中脑导水管周围灰质内神经降压素在电针镇痛中的作用

本工作以钾离子透入法引起大鼠甩尾反应的电流强度为痛反应指标,测定动物痛阈,观察到大鼠中脑导水管周围灰质（ＰＡＧ）内注入神经降压素（ＮＴ）后,大鼠痛阈和电针镇痛效应明显升高;注入抗神经降压素血清后,痛阈和电针镇痛效应明显降低。注入纳洛酮后,可明显减弱ＮＴ镇痛和电针镇痛的效应。提示,ＰＡＧ内ＮＴ参与电针镇痛的病理生理过程,且至少部分效应是通过内源性阿片肽系统中介的     

家兔隔核中去甲肾上腺素对皮肤与内脏痛阈的影响

本工作以电刺激内脏大神经或耳尖部皮肤测定清醒家兔内脏痛阈或皮肤痛阈,以探讨隔核去甲肾上腺素在内脏镇痛和皮肤镇痛中的作用以及与中脑导水管周围灰质(PAG)中内阿片肽系统的关系。实验观察到,双侧隔核内微量注射α受体激动剂可乐宁(10μg/2μl)或α受体阻断剂酚妥拉明(10μg/2μl)对内脏痛阈无明显影响。注入β受体激动剂异丙肾上腺素(1μg/2μl)使内脏痛阐明显升高;而注入β受体阻断剂心得安(1Cμg/2μl)则内脏痛阈明显降低。隔核内注入酚妥拉明(10μg/2μl)或心得安(10μg/2μl)均可使皮肤痛阈明显提高。提示,隔核内NA通过β受体调制内脏痛;通过α受体和β受体调制皮肤痛。隔核内注入异丙肾上腺素(1μg/2μl)明显地镇内脏痛,此作用可被PAG内注射纳洛酮(1μg/2μl)或注射抗亮啡肽抗血清(1:20,000)所减弱;但可使PAG内亮啡肽样物质释放量增加。这提示,隔核内NA的镇内脏痛作用与PAG的内阿片肽系统有关;其中亮非肽在这一过程中具有重要作用。     

Analgesic effects of N-acetyl-5HTP-5HTP amide are not directly related to brain serotonin levels.

A synthetic dipeptide, N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophan amide, was shown previously to inhibit the binding of serotonin to a soluble specific serotonin binding protein as well as to alter brain serotonin levels. When injected into rats intraventricularly, the dipeptide caused an increase in pain threshold, lasting for several hours, as determined by either a flinch-jump test or a tail-flick test. This effect was reversed by naloxone. The dipeptide is a very weak inhibitor of the binding of labelled naloxone or dihydromorphine to a membranous opiate receptor preparation. The analgesic activity of the dipeptide was not diminished by p-chlorophenylalanine or the setonergic neurotoxin 5,7-dihydroxytryptamine, which depleted brain serotonin levels. This implies that the analgesic action of the dipeptide is not mediated directly by its effect on serotonin concentration.     

孤啡肽在大鼠脑内对抗吗啡镇痛

脑内全新的阿片受体样受体（１９９４）及其内源性配体孤啡肽（１９９５）的发现形成了中枢神经系统阿片／抗阿片相互关系的研究领域中一个新的推动力。基于它们与阿片家族的高同源性及在脑内痛觉整合相关区域的丰富表达,本实验观察了ＯＦＱ在大鼠脑内对吗啡镇痛作用的影响。结果表明：（１）ＯＦＱ可以对抗脑室注射生理盐水引起的镇痛,后者可能是一种由内源性阿片系统介导的应激镇痛。（２）脑室注射ＯＦＱ在很大的剂量范围（４０     

beta-Endorphin controls vasopressin release during foot shock-induced stress in the rat

