Pharmacokinetic/pharmacodynamic modeling of rocuronium in myasthenic patients is improved by taking into account the number of unbound acetylcholine receptors

Patients with myasthenia gravis are more sensitive than healthy patients to nondepolarizing neuromuscular blocking drugs. We performed a pharmacokinetic/pharmacodynamic modeling study of rocuronium in eight myasthenic patients and eight matched control patients. Patients were anesthetized with propofol and sufentanil and a mixture of nitrous oxide/oxygen. Mechanomyographical monitoring of the adductor pollicis was applied. Rocuronium was infused at a rate of 25 micro g. kg(-1). min(-1) in myasthenic patients and 116.7 micro g. kg(-1). min(-1) in control patients and was terminated at 70% neuromuscular block. Arterial blood samples were drawn during onset and offset of the block and for 4 h after the administration of rocuronium. Plasma concentrations were determined by high-performance liquid chromatography. Pharmacokinetic/pharmacodynamic modeling was performed by using the Sheiner model and the unbound receptor model (URM), which takes into account the number of unbound acetylcholine receptors. The effective concentration at 50% effect and the steepness of the concentration-effect relationship were significantly decreased in myasthenic patients. Both the URM and the Sheiner model provided an adequate fit in myasthenic patients. The acetylcholine receptor concentration was significantly decreased in myasthenic patients. The URM explains the observed differences in time course and potency, whereas the Sheiner model does not. IMPLICATIONS: We performed a pharmacokinetic/pharmacodynamic modeling study in myasthenic patients and control patients. The unbound receptor model, which takes into account the number of unbound acetylcholine receptors in the biophase, was introduced and compared with the model proposed by Sheiner.     

Pharmacokinetic-pharmacodynamic relationship of rocuronium under stable nitrous oxide-fentanyl or nitrous oxide-sevoflurane anesthesia in children

BACKGROUND: The aim of this study was to compare pharmacokinetics and pharmacokinetic-pharmacodynamic (PK-PD) relationship of rocuronium in children anesthetized with nitrous oxide (N2O) and fentanyl or with N2O and sevoflurane. METHODS: Twenty-four children (3-11 years old, ASA PS I or II) were randomized to receive N2O/O2-fentanyl or N2O/O2-sevoflurane (one MAC) anesthesia. Neuromuscular transmission was monitored electromyographically. Initial bolus dose of rocuronium, 0.6 mg x kg(-1) was followed by continuous infusion, targeting at steady-state 95% T1 depression. Neuromuscular transmission was allowed to recover spontaneously. Plasma samples were collected at the moment of discontinuation of infusion, and 10, 20, 30, 50, 60 and 75 min afterwards. Concentrations of rocuronium were measured using high-performance liquid chromatography with electrochemical detection (HPLC-EC). Rocuronium PK was described by a two-compartment model and PD parameters were estimated using effect compartment and sigmoidal E(max) models. RESULTS: No differences in rocuronium PK parameters were observed between study groups. Clearance was 3.91 +/- 2.07 and 3.62 +/- 0.80 ml x min(-1) x kg(-1) in sevoflurane and fentanyl groups, respectively (P < 0.65). Effect compartment concentrations corresponding to 50% inhibition of T1 (EC50) were 1.41 +/- 0.45 and 2.32 +/- 1.00 microg x ml(-1) (P < 0.02), and rate constants for equilibration between plasma and effect compartment (k(e0)) values were 0.10 +/- 0.04 and 0.24 +/- 0.14 min(-1) (P < 0.009) in sevoflurane and fentanyl groups, respectively. CONCLUSIONS: Disposition of rocuronium was similar under stable N2O-fentanyl and N2O-sevoflurane anesthesia. Sevoflurane reduced rocuronium requirements as well as decreased EC50 relevant to inhibition of T1 and rocuronium transfer to effect compartment. Therefore, the potentiating effect of sevoflurane seems to be mainly of PD origin, probably due to an increased sensitivity of the neuromuscular junction.     

