下丘脑弓状核区参与由中脑导水管周围灰质到伏核的上行镇痛通路

在家兔中脑导水管周围灰质(PAG)内微量注射吗啡产生的镇痛作用可被伏核内注射β-内啡肽抗体所对抗,在损毁下丘脑弓状核区(ARH)后该对抗效应消失。但损毁ARH并不影响PAG注射吗啡所引起的镇痛作用,也不影响伏核注射纳洛酮对于PAG内注射吗啡引起镇痛的对抗作用,以上结果提示,(1)从PAG到伏核的上行镇痛通路中有ARH及β-内啡肽能纤维参与;(2)除β-内啡肽以外,伏核内尚有其它阿片肽发挥镇痛作用。     

蝎毒中枢镇痛机制的初步探讨

目的：研究BmK蝎毒是能过何种受体实现其中枢镇痛作用的;外侧隔核是否是BmK蝎毒产生中枢镇痛作用的重要部位之一。方法：用辐射热一甩尾法测定痛阈,用玻璃微电极记录束旁核的单位放电;通过不锈钢套管向侧脑室和外侧隔核内微量注射0.01％BmK蝎毒。结果：向大鼠侧脑室2μl0.01%蝎毒可明显升高痛阂。该效应可被侧脑室注射2μl0.25%纳洛酮完全翻转,向隔核内注射0.5μl0.01%BmK蝎毒,分别对束帝核中的71％（15／21）痛兴奋单位和83％（5／6）痛抑制单位对痛刺激的反应减北,而对痛无关单位的电活动夫明显影响。结论：BmK蝎毒的中枢镇痛作用可能主要是通过吗啡受体实现的;隔核是BmK蝎毒产生中枢镇痛作用的重要部位之一。     

家兔下丘脑弓状核区参与从伏核到中脑导水管周围灰质的下行镇痛通路

我们以往的工作表明,中脑导水管周围灰质(PAG)和伏核之间存在着双向性的联系,构成内源性镇痛系统的重要组成部分。本工作探讨下丘脑弓状核区(ARH)和β-内啡肽(β-EP)能纤维在这一神经联系中所起的作用。实验结果表明,在家兔伏核内微量注射吗啡产生的镇痛作用可被PAG内注射β-EP抗血清所对抗,当损毁ARH后上述对抗效应消失。但是,损毁ARH的家兔其基础痛阈仍保持在正常水平,伏核内注射吗啡仍能引起明显的镇痛效应,而且这种效应仍能被PAG内注射纳洛酮所削弱。以上结果提示,(1)从伏核到PAG的下行镇痛通路中有ARH及β-EP能纤维的参与;(2)除β-EP外PAG内尚有其它阿片肽发挥镇痛作用。     

家兔伏核注射吗啡引起的镇痛可被中脑导水管周围灰质注射纳洛酮或甲啡肽抗体所阻断

本实验室以往的资料表明,在家兔中脑导水管周围灰质(PAG)到伏核之间存在一条与镇痛有夫的神经通路,该通路以5-羟色胺(5-HT)和甲啡肽(ME)为其递质。本工作进一步探讨从伏核到PAG的下行镇痛通路。 以辐射热照射家兔嘴侧部皮肤,测量其躲避反应的潜伏期(ERL)作为痛反应阈,简称痛阈。通过预先埋植的慢性套管向伏核内微量注射吗啡,20min后向PAG内双侧注射纳洛酮(NX)或脑啡肽抗血清,观察ERL的变化。(1)伏核内注射吗啡20μg/1μl,引起ERL升高80％以上,作用持续50min以上。(2)PAG内注射NX(每侧0.5、1.0或2.0μg)可不同程度地阻断伏核内注射吗啡的镇痛效应,且呈明显的剂效关系。(3)PAG内注入甲啡肽抗血清(每侧1μl)可部分阻断伏核内注射吗啡的镇痛效应,而注入亮啡肽抗血清或正常兔血清则无效。 实验结果提示,从伏核到PAG存在一条下行镇痛通路,在PAG内可能以ME为其递质。该通路与PAG到伏核的上行镇痛通路构成一个环形的“中脑边缘镇痛回路”,并在针刺镇痛和吗啡镇痛中发挥重要作用。     

脊髓中的甲啡肽和强啡肽参与吗啡下行镇痛

在大鼠中脑导水管周围灰质(PAG)注射吗啡10μg 可引起明显的镇痛作用,并有部位特异性。在脊髓蛛网膜下腔注射抗甲啡肽 IgG20μg 或抗强啡肽 IgG20μg,均能大部分对抗 PAG内注射吗啡引起的镇痛作用,这提示甲啡肽和强啡肽参与自 PAG 到脊随的下行抑制作用。本实验利用蛋白质 A-琼脂糖 CL-4B 亲和层析柱从血清中纯化 IgG,这种方法简单,提纯速度快,且 IgG 纯度高,为中枢微量注射抗体研究神经肽的生理功能提供了方便。     

