吗啡短期戒断时大鼠伏核TRPV1受体对兴奋性突触后电流调节功能的变化

目的：研究吗啡短期戒断后,TRPV1受体功能变化对大鼠伏核中等大小有棘神经元接受的自发性兴奋性突触后电流的影响。方法：20只sD大鼠随机分配为对照组和吗啡组,每天分别接受10mg·kg-1的盐酸吗啡和生理盐水腹腔注射,连续5d。在自然戒断的d3制作伏核脑片,采用红外可视全细胞膜片钳记录技术,检测对照组和吗啡组大鼠的TRPV1受体功能变化对伏核中等大小有棘神经元接受的自发性兴奋性突触后电流的频率及幅度的影响。结果：（I）脑片灌流足量TRPV1受体激动剂capsaicin（CAP）后,对照组和吗啡组自发性兴奋性突触后电流的频率分别为基线水平的138．9±s5．3（％）和176．3±s8．8（％）,两组差异显著（P〈0．05）;幅度分别为基线水平的的101．9±s2．2（％）和103．9±s2．3（％）,无显著差异（P〉0．05）。（2）吗啡组脑片依次灌流TRPV1受体拮抗剂capsazepine（CPZ）及激动剂CAP后,记录到自发性兴奋性突触后电流的频率分别为基线水平的99．1±s1．8（％）和101．2±s0．9（％）,两组无显著差异（P〉0．05）。结论：大鼠反复吗啡暴露短期戒断时伏核TRPV1受体功能增强。     

丁螺环酮对吗啡戒断焦虑大鼠海马、杏仁核突触结构可塑性和CaMKⅡ的影响

目的獉獉:探讨丁螺环酮治疗吗啡依赖戒断焦虑的细胞和分子机制。方法獉獉:66只雄性SD大鼠随机分为生理盐水对照组(对照组)、吗啡戒断焦虑组(模型组)、丁螺环酮治疗组(治疗组)。吗啡剂量递增皮下注射10 d自然戒断,于戒断1-3 d丁螺环酮灌胃治疗行高架十字迷宫实验后,取海马CA3区和杏仁核组织,用电镜体视学方法定量检测其各组突触的数密度(Nv)、面密度(Sv)、突触连接带平均面积(S),Western-blot技术检测其CaMKⅡ的含量和磷酸化水平。结果獉獉:与模型组比较,治疗组大鼠进入开放臂的次数和时间明显增加(P<0.01或P<0.05);海马CA3区和杏仁核突触的Nv和Sv显著降低、S增加(P<0.01或P<0.05),CaMKⅡ蛋白含量和β亚基磷酸化水平显著下调(P<0.01或P<0.05)。结论獉獉:逆转吗啡戒断焦虑大鼠海马、杏仁核突触结构的可塑性和CaMKⅡ分子的变化可能是丁螺环酮缓解吗啡戒断焦虑的重要细胞和分子机制。     

PTD-BDNF对海马神经元兴奋性突触活动的作用*

［摘要］　目的：研究具有跨血脑屏障功能的PTD-BDNF对培养海马神经元细胞自发电活动的作用。方法：应用全细胞膜片钳技术,观察脑源性神经营养因子(BDNF)和蛋白转导结构域-脑源性神经营养因子(PTD-BDNF)对原代培养大鼠海马神经元自发突触活动的影响。结果：与对照组比较，BDNF与PTD-BDNF作用后均可明显增加海马神经元自发兴奋性突触后电流(sEPSC)和微小兴奋性突触后电流(mEPSC)的产生频率［sEPSC的频率：(1.4±0.5)vs(4.0±0.6)，(3.9±0.5)Hz，均为P<0.01；mEPSC的频率：(4.2±1.0)vs(7.9±1.9)，(7.6±1.8) Hz,均为P<0.01］，并增加sEPSC的幅度但并不影响mEPSC的幅度［sEPSC的幅度：(415.7±48.0)vs(743.7±95.7)，(693.7±99.9)pA，均为P<0.01；mEPSC的幅度：(34.7±4.7)vs(36.3±6.2)，(36.2±4.4)pA，均为P>0.05］。BDNF与PTD-BDNF两者之间比较差异均无统计学意义(P>0.05)。结论：PTD-BDNF可以增强大鼠海马神经元兴奋性突触活动，说明重组PTD-BDNF与BDNF有相似的电生理活性。     

