The effect on opioid peptides in the rat brain, after chronic treatment with the anabolic androgenic steroid, nandrolone decanoate

In recent years, an increase in abuse of anabolic androgenic steroids (AAS) has been seen among individuals not directly connected to sports. Clinical evidence suggests that abuse of these steroids may result in profound changes in personality, expressed by depressive symptoms, irritability and increased aggression. It is still unknown whether these alterations are related to changes in any particular transmitter system or whether they are persistent or reversible. In this study we focused on AAS effect on the endogenous dynorphin and enkephalin system in the brain. Male rats were given intramuscular injections of the AAS nandrolone decanoate (15 mg/kg), once daily for 2 weeks. The levels of the opioid peptide immunoreactivities (ir) were assessed by radioimmunoassay in two groups immediately after the treatment and in two other groups after additional 3 weeks without any drug treatment (recovery period). The result indicates that chronic AAS treatment increased the activity in the dynorphin B- and Met-enkephalin-Arg(6)Phe(7)-ir in the hypothalamus, striatum and periaqueductal gray (PAG) compared to controls. In addition, the steroid induced an imbalance between the dynorphin and the enkephalin opioid system in the nucleus accumbens, hypothalamus and PAG. This imbalance remained after the recovery period. Since increased peptide activity was found in brain regions regulating emotions, dependence, defensive reactions and aggression, it was suggested that the actual endogenous opioid systems are involved in previously reported AAS-induced changes in these behaviours.     

下丘脑弓状核参与左旋四氢巴马汀的镇痛作用(英文)

目的:研究弓状核在左旋四氢巴马汀(l-THP)镇痛效应中的作用,以阐明l-THP的镇痛作用机制。方法:应用辣根过氧化物酶(HRP)逆行追踪术追踪纹状体或伏膈核与PAG之间的纤维联系,HRP逆行追踪结合免疫组化观察投射神经元的性质,神经核团损毁和PAG核内注射药物观察对l-THP镇痛作用的影响。结果:纹状体或伏膈核通过弓状核或缰核间接与PAG联系,弓状核投射至PAG的神经元大部分是β内啡肽神经元。损毁弓状核后,l-THP的镇痛作用消失,而损毁缰核对l-THP的镇痛作用无明显影响。PAG核内注射纳洛酮能剂量依赖性翻转l-THP的镇痛作用。结论:弓状核的β内啡肽神经元在l-THP镇痛作用中起重要作用。     

Periaqueductal gray inhibition of trigeminal subnucleus caudalis unitary responses evoked by dentine and nonnoxious facial stimulation

The possible pain inhibitory effects of periaqueductal gray (PAG) stimulation were investigated in cats anesthetized with Nembutal and immobilized with Flaxedil. Unitary responses evoked by electrical stimulation of the upper canine dentine and by cutaneous facial noxious and nonnoxious stimuli were recorded extracellularly from the trigeminal subnucleus caudalis. A bipolar electrode was introduced into the PAG to test the effects of PAG excitation on the trigeminal response to dentine (TRED) and cutaneous nonnoxious stimulation. In some experiments, a similar electrode was lowered into the contralateral posterior thalamus to study the antidromic activation of subnucleus caudalis cells and the effects of thalamic stimulation on the TRED. Dentine stimulation evoked brief (6- to 15-ms) bursts of 1 to 10 spikes with 3- to 25-ms latencies. Most units (88%) were also activated by cutaneous facial stimulation. Stimulation of the posterior thalamus had no effect on the TRED or on responses to cutaneous stimulation, but activated antidromically 10% of the units. In 71% of the units PAG stimulation inhibited the TRED. In some of those cases (12%), the inhibitory effect persisted 30- to 60 s. The PAG stimulation could produce paradoxical effects, potentiating the TRED evoked by threshold intensity and inhibiting the TRED elicited by suprathreshold stimulation. About one-half the PAG points evoked detectable effects. Their location had no clear topographical distribution, although ventral sites were more potent than dorsal sites. Responses evoked by nonnoxious facial stimulation were also inhibited by the PAG.     