Decreased number of acetylcholine receptors is the mechanism that alters the time course of muscle relaxants in myasthenia gravis: a study in a rat model

BACKGROUND: In myasthenic patients, the time course of action of non-depolarizing neuromuscular blocking agents is prolonged and the sensitivity is increased. We used our antegrade perfused rat peroneal nerve anterior tibialis muscle model to investigate if this altered time course of effect and sensitivity can be explained by the decreased acetylcholine receptor concentration that is caused by the disease. METHODS: Functional acetylcholine receptors were reduced by administration of alpha-bungarotoxin or by injecting monoclonal antibodies against rat acetylcholine receptors (experimental autoimmune myasthenia gravis). After induction of anaesthesia, the model was set up and perfusion of the tibialis anterior muscle with blood was started. After stabilization of the twitch, rocuronium or pancuronium were infused until 90% block was obtained. Twitch data and infusion data were recorded and used to calculate the time course of effect and potency. RESULTS: The potency of neuromuscular blocking agents was increased and the offset of the neuromuscular block was prolonged in both the alpha-bungarotoxin groups and the experimental autoimmune myasthenia gravis groups compared to controls. CONCLUSION: This study shows that the increased sensitivity to neuromuscular-blocking agents in myasthenia gravis can be accounted for by a decreased number of acetylcholine receptors. It also shows that the antegrade perfused rat peroneal nerve anterior tibialis muscle model is a suitable model to study the effects of myasthenia gravis on the time course of effect of neuromuscular blocking agents.     

罗库溴铵、维库溴铵及混合应用对骨骼肌成人型、胎儿型乙酰胆碱受体的作用

目的研究罗库溴铵和维库溴铵及其混合应用对骨骼肌细胞膜上成人型乙酰胆碱受体(ε-nAChR)和胎儿型乙酰胆碱受体(γ-nAChR)的作用。方法先在HEK293细胞膜上,应用脂质体转染技术表达ε-nAChR和γ-nAChR,再用全细胞膜片钳技术,比较罗库溴铵和维库溴铵及其混合应用对ε-nAChR和γ-naAChR引起峰电流的影响。结果维库溴铵和罗库溴铵均能竞争性抑制乙酰胆碱对ε-nAChR和γ-nAChR的激动作用。罗库溴铵和维库溴铵抑制ε-nAChR的半数有效抑制浓度(IC50)为169.2±12.5和(8.3±2.7)μmol/L(P<0.01),抑制γ-nAChR的IC50分别为8.6±2.7和(55.0±10.4)μmol/L(P<0.05)。两药混合应用抑制ε-nAChR的IC50为(0.7±0.3)/μmol/L;抑制γ-nAChR的IC50为(36.3±14.2)μmol/L。结论罗库溴铵对γ-nAChR的抑制作用比对ε-nAChR的作用强,而维库溴铵的作用正相反;对于ε-nAChR罗库溴铵的效能低于维库溴铵,而对γ-nAChR作用则相反;两药混合后对ε-nAChR是协同作用,对γ-nAChR却是相加作用。     

不同液相浓度七氟醚和异氟醚对罗库溴铵结合骨骼肌成人型乙酰胆碱受体的影响

目的探讨不同液相浓度的挥发性麻醉药七氟醚、异氟醚对非去极化肌松药罗库溴铵抑制骨骼肌成人型乙酰胆碱受体(ε-nAChR)内向电流的影响。方法通过脂质体转染建立表达ε-nAChR的HEK293细胞,用全细胞膜片钳检测乙酰胆碱(Ach)激动受体峰电流。计算七氟醚、异氟醚、罗库溴铵抑制受体的半数有效抑制浓度(IC50)。分别用浓度为IC5、0.5IC50、IC50的液相七氟醚、异氟醚预处理ε-nAChR,记录0.5IC50浓度的罗库溴铵对受体内向电流的抑制率。各组以单独使用相应浓度罗库溴铵作为对照。结果七氟醚、异氟醚、罗库溴铵的IC50值分别为:(824.27±14.73)μmol/L;(1031.53±62.91)μmol/L、(150.45±12.5)μmol/L。三种浓度七氟醚、异氟醚增强罗库溴铵抑制Ach诱发电流的幅度不同,呈浓度依赖性(P<0.05);两种吸入麻醉药增强0.5IC50浓度罗库溴铵拮抗受体的作用相似。结论七氟醚、异氟醚增强罗库溴铵对ε-nAChR的阻滞作用呈浓度依赖性,且作用相似。     

Extremely prolonged neuromuscular blockade after rocuronium: a case report

It is known that the duration of rocuronium action can be prolonged in elderly patients and that such action shows important interindividual variability. We report a case of prolonged neuromuscular block lasting 11 h, in a woman subjected to kidney transplantation. The possible causes of such prolonged action, inherent to the drug, or related to external factors, are commented.     