粉防己碱对大鼠吗啡戒断反应的影响

目的:研究钙拮抗剂粉防己碱 (Tet)对大鼠吗啡戒断反应的影响。方法··:以剂量递增法形成吗啡依赖模型 ,用纳洛酮催促戒断 ,戒断症状按柳田知司评分法给予评分。结果··:吗啡阳性组戒断症状分值为26.5±s7.1;Tet(30mg·kg-1) +吗啡组和Tet(60mg·kg-1) +吗啡组的戒断症状分值分别为 :11.7±s4.6、6.6±s4.3 ,与吗啡阳性组相比有极显著性差异 (P<0.001)。结论··:Tet能抑制吗啡大鼠依赖的戒断症状。     

吗啡依赖及戒断大鼠下丘脑前阿黑皮素原mRNA的变化

目的··:观察大鼠吗啡依赖和戒断状态下脑内前阿黑皮素原 (POMC )mRNA的变化。方法·· :采用腹腔注射法 ,按剂量递增原则建立大鼠吗啡依赖动物模型 ,同时建立生理盐水对照组。吗啡依赖大鼠随机分为依赖组和戒断组。对照组和依赖组动物于末次注射后3h ,戒断组大鼠于末次注射后72h迅速断头处死取脑 ,收集各个脑区组织总RNA标本。以POMC反义RNA探针对得到的RNA标本进行NorthernBlot印迹杂交 ,用电子计算机图像处理系统对所得结果进行分析。结果·· :吗啡依赖大鼠下丘脑POMCmRNA的表达仅为生理盐水对照组的69.56%±s4.7 % ,戒断72h状态下的吗啡依赖大鼠下丘脑POMCmRNA的表达恢复至生理盐水对照组的78.26 %±s5.3 % ;海马、纹状体和垂体POMCmRNA表达均为阴性。结论··:吗啡依赖大鼠下丘脑POMCmRNA的表达较生理盐水对照组有显著下降 ,戒断72h状态下的吗啡依赖大鼠其下丘脑POMCmRNA的表达较依赖组大鼠有显著回升 ,但仍显著低于正常组水平。此结果从分子生物学水平证实阿片类药物依赖机制与其引起内源性阿片肽系统功能变化有关     

慢性吗啡处理及戒断对大鼠不同脑区突触素ⅠmRNA表达水平的影响

目的 :探讨慢性吗啡处理及戒断对大鼠中脑腹侧被盖区 (VTA)、伏隔核 (NAc)、中脑导水管灰质 (PAG)、杏仁核 (AMG)、海马CA1区 (HIPCA1)突触素ⅠmRNA表达水平的影响。方法 :吗啡组大鼠ip吗啡 10d ,每日两次 ,剂量递增 ,对照组大鼠注射等量生理盐水。于末次注射后 3h及 72h处死 ,取脑并做冰冻切片。利用原位杂交技术检测各脑区突触素ⅠmRNA的水平并作同期比较。结果 :3h处死时 ,吗啡组大鼠突触素ⅠmRNA表达水平在VTA显著高于同期对照 (P <0 .0 1) ,在NAc、HIPCA1显著低于同期对照 (P <0 .0 5 )。自然戒断 72h时 ,吗啡组大鼠突触素ⅠmRNA表达水平在VTA仍显著高于同期对照 (P <0 .0 1) ,在AMG、HIPCA1显著低于同期对照(P <0 .0 5 )。结论 :吗啡慢性处理及戒断大鼠突触素ⅠmRNA表达在不同脑区有选择性的改变 ,可能是阿片依赖及戒断的分子机制之一     

