioid receptor agonist, has been shown to protect rats from sepsis. Here we elucidated the mechanism for protective effect of DADLE against sepsis. Sepsis was established in Sprague-Dawley rats by means of cecal ligation and puncture (CLP). In this model, the serum levels of TNF-α and IL-1β were increased after 2-3 h, while those of HMGB1 were increased after 18 h. Administration of DADLE (5 mg/kg) concurrently with CLP improved survival, which was associated with the decreases in the serum levels of TNF-α, IL-1β and HMGB1. Importantly, DADLE administrated 4 h after CLP showed comparable protective effect as the concurrent administration, with decreased serum HMGB1 levels. Moreover, peritoneal macrophages isolated from rats were challenged with lipopolysaccharide (LPS). Concurrent or delayed DADLE administration at 10(-6) M suppressed the LPS-induced cell death. DADLE also suppressed the release of HMGB1 from macrophages that was induced by LPS, TNF-α or interferon-γ. In conclusion, DADLE protects rats from sepsis probably by decreasing the serum level of HMGB1. We propose DADLE as a candidate for septic shock therapy, even if it is administered after the onset of sepsis.

Topics: Animals; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; HMGB1 Protein; Humans; Interleukin-1beta; Lipopolysaccharides; Macrophages, Peritoneal; Male; NF-kappa B; p38 Mitogen-Activated Protein Kinases; Rats; Rats, Sprague-Dawley; Receptors, Opioid, delta; Sepsis; Survival Rate; Tumor Necrosis Factor-alpha

To study influence parapancreatic microirrigation on morphological and functional condition of a pancreas and transformations of enzymatic activity of blood serum and enzymatic activity of lymph of a chest lymphatic channel after an operative trauma of a duodenum.. Research is executed on 140 not purebred dogs which have been divided into six groups and united in two series. In the first series (30 dogs) were studied changes pancreatic exosecretion in the postoperative period of resection of duodenum (group 1.1), in the postoperative period of resection of duodenum with preliminary infiltration of a parapancreatic tissue of 0.5% by a solution of Novocain (group 1.2) and after resection of duodenum with application parapancreatic microirrigation (group 1.3). In the second series (110 dogs) were studied frequency of development of acute pancreatitis, enzymatic activity of blood serum and enzymatic activity of lymph of thoracal lymphatic duct after resection of duodenum (group 2.1) and in the postoperative period of resection of duodenum with preliminary infiltration of a parapancreatic tissue of 0.5% by a solution of Novocain (group 2.2) and after resection of duodenum with application parapancreatic microirrigation (group 2.3).. Application parapancreatic microirrigation does not lead to oppression pancreatic exosecretion at the first o'clock after duodenotomy, and substantially reduces the pancreatic hypersecretion observed in the postoperative period of resection of a duodenum. In addition, application parapancreatic microirrigation reduces frequency of development of acute pancreatitis and promotes less expressed increase enzymatic activity of blood serum and enzymatic activity of lymph thoracal lymphatic duct at development of the given complication after operational trauma of duodenum in comparison with resection of duodenum and after a resection of a duodenum executed against infiltration of a parapancreatic tissue of 0.5% by a solution of Novocain.

Topics: Acute Disease; Animals; Disease Models, Animal; Dogs; Duodenum; Enkephalin, Leucine-2-Alanine; Pancreas; Pancreatic Function Tests; Pancreatitis; Postoperative Complications; Therapeutic Irrigation

Delta opioid peptide [D-ala2,D-leU5]enkephalin (DADLE) induces hibernation in summer ground squirrels, and enhances preservation and survival of isolated or transplanted lungs and hearts. In the present study, we investigated the protective effect of DADLE in the central nervous system.. Adult Sprague-Dawley rats were pretreated with DADLE (4 mg/kg every 2 h x 4 injections, i.p.) or saline prior to unilateral occlusion of the middle cerebral artery (MCA). Daily behavioral tests revealed that ischemic animals treated with DADLE did not show any significant behavioral dysfunctions compared with saline-treated ischemic animals. Opioid antagonists only transiently inhibited the protective effect of DADLE, indicating the participation of non-opioid mechanisms in DADLE neuroprotection. Histological examination using triphenyltetrazolium chloride (TTC) revealed that brains from ischemic animals treated with DADLE, either alone or with adjuvant opioid blockers, exhibited almost completely intact striata. In contrast, brains from ischemic animals that received saline showed significant infarction in the lateral striatum. Analyses of apoptotic cell death revealed a significant increase in the p-53 mRNA expression in the striatum of ischemic animals that received saline, while those that received DADLE exhibited near normal striatal p-53 expression. This protective effect was accompanied by significant increments in protein levels of glial cell line-derived neurotrophic factor in the striatum of DADLE-treated ischemic animals.. These results indicate that DADLE protected against necrotic and apoptotic cell death processes associated with ischemia-reperfusion injury. The present study demonstrates that delta opioids are crucially involved in stroke, suggesting that the opioid system is important in the study of brain injury and protection.