Electroacupuncture induces c-Fos expression in the rostral ventrolateral medulla and periaqueductal gray in cats: relation to opioid containing neurons

Our previous studies have shown that electroacupuncture (EA) at the Neiguan-Jianshi (P5-P6) acupoints inhibits sympathetic outflow and attenuates excitatory visceral cardiovascular reflexes through enkephalin- or beta-endorphin-related opioid receptors in the rostral ventrolateral medulla (rVLM). It is not known whether EA at these acupoints activates neurons containing enkephalin or beta-endorphin in the rVLM as well as in the periaqueductal gray (PAG) that are involved in EA-mediated central neural regulation of sympathetic activity. The present study evaluated activated neurons in the rVLM and PAG by detecting c-Fos immunoreactivity, and identified the relationship between c-Fos nuclei and neuronal structures containing enkephalin or beta-endorphin in these regions. To enhance the detection of cell bodies containing enkephalin or beta-endorphin, colchicine (90-100 microg/kg) was injected into the subarachnoid space in anesthetized cats 28-30 h prior to EA or the sham-operated control for EA. Following bilateral barodenervation and cervical vagotomy, EA (1-4 mA, 2 Hz, 0.5 ms) was performed at the P5-P6 acupoints (overlying median nerve; n=7) for 30 min. Identical procedures, with the exception of electrical stimulation, were carried out in five control animals. EA decreased blood pressure (BP) in four of seven cats (5-15 mm Hg) while the sham procedure for EA produced no responses. Perikarya containing enkephalin were found in the rVLM and rarely in the PAG, while no cell bodies labeled with beta-endorphin were identified in either region. Compared to animals in the control group, more c-Fos immunoreactivity, located principally in close proximity to fibers containing enkephalin or beta-endorphin, was observed in the rVLM and ventrolateral PAG (vlPAG) in EA-treated cats. Moreover, neurons double-labeled with c-Fos and enkephalin in the rVLM were significantly increased in cats following EA stimulation (P<0.05). These data indicate that EA at the P5-P6 acupoints activates neurons in the rVLM and vlPAG. These activated neurons contain enkephalin in the rVLM, and most likely interact with nerve fibers containing enkephalin or beta-endorphin in both the rVLM and vlPAG. The results from this study provide the first anatomical evidence showing that EA at the P5-P6 acupoints has the potential to influence neuronal structures (perikarya, axons and/or dendrites) containing enkephalin or beta-endorphin in specific regions of the brain stem. These neurons likely form the substrate for EA's influence on sympathoexcitatory cardiovascular reflexes.     

地奥心血康干预阿司匹林抵抗患者的临床试验

目的 观察地奥心血康对阿司匹林抵抗患者的干预效果并探讨其作用机制.方法 将60例阿司匹林抵抗患者随机分为加大阿司匹林用量组(对照组,拜阿司匹林300 mg/d)30例,地奥心血康组(治疗组,地奥心血康1.6 g,每日3次)30例.两组均连续用药4周.观察并对比血小板平均聚集率、血栓素B2(TXB2)、6-酮-前列腺素F1α(6-K-PGF1α)及药物安全性.结果 治疗组有效率显著高于对照组;治疗组治疗1个月后以花生四烯酸(AA)和二磷酸腺苷(ADP)诱导的血小板聚集率及其下降值均显著低于对照组.与治疗前比较,对照组和治疗组的TXB2均升高明显(P<0.01).治疗组的6-K-PGF1α与对照组相比升高(P<0.05),与治疗前比较,对照组降低明显(P<0.01).与治疗前比较,对照组和治疗组的TXB2/6-K-PGF1α均降低(P<0.01,P<0.05).治疗组药物不良反应发生率显著低于对照组.结论 地奥心血康治疗阿司匹林抵抗有较好的疗效及安全性,其机制可能与其可降低TXB2同时升高6-K-PGF1α降低TXB2/6-K-PGF1α的作用有关.     

Intra-periaqueductal grey microinjections of an imidazo[1,2-b]pyridazine derivative, DM2, affects rostral ventromedial medulla cell activity and shows antinociceptive effect

The 6-methoxy-2-phenylimidazo[1,2-b]pyridazine-3-carboxylic acid, DM2, exerts anti-absence activity and blocks Cav3.1 channel, a T-type voltage-dependent Ca²⁺ channel subtype, in vitro. The current study investigated the effect of intra-ventrolateral periaqueductal grey (VLPAG) administration of DM2 on formalin-induced nocifensive responses in rats. In addition, the effect of intra-VLPAG microinjection of DM2 on the ongoing and tail flick-related activities of rostral ventromedial medulla (RVM) cell population was also investigated. Formalin was injected subcutaneously into the dorsal surface of the hind paws of awake rats. We found that DM2 reduced nocifensive responses in the late phase of the formalin test. Moreover, in the RVM, the intra-VLPAG microinjection of DM2 reduced the ongoing and tail flick-related activity of the nociceptive ON cells, whereas it increased the ongoing activity and reduced the tail flick-induced pause of the antinociceptive OFF cells, consistent with antinociception. Behavioural and electrophysiological effects were reproduced by intra-VLPAG microinjection of ethosuximide, a conventional T-type Ca²⁺ channel blocker. Finally, DM2 administration did not produce any adverse cardiovascular effects as blood pressure and heart rate remained unchanged. In conclusion, DM2 plays an analgesic role in vivo and changes RVM cell activity, consistent with antinociception. These effects were even more potent than those elicited by ethosuximide treatments.     