慢性吗啡处理及戒断对大鼠不同脑区突触素ImRNA表达水平的影响

目的 :探讨慢性吗啡处理及戒断对大鼠中脑腹侧被盖区 (VTA)、伏隔核 (NAc)、中脑导水管灰质 (PAG)、杏仁核 (AMG)、海马CA1区 (HIPCA1)突触素ⅠmRNA表达水平的影响。方法 :吗啡组大鼠ip吗啡 10d ,每日两次 ,剂量递增 ,对照组大鼠注射等量生理盐水。于末次注射后 3h及 72h处死 ,取脑并做冰冻切片。利用原位杂交技术检测各脑区突触素ⅠmRNA的水平并作同期比较。结果 :3h处死时 ,吗啡组大鼠突触素ⅠmRNA表达水平在VTA显著高于同期对照 (P <0 .0 1) ,在NAc、HIPCA1显著低于同期对照 (P <0 .0 5 )。自然戒断 72h时 ,吗啡组大鼠突触素ⅠmRNA表达水平在VTA仍显著高于同期对照 (P <0 .0 1) ,在AMG、HIPCA1显著低于同期对照(P <0 .0 5 )。结论 :吗啡慢性处理及戒断大鼠突触素ⅠmRNA表达在不同脑区有选择性的改变 ,可能是阿片依赖及戒断的分子机制之一     

一氧化氮合酶抑制剂抑制吗啡依赖及戒断大鼠脊髓神经元ERK的表达

目的探讨鞘内分别注射非选择性一氧化氮合酶(NOS)抑制剂L-NAME、选择性神经元型一氧化氮合酶(nNOS)抑制剂7-硝基吲哚(7-NI)对吗啡戒断大鼠戒断症状和痛敏行为以及脊髓神经元p-ERK表达的影响。方法采用吗啡依赖及戒断模型,分为正常对照组、依赖组、戒断组、L-NAME组(L-NAME)、7-NI组(7-NI),分别作行为学评分(n=8)、免疫组织化学(n=6)和免疫印迹检测(n=4)。结果实验结果表明,①鞘内注射L-NAME、7-NI可明显减轻吗啡依赖大鼠戒断症状,戒断组戒断症状评分为28.6±4.89,L-NAME组、7-NI组分别为22.1±4.52(P<0.05)、16.2±3.99(P<0.01);戒断组促诱发痛评分(touch evoked agitationscores,TEA score)为13.5±2.55,L-NAME组、7-NI组分别为9.8±3.11(P<0.05)、7.5±2.56(P<0.01)。②鞘内注射L-NAME、7-NI可明显减少胸腰段脊髓背角Fos阳性神经元的数目,L-NAME组、7-NI组分别为293±47、267±52,均低于戒断组(380±71,P<0.05,P<0.01)。③L-NAME、7-NI组p-ERK阳性神经元的数目分别为46.8±11.58、40.5±8.55,均低于戒断组(66.6±11.6,P<0.05,P<0.01),两给药组脊髓p-ERK蛋白的表达也减少。④W estern b lot显示:鞘内注射NOS明显抑制吗啡戒断大鼠脊髓p-ERK蛋白表达增加。结论脊髓水平NO参与吗啡依赖和戒断反应,ERK信号通路可能介导NO的上述作用。     