Topics: Animals; Apoptosis; Brain; Brain Infarction; Brain Ischemia; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; Glial Cell Line-Derived Neurotrophic Factor; Hibernation; Motor Activity; Rats; Rats, Sprague-Dawley; RNA, Messenger; Tumor Suppressor Protein p53

Topics: Animals; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; Reperfusion Injury; Shock, Hemorrhagic; Treatment Outcome

Emergency preservation and resuscitation (EPR) is a new approach for resuscitation of exsanguination cardiac arrest (CA) victims. EPR uses a cold aortic flush to induce deep hypothermic preservation during no-flow to buy time for transport and damage control surgery, followed by resuscitation with cardiopulmonary bypass (CPB). We reported previously that 20-60 min EPR in rats was associated with intact outcome, while 75 min EPR resulted in high mortality and neurological impairment in survivors. The delta opioid agonist DADLE ([D-Ala(2),D-Leu(5)]-enkephalin) was shown previously to be protective against ischemia-reperfusion injury in multiple organs, including brain. We hypothesized that DADLE could augment neurological outcome after EPR in rats. After rapid lethal hemorrhage, EPR was initiated by perfusion with ice-cold crystalloid to induce hypothermia (15 degrees C). After 75 min EPR, resuscitation was attempted with CPB. After randomization, three groups were studied (n=10 per group): DADLE 0mg/kg (D0), 4 mg/kg (D4) or 10mg/kg (D10) added to the flush and during reperfusion. Survival, overall performance category (OPC; 1=normal, 5=death), neurological deficit score (NDS; 0-10% normal, 100%=max deficit), and histological damage score (HDS) were assessed in survivors on day 3. In D0 group, 2/10 rats survived, while in D4 and D10 groups, 4/10 and 5/10 rats survived, respectively (p=NS). Survival time (h) was 26.7+/-28.2 in D0, 36.3+/-31.9 in D4 and 47.1+/-30.3 in D10 groups, respectively (p=0.3). OPC, NDS and HDS were not significantly different between groups. In conclusion, DADLE failed to confer benefit on functional or histological outcome in our model of prolonged rat EPR.

Topics: Animals; Cardiopulmonary Bypass; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; Hypothermia, Induced; Male; Random Allocation; Rats; Rats, Sprague-Dawley; Resuscitation; Shock, Hemorrhagic; Statistics, Nonparametric; Survival Rate

The current study investigated the roles of various subtypes of opioid receptors expressed in the thalamic nucleus submedius (Sm) in inhibition of mirror-image allodynia induced by L5/L6 spinal nerve ligation in rats. Morphine was microinjected into the Sm, which produced a dose-dependent inhibition of mirror-image allodynia; this effect was antagonized by pretreatment with non-selective opioid receptor antagonist naloxone. Microinjections of endomorphin-1 (mu-receptor agonist), or [D-Ala(2), D-Leu(5)]-enkephalin (DADLE, delta-/mu-receptor agonist), also inhibited mirror-image allodynia, and these effects were blocked by the selective mu-receptor antagonist, beta-funaltrexamine hydrochloride. The DADLE-induced inhibition, however, was not influenced by the delta-receptor antagonist naltrindole. The kappa-receptor agonist, spiradoline mesylate salt, failed to alter the mirror-image allodynia. These results suggest that Sm opioid receptor signaling is involved in inhibition of mirror-image allodynia; this effect is mediated by mu- (but not delta- and kappa-) opioid receptors in the rat model of neuropathic pain.

