White Matter Abnormalities in Multiple Sclerosis Evaluated by Quantitative Synthetic MRI, Diffusion Tensor Imaging, and Neurite Orientation Dispersion and Density Imaging

BACKGROUND AND PURPOSE

A number of MR-derived quantitative metrics have been suggested to assess the pathophysiology of MS, but the reports about combined analyses of these metrics are scarce. Our aim was to assess the spatial distribution of parameters for white matter myelin and axon integrity in patients with relapsing-remitting MS by multiparametric MR imaging.

MATERIALS AND METHODS

Twenty-four patients with relapsing-remitting MS and 24 age- and sex-matched controls were prospectively scanned by quantitative synthetic and 2-shell diffusion MR imaging. Synthetic MR imaging data were used to retrieve relaxometry parameters (R1 and R2 relaxation rates and proton density) and myelin volume fraction. Diffusion tensor metrics (fractional anisotropy and mean, axial, and radial diffusivity) and neurite orientation and dispersion index metrics (intracellular volume fraction, isotropic volume fraction, and orientation dispersion index) were retrieved from diffusion MR imaging data. These data were analyzed using Tract-Based Spatial Statistics.

RESULTS

Patients with MS showed significantly lower fractional anisotropy and myelin volume fraction and higher isotropic volume fraction in widespread white matter areas. Areas with different isotropic volume fractions were included within areas with lower fractional anisotropy. Myelin volume fraction showed no significant difference in some areas with significantly decreased fractional anisotropy in MS, including in the genu of the corpus callosum and bilateral anterior corona radiata, whereas myelin volume fraction was significantly decreased in some areas where fractional anisotropy showed no significant difference, including the bilateral posterior limb of the internal capsule, external capsule, sagittal striatum, fornix, and uncinate fasciculus.

CONCLUSIONS

We found differences in spatial distribution of abnormality in fractional anisotropy, isotropic volume fraction, and myelin volume fraction distribution in MS, which might be useful for characterizing white matter in patients with MS.

White matter alteration of the cingulum in Parkinson disease with and without dementia: evaluation by diffusion tensor tract-specific analysis

BACKGROUND AND PURPOSE

In PD, the neurodegenerative process begins in the brain stem and extends to the limbic system and finally into the cerebral cortex. We used diffusion tensor tractography to investigate the FA of the cingulate fiber tracts in patients with PD with and without dementia.

MATERIALS AND METHODS

Fifteen patients with PD, 15 patients with PDD, and 15 age-matched healthy controls underwent diffusion tensor imaging with a 3T MR imager. Diffusion tensor tractography images of the anterior and posterior cingulate fiber tracts were generated. Mean diffusivity and FA were measured along the tractography of the anterior and posterior cingulate fiber tracts. One-way ANOVA with the Scheffé post hoc test was used to compare results among the groups.

RESULTS

FA was significantly lower in patients with PDD than in healthy controls in both the anterior and the posterior cingulate fiber tracts (P = .003, P = .015) and significantly lower in patients with PD than in healthy controls (P = .003) in the anterior cingulate fiber tract. There were no significant mean diffusivity differences among the groups. MMSE and FA values of the anterior cingulate fiber tracts in patients with PDD were significantly correlated (r = 0.633, P < .05).

CONCLUSIONS

The reduced FA in patients with PD and PDD might reflect neuropathologic changes such as Lewy body pathology in the cingulate fibers. This abnormality might contribute to the dementing process in PD.

Conus medullaris spinal arteriovenous malformation in a patient with klippel-trenaunay-weber syndrome. A case report and review of the literature

SUMMARY

We describe a 24-year-old woman who presented with twice previously unverified subarachnoid hemorrhages from the conus medullaris spinal arteriovenous malformation with Parkes-Weber-syndrome. Spinal MRI examination is considered to be necessary for the diagnosis of Klippel-Trenaunay-Weber syndrome. For diagnosis of the spinal cord arteriovenous malformation, it is indispensable to search carefully for the presence of accompanying lesions. Transarterial glue embolizationis effective for the management of the spinal vascular lesion.

Hydrovenous Disorder in Vein of Galen Aneurysmal Dilatation: Special Focus on Tonsilar Prolapse

We analyzed five cases of vein of Galen aneurysmal dilatation (VGAD) and 12 cases of vein of Galen aneurysmal malformation (VGAM) using sagittal T1-weighted images. Tonsilar prolapse (TP) was confirmed in three cases, which were all VGAD. Two of these cases were treated by endovascular procedures. In one of these two cases, elevation of TP was observed after intervention. There were no signs of TP in the control group of 12 VGAMs. Venous hypertension interferes with cerebrospinal fluid (CSF) resorption resulting in increased brain fluid. TP frequently develops in high flow AVFs and is reversible if therapeutic intervention is performed by an experienced clinical team when appropriately indicated. We consider that TP in VGAD is mainly the result of cerebellar swelling due to chronic venous hypertension.