Long-lasting potentiation of a single-dose of rocuronium by amikacin: case report

We report for the first time to our knowledge long-lasting (4 hours) potentiation of single intubating dose of rocuronium by a single bolus of amikacin given 55 minutes later in a woman having no precipitating factor (renal failure, hepatic failure, ionic disorder, other drugs influencing neuromuscular function). This patient had received the same rocuronium dose one month sooner in similar circumstances (without aminoglycoside antibiotic drug) and had not presented any prolonged neuromuscular blockade at this time. Neuromuscular blockade should be monitored in every patient receiving aminoglycoside antibiotic with even a single intubating dose of neuromuscular blocking drug.     

七氟醚和异氟醚对罗库溴铵阻滞大鼠骨骼肌成人型乙酰胆碱受体的影响

目的 评价七氟醚和异氟醚对罗库溴铵阻滞大鼠骨骼肌成人型乙酰胆碱受体(ε-nAChR)的影响.方法 通过脂质体转染法构建表达ε-nAChR的HEK293细胞,采用全细胞膜片钳技术分别测定不同浓度七氟醚、异氟醚和罗库溴铵孵育后乙酰胆碱激动ε-nAChR的内向电流,拟合七氟醚、异氟醚和罗库溴铵浓度与ε-nAChR内向电流抑制率的浓度-效应曲线,计算3种药物抑制ε-nAChR内向电流的5％的浓度(IC5)、25％的浓度(IC25)和50％的浓度(IC50).分别用IC5、IC25和IC50七氟醚和异氟醚孵育重组HEK293细胞,然后加入IC25罗库溴铵共同孵育；用IC25七氟醚和异氟醚孵育重组HEK293细胞,然后用IC5、IC25、IC50罗库溴铵共同孵育；分别计算ε-nAChR内向电流抑制率.结果 IC5、IC25和IC50七氟醚或异氟醚与IC5和IC25罗库溴铵抑制ε-nAChR内向电流的效应呈协同作用,而与IC50罗库溴铵抑制ε-nAChR内向电流的效应呈相加作用；IC50七氟醚与IC25罗库溴铵抑制ε-nAChR内向电流的效应弱于异氟醚,而IC50七氟醚与IC25罗库溴铵抑制ε-nAChR内向电流的效应强于异氟醚,IC25七氟醚与IC5罗库溴铵抑制ε-nAChR内向电流的效应弱于异氟醚.结论 七氟醚或异氟醚与低浓度罗库溴铵阻滞大鼠骨骼肌ε-tAChR的效应呈协同作用,而与高浓度罗库溴铵的效应呈相加作用；低浓度七氟醚强化罗库溴铵阻滞ε-nAChR的效应弱于异氟醚,而高浓度七氟醚的效应强于异氟醚.     

Pharmacokinetic-pharmacodynamic modeling of morphine-6-glucuronide-induced analgesia in healthy volunteers: absence of sex differences

BACKGROUND: Morphine-6-glucuronide (M6G) is a metabolite of morphine and a micro-opioid agonist. To quantify the potency and speed of onset-offset of M6G and explore putative sex dependency, the authors studied the pharmacokinetics and pharmacodynamics of M6G in volunteers using a placebo-controlled, randomized, double-blind study design. METHODS: Ten men and 10 women received 0.3 mg/kg intravenous M6G and placebo (two thirds of the dose as bolus, one third as a continuous infusion over 1 h) on separate occasions. For 7 h, pain tolerance was measured using gradually increasing transcutaneous electrical stimulation, and blood samples were obtained. A population pharmacokinetic (inhibitory sigmoid Emax)-pharmacodynamic analysis was used to analyze M6G-induced changes in tolerated stimulus intensity. The improvement in model fits by inclusion of covariate sex was tested for significance. P values less than 0.01 were considered significant. Taking into account previous morphine data, a predictive pharmacokinetic-pharmacodynamic model was constructed to determine the contribution of M6G to morphine analgesia. RESULTS: M6G concentrations did not differ between men and women. M6G caused analgesia significantly greater than that observed with placebo (P < 0.01). The M6G analgesia data were well described by the pharmacokinetic-pharmacodynamic model. The M6G effect site concentration causing a 25% increase in current (C25) was 275 +/- 135 nm (population estimate +/- SE), the blood effect site equilibration half-life was 6.2 +/- 3.3 h, and the steepness parameter was 0.71 +/- 0.18. Intersubject variability was 167% for C25 and 218% for the effect half-life. None of the model parameters showed sex dependency. CONCLUSIONS: A cumulative dose of 0.3 mg/kg M6G, given over 1 h, produces long-term analgesia greater than that observed with placebo, with equal dynamics (potency and speed of onset-offset) in men and women. Possible causes for the great intersubject response variability, such as genetic polymorphism of the micro-opioid receptor and placebo-related phenomena, are discussed. The predictive pharmacokinetic-pharmacodynamic model was applied successfully and was used to estimate M6G analgesia after morphine in patients with normal and impaired renal function.     