Topics: Animals; Behavior, Animal; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; Hyperalgesia; Ligation; Male; Morphine; Naloxone; Naltrexone; Narcotic Antagonists; Neuralgia; Oligopeptides; Pain Measurement; Rats; Rats, Sprague-Dawley; Receptors, Opioid, mu; Spinal Nerves; Thalamic Nuclei

Mammalian hibernation is mediated by humoral agonists of the delta opioid receptor (DOR). Moreover, transfer of either humoral or synthetic DOR agonists to non-hibernators reportedly induces a state of improved myocardial ischemic tolerance.. To determine whether the DOR agonist D-Ala 2, D-Leu 5, enkephalin (DADLE) similarly elicits protection in noncardiac-i.e., mesenteric-tissue.. In Protocols 1 and 2, the authors developed and characterized an in vitro model of mesenteric ischemia/reperfusion in isolated rabbit jejunum by documenting the effect of increasing ischemic duration (0 to 120 minutes) and the relative importance of glucose and/or oxygen deprivation on the evolution of jejunal injury. In Protocol 3, jejunal segments were randomized to receive either no treatment (controls) or 15 minutes of pretreatment with 1 microM DADLE, followed by 60 minutes of simulated ischemia and 30 minutes of reperfusion. Jejunal injury was quantified by repeated, time-matched assessment of peak contractile force evoked by 1 microM acetylcholine (all protocols) and delineation of tissue necrosis (Protocol 1).. Development of significant jejunal injury required combined oxygen/glucose deprivation. Moreover, there was a direct relationship between ischemic duration and tissue injury, and a significant inverse correlation between reperfusion contractile force (% of baseline) and the extent of smooth muscle necrosis (r(2) = 0.87; p < 0.01). Most notably, mesenteric ischemia/reperfusion injury was attenuated by DADLE: reperfusion contractile force was 47 +/- 5% versus 36 +/- 5% in DADLE-treated versus control segments (p < 0.01).. Treatment with the delta opioid agonist DADLE increases ischemic tolerance of isolated rabbit jejunum.

Topics: Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Enkephalin, Leucine-2-Alanine; Glucose; Hypoxia; In Vitro Techniques; Ischemia; Jejunum; Muscle Contraction; Muscle, Smooth; Rabbits; Receptors, Opioid, delta; Reperfusion Injury; Splanchnic Circulation

This study evaluated the contribution of supraspinal opioid receptors to gastric mucosal protection in the rat. Intracerebroventricular (i.c.v.) and intracisternal (i.c.) injections of selective delta- [[D-Ala(2),D-Leu(5)]-enkephalin (DADLE), [D-Pen(2),D-Pen(5)]-enkephalin (DPDPE), deltorphin II], selective mu- [[D-Ala(2),Phe(4),Gly(5)-ol]-enkephalin (DAGO)] opioid receptor agonists and beta-endorphin (ligand of both receptor types) produced a dose-dependent inhibition of acidified ethanol-induced gastric mucosal damage. The ED(50) values for beta-endorphin, DAGO, DADLE, deltorphin II, and DPDPE were 3.5, 6.8, 75, 120, and 1100 pmol/rat, respectively, following i.c.v. and 0.8, 9.0, 45, 0.25, and 7 pmol/rat following i.c. injection. The gastroprotective effect of DADLE, deltorphin II, and DPDPE, but not that of DAGO, was inhibited by naltrindole, the selective delta-receptor antagonist. Since the delta(2)-receptor agonist deltorphin II was more potent than the delta(1)-receptor agonist DPDPE, the dominant role of central delta(2)-receptors in gastroprotection might be raised. The site of action for delta-receptor agonists is likely to be the brain stem since the peptides were more potent following i.c. than following i.c.v. administration. The gastroprotective effect was reduced following acute bilateral cervical vagotomy. Moreover, both the nitric-oxide synthase inhibitor N(G)-nitro-L-arginine (3 mg/kg i.v.) and the prostaglandin synthesis inhibitor indomethacin (20 mg/kg p.o.) decreased the protective effect of opioid peptides. The results indicate that 1) activation of supraspinal delta- and mu-opioid receptors induces gastric mucosal protection, 2) integrity of vagal nerve is necessary for the gastroprotective action of opioids, and 3) mucosal nitric oxide and prostaglandins may be involved in the opioid-induced gastroprotection.

