Intrathecal carbachol and clonidine produce a synergistic antiallodynic effect in rats with a nerve ligation injury

PURPOSE: Antiallodynic effects have been demonstrated after intrathecal administration of alpha-2 adrenoceptor agonists and cholinesterase inhibitors in rats. Intrathecal carbachol also increases the activity of cholinergic receptor system at the spinal level. However, there is no study regarding the antagonism of carbachol on touch-evoked allodynia and the interaction with clonidine. This study examines the intrathecal interaction between two drugs in a rat model of nerve ligation injury. METHODS: Rats were prepared with tight ligation of the left L5-6 spinal nerves and chronic intrathecal catheter implantation. Tactile allodynia was measured by using application of von Frey filaments to the lesioned hindpaw. Carbachol (0.3-10 microg) and clonidine (1-30 microg) were administered to obtain the dose-response curves and the 50% effective dose (ED(50)) for each drug. Fractions of ED(50) values (1/2, 1/4, 1/8, and 1/16) were administered intrathecally to establish the ED(50) of the carbachol-clonidine combination. Isobolographic and fractional analyses of drug interaction were performed. RESULTS: Intrathecal carbachol and clonidine alone produced a dose-dependent reduction of tactile allodynia without severe motor weakness or sedation. A carbachol-clonidine combination produced a dose-dependent increase in withdrawal threshold of the lesioned hindpaw with a reduced incidence and magnitude of side effects. Both analyses revealed a synergistic interaction after the coadministration of carbachol and clonidine. CONCLUSIONS: This study indicates that carbachol, like clonidine, provides a moderate antagonism on touch-evoked allodynia at the spinal level. The results suggest that intrathecally administered carbachol is synergistic when combined with clonidine.     

The antiallodynic and antihyperalgesic effects of neurotropin in mice with spinal nerve ligation

Although Neurotropin(R) (NTP) has been used clinically as an analgesic in Japan for many years, its effect on neuropathic pain in animal models has not been examined in detail. Its main effect has been indicated to be activation of the descending monoaminergic pain inhibitory systems. To study the effect of NTP on neuropathic pain, we subjected mice to spinal nerve ligation. NTP inhibited both tactile allodynia and mechanical and thermal hyperalgesia in a dose-dependent manner. When the effect of NTP was examined after depletion of monoamines in the spinal cord by intrathecal neurotoxins, the antiallodynic and antihyperalgesic effects were still observed after serotonergic denervation, but not after noradrenergic denervation. In addition, intracerebroventricular NTP increased withdrawal threshold and latency although intrathecal or local administration of NTP did not. These results suggest that the antiallodynic and antihyperalgesic effect of NTP on neuropathic pain induced by spinal nerve ligation is mediated principally through the action at supraspinal sites and through activation of spinal noradrenergic systems, possibly via the descending inhibitory pathway.     

The interaction between intrathecal neostigmine and GABA receptor agonists in rats with nerve ligation Injury

Nerve ligation injury may produce a pain syndrome that includes tactile allodynia. Reversal effects on tactile allodynia have been demonstrated after the intrathecal administration of gamma-aminobutyric acid (GABA) receptor agonists or cholinesterase inhibitors in rats. We examined the drug interactions between neostigmine and muscimol or baclofen in a rat model of nerve ligation injury. Rats were prepared with tight ligation of the left L5-6 spinal nerves and chronic intrathecal catheter implantation. Tactile allodynia was measured by applying von Frey filaments ipsilateral to the lesioned hindpaw. Thresholds for paw withdrawal were assessed. Neostigmine (0.3-10 microg), muscimol (0.1-10 microg), and baclofen (0.1-3.0 microg) were administered to obtain the dose-response curve and the 50% effective dose (ED(50)). Fractions of ED(50) values were administered intrathecally to establish the ED(50)s of drug combinations (neostigmine-muscimol and neostigmine-baclofen). The drug interactions were performed. Intrathecal neostigmine, muscimol, baclofen, and their combinations produced a dose-dependent increase in withdrawal threshold of the lesioned hindpaw. Both analyses revealed a synergistic interaction for the neostigmine-muscimol combination, whereas the effect of the neostigmine-baclofen combination was additive. These results suggest that the activation of both muscarinic and GABA(A) receptors is required for synergistic interaction. IMPLICATIONS: This study indicates that drug interaction is synergistic for the neostigmine-muscimol combination, whereas the effect of the neostigmine-baclofen combination is additive. In a rat model of nerve ligation injury, neostigmine, muscimol, baclofen, and their combinations provide an antagonism on touch-evoked allodynia at the spinal level.     

