naltrindole and Brain-Ischemia

Tan-67 is a selective non-peptidic δ-opioid receptor (DOR) agonist that confers neuroprotection against cerebral ischemia/reperfusion (I/R)-caused neuronal injury in pre-treated animals. In this study, we examined whether post-ischemic administration of Tan-67 in stroke mice is also neuroprotective and whether the treatment affects expression, maturation and processing of the amyloid precursor protein (APP). A focal cerebral I/R model in mice was induced by middle cerebral artery occlusion for 1 h and Tan-67 (1.5, 3 or 4.5 mg/kg) was administered via the tail vein at 1 h after reperfusion. Alternatively, naltrindole, a selective DOR antagonist (5 mg/kg), was administered 1 h before Tan-67 treatment. Our results showed that post-ischemic administration of Tan-67 (3 mg/kg or 4.5 mg/kg) was neuroprotective as shown by decreased infarct volume and neuronal loss following I/R. Importantly, Tan-67 improved animal survival and neurobehavioral outcomes. Conversely, naltrindole abolished Tan-67 neuroprotection in infarct volume. Tan-67 treatment also increased APP expression, maturation and processing in the ipsilateral penumbral area at 6 h but decreased APP expression and maturation in the same brain area at 24 h after I/R. Tan-67-induced increase in APP expression was also seen in the ischemic cortex at 24 h following I/R. Moreover, Tan-67 attenuated BACE-1 expression, β-secretase activity and the BACE cleavage of APP in the ischemic cortex at 24 h after I/R, which was abolished by naltrindole. Our data suggest that Tan-67 is a promising DOR-dependent therapeutic agent for treating I/R-caused disorder and that Tan-67-mediated neuroprotection may be mediated via modulating APP expression, maturation and processing, despite an uncertain causative relationship between the altered APP and the outcomes observed.

Topics: Amyloid beta-Protein Precursor; Animals; Brain Ischemia; Cerebral Cortex; Male; Mice, Inbred C57BL; Naltrexone; Narcotic Antagonists; Neurons; Neuroprotective Agents; Quinolines; Receptors, Opioid, delta; Stroke

Central poststroke pain is associated with specific somatosensory abnormalities, such as neuropathic pain syndrome. Although central poststroke pain is a serious condition, details pertaining to underlying mechanisms are not well established, making current standard treatments only partially effective. Here, we assessed the effects of tramadol, an analgesic drug mediated by opioid receptors, using a mouse model of global cerebral ischemia. Ischemia was induced by bilateral carotid artery occlusion (30 min) in male ddY mice. Development of hind-paw mechanical allodynia was measured 3 days after bilateral carotid artery occlusion using the von Frey test. Mechanical allodynia was significantly and dose dependently suppressed by intraperitoneal tramadol (10 or 20 mg/kg). These effects, which peaked at 10 min and continued for at least 60 min, were inhibited by naloxone (nonselective opioid receptor antagonist, 1 mg/kg, intraperitoneal). Tramadol antinociception was significantly negated by β-funaltrexamine (selective μ-opioid receptor antagonist, 20 mg/kg, intraperitoneal), but not naltrindole (selective δ-opioid receptor antagonist, 5 mg/kg, intraperitoneal) or nor-binaltorphimine (selective κ-opioid receptor antagonist, 10 mg/kg, intraperitoneal) after 5 min, by β-funaltrexamine and nor-binaltorphimine but not naltrindole after 10 min, and by all selective opioid receptor antagonists at 15 and 30 min after tramadol treatment. These results suggested that antinociception induced by tramadol through various opioid receptors was time dependent. Furthermore, it is possible that the opioid receptors involved in tramadol-induced antinociception change over time with the metabolism of this drug.