Topics: Animals; beta-Endorphin; Brain; Capsaicin; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Routes; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, D-Penicillamine (2,5)-; Enkephalin, Leucine-2-Alanine; Enkephalins; Enzyme Inhibitors; Ethanol; Gastric Mucosa; Hydrochloric Acid; Male; Narcotic Antagonists; Oligopeptides; Rats; Rats, Wistar; Receptors, Opioid, delta; Receptors, Opioid, mu; Stomach Ulcer; Vagotomy

The effects of the extremely selective mu-opioid receptor agonist, [D-Arg2,Lys4]-dermorphin-(1-4)-amide (DALDA), the mu-opioid receptor agonist morphine, the mu/delta agonist D-Ala2, Leu5, Arg6-enkephalin (dalargin), the kappa-opioid receptor agonist spiradoline, and the sigma1-receptor antagonist DuP 734 on ventricular fibrillation threshold (VFT) was investigated in an experimental post-infarction cardiosclerosis model and an immobilization stress-induced model in rats. Both models produced a significant decrease in VFT. The postinfarction cardiosclerosis-induced decrease in VFT was significantly reversed by intravenous administration of dalargin (0.1 mg/kg), DALDA (0.1 mg/kg), or morphine HCl (1.5 mg/kg). Pretreatment with naloxone (0.2 mg/kg) completely eliminated the increase in cardiac electrical stability produced by DALDA. Both spiradoline (8 mg/kg, i.p.) and DuP 734 (1 mg/kg, i.p.) produced a significant increase in VFT in rats with post-infarction cardiosclerosis. This effect of spiradoline was blocked by nor-binaltorphimine. The immobilization stress-induced decrease in VFT was significantly reversed by administration of either DALDA, spiradoline or DuP 734. In conclusion, activation of either mu- or kappa1-opioid receptors or blockade of sigma1-receptors reversed the decrease in VFT in both cardiac compromised models. Since DALDA and dalargin essentially do not cross blood brain barriers, their effects on VFT may be mediated through peripheral mu-opioid receptors.

Topics: Animals; Anti-Arrhythmia Agents; beta-Endorphin; Disease Models, Animal; Dynorphins; Enkephalin, Leucine-2-Alanine; Heart; Immobilization; Ligands; Morphine; Myocardial Infarction; Myocardium; Naloxone; Naltrexone; Narcotic Antagonists; Oligopeptides; Piperidines; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, delta; Stress, Physiological; Ventricular Fibrillation

Hypothermic cardioplegia provides adequate myocellular protection, yet stunning and dysfunction remain significant problems. Interestingly, the subcellular changes of hibernation parallel the altered biology of induced cardiac ischemia, but are well tolerated by hibernating mammalian myocardium. Hibernation induction trigger (HIT) from winter-hibernating animal serum induces hibernation in active animals. Hibernation induction trigger is opiate in nature and is similar to the delta 2 opioids.. To determine whether HIT could improve myocardial recovery following global ischemia, we gave 37 isolated rabbit hearts either standard cardioplegia or cardioplegia containing summer-active woodchuck, hibernating woodchuck, or black bear HIT serum or a delta 2 opioid, D-Ala2-Leu5-enkephalin, before 2 hours of global ischemia.. Hibernation induction trigger appeared not to have an active mechanism during ischemia, as all hearts had equal recovery. In contrast, when examining for a preischemia mechanism, 23 additional rabbits received 3 days pretreatment with summer-active woodchuck or HIT hibernating woodchuck or black bear serum, or were preperfused with D-Ala2-Leu5-enkephalin or D-pen2,5-enkephalin, a-delta 1 opioid, again before 2 hours of global ischemia. Postischemic ventricular function, coronary flows, myocardial oxygen consumption, and ultrastructural preservation were all significantly improved with HIT and D-Ala2-Leu5-enkephalin pretreatment.. "Natural" HIT protection is superior to standard cardioplegia alone and may have clinical application.

Topics: Analysis of Variance; Animals; Coronary Circulation; Disease Models, Animal; Enkephalin, D-Penicillamine (2,5)-; Enkephalin, Leucine-2-Alanine; Enkephalins; Female; Heart; Heart Arrest, Induced; Hibernation; Hypothermia, Induced; Male; Marmota; Myocardial Ischemia; Myocardial Stunning; Myocardium; Oxygen Consumption; Peptides; Premedication; Proteins; Rabbits; Receptors, Opioid, delta; Ursidae; Ventricular Function; Ventricular Function, Left; Ventricular Pressure

It has been established that preliminary administration of D-Ala2-Leu5-Arg6-enkephalin, D-Met2-Pro5-enkephalinamide, and D-phenylalanine to experimental animals prevents a stress-induced increase of the content of thromboxane in the blood plasma and myocardium and induces a rise of the level of prostacyclin, PGF2 and PGE in the heart and blood plasma. The authors hold that the changes in the level of prostanoids may mediate cardioprotective and anti-stressor rather than antiarrhythmic effects of enkephalins.