This study tested the possibility that beta-endorphin is involved in the regulation of vasopressin release during stress induced by inescapable electric foot shock. To this end, a specific anti-beta-endorphin antiserum or a control serum lacking the specific anti-beta-endorphin antibodies was administered to male rats. Plasma vasopressin concentrations, measured by radioimmunoassay, were not affected by brief foot shock stress in control rats, but were raised significantly by the stress in animals which had received an intracerebroventricular (i.c.v.) injection of the anti-beta-endorphin antiserum. In contrast, when the same volume of the anti-beta-endorphin antiserum was injected into a tail vein, foot shock stress produced only a slight effect on vasopressin release. I.c.v. injection of the antiserum changed neither basal nociceptive threshold nor stress-induced analgesia as revealed by the tail-flick latency. Vasopressin release induced by an osmotic stimulus was not influenced by the anti-beta-endorphin antiserum given i.c.v. The opiate antagonist naloxone or the glucocorticoid dexamethasone raised plasma vasopressin concentration in stressed rats which had received the control serum (i.c.v.); however, after i.c.v. injection of the anti-beta-endorphin antiserum neither naloxone nor dexamethasone elevated the plasma vasopressin concentration beyond the level reached by the anti-beta-endorphin antiserum (i.c.v.) alone. These results suggest that beta-endorphin inhibits the release of vasopressin during foot shock-induced stress in the rat.     

Kyotorphin (tyrosine-arginine): Further evidence for indirect opiate receptor activation

Analgesia, opiate receptor binding, and neurochemical effects of kyotorphin (tyrosine-arginine) were studied in the rat. It was found that while kyotorphin, $\text{in vivo}$, causes naloxone reversible analgesia, and affects dopamine metabolism and acetylcholine turnover in the same manner as do morphine and other opiate agents, the dipeptide does not bind to mu, delta or kappa opiate receptors $\text{in vitro}$. Taken together, these data support the concept that there is an indirect action of kyotorphin on opiate receptors.     

Muramyl dipeptide induces acute joint inflammation in the mouse

Acute joint inflammation was produced in BALB/c mice by a single intravenous injection of synthetic muramyl dipeptide (MDP), its stereoisomers and 6-O-acyl derivatives of MDP. Four adjuvant-active, but not five adjuvant-inactive MDP analogs induced acute swelling and erythema of the ankles and wrists which were detected around 6-10 hr, reached the maximum severity by 18-24 hr and subsided by days 3 to 4 after injection. Introduction of the stearoyl group, but not the alpha-branched long chain fatty acid group into the C-9 hydroxyl group of MDP enhanced and prolonged the joint lesions compared with MDP.     

Treatment with pertussis toxin does not prevent central effects of eel calcitonin.

To determine whether or not the CNS inhibitory activity of eel calcitonin (eCT) on adenylyl cyclase is the endocellular mechanism underlying the antinociceptive effect of the peptide, as shown for morphine analgesia, we administered Bordetella pertussis toxin (PTX) by intracerebroventricular (ICV) injection (0.5 microgram/rat) to block the receptor-mediated inhibition of adenylyl cyclase. In PTX-treated rats there was no change in eCT (2.5 micrograms/rat, ICV)-induced antinociceptive activity (hot-plate test) nor in eCT (100 ng/rat, ICV) inhibition of gastric acid secretion (Shay test) whereas morphine (5 micrograms/rat, ICV) analgesia was significantly reduced. In vitro studies showed no reduction of eCT binding in the CNS of rats treated with PTX in vivo. Moreover, PTX treatment did not change the inhibitory effect of eCT on adenylyl cyclase in isolated membranes from rat striatum in contrast with opiates (DAME and morphine) whose effects were lost. As PTX is known to inactivate the guanidine binding inhibitory protein Gi, these data suggest that a G protein, distinct from the Gi protein involved in the coupling of opiate receptors into a functional response, could be responsible for regulating the intracellular pathways resulting in eCT-induced antinociceptive effect and inhibition of gastric acid secretion.     

Antinociceptive effects of intraventricular or systemic administration of vasopressin in the rat

The effects of intraventricular administration of lysine-vasopressin on pain sensitivity in the rat were determined in the tail-flick test. Vasopressin (16–100 μg) was found to induce potent and dose-dependent antinociceptive actions, lasting up to one hour. An additional experiment demonstrated that analgesia induced by vasopressin was not blocked by naloxone, suggesting that this analgesia is independent of opiate receptor systems. Vasopressin was also found to be equally effective in elevating tail-flick latency after systemic administration. These results, together with others, suggest a possible role of vasopressin systems in the regulation of pain sensitivity.     