Why does the agonist [18F]FP-TZTP bind preferentially to the M2 muscarinic receptor?

PURPOSE

Preferential binding of FP-TZTP at the M(2) receptor in vivo led to investigation of [(18)F]FP-TZTP as a potential PET tracer for Alzheimer's disease, in which a substantial reduction of M(2) receptors has been observed in autopsy studies. We hereby investigated in vitro the FP-TZTP behavior to further elucidate the properties of FP-TZTP that lead to its M(2) selectivity.

METHODS

Chinese hamster ovarian cells expressing the five subtypes of human muscarinic receptor as well as the wild type were harvested in culture to assess equilibrium binding. Specific binding was calculated by subtraction of non-specific binding from total binding. Internal specific binding was calculated by subtraction of external specific binding from the total specific binding. Saturation assays were also performed to calculate B(max), K(i), and IC(50). In addition, equilibrium binding and dissociation kinetic studies were performed on rat brain tissue. Selected regions of interest were drawn on the digital autoradiograms and [(18)F]FP-TZTP off-rates were determined by measurement of the rate of release into a buffer solution of [(18)F]FP-TZTP from slide-bound cells that had been preincubated with [(18)F]FP-TZTP.

RESULTS

At equilibrium in vitro, M(2) subtype selectivity of [(18)F]FP-TZTP was not evident. We demonstrated that ATP-dependent mechanisms are not responsible for FP-TZTP M(2) selectivity. In vitro off-rate studies from rat brain tissue showed that the off-rate of FP-TZTP varied with the percentage of M(2) subtype in the tissue region.

CONCLUSION

The slower dissociation kinetics of FP-TZTP from M(2) receptors compared with the four other muscarinic receptor subtypes may be a factor in its M(2) selectivity.

Spontaneous subacute intratumoral hemorrhage of hepatic cavernous hemangioma

We report a case of giant hepatic cavernous hemangioma associated with spontaneous subacute intratumoral hemorrhage. Magnetic resonance imaging showed an oval, homogeneous, high-intensity lesion with a low-intensity rim in the original high-intensity tumor on T2-weighted images. On T1-weighted images, this oval lesion showed heterogeneous high intensity with peripheral higher intensity. The histologic specimen confirmed hepatic hemangioma with intratumoral hemorrhage.

Regional brain uptake of the muscarinic ligand, [18F]FP-TZTP, is greatly decreased in M2 receptor knockout mice but not in M1, M3 and M4 receptor knockout mice

A muscarinic receptor radioligand, 3-(3-(3-fluoropropyl)thio) -1,2,5,thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (fP-TZTP) radiolabeled with the positron emitting radionuclide (18)F ([(18)F]FP-TZTP) displayed regional brain distribution consistent with M2 receptor densities in rat brain. The purpose of the present study is to further elucidate the subtype selectivity of [(18)F]FP-TZTP using genetically engineered mice which lacked functional M1, M2, M3, or M4 muscarinic receptors. Using ex vivo autoradiography, the regional brain localization of [(18)F]FP-TZTP in M2 knockout (M2 KO) was significantly decreased (51.3 to 61.4%; P<0.01) when compared to the wild-type (WT) mice in amygdala, brain stem, caudate putamen, cerebellum, cortex, hippocampus, hypothalamus, superior colliculus, and thalamus. In similar studies with M1KO, M3KO and M4KO compared to their WT mice, [(18)F]FP-TZTP uptakes in the same brain regions were not significantly decreased at P<0.01. However, in amygdala and hippocampus small decreases of 19.5% and 22.7%, respectively, were observed for M1KO vs WT mice at P<0.05. Given the fact that large decreases in [(18)F]FP-TZTP brain uptakes were seen only in M2 KO vs. WT mice, we conclude that [(18)F]FP-TZTP preferentially labels M2 receptors in vivo.

Epidural blood patch for treatment of spontaneous intracranial hypotension

Spontaneous intracranial hypotension is an uncommon disease caused by cerebrospinal fluid leakage. We reported a case of a 42-year-old male with postural headache who was diagnosed as having spontaneous intracranial hypotension. His headache did not completely improve by conservative therapies, so he underwent an autologous epidural blood patch. The site of cerebrospinal fluid restoration was identified at the level from the C2 to Th7 epidural space by 111In-DPTA cisternography and computed tomography coupled with myelography, and cervical EBP was performed. Because cerebrospinal fluid drops from the catheter, it is useful to identify the location of the catheter tip under contrast injection X-ray. Rapid and dramatic relief from the headache was obtained, and no serious complications occurred.