Synergistic effect between intrathecal non-NMDA antagonist and gabapentin on allodynia induced by spinal nerve ligation in rats

BACKGROUND: Glutamate and non-N-methyl-D-aspartate (NMDA) receptors have been implicated in the development of neuroplasticity in the spinal cord in neuropathic pain. The spinal cord has been identified as one of the sites of the analgesic action of gabapentin. In the current study, the authors determined the antiallodynic effect of intrathecal 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) in a rat model of neuropathic pain. Also tested was a hypothesis that intrathecal injection of CNQX and gabapentin produces a synergistic effect on allodynia in neuropathic rats. METHODS: Allodynia was produced in rats by ligation of the left L5 and L6 spinal nerves. Allodynia was determined by application of von Frey filaments to the left hind paw. Through an implanted intrathecal catheter, 10-100 microg gabapentin or 0.5-8 microg CNQX disodium (a water-soluble formulation of CNQX) was injected in conscious rats. Isobolographic analysis was performed comparing the interaction of intrathecal gabapentin and CNQX using the ED50 dose ratio of 15:1. RESULTS: Intrathecal treatment with gabapentin or CNQX produced a dose-dependent increase in the withdrawal threshold to mechanical stimulation. The ED50 for gabapentin and CNQX was 45.9+/-4.65 and 3.4+/-0.22 microg, respectively. Intrathecal injection of a combination of CNQX and gabapentin produced a strong synergistic antiallodynic effect in neuropathic rats. CONCLUSIONS: This study shows that intrathecal administration of CNQX exhibits an antiallodynic effect in this rat model of neuropathic pain. Furthermore, CNQX and gabapentin, when combined intrathecally, produce a potent synergistic antiallodynic effect on neuropathic pain in spinal nerve-ligated rats.     

鞘内注射MRS2395对慢性坐骨神经结扎大鼠脊髓背角钙离子接头蛋白-1表达的影响

目的 观察鞘内注射P2Y12受体拮抗剂MRS2395对慢性坐骨神经结扎(CCI)大鼠热痛阈及脊髓背角钙离子接头蛋白-1(Iba1)表达变化的影响.方法 成年SD大鼠40只,随机均分为五组:假手术组(A组)、CCI模型组(鞘内注射生理盐水,B组)、CCI+鞘内注射MRS2395 1 pmol/L组(C组);CCI+鞘内注射MRS2395 10 pmol/L组(D组);CCI+鞘内注射MRS2395 100 pmol/L组(E组).B、C、D、E组大鼠均于鞘内置管5d之后行慢性坐骨神经结扎,分别连续14d鞘内注射生理盐水、MRS2395 1、10、100 pmol/L,2次/天,分别在术后第1、7、10、14天测定首次给药1h后的热缩足潜伏期(TWL);分别在第7、14天灌注大鼠取脊髓做冰冻切片,观察大鼠脊髓背角Iba1表达的变化.结果 术后第1、3、5、7、10、14天B、C、D、E组大鼠TWL明显短于A组,且C、D、E组TWL明显长于B组(P＜0.05).与A组相比,术后第7、14天B、C、D、E组Iba1阳性细胞个数、平均光密度值明显增加(P＜0.05).与B组比较,术后第7、14天C、D、E组脊髓背角Iba1阳性细胞数目明显减少,其平均光密度值明显降低(P＜0.05).结论 鞘内注射P2Y12受体拮抗剂MRS2395可以明显抑制CCI大鼠背角小胶质细胞激活和热痛敏症状,提示P2Y12受体拮抗剂可能通过抑制脊髓小胶质细胞的活化而发挥镇痛作用.     