Topics: Analgesics, Opioid; Animals; Brain Ischemia; Disease Models, Animal; Dose-Response Relationship, Drug; Hyperalgesia; Male; Mice; Naltrexone; Narcotic Antagonists; Pain Measurement; Pain Threshold; Tramadol

δ-opioid receptor (DOR) activation reduced brain ischemic infarction and attenuated neurological deficits, while DOR inhibition aggravated the ischemic damage. The underlying mechanisms are, however, not well understood yet. In this work, we asked if DOR activation protects the brain against ischemic injury through a brain-derived neurotrophic factor (BDNF) -TrkB pathway.. We exposed adult male Sprague-Dawley rats to focal cerebral ischemia, which was induced by middle cerebral artery occlusion (MCAO). DOR agonist TAN-67 (60 nmol), antagonist Naltrindole (100 nmol) or artificial cerebral spinal fluid was injected into the lateral cerebroventricle 30 min before MCAO. Besides the detection of ischemic injury, the expression of BDNF, full-length and truncated TrkB, total CREB, p-CREB, p-ATF and CD11b was detected by Western blot and fluorescence immunostaining.. DOR activation with TAN-67 significantly reduced the ischemic volume and largely reversed the decrease in full-length TrkB protein expression in the ischemic cortex and striatum without any appreciable change in cerebral blood flow, while the DOR antagonist Naltrindole aggregated the ischemic injury. However, the level of BDNF remained unchanged in the cortex, striatum and hippocampus at 24 hours after MCAO and did not change in response to DOR activation or inhibition. MCAO decreased both total CREB and pCREB in the striatum, but not in the cortex, while DOR inhibition promoted a further decrease in total and phosphorylated CREB in the striatum and decreased pATF-1 expression in the cortex. In addition, MCAO increased CD11b expression in the cortex, striatum and hippocampus, and DOR activation specifically attenuated the ischemic increase in the cortex but not in the striatum and hippocampus.. DOR activation rescues TrkB signaling by reversing ischemia/reperfusion induced decrease in the full-length TrkB receptor and reduces brain injury in ischemia/reperfusion.

Topics: Activating Transcription Factor 1; Animals; Blotting, Western; Brain; Brain Ischemia; Brain-Derived Neurotrophic Factor; CD11b Antigen; Cerebrovascular Circulation; Cyclic AMP Response Element-Binding Protein; Infarction, Middle Cerebral Artery; Male; Naltrexone; Quinolines; Rats; Rats, Sprague-Dawley; Receptor, trkB; Receptors, Opioid, delta; Reperfusion Injury

This study was designed to investigate whether delta opioid receptor (DOR) is involved in the neuroprotective effect induced by hypoxic preconditioning (HPC) in the asphyxial cardiac arrest (CA) rat model. Twenty-four hours after the end of 7-day HPC, the rats were subjected to 8-min asphyxiation and resuscitated with a standardized method. In the asphyxial CA rat model, HPC improved the neurological deficit score (NDS), inhibited neuronal apoptosis, and increased the number of viable hippocampal CA1 neurons at 24 h, 72 h, or 7 days after restoration of spontaneous circulation (ROSC); however, the above-mentioned neuroprotection of HPC was attenuated by naltrindole (a selective DOR antagonist). The expression of hypoxia-inducible factor-1α (HIF-1α) and DOR, and the content of leucine enkephalin (L-ENK) in the brain were also investigated after the end of 7-day HPC. HPC upregulated the neuronal expression of HIF-1α and DOR, and synchronously elevated the content of L-ENK in the rat brain. HIF-1α siRNA was used to further elucidate the relationship between HIF-1α and DOR in the HPC-treated brain. Knockdown of HIF-1α by siRNA markedly abrogated the HPC induced upregulation of HIF-1α and DOR. The present study demonstrates that the expression of DOR in the rat brain is upregulated by HIF-1α following exposure to 7-day HPC, at the same time, HPC also increases the production of endogenous DOR ligand L-ENK in the brain. DOR activation after HPC results in prolonged neuroprotection against subsequent global cerebral ischemic injury, suggesting a new mechanism of HPC-induced neuroprotection on global cerebral ischemia following CA and resuscitation.

Topics: Animals; Apoptosis; Arousal; Asphyxia; Behavior, Animal; Blotting, Western; Brain Ischemia; Brain Stem; Enkephalin, Leucine; Fluorescent Antibody Technique; Heart Arrest; Hypoxia-Inducible Factor 1, alpha Subunit; Hypoxia, Brain; In Situ Nick-End Labeling; Ischemic Preconditioning; Male; Motor Activity; Naltrexone; Narcotic Antagonists; Postural Balance; Rats; Real-Time Polymerase Chain Reaction; Receptors, Opioid, delta; RNA, Small Interfering; Seizures; Survival Analysis