Usefulness of Multidetector 3D-CT Angiography in the Evaluation of Infantile Perimedullary Spinal Arteriovenous Fistula

SUMMARY

We report an infantile huge perimedullary spinal arteriovenous fistula (SAVF) associated with Hereditary-Hemorrhagic-Telangiectasia (HHT), which was treated by glue embolization in one session. Three-dimensional Multidetector Computed Tomography Angiography (3D-MCTA) was useful in pre- and post-endovascular intervention.

Local and global cerebral blood flow and glucose utilization in the alpha-galactosidase A knockout mouse model of Fabry disease

Fabry disease is an X-linked lysosomal disorder characterized by deficient alpha-galactosidase A activity and intracellular accumulations of glycosphingolipids, mainly globotriaosylceramide (Gb3). Clinically, patients occasionally present CNS dysfunction. To examine the pathophysiology underlying brain dysfunction, we examined glucose utilization (CMR(glc)) and cerebral blood flow (CBF) globally and locally in 18 brain structures in the alpha-galactosidase A gene knockout mouse. Global CMR(glc) was statistically significantly reduced by 22% in Fabry mice (p < 0.01). All 18 structures showed decreases in local CMR(glc) ranging from 14% to 33%. The decreases in all structures of the diencephalon, caudate-putamen, brain stem, and cerebellar cortex were statistically significant (p < 0.05). Global cerebral blood flow (CBF) and local CBF measured in the same 18 structures were lower in Fabry mice than in control mice, but none statistically significantly. Histological examination of brain revealed no cerebral infarcts but abundant Gb3 deposits in the walls of the cerebral vessels with neuronal deposits localized to the medulla oblongata. These results indicate an impairment in cerebral energy metabolism in the Fabry mice, but one not necessarily due to circulatory insufficiency.

Sublethal cerebral ischemia inhibits caspase-3 activation induced by subsequent prolonged ischemia in the C57Black/Crj6 strain mouse

Caspase-3 activation has been implicated in ischemic neuronal death. In the present study, we examined if cerebral ischemic tolerance induced by sublethal ischemia is associated with an attenuation of caspase-3 activation in a mouse forebrain ischemia model. Forebrain ischemia in C57Black/Crj6 strain mice was induced by bilateral common carotid artery occlusion (BCCAO) for 18 min. Two episodes of 6-min ischemia were carried out as preconditioning 48 and 72 h before the 18-min BCCAO. Caspase-3-like activity was determined by fluorescently monitoring the release of amino-4-methylcoumarin from N-acetyl-Asp-Glu-Val-Asp-7-amino-4-methylcoumarin in the striatal protein extracts at 4, 24, and 72 h after reperfusion. The results showed that the ischemic preconditioning significantly attenuated caspase-3 activation at 4, 24, and 72 h after reperfusion, and reduced neuronal loss caused by the 18-min ischemia as examined on the 7th day after reperfusion. The present results suggest that the neuroprotection achieved by ischemic preconditioning is related to an attenuation of caspase-3 activation.

The placement of the epidural catheter at the predicted site by electrical stimulation test

More accurate segmental and sagittal positioning of the epidural catheter tip is required for the success of continuous epidural analgesia, spinal cord monitoring, and percutaneous epidural spinal cord stimulation. We examined the usefulness of an electrical stimulation test for verifying the proper placement of the epidural catheter tip at the predicted site in the posterior epidural space by using a locally developed epidural catheter with electrodes at its tip. The test included the observation of segmental bilateral muscle twitches and the patient's report of feeling in the region stimulated by moving the epidural catheter electrode back and forth and changing the direction of the bevel of the Tuohy needle. The success rate of midline placement at the required spinal segment was significantly more frequent (99%; P < 0.001) in the group (n = 289) receiving the electrical stimulation test compared with the group (n = 277) not receiving the test (success rate 57%). The results indicate the usefulness of this method. We concluded that the electrical stimulation test is effective for verifying the proper placement of the catheter electrode tip.

IMPLICATIONS

Ideally the epidural catheter tip should be positioned in the posterior epidural space near the midline. We concluded that the electrical stimulation test is effective for verifying the proper placement of the catheter electrode tip.