罗库溴铵对鼠海马皮层锥体神经元乙酰胆碱受体的影响

目的 观察罗库溴铵对鼠海马皮层锥体神经元乙酰胆碱受体(AchR)通道电生理学的影响。方法应用急性分离法与膜片钳贴附式单通道记录技术,观测不同浓度罗库溴铵(0、0.05、0.1、0.2、0.4mmol·L-1)或与0.1 mmol·L-1阿托品对SD大鼠海马皮层锥体神经元胞体上AchR通道电生理学参数的作用。结果 (1)R0.05组中电导、开放概率(P0)、短时程开放时间常数(τ01)大于或长于对照组(P<0.05或0.01),长时程开放时间常数(τ02)、短时程关闭时间常数(τc1)、长时程关闭时间常数(τc2)则无统计学差异(P>0.05);其余各组6项参数均大于或长于对照组(P<0.05或0.01)。(2)同时加入罗库溴铵与阿托品,R0.05组各参数与对照组比较无统计学差异(P>0.05);其余各组6项参数(R0.1组中除τ01外)均大于或长于对照组(P<0.05或0.01)。结论 0.05～0.4 mmol·L-1罗库溴铵可不同程度致使鼠海马皮层锥体神经元AchR通道兴奋;浓度为0.05 mmol·L-1时可能主要作用于其毒蕈碱型AchR;浓度达0.1～0.4mmol·L-1时则可能以兴奋烟碱型AchR通道为主。研究结果提示,罗库溴铵一旦透过受损害的血脑屏障,可能引起中枢系统的不良反应。     

Priming with rocuronium accelerates neuromus-cular block in children: a prospective randomized study

PURPOSE: To determine the effects of a priming technique with respect to onset time and duration of action of rocuronium (1.5 x ED(95), 2.0 x ED(95)) in a pediatric patient population. METHODS: Eighty-four children, age one to seven years undergoing elective pediatric surgery, were studied in a randomized controlled trial. Neuromuscular function was assessed by accelerometry in response to single-twitch stimulation to assess onset of neuromuscular block, followed by train-of-four (TOF) stimulation at the wrist every 15 sec. Children were randomly allocated to one of four groups: Groups 1 and 3 received saline placebo, followed one minute later by a single bolus dose of rocuronium 0.45 mg.kg(-1) iv (1.5 x ED(95)) and 0.6 mg kg(-1) iv (2.0 x ED(95)), respectively. Patients in Groups 2 and 4 received an initial dose of rocuronium 0.045 mg.kg(-1) iv and 0.06 mg.kg(-1) iv, respectively, followed one minute later by rocuronium 0.405 mg.kg(-1) and 0.54 mg.kg(-1)iv, respectively. RESULTS: Rocuronium priming significantly accelerated the time to maximum rocuronium-induced neuromuscular block when compared to placebo [median (95% confidence interval)]: 122.5 (98-186) vs 92.5 (68-116) sec (1.5 x ED(95), Group 1 vs Group 2, P < 0.05) and 85 (60-142) vs 55 (48-72) sec (2.0 x ED(95), Group 3 vs Group 4, P < 0.05), respectively. Spontaneous recovery to a TOF-ratio >or= 0.9 was dose-dependent and not influenced by priming. CONCLUSION: Priming accelerated the onset of rocuronium in children. A priming interval of one minute and a cumulative dose of rocuronium 1.5 x ED(95) resulted in an onset of neuromuscular block comparable to a single dose of rocuronium (2.0 x ED(95)).     