Topics: Animals; Anti-Arrhythmia Agents; Disease Models, Animal; Drug Evaluation, Preclinical; Enkephalin, Leucine-2-Alanine; Enkephalin, Methionine; Heart; Myocardial Ischemia; Myocardium; Prostaglandins; Stress, Physiological; Ventricular Fibrillation

In acute experiments on cats it has been shown that dalargin possess antiarrhythmic affect in myocardial ischemia. Antiarrythmic effect of dalagrig may be connected both with reflex and with direct action of dalargin on neurons structure, which

Topics: Animals; Anti-Arrhythmia Agents; Cats; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Enkephalin, Leucine-2-Alanine; Female; Heart; Heart Rate; Male; Myocardial Ischemia; Vagotomy; Ventricular Fibrillation

Topics: Acute Disease; Animals; Anti-Arrhythmia Agents; Bradycardia; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; Epinephrine; Heart Rate; In Vitro Techniques; Infusions, Intravenous; Male; Rats; Rats, Wistar

Male Wistar rats were used to examine the cardiodepressive action of experimentally induced generalized infection and bacterial shock and the ability of the synthetic opioid dalargin to enhance resistance the damaging effect of bacterial intoxication. The cardiac performance of the infected rats was studied in a model of an isolated perfused heart with the working left ventricle. In the rats, generalized Staphylococcus infection was ascertained to result in a dose-dependent inhibition of heart performance at all study stages, showing the peak of cardiodepressive action on days 3 of postinfection. The experimental animals given dalagin displayed a high infection resistance, as manifested predominantly by prevented profound cardiac disorders due to systemic administration of dalargin or by a positive inotropic effect of the drug supplemented to perfusate, the effect being particularly pronounced in bacterial shock or in early generalized infection.

Topics: Animals; Cardiac Output, Low; Disease Models, Animal; Drug Evaluation, Preclinical; Enkephalin, Leucine-2-Alanine; Hemodynamics; Male; Placebos; Rats; Rats, Inbred Strains; Shock, Septic; Staphylococcal Infections; Staphylococcus aureus

Dalargin is a Soviet synthetic analog of leu-enkephalin. It was used in a complex of anesthesiological protection (in the form of permanent infusion at a rate of 40-55 micrograms/kg/h) in 331 patients who suffered different operations on the heart, lungs and abdominal cavity. Potential mechanisms of the protective action of the drug were studied in experimental surgical distress. It was found advisable that dalargin may be included into combined general anesthesia to maintain intraoperative organ protection, to stabilize vital functions of the patient at the most crucial and traumatic stages of intervention, and to decrease requirements of narcotic analgetics. It is assumed that dalargin may interact with peripheral opiate receptors. The interaction is likely to be viewed as the main mechanism by which the protective properties of the drug are realized.

Topics: Abdomen, Acute; Anesthesia, General; Animals; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; Heart Diseases; Hemodynamics; Humans; Intraoperative Complications; Lung Diseases; Models, Biological; Rats; Stress, Physiological; Sympatholytics

Development of posthypoxic and reoxygenation depression of cardiac activity following a time-portioned disconnection of the apparatus for artificial ventilation of the lungs in rats was restricted by a preventive intravenous infusion of a synthetic opioid peptide--dalargin. Resistance to a stressor effect of hypoxia (ischemia-reperfusion) which was assessed by the degree of restoration of the integral index of the blood circulation--cardiac output could be mediated by correction of Ca-homeostasis of cardiomyocytes by means of dalargin. Elimination of all side effects with a blocker of opioid receptors--naloxon points to a possibility of realization of a protective antihypoxic action.

Topics: Acute Disease; Animals; Asphyxia; Disease Models, Animal; Drug Evaluation, Preclinical; Enkephalin, Leucine-2-Alanine; Hemodynamics; Hypoxia; Myocardial Reperfusion Injury; Rats; Rats, Inbred Strains; Respiration, Artificial; Time Factors

In cat experiments, the effects of dalargin were examined on blood pressure in the animals with its various baseline levels and on the development of ischemic arrhythmias. Dalargin was demonstrated to produce a modulating effect on blood pressure and to reduce the incidence of ventricular fibrillation in myocardial ischemia.