Enkephalins and gastrin fragments: possible existence of different analgesic mechanisms

The mechanism of analgetic action of pentagastrin, its tripeptide fragment (MAF), synthetic met- and leu-enkephalins was studied in rats. The analgetic effect of the peptides was evaluated from the tail extracting test. Also, the content of biogenic amines in the rat brain and interaction of the peptides with opiate receptors of the guinea-pig ileum were examined. It was demonstrated that analgesia induced by pentagastrin or MAF differs from that obtained after intraventricular injection of the enkephalins. The effect of the latter ones is not consequent on their interaction with classic opiate receptors. It was also discovered that pentagastrin, MAF and enkephalins produce a different action on metabolism of biogenic amines. The possibility of analgesia unmediated by specific peptide binding to opiate receptors is discussed.     

Arginine vasopressin induces periaqueductal gray release of enkephalin and endorphin relating to pain modulation in the rat

Previous study has proven that microinjection of arginine vasopressin (AVP) into periaqueductal gray (PAG) raises the pain threshold, in which the antinociceptive effect of AVP can be reversed by PAG pretreatment with V2 rather than V1 or opiate receptor antagonist. The present work investigated the AVP effect on endogenous opiate peptides, oxytocin (OXT) and classical neurotransmitters in the rat PAG. The results showed that AVP elevated the concentrations of leucine-enkephalin (L-Ek), methionine-enkephalin (M-Ek) and beta-endorphin (beta-Ep), but did not change the concentrations of dynorphinA(1-13) (DynA(1-13)), OXT, classical neurotransmitters including achetylcholine (Ach), choline (Ch), serotonin (5-HT), gamma-aminobutyric acid (GABA), glutamate (Glu), dopamine (DA), norepinephrine (NE) and epinephrine (E), and their metabolic products in PAG perfusion liquid. Pain stimulation increased the concentrations of AVP, L-EK, M-Ek, beta-Ep, 5-HT and 5-HIAA (5-HT metabolic product), but did not influence the concentrations of DynA(1-13), OXT, the other classical neurotransmitters and their metabolic products. PAG pretreatment with naloxone - an opiate receptor antagonist completely attenuated the pain threshold increase induced by PAG administration of AVP, but local pretreatment of OXT or classical neurotransmitter receptor antagonist did not influence the pain threshold increase induced by PAG administration of AVP. The data suggested that AVP in PAG could induce the local release of enkephalin and endorphin rather than dynophin, OXT and classical neurotransmitters to participate in pain modulation.     

Effect of naloxone on analgesia induced by food deprivation

Naloxone (4 mg/kg) or saline was administered to animals under food deprived and non-deprived conditions prior to testing pain sensitivity in the tail flick test. Food deprived animals exhibited significantly elevated latencies in comparison to latencies observed under non-deprived conditions. This analgesia was diminished by treatment with the opiate receptor antagonist, naloxone. These findings suggest that analgesia induced by food deprivation is mediated in part by opiate receptor systems.     

镇痛多肽——内吗啡肽-1的人工合成及活性研究

 用液相合成方法合成了具有镇痛作用的μ阿片受体的内源性配体——内吗啡肽 - 1(endomorphin- 1 ) ,该四肽为 Tyr- Pro- Trp- Phe NH2 .液相合成法是在氨基酸的 N端用 Boc(叔丁氧羰酰基 )作保护基 ,C端用 HOSu(N-羟基琥珀酰亚胺 )活化 ,与未加保护基的氨基酸在碱性条件下接肽 .先分别合成 C端二肽和 N端二肽 ,再缩合为四肽 ,产物的保护基用盐酸脱帽去除 .中间产物用薄层层析和熔点鉴定其纯度 ,最终得到了高纯度的四肽 .小白鼠脑室注射 (i.c.v)测定表明 ,8.2 5nmol剂量给药 ,其镇痛活性为 87% ,明显高于吗啡 (morphine) .     

