Effects of kyotorphin and analogues on nociception and pentylenetetrazole seizures

Kyotorphin (Kyo) is synthesized in specific brain regions where it may modulate synaptic transmission and directly excites cortical neurons, and indirectly exerts opioid actions to produce analgesia via release of met-enkephalin. Kyo is formed by specific enzyme from L-tyrosine and L-arginine in the presence of ATP and Mg2+ in the brain. Kyo and its analogues Tyr-Cav, Tyr (Cl2)-Cav exerted naloxone-reversible antinociception by paw-pressure test. Kyo exerted anticonvulsive effect on the pentylenetetrazole (PTZ) seizure model. AIM: To investigate the analgesic and the anticonvulsive effects of Kyo, Tyr-Cav and Tyr(Cl2)-Cav during acute pain and PTZ seizure model. METHODS: Changes in the nociceptive effects were examined in male Wistar rats by the tail flick (TF) and hot plate (HP) tests. Kyo, Tyr-Cav, Tyr(Cl2)-Cav were applied in rats intracerebroventricularly (i.c.v.) at a dose of 20 microg/20 microl. The anticonvulsive effects of peptides were studied on a PTZ seizure model. The peptides were applied in male mice at a dose of 20 microg/mouse (i.c.v.). RESULTS: Kyo, Tyr-Cav, Tyr(Cl2)-Cav exerted analgesic effects in both nociceptive tests used. The effects were more pronounced for L-Arg, L-Cav, Tyr-Cav and Tyr(Cl2)-Cav. In PTZ seizure model Kyo and its analogues exerted strong inhibition on seizure intensity compared with control group. CONCLUSION: Taken together, these results reveal Kyo, Tyr-Cav and Tyr(Cl2)-Cav as a behaviorally active peptide in experimental animal models.     

Treatment of posttraumatic dystrophy

Reflex sympathetic dystrophy, posttraumatic dystrophy or complex regional pain syndrome is a particular type of chronic pain. Although the origin is unknown, some believe that wide-dynamic range neurons located in the dorsal horn of the spinal cord play an essential role. Others consider the role of psychogenic factors underestimated. Until now, controlled clinical trials mainly directed at modulation of the sympathetic system have not revealed clearly effective therapies. Tests with guanethidine, phenylephrine, phentolamine or lidocaine have essentially been negative. Use of low dose glucocorticoids, dimethylsulphoxide, biphosphonates and epidurally applied clonidine require confirmation in studies of larger size. There are indications that invasive electrical spinal cord stimulation may have some effect; randomized studies in patients with posttraumatic dystrophy are needed. So far, only application of physical therapy at an early stage has clearly shown effective pain relief and would also lead to cost reduction.     

Nociceptive neurons

Pain is generated by activation of specific dorsal root ganglion (DRG) neurons termed the nociceptive neurons. The nociceptive DRG neurons express 3 categories of ionic channels a. channels gated by pain stimuli, b. channels responsible for the transmission of information from sensory receptors to the spinal cord, c. channels responsible for the release of neurotransmitters in the spinal cord. There is evidence that kinetic properties, molecular structure and functional significance of the ionic channels expressed in nociceptive DRG neurons are different compared to the other types of DRG neurons. The ionic channels are strictly controlled by receptors for neurotransmitters expressed in the plasma membrane of nociceptive DRG neurons.     

Effects of Tyr-MIF's family of peptides on immobilization stress-induced antinociception in rats