家兔杏仁核内的5-羟色胺和内源性吗啡样物质在电针镇痛和吗啡镇痛中起重要作用

本工作的目的是要确定杏仁核内的吗啡样物质(内啡素)和5-羟色胺(5-HT)是否参与电针镇痛和吗啡镇痛。经慢性埋植套管向家兔杏仁核内微量注射阿片受体阻断剂纳洛酮,或5-HT受体阻断剂肉桂硫胺,可使电针的镇痛效果显著减弱,尤以注入中央杏仁核作用最为显著,双侧注射效果大于单侧,注入核外则无效。杏仁核内注入5-HT 的前体5-HTP,或脑啡肽降解酶抑制剂 D-苯丙氨酸可使电针镇痛显著加强。上述措施凡是加强或对抗电针镇痛的,也能加强或对抗吗啡镇痛。以上结果表明,电针刺激或注射吗啡可能在杏仁核内引起5-HT 和内啡素(很可能是脑啡肽)的释放,而发挥镇痛效应。     

克班宁的镇痛作用部位及作用机制探讨

以探究克班宁的镇痛作用部位并初步明确其镇痛机制为目的。采用小鼠足趾注射甲醛法、热板法及腹腔注射醋酸(扭体法)所致疼痛模型,探讨克班宁的镇痛作用;以小鼠输精管经壁电刺激法,了解克班宁对吗啡受体的影响。结果发现克班宁在3.2 mg/kg时对三种疼痛模型均显示明显的抑制作用,并能明显抑制小鼠输精管经壁电刺激所引起的收缩,且该收缩不能被纳络酮所拮抗。因此,克班宁可能具有中枢样镇痛作用,但作用机制与吗啡受体无关。     

抑制伏核内脑啡肽的降解使电针镇痛和吗啡镇痛得到加强

将“脑啡肽酶”抑制剂 Thiorphan 或氨肽酶抑制剂 Bestatin 经慢性埋植套管注入家兔一侧状核内,观察到明显的镇痛作用,在1—4μg 范围内呈现明确的剂量-效应关系。该作用可为伏核内注射纳洛酮或甲啡肽抗体所完全翻转,亮啡肽抗体则无效。表明伏核内注射 Thior-Phan 或 Bestatn 所产生的镇痛效应主要是通过甲啡肽而完成的。伏核内注射微量 Thiorphan 或 Bestatin 使电针镇痛的后效应明显加强,并能增强吗啡的镇痛作用。表明电针和吗啡的镇痛效果至少有一部分是通过在伏核内释放出脑啡肽(特别是甲啡肽)而实现的。     

家兔中脑导水管周围灰质中注射八肽胆囊收缩素(CCK-8)拮抗吗啡镇痛和电针镇痛

家兔单侧PAG内注射CCK-83ng,能使静脉注射4mg/kg吗啡引起的镇痛作用降低73％或使电针镇痛效果降低67％。在1.5—6.0ng范围内呈量效关系。无硫的CCK-8无此作用。PAG内注射CCK受体拮抗剂proglumide 4μg可翻转CCK-8的抗吗啡镇痛作用。说明PAG部位注射外源性CCK-8可通过CCK受体对抗阿片镇痛。 PAG内注射CCK-8抗血清可显著增强静脉注射2mg/kg吗啡的镇痛效果。PAG内注射CCK抗血清本身也能引起痛阈轻度升高。说明PAG内有内源性的CCK-8发挥紧张性的抗阿片镇痛作用。     

大鼠脊髓中的去甲肾上腺素在吗啡镇痛中的作用

本文报道中枢去甲肾上腺素(NE)能下行系统的脊髓末梢以及脊髓内的α受体在吗啡镇痛机制中的作用。结果显示,皮下注射6mg/kg 吗啡可使脊髓中的 NE 代谢终产物3-甲氧基4-羟基苯乙二醇硫酸盐(MHPG·SO_4)含量升高,提示脊髓 NE 的更新加速;反复多次注射吗啡引起吗啡镇痛耐受的动物,该反应消失。脊髓蛛网膜下腔注射α受体阻断剂酚妥拉明可部分对抗全身注射小剂量吗啡的镇痛作用,选择性的α_1受体阻断剂哌唑嗪或α_2受体阻断剂育亨宾有类似作用。阻断脊髓α_1或α_2受体对脊髓蛛网膜下腔直接注射微量吗啡的镇痛作用无显著影响,以上结果表明,下行 NE 能系统在吗啡镇痛机制中具有重要作用。     