大鼠股神经结扎损伤修复方法的实验研究

目的探讨股神经结扎后不同时期,分别采用缝线解除、缝线解除加神经外膜松解和结扎处股神经切除后吻合3种方法修复后的效果,为临床上修复医源性周围神经结扎损伤提供参考。方法健康成年SD雌性大鼠120只,体重(200±20)g,制备左侧股神经结扎动物模型后随机分为3组,每组40只。A组为缝线解除组,B组为缝线解除加神经外膜松解组,C组为结扎处股神经切除后吻合组;每组根据对股神经修复时间不同分为即时修复(0期)和1、3、5个月修复(分别为1、2、3期),每期各10只。每期修复术后3个月,检测大鼠运动功能(足基角、跟尾角)、神经电生理(股神经动作电位和传导速度)、股四头肌湿重,取股四头肌和股神经行组织学观察并计数肌纤维数量和神经纤维通过率。结果足基角:在0、1、2、3期,A组均显著低于C组(P<0.05),A、B组间差异均无统计学意义(P>0.05)。跟尾角:在0、1、2、3期,A组均显著低于C组(P<0.05);在1、2、3期,B组均显著低于C组(P<0.05)。股四头肌湿重:除1期外,B组均显著大于C组,差异有统计学意义(P<0.05);在0、2期,A组均显著大于C组(P<0.05);除3期A组显著小于B组(P<0.05)外,其余各期A、B组间比较差异均无统计学意义(P>0.05)。股神经动作电位:在0、1期,A组与B、C组比较,差异均有统计学意义(P<0.05);在2、3期,除3期A组显著高于C组(P<0.05)外,其余各组间比较差异均无统计学意义(P>0.05)。股神经传导速度:在0、1、3期,A组均显著高于C组(P<0.05);在0、1期A组均显著高于B组(P<0.05),在1、2期A、B组间比较差异无统计学意义(P>0.05);B组仅0期显著高于C组(P<0.05)。股四头肌肌纤维计数:在1、2期各组间差异均无统计学意义(P>0.05);在0期,A、B组均显著高于C组(P<0.05);在3期,A组显著高于B组(P<0.05)。股神经纤维通过率:除2期A组较B、C组增加(P<0.05)外,其余各期各组间比较差异均无统计学意义(P>0.05)。结论股神经结扎后,采用股神经缝线解除的修复效果最佳,其次是股神经缝线解除加神经外膜松解,而股神经结扎处神经切除后吻合效果最差。     

周围神经缺损神经移植修复对神经元细胞凋亡的影响

目的：应用移植神经的方法修复周围神经损伤,观察其对神经元的保护作用。方法：选用雄性SD大鼠30只。随机分成正常对照组、神经缺损组、神经损伤组、神经移植组,实验组每组9只大鼠,并按手术先后随机分成7、14、28d3个时间组。将大鼠左侧坐骨神经在梨状肌下缘碾挫或切除0．5cm,分别制备神经损伤或缺损动物模型,并采用神经原位移植的方法修复神经缺损。按术后不同时间处死动物。于术后7、14、28d取L4－6脊髓作TUNEL标记检测,标记凋亡的运动神经元数目。切片作HE、甲苯胺兰染色后计算脊髓内运动神经元的数目。结果：在术后28d,神经移植组的凋亡细胞明显少于另2组（U1＝2．10;U2＝2．89 P＜0．05）。各时间组的神经元数目,神经移植组明显多于另2组（t1=6.84;t2=6.95 P＜0．05）。结论：移植神经对周围神经损伤后的相应神经元,有一定的保护作用。     

Antiallodynic effects of systemic and intrathecal morphine in the spared nerve injury model of neuropathic pain in rats

BACKGROUND: The efficacy of opioids for neuropathic pain remains controversial. The effects of morphine on pain behavior were investigated in two animal models of neuropathic pain: the spared nerve injury (SNI) model and the spinal nerve ligation (SNL) model. METHODS: Nerve injuries were created in rats either by tight ligation and section of the left tibial and common peroneal nerves (SNI) or by unilateral ligation of L5 and L6 spinal nerves (SNL). Paw withdrawal threshold to mechanical stimuli was measured using the up-down method in the hairy and glabrous skin territories of the sural nerve for SNI rats or in the mid-plantar paw of SNL rats. RESULTS: Before SNI, the median paw withdrawal thresholds in hairy and glabrous skin were similar (26 g [25%, 75% quartiles: 26, 26 g]). The paw withdrawal threshold decreased after SNI in both hairy and glabrous skin (P < 0.001). Thirty days after the SNI, the threshold in hairy skin (0.3 g) was significantly lower than in glabrous skin (1.9 g; P < 0.001). In blinded experiments, both subcutaneous and intrathecal morphine (0.1-10 microg) dose-dependently attenuated mechanical allodynia induced by SNI measured in the hairy skin, an effect that was naloxone reversible. The ED50 for the intrathecal morphine was 0.52 microg (95% confidence interval, 0.31-0.90 microg). Morphine (1 microg intrathecal) attenuated SNI-induced mechanical allodynia in glabrous skin with potency similar to that in hairy skin. In SNL rats, morphine (30 microg intrathecal) almost completely reversed the SNL-induced mechanical allodynia. CONCLUSIONS: (1) SNI-induced mechanical allodynia is characterized by a lower paw withdrawal threshold in hairy versus glabrous skin; (2) systemic and intrathecal morphine reverse SNI-induced mechanical allodynia in a dose-dependent fashion; and (3) intrathecal morphine also reverses SNL-induced mechanical allodynia. These results suggest that intrathecal opioids are likely to be effective in the treatment of neuropathic pain.     