The Tyr-MIF-1 family of peptides includes MIF-1, Tyr-MIF-1, Tyr-W-MIF-1 and Tyr-K-MIF-1, which have been isolated from bovine hypothalamus and cortex of human brain. Data in the literature suggest that peptides of Tyr-MIF-1's family have opioid-like and anti-opioid actions. All these peptides interact with opioid receptors and in addition bind to non-opiate sites specific for each of the peptides and able to inhibit the expression of some forms of stress-induced analgesia (SIA) in various species. AIM: To examined the effects of the Tyr-MIF-1's peptides on immobilization stress-induced antinociception. METHODS: Tyr-MIF-1's peptides were given to male Wistar rats intraperitoneally before or after 1 hour of restraint. The changes in the mechanical nociceptive threshold of the animals were measured by the Randall-Selitto paw pressure test. RESULTS: Immobilization of the rats increased the pain threshold at least 1 h. Tyr-MIF-1's peptides have contrasting effects on immobilization stress-induced antinociception in paw-pressure test in rats. When administered before immobilization procedure they potentiated the immobilization stress-induced antinociception, while if given after immobilization, they reduced it. Antinociceptive effects of Tyr-MIF-1, Tyr-W-MIF-1 and Tyr-K-MIF-1 were reduced in condition of stress. CONCLUSION: Tyr-MIF-1's peptides exerted antiopioide effects under condition of stress in paw-pressure test. These antiopioide effects were more pronounced when peptides were injected after stress exposure.     

鞘内注射布托啡诺对福尔马林诱导大鼠脊髓背角NMDAR的影响

目的观察鞘内注射布托啡诺对福尔马林炎性痛大鼠脊髓背角N-甲基-D-天冬氨受体（NMDAR）表达的影响。方法健康雄性SD大鼠20只,体重220～280g。随机分为4组（n=5）：对照组（C组）,鞘内注射生理盐水组（N组）,鞘内注射12．5μg布托啡诺组（B1组）,鞘内注射25μg布托啡诺组（B2组）。在大鼠的左后足掌面皮下注射5％福尔马林50μl致痛前30min,N组、B1组和B2组分别注射生理盐水、12．5μg布托啡诺、25μg布托啡诺,C组在福尔马林注射前不注射任何试剂。记录福尔马林诱导出注射后爪的双相理毛行为时间（在福尔马林注射后第1时相,0—5min;第2时相,10—60min）。所有大鼠均在注射后2h处死,用免疫组化法测定大鼠L5节段脊髓背角NMDA受体的表达。结果与C组相比,N组和B1组对福尔马林诱导的第1和2时相．影响差异无统计学意义（P〉0．05）,3组脊髓背角NMDA受体表达均增加,相比较差异无统计学意义（P〉0．05）。与C组比较,B2组引起第1和2时相的后爪理毛行为的总计反应时间明显减少,并显著降低福尔马林致痛大鼠L5脊髓背角NMDA受体表达（P〈0．05）。结论鞘内注射布托啡诺能够对福尔马林诱导的疼痛行为产生明显的抑制作用,并具有剂量依赖性,其镇痛机制与通过抑制NMDA受体激活产生有关。     

Effect of beta-endorphin on steroidogenesis by bovine luteal cells

To determine if opioid peptides have a local effect on the modulation of progesterone (P4) synthesis, a study was made of the effect of beta-endorphin and leu-enkephalin on P4 production by pure preparations of small luteal cells and dissociated luteal cells comprising both small and large cells from cows 2-3 months pregnant. Corpora lutea were dispersed by collagenase, and the large and small luteal cells were separated using Percoll gradients. Viable luteal cells (5 x 10(5)) were incubated in 0.5 mL of Eagle medium for 2 h at 37 degrees C, in an atmosphere of 5% CO2. Cells were treated with 8-bromoadenosine 3',5'-monophosphate (8Br-cAMP), hCG, beta-endorphin (BE) and leu-enkephalin (LE) alone or in combination. When small luteal cells were used, P4 synthesis was significantly enhanced in the presence of opioid peptides alone (P less than 0.01); there was an additive effect with 8Br-cAMP and with hCG. For dissociated luteal cells, opioid peptides alone had no effect on P4 production but the stimulation of P4 production induced by 8Br-cAMP or hCG was significantly (P less than 0.01) inhibited in the presence of opioid peptides. In contrast, dissociated luteal cells that were preincubated with PGF2 alpha (degranulation) responded to the presence of BE with increased P4 synthesis similar to that seen with the pure preparation of small luteal cells. It is concluded that opioid peptides play an auto/paracrine role in both basal and tropic hormone-induced stimulation of steroidogenesis by the bovine luteal cell.     