褪黑素对吗啡戒断大鼠脑脊液和血浆中cAMP水平抑制的影响

目的·· :探讨褪黑素(melatonin,MT)抑制吗啡戒断反应的作用及其与脑脊液(CSF)和血浆中cAMP含量的关系。方法··:建立吗啡依赖大鼠自然戒断模型 ,脑室插管及放免测定吗啡依赖大鼠CSF和血浆中cAMP含量。结果·· :(1)MT对大鼠吗啡戒断反应有明显的抑制作用;(2)吗啡依赖大鼠CSF中(20.07pmol·ml-1±s4.62pmol·ml-1)和血浆中(76.40pmol·ml-1±s8.71pmol·ml-1)cAMP含量均低于正常大鼠,P<0.01 ;吗啡戒断大鼠CSF中(38.19pmol·ml-1±s6.62pmol·ml-1)和血浆中(96.65pmol·ml-1±s5.32pmol·ml-1)cAMP含量则明显高于吗啡依赖大鼠,P<0.001;(3)MT可使吗啡戒断大鼠CSF中(23.28pmol·ml-1±s4.10pmol·ml-1)和血浆中(61.72pmol·ml-1±s3.49pmol·ml-1)cAMP含量明显降低,P<0.01和P<0.001。结论·· :MT可抑制大鼠吗啡戒断反应 ,并与MT降低CSF和血浆中cAMP的含量有关。     

大鼠远位触液神经元一氧化氮合酶的表达及其与吗啡戒断的关系

目的观测神经元型一氧化氮合酶(nNOS)在大鼠远位接触脑脊液神经元(CSF-CNs)中的表达,探索nNOS远位触液神经元在吗啡依赖和戒断形成过程中的作用。方法♂成年SD大鼠(260±20)g,侧脑室引入30%霍乱毒素亚单位B与辣根过氧化物酶复合物(CB-HRP)追踪定位鉴别远位触液神经元。取材相关部位,连续冠状冰冻切片,TMB-ST法行CB-HRP呈色反应,进一步nNOS免疫组织化学双重标记。行为学观测并计数各组动物相同层面脑片上CB-HRP和CB-HRP/nNOS两种标记细胞的表达情况。结果戒断组大鼠,戒断症状及总评分较对照组和吗啡依赖组大鼠差异有显著性(P<0.01);给NOS抑制剂组戒断症状评分较戒断组明显降低(P<0.05)。各组动物脑片恒定部位出现CB-HRP阳性标记神经元,差异无显著性。正常组、对照组及依赖组计数到约3%~8.0%的CB-HRP/nNOS双标记神经元,差异无显著性;戒断组大鼠计数到56.9%的CB-HRP/nNOS双标记神经元,较对照组及依赖组明显增加(P<0.01);NOS抑制剂组大鼠计数到32.0%CB-HRP/nNOS双标记神经元,较戒断组CB-HRP/nNOS双标记神经元明显减少(P<0.05)。结论大鼠脑实质内存在nNOS远位触液神经元,nNOS远位触液神经元可能参与了吗啡戒断的形成。     

Activation of cannabinoid CB1 and CB2 receptors suppresses neuropathic nociception evoked by the chemotherapeutic agent vincristine in rats

BACKGROUND AND PURPOSE: The ability of cannabinoids to suppress mechanical hypersensitivity (mechanical allodynia) induced by treatment with the chemotherapeutic agent vincristine was evaluated in rats. Sites of action were subsequently identified. EXPERIMENTAL APPROACH: Mechanical hypersensitivity developed over the course of ten daily injections of vincristine relative to groups receiving saline at the same times. Effects of the CB1/CB2 receptor agonist WIN55,212-2, the receptor-inactive enantiomer WIN55,212-3, the CB2-selective agonist (R,S)-AM1241, the opiate agonist morphine and vehicle on chemotherapy-induced neuropathy were evaluated. WIN55,212-2 was administered intrathecally (i.t.) or locally in the hindpaw to identify sites of action. Pharmacological specificity was established using competitive antagonists for CB1 (SR141716) or CB2 receptors (SR144528). KEY RESULTS: Systemic administration of WIN55,212-2, but not WIN55,212-3, suppressed vincristine-evoked mechanical allodynia. A leftward shift in the dose-response curve was observed following WIN55,212-2 relative to morphine treatment. The CB1 (SR141716) and CB2 (SR144528) antagonists blocked the anti-allodynic effects of WIN55,212-2. (R,S)-AM1241 suppressed vincristine-induced mechanical hypersensitivity through a CB2 mechanism. Both cannabinoid agonists suppressed vincristine-induced mechanical hypersensitivity without inducing catalepsy. Spinal sites of action are implicated in cannabinoid modulation of chemotherapy-induced neuropathy. WIN55,212-2, but not WIN55,212-3, administered i.t. suppressed vincristine-evoked mechanical hypersensitivity at doses that were inactive following local hindpaw administration. Spinal coadministration of both the CB1 and CB2 antagonists blocked the anti-allodynic effects of WIN55,212-2. CONCLUSIONS AND IMPLICATIONS: Cannabinoids suppress the maintenance of vincristine-induced mechanical allodynia through activation of CB1 and CB2 receptors. These anti-allodynic effects are mediated, at least in part, at the level of the spinal cord.     