Analgesia Induced by Microwave Irradiation of an Acupuncture Point under Conditions of Visceral Pain in Mice: Role of the Serotonergic Cerebral System

We studied behavioral manifestations of analgesic effects induced in mice by irradiation of the E36 acupuncture point (AcP) by low-intensity microwaves under conditions of visceral pain evoked by i.p. injections of 0.08 ml of a 2% solution of acetic acid. We also examined changes in these analgesic effects resulting from a drop in the level of serotonin after i.p. injection of 300 mg/kg of a blocker of synthesis of serotonin, DL-parachlorophenylalanine (PChPhA). Two modes of irradiation were tested, with a wide frequency range (30 to 300 GHz) and amplitude modulation (mode 1) and with a stable frequency (61 ± ± 4 GHz, mode 2). Irradiation in mode 1 provided a higher level of analgesia than that in mode 2 (decreases in the duration of manifestations of the pain reaction were, on average, 35.7 and 20.4%, respectively). The level of analgesia dropped after injections of PChPhA; the durations of behavioral pain manifestations 24 h after such injections were greater than those in the group with no injections of the blocker by 41.3 and 12.1% in irradiation modes 1 and 2, respectively. The respective figures 48 h after PChPhA injections were 52.0 and 16.1%. Thus, under conditions of visceral pain, irradiation of the AcP by low-intensity microwaves provides noticeable analgesia, and the serotonergic brain system mediates the development of analgesia under the above-mentioned conditions. Neirofiziologiya/Neurophysiology, Vol. 37, No. 3, pp. 250–256, May–June, 2005.     

Intrathecal Infusion of Hydrogen-Rich Normal Saline Attenuates Neuropathic Pain via Inhibition of Activation of Spinal Astrocytes and Microglia in Rats

Background

Reactive oxygen and nitrogen species are key molecules that mediate neuropathic pain. Although hydrogen is an established antioxidant, its effect on chronic pain has not been characterized. This study was to investigate the efficacy and mechanisms of hydrogen-rich normal saline induced analgesia.

Methodology/Principal findings

In a rat model of neuropathic pain induced by L5 spinal nerve ligation (L5 SNL), intrathecal injection of hydrogen-rich normal saline relieved L5 SNL-induced mechanical allodynia and thermal hyperalgesia. Importantly, repeated administration of hydrogen-rich normal saline did not lead to tolerance. Preemptive treatment with hydrogen-rich normal saline prevented development of neuropathic pain behavior. Immunofluorochrome analysis revealed that hydrogen-rich normal saline treatment significantly attenuated L5 SNL-induced increase of 8-hydroxyguanosine immunoreactive cells in the ipsilateral spinal dorsal horn. Western blot analysis of SDS/PAGE-fractionated tyrosine-nitrated proteins showed that L5 SNL led to increased expression of tyrosine-nitrated Mn-containing superoxide dismutase (MnSOD) in the spinal cord, and hydrogen-rich normal saline administration reversed the tyrosine-nitrated MnSOD overexpression. We also showed that the analgesic effect of hydrogen-rich normal saline was associated with decreased activation of astrocytes and microglia, attenuated expression of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in the spinal cord.

Conclusion/Significance

Intrathecal injection of hydrogen-rich normal saline produced analgesic effect in neuropathic rat. Hydrogen-rich normal saline-induced analgesia in neuropathic rats is mediated by reducing the activation of spinal astrocytes and microglia, which is induced by overproduction of hydroxyl and peroxynitrite.     

促肾上腺皮质激素对慢痛大鼠脊髓生长抑素、c-fos表达及痛反应的影响

本研究应用免疫组化、原位杂交和痛级均数测定法,探讨鞘内注射促肾上腺皮质激素（ＡＣＴＨ）对甲醛引起大鼠脊髓内生长抑素（Ｓｏｍ）、ｃｆｏｓ表达及痛反应的影响。结果表明,足底注射甲醛可使大鼠脊髓内ｃｆｏｓ样免疫反应（ＦＬＩ）、Ｓｏｍ样免疫反应（ＳｏｍＬＩ）、ＦＬＩ／ＳｏｍＬＩ及前Ｓｏｍ原ｍＲＮＡ（ＰＰＳｍＲＮＡ）神经元数目显著增多以及痛级均数（ＰＩＲ）显著升高。而鞘内注射ＡＣＴＨ可显著抑制甲醛引起的大鼠脊髓内ＦＬＩ、ＳｏｍＬＩ、ＦＬＩ／ＳｏｍＬＩ及ＰＰＳｍＲＮＡ增多和ＰＩＲ升高效应。鞘内预先注射赛庚啶可阻断ＡＣＴＨ的抑制效应,而荷包牡丹碱、纳洛酮则无影响。结果提示,５羟色胺受体可能参与ＡＣＴＨ抑制甲醛引起的痛反应。     