三磷酸甲酯中毒致母鸡脊髓神经元凋亡的研究

目的　研究细胞凋亡机制在有机磷中毒后的动物迟发性神经病 (OPIDN)中所起的作用及其动态病理改变。方法　采用给母鸡一次性肌内注射三磷酸甲酯染毒的方法建立OPIDN动物模型 ,以染毒后 3、5、7、10、14、18d为时间点分别取材 ,以HE染色、尼氏法和原位末端标记法 (TUNEL)观察其第三腰髓 (L3 )的病理改变、神经元数量及细胞凋亡的变化。结果　母鸡于肌内注射三磷酸甲酯后第 9天前后出现进行性共济失调和肌无力等OPIDN的典型症状。HE染色示染毒后 5d后母鸡脊髓前角大神经元出现细胞核红色深染 ,至 18d消失 ;尼氏法染色示母鸡脊髓前角神经元数量呈进行性减少 [从 (82±4)个 /mm2 到 (66± 6)个 /mm2 ] ;TUNEL法示母鸡腰段脊髓TUNEL阳性细胞于染毒后 5d左右开始出现[(2 2± 2 )个 /mm2 ] ,以 7d[(2 7± 3 )个 /mm2 ]数量最多 ,18d消失。结论　在母鸡OPIDN发病过程中出现腰髓前角神经元细胞凋亡现象。提示细胞凋亡可能在OPIDN发病机制中起重要作用     

Acute inhibition of corticostriatal synaptic transmission in the rat dorsal striatum by ethanol.

The purpose of this study was to examine the effects of ethanol on synaptic transmission in the dorsal striatum in rat brain slices. The effects of ethanol on corticostriatal synaptic transmission were tested by whole-cell voltage-clamp recording. Ethanol significantly decreased corticostriatal excitatory postsynaptic currents (EPSCs) in a dose-dependent manner (10-200 mM). However, the paired-pulse ratio was not affected by the ethanol (100 mM) treatment. The amplitude of miniature EPSCs (mEPSCs) from these neurons, recorded without cortical stimulation, was decreased, but the frequency of the mEPSCs remained unchanged. Ethanol also decreased currents induced by the local pressure injection of glutamate into dorsal striatal neurons. These results suggest that ethanol inhibits glutamatergic synaptic transmission in the dorsal striatum, possibly through a postsynaptic mechanism.     

The brain and the pain: neurotransmitters and neuronal pathways of pain perception and response

The pain, an unpleasant feeling, induces several central nervous system mechanisms, like sensory-discriminative, motivational-affective activities, behavioral changes and it activates various responses, including antinociceptive actions. Accordingly, signals from the nociceptive neurons in the spinal cord and the sensory trigeminal nucleus ascend in various neuronal pathways and target several brain areas. Here, five ascending pain-conducting neuronal pathways and two spinal reflex routes are briefly summarized. The spinal and supraspinal antinociceptive mechanisms are described in more detail. During the past two decades, endogenous opioids, cannabinoids and their receptors have been discovered, localized and cloned. Five groups of endogenous opiates are known: beta-endorphin, enkephalins, dynorphins, endomorphins, and nociceptin. Two endogenous cannabinoids have already been described in the brain: the anandamide and the 2-arachidonyl-glycerol. The site of their antinociceptive (analgesic) actions in the brain are briefly summarized.     