Topics: Animals; Blood Pressure; Cats; Coronary Disease; Coronary Vessels; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; Female; Male; Vasodilator Agents

For experimental verification of the authors' hypothesis on the role of the mechanism of adaptative disintegration in pathogenesis of trauma disease the essence of which consists in inadequacy of emergency adaptation of the organism to a critical and middle degree of the injury by the time and amplitude, an investigation on 89 rabbits has been performed with modeling of extensive wound of soft tissues of the femur. The correction of the neuroendocrine response of the organism to trauma by injection of synthetic opiopeptide dalargin++ was made. The use of dalargin changed quantitatively and qualitatively the neuroendocrine reaction to the injury and optimized the wound process and restoration of the homeostasis parameters.

Topics: Adaptation, Physiological; Animals; Disease Models, Animal; Enkephalin, Leucine-2-Alanine; Hindlimb; Homeostasis; Male; Rabbits; Shock, Traumatic; Wounds, Gunshot

Three series of experiments were performed in Wistar male rats. The first series covered the study of the function of isolated perfused hearts and the status of the gastric mucosa in intact animals. In series II and III, Stages IIIB-IV contact burn of 25% body surface was induced by a special device. The animals were observed for 24 hours. Following 23.5 hours of burn, the rats were injected placebo (Series II) or the synthetic Leu-enkephalin analogue dalargin, 10 micrograms/kg in the same amounts as placebo (Series III). After observation, the animals' hearts and stomachs were isolated and explored. In Series II, there was a considerable decrease in all the indices of cardiac function as compared to the controls, the ulcer index that characterizes the severity of stress-induced gastric mucosa injury was found to be 8.2. In Series III, the indices of cardiac function were even substantially higher than those in intact animals, the ulcer index was reduced to 0.01. Thus, dalargin, a Soviet synthetic Leu-enkephalin analogue, possesses marked anti-stress and cardioprotective effects in severe thermal trauma. The paper also considers the likely mechanisms responsible for the phenomena observed.

Topics: Animals; Burns; Disease Models, Animal; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Gastric Mucosa; Heart; Heart Failure; In Vitro Techniques; Male; Models, Cardiovascular; Rats; Rats, Inbred Strains; Stomach Ulcer; Stress, Physiological

Dalargin injected subcutaneously at a dose of 10 micrograms/kg decreased 4-5 fold ulcer manifestations in rats with cysteamine-induced duodenal ulcers. Intracerebroventricular dose of 2 micrograms diminished the manifestations to a lesser extent Dalargin only at a dose exceeding 500 micrograms intraperitoneally decreased significantly the in vivo binding of 3H-D-Ala2, D-Leu5-enkephalin with brain opiate receptors. We believe that Dalargin injected peripherally in small doses does not penetrate the blood-brain barrier and that its antiulcer activity is due to the interaction with peripheral opioid receptors. It seems possible that the disturbances in the central/peripheral ratio of the opioid activity plays an important role in the pathogenesis of duodenal peptic ulcer.

Topics: Animals; Anti-Ulcer Agents; Brain; Cysteamine; Disease Models, Animal; Duodenal Ulcer; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Injections, Intraventricular; Injections, Subcutaneous; Male; Rats; Rats, Inbred Strains; Receptors, Opioid

The role and possible clinical use of regulatory peptides, a new type of regulatory substances, is discussed. Special attention is paid to the opioid peptides and their analogues. The new drug dalargin has been developed on the basis of the endogenous opioid peptide leucine-encephalin. Its action has been studied using experimental models. It has been established that the optimal dose (10 micrograms/kg) of dalargin is effective in preventing ulceration in the cystamine duodenal ulcer rat model and the development of stomach erosive lesions in immobilization stress, reducing the degree of liver degeneration in CCl4 poisoning, etc. With an increase of the dose of dalargin the effect "escapes". Dalargin is primarily bound by delta-receptors, it produces no analgetic effect and does not enter the brain. Dalargin exhibits a pronounced cytoprotective and regeneratory action and may take an important place in treating the internal organ diseases.

Topics: Animals; Carbon Tetrachloride Poisoning; Cells, Cultured; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Duodenal Ulcer; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Hemorrhage; Humans; Lymphocytes; Mice; Necrosis; Pancreas; Rats; Receptors, Opioid; Stomach Ulcer

Topics: Animals; Disease Models, Animal; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Male; Naloxone; Naltrexone; Narcotic Antagonists; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, mu; Seizures