Prostaglandin hyperalgesia, V: a peripheral analgesic receptor for opiates

Prostaglandin E2 injected in the rat paw causes hyperalgesia which is antagonized by local injections of opiate and opiate antagonists. In the present investigation in rats it is shown that naloxone has an analgesic effect at doses as low as 2 micrograms/site, injected into the rat hind paw. At a dose that has no analgesic effect (1 microgram/site) naloxone antagonized the analgesia produced by either local or systemic administration of morphine. Local administration of levorphanol (50 micrograms/site) caused a 50% reduction in the intensity of the hyperalgesia induced by prostaglandin E2. A dose four times greater of its isomer, dextrorphan, had little analgesic effect. The present results support the suggestion that this peripheral analgesia is the result of an action of opiates in receptors located at the nociceptors.     

5-Hydroxytryptophyl peptides: potent inhibitors of a storage compartment of serotonin.

Several analogues of 5-hydroxytryptophan were tested for their ability to inhibit the binding of serotonin to serotonin-binding protein (SBP), a protein found within serotonergic neurons which has a high affinity for serotonin. An N-substituted dipeptide, N-acetyl-5-hydroxytryptophan-5-hydroxytryptophan amide, was found to be an inhibitor of this binding. The inhibition (50% at 1.0 μM) was specific, since it did not affect other known sites of serotonin binding. The binding of serotonin to its membrane receptor was not affected by the dipeptide (up to 10 μM). Uptake of serotonin by synaptosomes was only slightly affected (9% at 10 μM), and aromatic-L-amino-acid carboxy-lyase(EC 4.1.1.28) and amine: oxygen oxidoreductase (deaminating) (flavin-containing) (EC 1.4.3.4) were not inhibited (10 μM and 5 mM respectively), The peptide was not hydrolyzed by honiogenates of brain or myenteric plexus. The ¹⁴C-labelled dipeptide was shown to be taken up by synaptosomes. However, the uptake of the peptide was not affected either by drugs that inhibit serotonin uptake or by serotonin itself although the uptake was abolished by excess 5-hydroxytryptophan. Intraventricular injection of N-acetyl dipeptide caused a biphasic effect depending on dose. Lower doses (10nmol) induced a decrease in serotonin brain levels (40%). Higher doses (300 nmol) caused a 95% increase in serotonin levels. It is suggested that 5-hydroxytryptophyl peptides may be used as potent specific inhibitors of SBP, a storage compartment of serotonin.     

Neonatal animal models of opiate withdrawal

The symptoms of opiate withdrawal in infants are defined as neonatal abstinence syndrome (NAS). NAS is a significant cause of morbidity in term and preterm infants. Factors, such as polysubstance abuse, inadequate prenatal care, nutritional deprivation, and the biology of the developing central nervous system contribute to the challenge of evaluating and treating opiate-induced alterations in the newborn. Although research on the effects of opiates in neonatal animal models is limited, the data from adult animal models have greatly contributed to understanding and treating opiate tolerance, addiction, and withdrawal in adult humans. Yet the limited neonatal data that are available indicate that the mechanisms involved in these processes in the newborn differ from those in adult animals, and that neonatal models of opiate withdrawal are needed to understand and develop effective treatment regimens for NAS. In this review, the behavioral and neurochemical evidence from the literature is presented and suggests that mechanisms responsible for opiate tolerance, dependence, and withdrawal differ between adult and neonatal models. Also reviewed are studies that have used neonatal rodent models, the authors' preliminary data based on the use of neonatal rat and mouse models of opiate withdrawal, and other neonatal models that have been proposed for the study of neonatal opiate withdrawal.