Different studies have supported neuroprotective effects of Corticotropin-releasing hormone (CRH) against various excitotoxic and oxidative insults in vitro. However, the physiological mechanisms involved in this protection remain largely unknown. The present study was undertaken to determine the impact of CRH administration (at concentrations ranging from 200 fmol to 2 nmol) before and at delayed time intervals following potassium cyanide (KCN)-induced insult in rat primary cortical neurons. A second objective aimed to determine whether kappa and delta opioid receptor (KOR and DOR) blockade, using nor-binaltorphimine and naltrindole respectively (10 microM), could alter CRH-induced cellular protection. Our findings revealed that CRH treatments before or 3 and 8 h following KCN insult conferred significant protection against cortical injury, an effect blocked in cultures treated with alpha-helical CRH (9-41) prior to KCN administration. In addition, KOR and DOR blockade significantly reduced CRH-induced neuronal protection observed 3 but not 8 h post-KCN insult. Using western blotting, we demonstrated increased dynorphin, enkephalin, DOR and KOR protein expression in CRH-treated primary cortical neurons, and immunocytochemistry revealed the presence of opioid peptides and receptors in cortical neurons. These findings suggest protective effects of CRH against KCN-induced neuronal damage, and the contribution of the opioid system in modulating CRH actions.

Topics: Animals; Brain Ischemia; Cell Death; Cells, Cultured; Corticotropin-Releasing Hormone; Dynorphins; Enkephalins; Indoles; Naltrexone; Narcotic Antagonists; Nerve Tissue Proteins; Neurons; Neuroprotective Agents; Potassium Cyanide; Rats; Rats, Sprague-Dawley; Receptors, Corticotropin-Releasing Hormone; Receptors, Opioid, delta; Receptors, Opioid, kappa; RNA, Messenger

This work was performed to determine the role of delta-opioid receptor (DOR) in protection against acute ischemia/reperfusion injury. Transient (1 h) focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO). DOR agonist TAN-67 (30 nmol, 60 nmol, 200 nmol), DOR antagonist naltrindole (20 nmol, 50 nmol, 100 nmol) or artificial cerebral spinal fluid (aCSF) was injected respectively into the lateral cerebroventricle of the rat 30 min before the induction of brain ischemia. Neurological deficits were assessed by the five-grade system (Longa's methods). The brain infarct was measured by cresyl violet (CV) staining and infarct volume was analyzed by an image processing and analysis system. The expression of DOR was detected by Western blot. The results showed that 60 nmol TAN-67 significantly reduced the infarct volume (P<0.05), attenuated neurological deficits (P<0.05) and tended to increase the expression of about 60 kDa DOR protein (P>0.05), while 100 nmol naltrindole aggravated ischemic damage and decreased about 60 kDa DOR protein expression (P<0.05). These results suggest that DOR activation protects the brain against acute ischemia/reperfusion injury in rat.

Topics: Animals; Brain; Brain Ischemia; Infarction, Middle Cerebral Artery; Injections, Intraventricular; Naltrexone; Quinolines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, delta; Reperfusion Injury

Preconditioning with repeated electroacupuncture (EA) could mimic ischemic preconditioning to induce cerebral ischemic tolerance in rats. The present study was designed to investigate whether mu (micro)-, delta (delta)- or kappa (kappa)-opioid receptors are involved in the neuroprotection induced by repeated EA preconditioning.. The rats were pretreated with naltrindole (NTI), nor-binaltorphimine (nor-BNI) or D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), which is a highly selective delta-, kappa- or micro-opioid receptor antagonist respectively, before each EA preconditioning (30 minutes per day, 5 days). Twenty-four hours after the last EA treatment, the middle cerebral artery occlusion (MCAO) was induced for 120 minutes. The brain infarct volume was determined with 2, 3, 5-triphenyltetrazolium chloride staining at 24 hours after MCAO and compared with that in rats which only received EA preconditioning. In another experiment, the met-enkephalin-like immunoreactivity in rat brain was investigated by immunohistochemistry in both EA preconditioning and control rats.. The EA preconditioning reduced brain infarct volume compared with the control rats (P = 0.000). Administration of both NTI and CTOP attenuated the brain infarct volume reduction induced by EA preconditioning, presenting with larger infarct volume than that in the EA preconditioning rats (P < 0.001). But nor-BNI administration did not block the infarct volume reduction induced by EA preconditioning, presenting with smaller infarct volume than the control group rats (P = 0.000). The number of met-enkephalin-like immunoreactivity positive neurons in the EA preconditioning rats was more than that of the control rats (P = 0.000).. Repeated EA preconditioning stimulates the release of enkephalins, which may bind delta- and micro-opioid receptors to induce the tolerance against focal cerebral ischemia.