Magnesium chloride and ruthenium red attenuate the antiallodynic effect of intrathecal gabapentin in a rat model of postoperative pain

BACKGROUND: Gabapentin, a gamma-aminobutyric acid analog anticonvulsant, has been shown to possess antinociceptive effects in animal models and clinical trials. An endogenous binding site of [3H]gabapentin has been revealed to be the alpha(2)delta subunit of voltage-dependent Ca2+ channels. Magnesium chloride, ruthenium red, and spermine have been shown to modulate [3H]gabapentin binding to this binding site in vitro. In this study, the authors examined whether intrathecal magnesium chloride, ruthenium red, or spermine could affect the antiallodynic effect of intrathecal gabapentin in a rat model of postoperative pain. METHODS: Under isoflurane anesthesia, male Sprague-Dawley rats received an incision over the plantar surface of the right hind paw to produce punctate mechanical allodynia. Withdrawal thresholds to von Frey filament stimulation near the incision site were measured before incision, 2 h after incision, and every 30 min after intrathecal coadministration of gabapentin with normal saline or different doses of magnesium chloride, ruthenium red, or spermine for 2 h. RESULTS: Intrathecal gabapentin (30, 100, 200 microg) dose-dependently reduced incision-induced allodynia. Hexahydrated magnesium chloride (5, 10, 20 microg) and ruthenium red (0.2, 2, 20 ng) noncompetitively inhibited the antiallodynic effect of gabapentin. Spermine at doses not inducing motor weakness (30, 60 microg) did not affect the antiallodynic effect of gabapentin. The antiallodynic effect of intrathecal morphine (1.5 microg) was not affected by hexahydrated magnesium chloride (20 microg), ruthenium red (20 ng), or spermine (60 microg). CONCLUSIONS: These results provide behavioral evidence to support that the alpha(2)delta subunit of Ca2+ channels may be involved in the antiallodynic action of intrathecal gabapentin in the postoperative pain model.     

鞘内注射DREAM-shRNA对神经病理性痛大鼠的镇痛效应

目的 评价鞘内注射转录因子下游调控元件拮抗因子-短发夹RNA(DREAM-shRNA)对神经病理性痛大鼠的镇痛效应.方法 健康雄性SD大鼠,体重280-320g,采用坐骨神经慢性缩窄性损伤(CCI)法建立大鼠神经病理性痛模型,于CCI后第3天鞘内置管.取鞘内置管成功的大鼠24只,随机分为4组,每组6只,假手术组(Sham组):仅暴露坐骨神经,不结扎;神经病理性痛组(NP组):于CCI后第8天鞘内注射生理盐水10μl;RNA干扰组(RNAi组):于CCI后第8天鞘内注射含DREAM-shRNA的慢病毒5μl、生理盐水5μl;空白载体组(BV组):于CCI后第8天鞘内注射慢病毒空白载体5μl、生理盐水5μl,连续注射7d.于CCI前1d(基础状态)、CCI后第7～14天(T1-8)测定热痛阈和机械痛阈,于CCI后第15天测定脊髓背角绿色荧光蛋白(GFP)的表达水平.结果 与基础值比较,NP组和BV组热痛阈降低,Sham组T1-4时热痛阈降低,RNAi组T1-4,6时热痛阈降低,4组CCI后各时点机械痛阈降低(P<0.05或0.01);与T1时比较,NP组和BV组其余时点热痛阈和机械痛阈降低.RNAi组T3-5,时热痛阈降低,T1时热痛阈和机械痛阈升高(P<0.05或0.01);与Sham组比较.NP组和BV组热痛阈和机械痛阈降低,RNAi组T2时机械痛阈降低,T5时升高(P<0.05),热痛阈差异无统计学意义(P>0.05);与NP组比较.RNAi组热痛阈和机械痛阈升高(P<0.05).仅RNAi组脊髓背角有GFP表达,其余3组脊髓背角未见GFP表达.结论 鞘内连续注射DREAM-shRNA可在一定程度上缓解大鼠神经病理性痛.     