大鼠中脑水管周灰质腹外侧部的细胞构筑差异(Ⅰ)形态计量学分析

采用形态计量学方法,分析了大鼠中脑水管周灰质(PAG)腹外侧部内侧区(Mo),外侧区内(L_1)、中(L_2)、外(L_3)三带的细胞构筑差异。PAG 腹外侧部神经元有多极、三角形、梭形和卵圆形4种基本细胞类型,根据胞体直径,每型神经元又分为大(16—22μm)、中(8—16μm)、小(<8μm)3种。由Mo 至L_3,每单位体积组织内神经元数量逐渐增加,在细胞分类上主要为大、中神经元增加。93.3%的大神经元和76.4%的中神经元分布在L_3和L_2,Mo 无大神经元分布.胶质细胞数量亦表现增多,但胶质细胞/神经无比值下降。上述结果表明PAG 腹外侧部各区、带之间存在构筑差异,L_3、L_2可能是功能较活跃区域。     

µ1‐Opioid receptors in the dorsomedial and ventrolateral columns of the periaqueductal grey matter are critical for the enhancement of post‐ictal antinociception

Generalised tonic and tonic–clonic seizures are followed by significant increase in nociceptive thresholds in both laboratory animals and humans. The endogenous opioid peptides play a role in antinociceptive signalling, and the periaqueductal grey matter (PAG) is recruited to induce analgesia. Thus, the aim of this investigation was to evaluate the role of µ₁‐opioid receptors in the dorsomedial (dm) and ventrolateral (vl) columns of PAG in post‐ictal antinociception. Pentylenetetrazole (PTZ; 64 mg/kg), which is an ionotropic GABA‐mediated Cl^? influx antagonist, was intraperitoneally (IP) administered to induce tonic–clonic seizures in Wistar rats. The tail‐flick test was used to measure the nociceptive threshold. Microinjections of naltrexone (5.0 µg/0.2 µL), which is a non‐selective opioid receptor antagonist, in both dmPAG and vlPAG decreased the tonic–clonic seizure‐induced antinociception in seizing animals from 10 to 120 min after seizures. Furthermore, microinjections of the µ₁‐opioid receptor‐selective antagonist naloxonazine (5.0 µg/0.2 µL) into the dmPAG decreased post‐ictal antinociception immediately after convulsive reactions and from 10 to 90 min after seizures. However, vlPAG‐pretreatment with naloxonazine at the same concentration decreased the post‐ictal antinociception 30 min after the onset of tonic–clonic seizures and the nociceptive threshold returned to basal values 120 min after seizures. These findings indicate that µ₁‐opioid receptor‐signalling mechanisms in both dmPAG and vlPAG play a relevant role in the organisation of post‐ictal antinociception. In addition, µ₁‐opioid receptors in the dmPAG rather than in vlPAG seem to be more critically recruited during the antinociception induced by generalised tonic–clonic seizures.     

韩氏针刺对海洛因依赖大鼠PAG神经元单位放电的影响

目的初步探讨韩氏针刺对海洛因依赖大鼠PAG神经元单位放电的影响及其作用机制。方法将36只大鼠随机分为对照组、模型组和针刺组,每组12只,模型组和针刺组按逐日递增的原则皮下注射海洛因建立成瘾模型。玻璃微电极记录模型大鼠及针刺治疗后大鼠PAG神经元单位放电的变化。结果 PAG神经元单位放电有单个不匀、束簇状和混合型三种形式,模型组混合型、中频放电所占比例显著高于对照组（P〈0.05）,针刺组放电形式及放电频率接近对照组,与模型组相比有差异（P〈0.05）。结论韩氏针刺治疗可以部分恢复由于海洛因依赖导致的大鼠神经元单位放电变化,为海洛因戒断治疗提供了理论依据。