Opioids in the perifornical lateral hypothalamus suppress ethanol drinking

The opioid system is known to enhance motivated behaviors, including ethanol drinking and food ingestion, by acting in various reward-related brain regions, such as the nucleus accumbens, ventral tegmental area and medial hypothalamus. There is indirect evidence, however, suggesting that opioid peptides may act differently in the perifornical lateral hypothalamus (PF/LH), causing a suppression of consummatory behavior. Using brain-cannulated Sprague–Dawley rats trained to voluntarily drink 7% ethanol, the present study tested the hypothesis that opioids in the PF/LH can reduce the consumption of ethanol, with animals receiving PF/LH injections of the δ-opioid receptor agonist D-Ala2-met-enkephalinamide (DALA), the μ-receptor agonist [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO), the κ-receptor agonist (±)-trans-U-50,488 methanesulfonate (U-50,488H), or the general opioid antagonist methylated naloxone (m-naloxone). The consumption of ethanol, lab chow, and water was monitored for 4 h after injection. The results showed that the three opioid receptor agonists injected into the PF/LH specifically and significantly reduced ethanol intake, while causing little change in chow or water intake, and the opposite effect, enhanced ethanol intake, was observed with the opioid antagonist. Of the three opioid agonists, the δ-agonist appears to produce the most consistent and long-lasting suppression of consumption. This effect was not observed with injections 2 mm dorsal to this area, focusing attention on the PF/LH as the main site of action. These results suggest that the opioid peptides have a specific role in the PF/LH of reducing ethanol drinking, which is distinct from their more commonly observed appetitive actions in other brain areas. The additional finding, that m-naloxone in the PF/LH stimulates ethanol intake in contrast to its generally suppressive effect in other regions, focuses attention on this hypothalamic area and its distinctive role in contributing to the variable effects sometimes observed with opioid antagonist therapy for alcoholism.     

Localization of mercury in CNS of the rat. I. Mercuric chloride (HgCl2) per os

Adult Wistar rats of both sexes were exposed to mercuric chloride (HgCl2) through drinking water (20 mg HgCl2 liter-1 distilled water) ad libitum during an 8-month period. Animals were subsequently sacrificed by transcardial perfusion with glutaraldehyde. Coronal sections of the brain and cervical spinal cord were examined according to a histochemical technique based on a physical development process which renders mercury deposits visible. Mercury was found unevenly distributed in the brain and spinal cord with the heaviest deposits found within the motor nuclei of the rhombencephalon. In cerebral cortex, the highest concentration of mercury was found in the striate area. Mercury was also localized within the deep nuclei of cerebellum; none was found within Purkinje cells. A proportionately high amount of mercury was additionally found in the anterior horn motoneurons of the spinal cord. In general, mercury was found primarily within neurons, but it was also observed in the cytoplasm of glia and ependymal cells.     

超前镇痛的临床应用研究进展及有效性分析

最有效的术后疼痛治疗应当是预先给药,超前阻止或减轻手术过程中中枢神经的致敏作用以及感受伤害的传人,达到减轻术后疼痛、延长镇痛时间和减少止痛药的需求量。在术后患者自控镇痛时,超前镇痛或预防性镇痛已经成为麻醉师常用的治疗方法。尽管国内外对于超前镇痛临床有效性的结论尚未统一,采取有效措施预防手术伤害性刺激引起外周及中枢敏化的理念已得到公认,且有关超前镇痛的基础和临床研究仍在继续并日趋成熟。如何实施超前镇痛,提高临床镇痛效应。目前尚缺乏超前镇痛临床规范,真实镇痛效果如何尚难以确定。持续和多模式的预防性镇痛是疼痛治疗发展的方向。本文主要对超前镇痛的定义、机制,超前镇痛的常用药物和方法及超前镇痛的争议及规范化进行综述。     

Which Opioid Receptor Mechanism Modulates Feeding?

There is substantial evidence for the role of endogenous opioid peptides in the regulation of appetite. This communication examines the possible opioid peptide mechanism(s) which are involved in appetite regulation. In the rat, activation of both the dynorphin-kappa opioid receptor and the beta-endorphin-epsilon opioid receptor appear to enhance feeding, most probably acting in different areas of the central nervous system. It also appears that rats may have a mu anorectic system. Too few studies have been undertaken to define whether the delta or sigma receptor systems are also involved in feeding responses. It is becoming apparent that a great deal of species diversity exists in the feeding responses to opiates, making it difficult to extrapolate the results obtained in rats to other species. In humans, studies with naloxone suggest an opioid sensitive feeding system which possibly is specifically involved in the regulation of carbohydrate uptake. In addition, we report here preliminary data suggesting the presence of a mu anorectic system in humans. Thus, analogous to the findings for the role of opioid receptors in analgesia, it appears that multiple opioid receptors may be involved in appetite regulation, each receptor relating to a different aspect of feeding.     