Differential cross-tolerance development between single and repeated immobilization stress on the antinociceptive effect induced by β-endorphin, 5-hydroxytryptamine,morphine, and WIN55,212-2 in the inflammatory mouse pain mode

We have evaluated the possible underlying mechanisms of immobilization stress-induced analgesia (SIA) by behavioral cross-tolerance studies and molecular studies. In the behavioral studies, the cross-tolerance between single or repeated immobilization SIA and the antinociceptive effects of β-endorphin, morphine, 5-hydroxytryptamine (5-HT), or WIN55,212-2 were assessed. Both single and repeated (×7) immobilization stress significanly attenuated the β-endorphin and 5-hydroxytryptamine-induced antinociception in the 2nd phase of formalin response, respectively. However, these cross-tolerances disappeared in prolonged repetition of the stress (×14). Neither single nor repeated (×7 and ×14) immobilization stress affected the antinociceptive effect of morphine or WIN55,212-2 at all. We also found that immobilization stress activated hypothalamic proopiomelanocortin (POMC) gene and β-endorphin expression. Since, it has potent inhibitory activity on the noxious stimuli-induced POMC expression, immobilization stress seemed to dissipate the POMC gene expression process. Meanwhile, we did not find any changes in the opioid receptors’ (mu-, delta- and kappa-receptor) and the cannabinoid receptors’ (CB1 and CB2) expressions in the midbrain regions elicited by single or repeated stress. These results suggested that a single immobilization stress activates the descending pain modulatory system, which is mainly mediated through endorphinergic and serotonergic activation. Moreover, the tolerance of SIA induced by repeated stresses may be due to the prolonged activation of these systems induced by repeated immobilization.     

Inhibitory effects of cannabinoid receptor ligands on electrically-evoked responses in rat isolated tracheal ring segments.

We have examined the possible existence of cannabinoid receptors in the isolated rat tracheal ring segments by studying the effects of some cannabinoid receptor ligands on electrically-induced contractions. Anandamide (10(-8)-3 x 10(-5)m), an endogenous ligand for cannabinoid receptors, and WIN 55,212-2 (10(-9)-3 x 10(-5)m), a moderately selective CB(2)agonist, inhibited electrically evoked contractions of the rat tracheal ring segments in a concentration-related manner. Addition of phentolamine (10(-6)m) to Krebs Henseleit solution to block alpha(2)-adrenoceptors did not affect anandamide-induced inhibition of the electrically evoked contractions. The EC(25)(-log m) values were 5.25+/-0.2 and 5.8+/-0. 4 for anandamide and WIN 55,212-2, respectively. The maximal inhibition produced by the highest concentration of the agonists used was 51.4+/-5.8% for anandamide and 35.1+/-19.5% for WIN 55, 212-2. WIN 55,212-3 also produced a concentration-dependent inhibition of the electrically evoked contractions. The maximal inhibition produced by WIN 55,212-3 was 15.8+/-2.4. The inhibitory effects of anandamide and WIN 55,212-2 were not attenuated by SR141716A (10(-6)m), a selective CB(1)receptor antagonist. Anandamide (10(-8)-3 x 10(-5)m) did not relax rat tracheal ring segments pre-contracted with carbachol (10(-6)m). These results suggest that anandamide and WIN 55,212-2 produce pre-junctional inhibitory effects in the rat trachea and that these effects were likely mediated through cannabinoid CB(2)receptors. These effects were probably non-cannabinoid receptor-mediated considering the high concentrations of the agents required to produce inhibitory responses and the effectiveness of WIN 55,212-3.     