Topics: Animals; Brain Ischemia; Electroacupuncture; Enkephalin, Methionine; Immunohistochemistry; Ischemic Preconditioning; Male; Naltrexone; Rats; Rats, Sprague-Dawley; Receptors, Opioid, delta; Receptors, Opioid, mu; Somatostatin

Cerebral ischemic insult, mainly induced by cardiovascular disease, is one of the most severe neurological diseases in clinical. There's mounting evidence showing that delta opioid agonist [D-Ala2, D-Leu5] enkephalin (DADLE) has a tissue-protective effect. However, whether this property is effective to prevent neuronal death induced by forebrain ischemia is not clear. This study was aimed to investigate whether intracerebroventricular (ICV) administration of DADLE has a neuroprotective effect against forebrain ischemia in rats. We found in our study that administration of DADLE 45 min before forebrain ischemia had significant protective effect against CA1 neuronal lose. Further more, we found that DADLE had a dose-dependent protection for improving behavioral retardation revealed by Morris water maze and motor score test, while naltrindole, the antagonist of delta opioid receptor, partially abolished neuroprotective effect of DADLE, which implicated that both opioid and non-opioid systems are involved in ischemic insults and neuroprotection.

Topics: Animals; Behavior, Animal; Brain Ischemia; Cell Death; Dose-Response Relationship, Drug; Enkephalin, Leucine-2-Alanine; Injections, Intraventricular; Male; Naltrexone; Narcotic Antagonists; Neurons; Neuroprotective Agents; Prosencephalon; Rats; Rats, Sprague-Dawley

It has been reported that delta-opioid (DOP) receptor agonists may be neuroprotective in the central nervous system. However, the DOP agonist [d-Ala(2), d-Leu(5)]enkephalin (DADLE) does not produce neuroprotection in severe forebrain ischaemia. The aim of this study was to examine the effects of DADLE on hippocampal neurone survival against less severe forebrain ischaemia.. Intraperitoneal injection of DADLE (0 or 16 mg kg(-1)) in male Sprague-Dawley rats was performed 30 min before ischaemia. Severe (10 min), moderate (8 min), or mild (6 min) forebrain ischaemia was produced by bilateral carotid occlusion combined with hypotension (35 mm Hg) under isoflurane (1.5%) anaesthesia. Naltrindole (10 mg kg(-1)) (DOP antagonist) was administered 30 min before DADLE in order to confirm DOP receptor activation in the neuroprotective efficacy of DADLE. Naltrindole alone was also administered 30 min before ischaemia to examine endogenous DOP agonism as a self-protecting mechanism against ischaemia. All animals were evaluated neurologically and histologically after a 1 week recovery period.. DADLE improved neurone survival in hippocampal CA3 and dentate gyrus (DG) sectors. CA1 neurones were not protected against moderate and mild ischaemia. Naltrindole abolished DADLE neuroprotection in the CA3 and DG after both moderate and mild ischaemia. Interestingly, regardless of co-administration of DADLE, naltrindole significantly worsened neuronal injury in the CA1 region after mild ischaemia.. These results suggest that DADLE provides limited neuroprotection to relatively ischaemia-resistant regions but not to selectively vulnerable regions. This was probably mediated by DOP stimulation. Pre-ischaemic treatment with a DOP antagonist, regardless of co-administration of DADLE, worsened neuronal damage at the selectively vulnerable regions only after mild forebrain ischaemia. These data suggest that DOP activation with endogenous DOP ligand may be involved in self-protecting ischaemia-sensitive regions of the brain.

Topics: Animals; Brain Ischemia; Cell Survival; Drug Evaluation, Preclinical; Enkephalin, Leucine-2-Alanine; Hippocampus; Male; Naltrexone; Narcotic Antagonists; Neurons; Neuroprotective Agents; Prosencephalon; Rats; Rats, Sprague-Dawley; Receptors, Opioid, delta