Interactions between cannabinoid and opioid receptor systems in the mediation of ethanol effects

Over the past few years, advances in the investigation of the neurochemical circuits involved in the development and treatment of alcohol dependence have identified peptides and receptors as potential key targets in the treatment of problems related to alcohol consumption. The endogenous opioid system is modified by alcohol intake in areas of the brain related to reward systems, and differential basal levels of opioid gene expression are found in rodents with a high preference for ethanol. This suggests a greater vulnerability to alcohol consumption in relation to differences in genetic background. Further evidence of the involvement of opioid peptides in alcohol dependence is the ability of the opioid antagonist naltrexone to reduce alcohol intake in animal models of dependence and in alcohol-dependent patients. Abundant evidence indicates that the activation of cannabinoid receptors stimulates the release of opioid peptides, therefore the cannabinoid receptor antagonists may presumably alter opioid peptide release, thus facilitating the reduction of ethanol consumption. However, little is known about the effects of ethanol on the endogenous cannabinoid system, the vulnerability of cannabinoid receptors to alcohol intake or their neurochemical implications in reducing consumption of alcohol. In this paper, we review the role of opioid and cannabinoid receptor systems, their vulnerability to alcohol intake and the development of dependence, and the targeting of these systems in the treatment of alcoholism.     

天麻素对神经病理性疼痛大鼠的镇痛作用及其机制研究

目的探讨天麻素对神经病理性疼痛大鼠的镇痛作用及其机制,为临床开发新的镇痛药物奠定基础。方法 SD大鼠随机分为坐骨神经慢性压迫性损伤组(n=32)和假手术组(n=8),自术后第8天分别腹腔注射天麻素治疗,用电子Von-Frey测痛仪测定大鼠机械缩足反射阈值,热痛刺激仪测定大鼠热痛缩足反应潜伏期。取脊髓腰膨大及L4/L6背根神经节,采用Western blotting法测定脊髓背角和背根神经节p-ERK1/2的表达。结果与假手术组相比,对照组和天麻素治疗组各时点机械缩足反射阈值降低、热痛缩足反应潜伏期缩短,脊髓背角及背根神经节p-ERK1/2均出现表达上调(P<0.05);与对照组相比,天麻素治疗组在给药后7 d机械缩足反射阈值回升、热痛缩足反应潜伏期延长;在给药14 d后脊髓背角及背根神经节p-ERK1/2表达下调(P<0.05)。结论天麻素可减轻大鼠神经病理性痛,其机制可能与抑制脊髓背角和背根神经节p-ERK1/2通路激活有关。     

Opioid peptides encrypted in intact milk protein sequences

Opioid agonistic and antagonistic peptides which are inactive within the sequence of the precursor milk proteins can be released and thus activated by enzymatic proteolysis, for example during gastrointestinal digestion or during food processing. Activated opioid peptides are potential modulators of various regulatory processes in the body. Opioid peptides can interact with subepithelial opioid receptors or specific luminal binding sites in the intestinal tract. Furthermore, they may be absorbed and then reach endogenous opioid receptors.     

Restoration of stressor-induced calcium dysregulation and autophagy inhibition by polyphenol-rich açaí (Euterpe spp.) fruit pulp extracts in rodent brain cells in vitro