Cannabinoid CB1 receptor-mediated inhibition of acetylcholine release in the brain of NMRI, CD-1 and C57BL/6J mice

Cannabinoid CB1 receptors occur as presynaptic receptors producing inhibition of neurotransmitter release. To elucidate their physiological role, experiments on tissues from CB1 receptor knockout mice would be helpful. We studied whether CB1 receptor-mediated inhibition of acetylcholine release is detectable in the brain of NMRI mice and of CD-1 and C57BL/6J mice (the latter two strains representing the wild-type strains of the two CB1 receptor knockout mouse models). Brain slices preincubated with [3H]choline were superfused and tritium overflow was evoked electrically (3 Hz) or by introduction of Ca2+ into Ca2+-free K+-rich medium (35 mM) containing tetrodotoxin. The eletrically evoked tritium overflow from NMRI mouse hippocampal slices was inhibited (maximally by 60%) by the cannabinoid receptor agonists CP-55,940 and WIN 55,212-2 but not affected by WIN 55,212-3 (the inactive enantiomer of WIN 55,212-2; pEC50=7.9, 7.4 and <5.5). The concentration-response curve of WIN 55,212-2 was shifted to the right by the CB1 receptor antagonist SR 141716 (apparent pA2=8.6). Compared to hippocampal slices from NMRI mice, WIN 55,212-2 1 microM inhibited the electrically evoked overflow (1) from cortical slices from NMRI mice to a lesser extent and from striatal slices not at all, (2) from hippocampal slices from CD-1 and C57BL/6J mice to an identical extent and (3) from hippocampal slices from Sprague-Dawley rats to at least the same extent. SR 141716 0.32 microM abolished the effect of WIN 55,212-2 1 microM in hippocampal slices from NMRI, CD-1 and C57BL/6J mice and in cortical slices from NMRI mice. The electrically evoked tritium overflow from NMRI mouse hippocampal slices was also inhibited by the muscarinic receptor agonist oxotremorine (maximum effect of 85%; pEC50=6.5) and this effect was antagonized by the muscarinic receptor antagonist AF-DX 384 (apparent pA2=8.3). The Ca2+-evoked tritium overflow from NMRI mouse hippocampal slices was inhibited by WIN 55,212-2 in a manner sensitive to SR 141716. In conclusion, the cholinergic axon terminals of the NMRI mouse hippocampus are endowed with presynaptic CB1 receptors. Such receptors are also detectable in the hippocampus of CD-1 and C57BL/6J mice. The maximum extent of the CB1 receptor-mediated inhibition of acetylcholine release is lower than the maximum effect mediated via the autoreceptor.     

Cross-sensitization and cross-tolerance between exogenous cannabinoid antinociception and endocannabinoid-mediated stress-induced analgesia