The hemodynamic effects of ephedrine on the onset time of rocuronium in pigs

Several studies have found a correlation between the onset time of muscle relaxants, cardiac index, and muscle blood flow. Ephedrine increases these hemodynamic variables and shortens onset time of rocuronium in humans. Our aim in this animal study was to determine the effect of ephedrine on the onset time of rocuronium, cardiac index, and muscle blood flow after administration of thiopental. At predefined measuring points, mean arterial blood pressure and cardiac index were measured invasively and onset time was determined mechanomyographically. Twenty-four pigs were randomly assigned to three groups. Group I received etomidate and subsequently rocuronium (2 x 95% effective dose). Instead of etomidate, Group II received thiopental. In Group III, ephedrine 100 mug/kg was given before thiopental; additionally, muscle blood flow was measured (fluorescent microspheres). Although there were differences in hemodynamics between Groups I and II, this was not reflected in different onset times of rocuronium. In Group III, ephedrine compensated the thiopental-induced decrease of mean arterial blood pressure, cardiac index, and muscle blood flow, but no significant shortening of onset time (Group I: 74 +/- 21 s; Group II: 71 +/- 24; Group III: 69 +/- 22 s) was found. Our results demonstrated that ephedrine-related increases in cardiac index and blood flow did not shorten onset time of rocuronium in healthy pigs.     

不同地域患者罗库溴铵药效学的比较多中心研究

目的比较中国、奥地利和美国3个不同地域的当地患者罗库溴铵作用的量效关系和时效关系。方法选择中国大连、美国英格伍德、奥地利格拉茨3个医学中心择期手术患者各18例,异丙酚、芬太尼静脉麻醉诱导后,累积剂量法进行药效学观察,首剂静脉注射罗库溴铵50μg/kg,起效后重复首剂静脉给药6次,再静脉注射罗库溴铵300μg,采用肌机械运动监测仪记录肌肉收缩强度,对数剂量．概率单位绘制剂量-反应曲线。比较3个地域患者罗库溴铵的ED50、ED90和ED95以及Dur25和Dur0．8。结果大连和格拉茨患者罗库溴铵的ED50、ED90和ED95均高于英格伍德患者,格拉茨患者的ED50、ED90和ED95高于大连患者（P＜0．05）;大连和格拉茨患者的Dur25和Dur0．8均短于英格伍德患者（P＜0．05）,格拉茨患者的Dur25短于大连患者（P＜0．05）,但两者Dur0．8的差异无统计学意义（P＞0．05）。结论3个地域患者罗库溴铵作用的量效关系和时效关系有明显的差别,临床用量需要考虑地域因素的影响。     

Effects of sugammadex and rocuronium mast cell number and degranulation in rat liver

We investigated the effect of rocuronium‐ and sugammadex‐induced mast cell increase and degranulation in rat portal triads. Forty‐two rats, in six groups, received either rocuronium 1 mg.kg^?1; sugammadex 15 mg.kg^?1; sugammadex 100 mg.kg^?1; rocuronium 1 mg.kg^?1 and 5 min later, sugammadex 15 mg.kg^?1; rocuronium 1 mg.kg^?1 and 5 min later, sugammadex 100 mg.kg^?1; or isotonic saline. Total mast cell numbers were significantly higher with rocuronium only, than in all other groups (p < 0.003), although in all active groups, the number was greater than the control. Total mast cell number was significantly higher with rocuronium and low‐dose sugammadex compared with low‐dose sugammadex only. The number of tryptase‐positive mast cells with rocuronium only was significantly higher than in all other groups (p < 0.003). Tryptase‐positive mast cell numbers in both groups receiving both rocuronium and sugammadex were significantly higher compared with both groups receiving sugammadex only. Rocuronium increased mast cell numbers, and degranulation was mitigated by sugammadex. These results suggest that sugammadex may be beneficial in treatment of rocuronium‐induced anaphylaxis.     

Large-for-size liver transplantation: a flowmetry study in pigs

Background

Ischemia–reperfusion injury is partly responsible for morbidity in pediatric liver transplantation. Large-for-size (LFS) liver transplantation has not been fully studied in the pediatric population, and the effects of reperfusion injury may be underestimated.

Materials and methods

Thirteen Landrace–Large white pigs weighing 23 kg (range, 17–38 kg) underwent orthotopic liver transplantation. They were divided into two groups according to the size of the donor body: LFS and control (CTRL). After transplantation, the abdominal cavity of the recipient was kept open and portal venous flow (PVF) was measured after 1 h. The ratio of recipient PVF (PVFr) to donor PVF was used to establish correlations with ischemia and reperfusion parameters. Liver biopsies were taken 1 h after transplantation to assess ischemia and reperfusion and to quantify the gene expression of endothelial nitric oxide synthase, interleukin 6, BAX, and BCL.