An obligatory role for spinal cholinergic neurons in the antiallodynic effects of clonidine after peripheral nerve injury

BACKGROUND: Indirect evidence supports a role of spinal cholinergic neurons in tonically reducing response to noxious mechanical stimulation and in effecting analgesia from alpha2-adrenergic agonists. This study directly assessed the role of cholinergic neurons in regulating the level of mechanical allodynia and in participating in the antiallodynic effect of the clinically used alpha2-adrenergic agonist, clonidine, in an animal model of neuropathic pain. METHODS: Allodynia was produced in rats by ligation of the left L5 and L6 spinal nerves. Rats received a single intrathecal injection of saline or one of three different doses of the cholinergic neurotoxin, ethylcholine mustard aziridinium ion (AF64-A; 2, 5, and 15 nmol). Seven days later, allodynia was assessed before and after intrathecal injection of 15 microg clonidine. The spinal cord was removed, and spinal cord acetylcholine content, cholinergic neuron number and distribution, and alpha2-adrenergic receptor expression were determined. RESULTS: AF64-A administration reduced both the number of cholinergic cells and the acetylcholine content of the lumbar dorsal spinal cord by 20-50% but did not affect level of mechanical allodynia. AF64-A did, however, completely block the anti-allodynic effect of clonidine. AF64-A did not reduce alpha2-adrenergic ligand binding in dorsal lumbar cord. CONCLUSIONS: These data suggest that spinal cholinergic tone does not affect the level of mechanical allodynia after peripheral nerve injury. There is a quantitative reliance on spinal cholinergic neurons in the allodynia relieving properties of intrathecal clonidine, and this reliance does not depend on alpha2-adrenergic receptors colocalized on spinal cholinergic interneurons.     

鞘内注射外源性神经生长因子对利多卡因致大鼠脊髓损伤的保护作用

目的 探讨鞘内注射外源性神经生长因子（nerve growth factor,NGF）对利多卡因致脊髓神经毒性损伤的保护作用.方法 选择鞘内置管成功的大鼠60只,按随机数字表法分为生理盐水对照组（S组）和NGF治疗组（N组）两个大组,每大组分为P0、P1、P8三个不同时点的亚组,每组10只.S组P0亚组：仅行假手术,S组P1亚组,鞘内注射20％盐酸利多卡因20 μl;S组P8亚组,鞘内注射20％盐酸利多卡因20μl,连续7d鞘内注射NS,每次注射0.9％NS 20 μl;N组P0亚组：仅行假手术;N组P1亚组：鞘内注射20％盐酸利多卡因20 μl;N组P8亚组：鞘内注射20％盐酸利多卡因20μl,连续7d鞘内注射NGF,每次注射NGF 10 μg/20μl..连续评测两组中P8亚组大鼠的热痛阈值（tail-flick latency,TFL）及运动功能评分（motor function,Mr）,观察比较两组大鼠各亚组光镜及透射电镜下脊髓的病理改变.结果 与S组P8亚组比较,在5d～8d4个时点N组P8亚组的TFL最大镇痛效应百分率（percent of maximal possible potential effect,％MPE）（％MPETFL）显著降低[（62.5±20.3）％vs（32.6±23.5）％,（51.9±23.7）％vs（25.8±26.3）％,（43.8±22.5）％vs（20.5±24.3）％,（38.4±25.7）％vs（18.5±23.7）％]（P＜0.05）;且MF评分显著降低[3vs0,3vs0,3 vs0,3vs0]（P＜0.05）.光镜病理改变：S组P8亚组脊髓后角白质广泛水肿、脊膜细胞大量增生、广泛空泡变性;N组P8亚组见后角白质神经纤维水肿,脊膜细胞少量增生,空泡变性不明显.透射电镜病理改变：S组P8亚组见有髓神经纤维的髓鞘板层结构广泛肿胀疏松,无髓神经纤维模糊不清;N组P8亚组见有髓神经纤维的髓鞘板层结构局部疏松,可见肿胀的无髓神经纤维.结论 鞘内注射NGF能够减轻利多卡因引起的脊髓毒性损伤,改善脊髓神经细胞的超微结构.     