Footshock stress induces both endocannabinoid mobilization and antinociception. The present studies investigated behavioral plasticity in cannabinoid antinociceptive mechanisms following repeated activation using the tail-flick test. A secondary objective was to ascertain whether blockade of stress antinociception by the CB(1) antagonist rimonabant could be attributed to changes in locomotor activity. The cannabinoid agonist WIN55,212-2 induced hypoactivity in the open field relative to vehicle-treated controls. By contrast, rimonabant, administered at a dose that virtually eliminated endocannabinoid-mediated stress antinociception, failed to alter locomotor behavior (i.e. time resting, ambulatory counts, distance traveled) in rats subjected to the same stressor. Rats exposed acutely to footshock were hypersensitive to the antinociceptive effects of WIN55,212-2 and Delta(9)-tetrahydrocannabinol (Delta(9)-THC). The converse was also true; acute Delta(9)-THC and WIN55,212-2 administration potentiated stress antinociception, suggesting a bidirectional sensitization between endocannabinoid-mediated stress antinociception and exogenous cannabinoid antinociception. Stress antinociception was also attenuated following chronic relative to acute treatment with WIN55,212-2 or Delta(9)-THC. Repeated exposure to footshock (3 min/day for 15 days), however, failed to attenuate antinociception induced by either footshock stress or WIN55,212-2. Our results demonstrate that endocannabinoid-mediated stress antinociception cannot be attributed to motor suppression. Our results further identify a functional plasticity of the cannabinoid system in response to repeated activation. The existence of cross-sensitization between endocannabinoid-mediated stress antinociception and exogenous cannabinoid antinociception suggests that these phenomena are mediated by a common mechanism. The observation of stress-induced hypersensitivity to effects of exogenous cannabinoids may have clinical implications for understanding marijuana abuse liability in humans.     

Suppression by baclofen of the stimulation of alcohol intake induced by morphine and WIN 55,212-2 in alcohol-preferring rats

Administration of morphine and cannabinoids stimulates alcohol intake in rats. The present study investigated whether the promoting effect of morphine and of the cannabinoid receptor agonist, WIN 55,212-2 [(R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone], on alcohol intake was prevented by the gamma-aminobutyric (GABA)(B) receptor agonist, baclofen. Sardinian alcohol-preferring (sP) rats were given alcohol (10%, v/v) and water under the standard homecage two-bottle-free choice regimen with unlimited access for 24 h/day. Baclofen (0, 0.5 and 1 mg/kg; i.p.) was administered acutely 30 min before lights off. Morphine (0 and 1 mg/kg, s.c.) or WIN 55,212-2 (0 and 2 mg/kg, i.p.) was administered acutely 10 min after baclofen. Alcohol intake was recorded 60 min after lights off. As predicted, both morphine and WIN 55,212-2 produced a specific and marked increase in alcohol intake. Pretreatment with baclofen, which failed to alter alcohol intake when given alone, dose-dependently suppressed morphine- and WIN 55,212-2-induced promotion of alcohol drinking. These results suggest the involvement of the GABA(B) receptor in the neural circuitry mediating the stimulating effect of morphine and cannabinoids on alcohol consumption in sP rats.     

Inhibitory effect of the cannabinoid receptor agonist WIN 55,212-2 on pentagastrin-induced gastric acid secretion in the anaesthetized rat

The effect of the cannabinoid (CB) receptor agonist WIN 55,212-2 on gastric acid secretion was studied in the anaesthetized rat after stimulation with pentagastrin. WIN 55,212-2 (0.5-2 mg/kg, i.v.) was inactive on basal secretion but caused a marked inhibition (80%) of the acid secretion stimulated by pentagastrin (10 microg/kg, i.v.). The enantiomer WIN 55,212-3 (1-3 mg/kg, i.v.) did not significantly modify basal or pentagastrin-induced acid secretion. The inhibitory effect of WIN 55,212-2 against pentagastrin was prevented by the administration of the selective cannabinoid CB1 receptor antagonists SR141716A (1 mg/kg, i.v.) and LY320135 (1 mg/kg, i.v.); by contrast, the CB2 receptor antagonist SR144528 (0.3-1 mg/kg, i.v.) was without effect. The selective CB2 receptor agonist JWH-015 (0.1-10 mg/kg, i.v.) was inactive on the increase of acid output stimulated by pentagastrin. These results suggest that the inhibitory effect of WIN 55,212-2 on pentagastrin-stimulated acid secretion in the anaesthetized rat is mediated by specific cannabinoid receptors. Moreover, the antagonism of WIN 55,212-2-induced effects by the selective CB1 receptor antagonists SR141716A and LY320135 together with the ineffectiveness of both the CB2 receptor agonist JWH-015 and the CB2 receptor antagonist SR144528 indicate that CB1 receptor subtypes are predominantly involved in the antisecretory effect of WIN 55,212-2.     