Cholera and pertussis toxins inhibit differently hypothermic and anti-opioid effects of neuropeptide FF

In mice pretreated intracerebroventricularly (i.c.v.) with pertussis or cholera toxins, effects of neuropeptide FF (NPFF), on hypothermia and morphine-induced analgesia, were assessed. NPFF and a potent NPFF agonist, 1DMe (0.005-22 nmol) injected into the lateral ventricle decreased morphine analgesia and produced naloxone (2.5 mg x kg(-1), s.c.)-resistant hypothermia after administration into the third ventricle. Cholera toxin (CTX 1 microg, i.c.v.) pretreatment (24 or 96 h before) inhibited the effect of 1DMe on body temperature, but failed to reverse its anti-opioid activity in the tail-flick test. CTX reduced hypothermia induced by a high dose of morphine (8 nmol, i.c.v.) but not the analgesic effect due to 3 nmol morphine. Pertussis toxin (PTX) pretreatment inhibited both morphine-hypothermia and -analgesia but did not modify hypothermia induced by 1DMe. The present results suggest that NPFF-induced hypothermia depends on the stimulation of Gs (but not Gi) proteins. In contrast, anti-opioid effects resulting from NPFF-receptor stimulation do not involve a cholera toxin-sensitive transducer protein.     

Comparison between naloxone reversal of morphine and electrical stimulation induced analgesia in the rat mesencephalon

Comparisons were made between the efficacy of naloxone to reverse analgesia induced by electrical stimulation (SPA) of the periaqueductal gray matter and analgesia induced by microinjections of morphine into the same brain region. Naloxone at 1 or 10 mg/kg was ineffective in antagonizing SPA during the first two minutes post-stimulation. Although some antagonism did appear 3–5 minutes after stimulation, the effect was neither consistent nor dose-dependent. Morphine, on the other hand, was antagonized in a dose-dependent and complete fashion by naloxone. The assumption that similar mechanisms underlie both opiate and electrical stimulation induced analgesia is discussed.     

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。     

Naloxone blocks opioid peptide release in periaqueductal gray and amygdala elicited by morphine injected into N. accumbens.

Previous studies from this laboratory suggested that the periaqueductal gray (PAG), nucleus accumbens, and amygdala might take part in a serial, unidirectional mesolimbic loop to play their roles in pain modulation. It has been proposed that morphine injected into one of these nuclei would cause the release of opioid peptides in one nucleus after another. This working hypothesis was examined in the present study by perfusing simultaneously the PAG and the amygdala after microinjection of morphine into the N. accumbens. It was found that microinjection of morphine increased the content of immunoreactive enkephalins (ir-ENK) and immunoreactive beta-endorphin (ir-beta-EP) in the perfusate of the PAG and the amygdala. When the perfusion fluid contained 3 microM of naloxone, the increase of ir-ENK and ir-beta-EP was reduced significantly. These results indicate that the three nuclei were not serially connected in a unidirectional loop.     

家兔中脑导水管周围灰质中注射八肽胆囊收缩素（CCK—8）拮抗吗啡镇痛和...

We have reported that intracerebroventricular (i. c. v.) injection of 1-4 ng of CCK-8 to the rat produced a remarkable antagonistic effect on morphine analgesia. In order to study the species specificity and the site of action, CCK-8 was microinjected into the PAG of the rabbit, and its influence on morphine analgesia and electroacupuncture analgesia was observed. The latency of the escape response (ERL) to radiant heat focused on the snout was measured as an index of the pain threshold. Microinjections were made via cannulae chronically implanted into the PAG. The drug solutions were delivered in a volume of 1 microliter, at a speed of 0.125 microliter/min. The ERL was measured for a period of 60 or 70 minutes at 10 min intervals. 1. CCK-8 administered unilaterally to the PAG of the rabbit at a dose of 3 ng antagonized the analgesia induced by morphine (4 mg/kg, i. v.) by 73% (P less than 0.001), and reduced the analgesic effect of electroacupuncture by 67% (P less than 0.001). These effects were dose-dependent within the range from 1.5 ng to 6.0 ng. The effect of CCK-8 was reversed by CCK receptor blocker proglumide (4 microliters, intra-PAG injection). Unsulfated CCK-8 (CCK-us) had no effect in this regard. These results indicate that in the PAG of the rabbit, exogenously administered CCK-8 was capable of antagonizing opioid analgesia by the activation of CCK receptors. 2. Two groups of rabbits were given with morphine (2 mg/kg, i. v.) and simultaneous injection of CCK-8 antiserum (CCK-AS, 1 microliter) or normal rabbit serum (NRS) into the PAG.(ABSTRACT TRUNCATED AT 250 WORDS)     