鞘内注射芬太尼联合电针对慢性炎性痛大鼠的镇痛效果

目的探讨鞘内注射芬太尼联合电针对大鼠慢性炎性痛的镇痛效果及相关机制。方法采用完全弗氏佐剂(CFA)关节炎大鼠模型,将30只鞘内置管成功的成年SD雌性大鼠随机分为5组(n=6):对照组(A组,仅予以鞘内置管)、致炎组(B组,鞘内注射生理盐水25μl连续1周,1次／d)、电针组(C组,模型成功后第1天和第4天,采用电针仪电针大鼠“阳陵泉”和“足三里”两穴,强度≤2 mA,频率2／100Hz,时间30min)、芬太尼组(D组,鞘内注射25μl芬太尼,剂量1μg,1次/d,连续1周)和针药合用组(E组,处理与给药方法同C组、D组)。CFA致痛后第4天模型建立成功,开始电针刺激和给药处理。从给药第1天开始,每天9:00以热板法测量大鼠痛敏分数,连续观察7 d;于给药第7天,10％水合氯醛液按375 mg·kg-1腹腔麻醉大鼠,快速取出脊髓L4-6段,以毛细管电泳仪和免疫组化方法检测脊髓(L4-6)谷氨酸(GLU)含量及脊髓背角P物质(SP)表达。结果B组痛敏分数,脊髓(L4-6)谷氨酸含量和患侧腰髓背角SP的表达均比其它组增加(P<0．05);与C组及D组相比,E组痛敏分数,GLU含量和SP表达均降低(P<0．05)。结论鞘内注射芬太尼加强了电针的镇痛作用,针药合用减轻了慢性炎性痛所致的中枢敏化作用。     

Effects of intrathecal administration of FK506 after sciatic nerve crush injury

Although various administration routes of FK506 have been published, intrathecal administration of FK506 has not previously been reported in the literature. A daily dose of 0.05 mg/kg of FK506 was given (a small dose compared with those reported in the available literature). The authors used this small dose to obtain lower immunosuppression and neurotoxicity, and a higher axonal regeneration rate. A total number of 40 female Wistar rats were used and randomly divided into four groups: control, sham, FK506-treated, and vehicle-treated. Sciatic nerve regeneration was evaluated by walking track analysis, an electrostimulation test, and light microscopic evaluation. There was a statistically significant difference ( P < 0.05) between FK506-treated and vehicle-treated groups at the end of 6 weeks according to both the walking track analysis and the electrostimulation test. Comparing the stimulus thresholds of the sham and FK506-treated group, no significant difference ( P > 0.05) was observed. Evaluation of the data revealed that FK506 had a beneficial effect on sciatic nerve regeneration.     

The effect of intrathecal administration of magnesium sulphate in rats

Somatosensory evoked potential, locomotion and vocalisation upon tail pinch in rats was studied in order to determine whether intrathecal magnesium sulphate administration causes spinal anaesthesia. In Wistar rats with indwelling intrathecal catheters, cortical somatosensory evoked potential was recorded following stimulation via electrodes inserted into the hind paw under chloral hydrate anaesthesia before and after intrathecal administration of 10 μl of either magnesium sulphate (12.3% or 24.6%) or lignocaine (4% or 8%). Locomotion and vocalisation after tail pinch were tested following intrathecal administration of the same two drugs in conscious rats. Somatosensory evoked potential amplitude was diminished after administration of lignocaine (p < 0.05) but did not change after magnesium sulphate. Latency of P1 was increased by lignocaine and by magnesium sulphate 12.3% (p < 0.05). Although lower extremity paralysis was observed in both groups, its duration with magnesium sulphate was much longer than with lignocaine. Vocalisation was recognised after magnesium sulphate 12.3%, but was not observed after lignocaine 8% during paralysis (p < 0.05). We believe that magnesium sulphate caused motor paralysis, but not complete analgesia.