Pre-emptive antinociceptive effects of a synthetic cannabinoid in a model of neuropathic pain

The antinociceptive effects of WIN55,212-2, a synthetic cannabinoid, were evaluated in the model of partial sciatic nerve ligation after daily subcutaneous administration of 0.1 mg/kg a week before and two weeks after surgery. Mechanical allodynia and thermal hyperalgesia were evaluated in 46 rats allocated to receive: (1) Vehicle (before surgery)-Vehicle (after surgery); (2) Vehicle-WIN55,212-2; (3) WIN55,212-2-Vehicle; (4) WIN55,212-2-WIN55,212-2; (5) AM251+vehicle; (6) AM251+WIN55,212-2; (7) AM630+vehicle; (8) AM630+WIN55,212-2; (9) Sham receiving vehicle; and (10) Sham receiving WIN55,212-2. The decreased in mechanical allodynia and thermal hyperalgesia by WIN55,212-2 was significantly greater when it was administered during one week before surgery. In conclusion, pre-emptive use of cannabinoids produced greater antinociceptive effects in a model of neuropathic pain and this effect is mediated by cannabinoid CB(1) and CB(2) receptors.     

Modulation by female sex hormones of the cannabinoid-induced catalepsy and analgesia in ovariectomized mice

Cannabinoids are psychoactive compounds with many pharmacological properties such as analgesia, sedation and catalepsy most of which are mediated by cannabinoid CB1 receptors. In the present study, we evaluated whether the ovarian sex hormones are involved in the cannabinoid-induced catalepsy and analgesia in ovariectomized female mice. Female NMRI mice (weighing 25-30 g) were divided into 3 main groups: unoperated, sham-operated and ovariectomized. Both the catalepsy and analgesia induced by different doses of the synthetic cannabinoid WIN 55,212-2 (2 and 4 mg/kg, i.p.) were examined in the groups in the presence or absence of the cannabinoid CB1 antagonist AM251 (0.5 mg/kg). We also evaluated effects of estradiol valerate (10 mg/kg) and progesterone (25 mg/kg) on catalepsy and analgesia induced by WIN 55,212-2 in ovariectomized mice. The antinociceptive effect of WIN 55,212-2 was significantly (P<0.01) enhanced in ovariectomized mice, which was prevented by pretreatment with estradiol but not by progesterone. There was no significant difference in the cannabinoid-induced catalepsy between control and ovariectomized mice. However, pretreatment with progesterone but not estradiol potentiated the cataleptic effect of low dose of WIN 55,212-2 (2 mg/kg) in ovariectomized mice (P<0.01). The present data demonstrated for the first time that ovarian sex steroids could modulate both cannabinoid-induced catalepsy and analgesia in female ovariectomized mice.     

Cannabinoid CB1-mediated inhibition of stress-induced gastric ulcers in rats

The effect of cannabinoid drugs (i.p.) on cold/restraint stress-induced gastric ulcers was studied in rats. The cannabinoid receptor agonist (WIN 55,212-2, 0.1-1 mg/kg), but not the less active isomer WIN 55,212-3 (1 mg/kg), reduced gastric ulceration. The protective effect of WIN 55,212-2 (1 mg/kg) was counteracted by the cannabinoid CB1 receptor antagonist SR141716A, but not by the cannabinoid CB2 receptor antagonist SR144528. These results indicate that the antiulcer effect of the cannabinoid receptor agonist WIN 55,212-2 is mediated by cannabinoid CB1 receptors.