Results

Recipient weight, total ischemia time, and warm ischemia time were similar between groups. Among hemodynamic and metabolic analyses, pH, central arteriovenous PCO₂ difference, and AST were statistically worse in the LFS group than in the CTRL group. The same was found with endothelial nitric oxide synthase (0.41 ± 0.18 versus 1.56 ± 0.78; P = 0.02) and interleukin 6 (4.66 ± 4.61 versus 16.21 ± 8.25; P = 0.02). In the LFS group, a significant decay in the PVFr was observed in comparison with the CTRL group (0.93 ± 0.08 and 0.52 ± 0.11, respectively; P < 0.001).

Conclusions

The implantation of a graft was responsible for poor hemodynamic status of the recipient 1 h after transplantation. Furthermore, the LFS group demonstrated markers of ischemia and reperfusion that were worse when compared with the CTRL group and exhibited a more significant decrease in PVF from donor to recipient.     

Skin sensitivity to rocuronium and vecuronium: a randomized controlled prick-testing study in healthy volunteers

Prick tests are frequently used for the authentication of neuromuscular blocking drugs (NMBDs) as causative drugs for anaphylactic reactions during anesthesia. Unfortunately, the actual threshold concentration for skin testing remains debatable for most NMBDs. We studied the flare and wheal responses to prick tests with rocuronium and vecuronium. Thirty healthy, nonatopic, anesthesia-naive male and female volunteers (14 men and 16 women) from 18 to 40 yr of age were assigned randomly to receive a total of 10 prick tests-4 ascending dilutions (1:1000, 1:100, 1:10, and 1) of rocuronium and vecuronium and 2 controls-on both forearms. An assessor blinded to the assignment monitored systemic and skin responses to NMBDs and measured wheal and flare surfaces immediately after and 15 min after prick tests. None of the volunteers experienced any immediate systemic or cutaneous responses to rocuronium or vecuronium. Although a dilution of 1:1000 of both NMBDs failed to promote any skin response at 15 min, 50% and 40% of the subjects had a positive skin reaction to undiluted rocuronium and vecuronium, respectively. We demonstrated a sex effect related to smaller threshold concentration-induced cutaneous reactions in female volunteers to both muscle relaxants. Our observation questions the reliability of prick testing with undiluted solutions of rocuronium and vecuronium for the diagnosis of allergy. IMPLICATIONS: Building concentration-skin response curves to prick tests with rocuronium and vecuronium in healthy, nonatopic, anesthesia-naive male and female volunteers demonstrated that the nonreactive concentration for both muscle relaxants is the 1:1000 dilution of the stock solutions. Our observation calls into question the past practice of prick-testing skin for sensitivity to neuromuscular blocking drugs by using undiluted solutions.     

Pharmacokinetics of intravesical gemcitabine: a preclinical study in pigs

INTRODUCTION: Gemcitabine is a deoxycytidine analogue, used intravenously in the treatment of several tumours, including transitional cell carcinoma of the bladder. It has been shown to be effective and well tolerated when given systemically. We investigated the use of this agent administered intravesically in pigs for histological studies of the bladder and pharmacokinetic research. MATERIAL AND METHODS: Two groups of 5 female pigs each received once 175mg and 350mg gemcitabine intravesically for 2 hours. A third group of 5 pigs received 350mg gemcitabine weekly for 6 weeks. Animals were observed for clinical signs of toxicity. Blood was withdrawn for gemcitabine pharmacokinetics and in group 3 also for peripheral blood counts. The animals were euthanized 24 hours after (the last) instillation. Histological examination of the bladder wall was performed. RESULTS: Doses of 175 and 350mg gemcitabine were well tolerated. The animals showed no signs of deterioration of their well-being. Peripheral blood counts showed no signs of immunosuppression in the third group. In none of the pigs systemic absorption was seen, up to 4 hours after the beginning of instillation. Histology showed in all cases normal bladder wall histology, except for some cases with mild signs of infection (mainly group 3). CONCLUSION: The use of gemcitabine as an intravesical agent in pigs is well tolerated, has no bladder toxicity and is not absorbed systemically.     

Neurotransmitter regulation of neural development: acetylcholine and nicotinic receptors

Several neurotransmitter systems have been related to developmental processes during the past decade. In this review, we discuss the evidence that the nicotinic acetylcholine receptors could have an additional function during development that may be unrelated to their role in cholinergic neurotransmission in the vertebrate brain. Both temporal expression data and in vitro and in vivo studies with nicotinic agonists and antagonists have provided direct support for a role of nicotinic receptors in neural developmental processes such as neurite outgrowth and differentiation. A similar picture has emerged for other neurotransmitter and receptor systems as well, which generates a new view of neural processes during both development and mature life.