ObjectivesOxidative damage to lipids, proteins, and nucleic acids in the brain often causes progressive neuronal degeneration and death that are the focal traits of chronic and acute pathologies, including those involving cognitive decline. The aim of this study was to investigate the specific effects of both Euterpe oleracea and Euterpe precatoria açaí fruit pulp on restoring stressor-induced calcium dysregulation, stunted growth of basal dendrites, and autophagy inhibition using embryonic hippocampal and HT22 hippocampal neurons.MethodsWater-soluble whole fruit pulp extracts from two açaí species were applied to rat primary neurons and HT22 hippocampal neurons with varied time and concentrations. Recovery of neurons from dopamine-induced Ca²⁺ dysregulation was measured by live cell imaging using fluorescent microscopy. The effect of açaí fruit pulp extracts on neurons following chemically-induced autophagy inhibition was measured using both immunofluorescence and immunohistochemical techniques.ResultsIt has been postulated that at least part of the loss of cognitive function in aging may depend on a dysregulation in calcium ion (Ca²⁺) homeostasis and a loss of autophagy function in the brain, which affects numerous signaling pathways and alters protein homeostasis. In the present study, polyphenol-rich fruit pulp extracts from two species of açaí, Euterpe precatoria and Euterpe oleracea, when applied to rat hippocampal primary neuronal cells (E18), caused a significant (P < 0.05) recovery of depolarized brain cells from dopamine-induced Ca²⁺ influx. Autophagy, a protein homeostasis mechanism in brain, when blocked by known inhibitors such as bafilomycin A1 or wortmannin, caused a significant reduction in the growth of primary basal dendrites in rodent primary hippocampal neurons and significant accumulation of polyubiquitinated proteins in mouse HT22 hippocampal neurons in culture. However, pretreatment with açaí extracts up to 1 mg/mL significantly increased the length of basal dendrites and attenuated the inhibitor-induced autophagy dysfunction. Açaí extracts activated the phosphorylation of mammalian target of rapamycin, increased the turnover of autophagosomes and MAP1 B LC3-II, and decreased accumulation of LC3-ubiquitin binding P62/SQSTM1.ConclusionAlthough the polyphenol profile of Euterpe precatoria showed substantially higher concentrations of major flavonoids han Euterpe oleracea, the relative effects were essentially similar for both species. The study adds to growing evidence that supports the putative health effects of açaí fruit species on brain cells.     

Basal firing rate of rat locus coeruleus neurons affects sensitivity to ethanol

Intracellular recordings were made from spontaneously active rat locus coeruleus (LC) neurons in a totally submerged brain slice preparation. Bath application of ethanol (ETOH) (1-60 mM) inhibited the spontaneous firing of LC neurons. These ETOH concentrations are equal to or below ETOH concentrations found in the brain during mild to moderate intoxication. The basal frequency of spontaneous firing of LC neurons ranged from 0.4-7 Hz. For 9 LC neurons which showed complete block of firing by ETOH, the latency to block was found to be directly related to the logarithm of the firing rate (correlation coefficient 0.94). This relationship was not secondary to a relationship between membrane potential and latency to block since for the same 9 neurons, membrane potential and latency to block were not significantly correlated. We conclude that the basal firing rate of a neuron can affect its sensitivity to the inhibitory effects of ETOH.     

纳洛酮在急性重型颅脑损伤中的应用观察

目的观察早期大剂量纳洛酮治疗重型颅脑损伤中的应用效果。方法选择脑外伤后格拉斯哥(GCS)评分3～8分患者59例,随机分为纳洛组34例与对照组25例。对照组给予脱水剂,糖皮质激素,抗菌药物及营养脑细胞药+脑复康常规治疗;纳洛酮组在对照组治疗基础上加用纳洛酮10 d,观察两组治疗后GCS评分,呼吸循环指标及觉醒时间等变化。结果纳洛酮组治疗后,意识觉醒时间缩短,呼吸循环衰竭发生率低。结论纳洛酮在解除颅脑损伤中由内源性阿片肽引起的中枢及外周循环抑制有显著作用。     

Toluene alters p75NTR expression in the rat brainstem

Toluene is a neurotoxic organic solvent widely used in industry. Acute toluene administration in rats induced a significant increase in the numbers of neural cells immunostained for p75NTR in several brainstem regions, such as the raphe magnus and the nucleus of the solitary tract, as well as in the lateral reticular, gigantocellular, vestibular and ventral cochlear nuclei, without any in the facial and spinal trigeminal nuclei and the dorsal horn of the spinal cord. These data suggest that p75NTR could be involved in toluene-induced neurotoxic efffects in the rat brainstem.