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     

Naloxone blocks the release of opioid peptides in periaqueductal gray and N. accumbens induced by intra-amygdaloid injection of morphine

The working hypothesis that the periaqueductal gray (PAG), N. accumbens and amygdala were connected serially in a unidirectional loop for antinociception, in which Met-enkephalin and β-endorphin were considered to be two important analgesic neurotransmitters, was examined by simultaneously perfusing the PAG and N. accumbens after microinjection of morphine into the amygdala. Intra-amygdaloid injection of morphine increased the release of enkephalins and β-endorphin in the PAG and N. accumbens. When the perfusion fluid contained 3 μM of naloxone, the release of enkephalins and β-endorphin was reduced in both the PAG and the N. accumbens. These results do not support the hypothesis of a unidirectional loop and its putative sequence.     

孤束核参与刺激下丘脑室旁核的镇痛作用

本实验用电刺激鼠尾-嘶叫法测痛,观察电刺激下丘脑室旁核的镇痛效应,并采用核团损毁和核团内微量注射药物等方法分析其镇痛通路。实验结果如下:(1)电刺激下丘脑室旁核能产生明显的镇痛效应。同时,放射免疫测定发现脑干加压素含量升高。(2)损毁孤束核能取消刺激下丘脑室旁核的镇痛效应,但对基础痛阈无影响。(3)孤束核内微量注射加压素拮抗剂[d(CH_2)_5 TYr(Me)-AVP]60ng/0.6μl 和加压素抗血清0.6μl 都可明显对抗刺激下丘脑室旁核的镇痛效应。(4)直接在孤束核内微量注射加压素60ng/0.6μl,能模拟刺激下丘脑室旁核的镇痛效应。实验结果表明:电刺激下丘脑室旁核能产生镇痛效应,其机理之一可能是兴奋了下丘脑室旁核中加压素能神经元胞体,后者通过下行投射纤维在孤束核中释放加压素,影响孤束核神经元的活动,从而产生镇痛。     

Central integration of muscle reflex and arterial baroreflex in midbrain periaqueductal gray: roles of GABA and NO

It has been suggested that the midbrain periaqueductal gray (PAG) is a neural integrating site for the interaction between the muscle pressor reflex and the arterial baroreceptor reflex. The underlying mechanisms are poorly understood. The purpose of this study was to examine the roles of GABA and nitric oxide (NO) in modulating the PAG integration of both reflexes. To activate muscle afferents, static contraction of the triceps surae muscle was evoked by electrical stimulation of the L7 and S1 ventral roots of 18 anesthetized cats. In the first group of experiments (n = 6), the pressor response to muscle contraction was attenuated by bilateral microinjection of muscimol (a GABA receptor agonist) into the lateral PAG [change in mean arterial pressure (DeltaMAP) = 24 +/- 5 vs. 46 +/- 8 mmHg in control]. Conversely, the pressor response was significantly augmented by 0.1 mM bicuculline, a GABAA receptor antagonist (DeltaMAP = 65 +/- 10 mmHg). In addition, the effect of GABAA receptor blockade on the reflex response was significantly blunted after sinoaortic denervation and vagotomy (n = 4). In the second group of experiments (n = 8), the pressor response to contraction was significantly attenuated by microinjection of L-arginine into the lateral PAG (DeltaMAP = 26 +/- 4 mmHg after L-arginine injection vs. 45 +/- 7 mmHg in control). The effect of NO attenuation was antagonized by bicuculline and was reduced after denervation. These data demonstrate that GABA and NO within the PAG modulate the pressor response to muscle contraction and that NO attenuation of the muscle pressor reflex is mediated via arterial baroreflex-engaged GABA increase. The results suggest that the PAG plays an important role in modulating cardiovascular responses when muscle afferents are activated.     

Opioid antinociception and positive reinforcement are mediated by different types of opioid receptors

Fentanyl (FEN) and diprenorphine's (DIPR) potentials for analgesia and reinforcement were assayed using rats. Analgesia was measured by the classic tail-flick test. The test germane to opioid reinforcement involved measuring pressing rates for direct electrical stimulation of the lateral hypothalamus and ventral tegmental area. FEN, as does morphine and heroin, produced strong analgesia and enhanced pressing rates for brain stimulation. DIPR produced no analgesia and antagonized FEN's analgesia. DIPR, at doses antagonizing FEN's analgesia, enhanced pressing for brain stimulation. DIPR's enhancement of pressing was antagonized by naloxone (100 micrograms/kg). When FEN and DIPR were given concurrently, pressing for brain stimulation was not reduced and was greater than after FEN alone was given. These data support a conclusion that different types of receptors are associated with opioid analgesia and reinforcement.