Continuous intra-jugular venous blood-gas monitoring with the Paratrend 7 during hypothermic cardiopulmonary bypass

We measured the accuracy of the continuous intra-vascular blood-gas monitoring system (Paratrend 7, PT7) placed in the jugular venous bulb in 18 adult patients having cardiac or aortic surgery with hypothermic cardiopulmonary bypass (CPB). After induction of anaesthesia, a PT7 sensor was inserted through a 20-gauge venous catheter into the right jugular venous bulb. Blood samples were drawn from the venous catheter and measured with a blood gas analyser (BGA). Five to eight paired measurements using the PT7 and blood samples were made per patient, and bias and precision were calculated for each patient using the Bland-Altman method. The ranges for the blood sample measurements were: pH 7.12 to 7.59, PCO(2) 3.7 to 9.6 kPa, PO(2) 3.5 to 16.0 kPa, oxygen saturation 40 to 99%, bicarbonate 18.6 to 34.4 mmol l(-1), and base excess -7.8 to 12.5 mmol l(-1). Bias and precision values were 0.014/0.071 for pH, 0/0.90 kPa for PCO(2), and -0.16/1.18 kPa for PO(2). These values were comparable with those previously made on arterial blood. However, precision for oxygen saturation in each patient varied 2.3 to 23.6% (95% CI: 6.3 to 12.9%), which was unsatisfactory for clinical measurements. Deep hypothermia ( approximately 19.6 degrees C) and marked haemodilution ( approximately 13.5%) during CPB did not influence the reliability of the PT7 sensor. Thus, we concluded that continuous intra-jugular venous blood-gas monitoring is clinically feasible using the PT7 and may provide valuable information during CPB.

A forebrain ischemic preconditioning model established in C57Black/Crj6 mice

Although many kinds of rat and gerbil cerebral ischemic preconditioning models are available, only a focal ischemic preconditioning model in mice has been reported. As most genetic alterations have been performed in mice, it is urgent to develop mouse ischemic preconditioning models for investigating the molecular mechanisms of ischemic preconditioning in transgenic mice. In the present study, we developed a forebrain ischemic preconditioning model in C57Black/Crj6 (C57BL/6) mice. Forebrain ischemia was induced in C57BL/6 mice (8-10 weeks old) by bilateral common carotid artery occlusion (BCCAO) for 18 min. The conditioning ischemic insult lasting for 6 min was carried out 48 h before the 18-min BCCAO. On the seventh day after BCCAO, neuronal damage was visualized by microtubule-associated protein-2 immunohistochemistry and quantified by cresyl violet staining. Terminal deoxytransferase-mediated dUTP-nick end labeling (TUNEL) was performed 72 h after reperfusion to detect DNA fragmentation. Ischemia for 18 min resulted in injury to the striatum, cortex and hippocampus. In comparison to the hippocampus, striatal neuronal injury was more severe and reproducible. Although the conditioning ischemia itself caused neither noticeable striatal neuronal damage nor DNA fragmentation, it significantly reduced striatal neuronal damage and DNA fragmentation caused by the subsequent 18-min ischemia. These results indicate that striatal neuronal injury after transient BCCAO can be strongly reduced by a sublethal ischemic episode in C57BL/6 mice. As many kinds of gene-altered C57BL/6 mice are available, this preconditioning model may be useful for investigating the molecular mechanisms of ischemic preconditioning in transgenic mice.

Both caspase-dependent and caspase-independent pathways may be involved in hippocampal CA1 neuronal death because of loss of cytochrome c From mitochondria in a rat forebrain ischemia model

In a rat forebrain ischemia model, the authors examined whether loss of cytochrome c from mitochondria correlates with ischemic hippocampal CA1 neuronal death and how cytochrome c release may shape neuronal death. Forebrain ischemia was induced by bilateral common carotid artery occlusion with simultaneous hypotension for 10 minutes. After reperfusion, an early rapid depletion of mitochondrial cytochrome c and a late phase of diffuse redistribution of cytochrome c occurred in the hippocampal CA1 region, but not in the dentate gyrus and CA3 regions. Intracerebroventricular administration of Z-DEVD-FMK, a relatively selective caspase-3 inhibitor, provided limited but significant protection against ischemic neuronal damage on day 7 after reperfusion. Treatment with 3 minutes of ischemia (ischemic preconditioning) 48 hours before the 10-minute ischemia attenuated both the early and late phases of cytochrome c redistribution. In another subset of animals treated with cycloheximide, a general protein synthesis inhibitor, the late phase of cytochrome c redistribution was inhibited, whereas most hippocampal CA1 neurons never regained mitochondrial cytochrome c. Examination of neuronal survival revealed that ischemic preconditioning prevents, whereas cycloheximide only delays, ischemic hippocampal CA1 neuronal death. DNA fragmentation detected by terminal deoxytransferase-mediated dUTP-nick end labeling (TUNEL) in situ was largely attenuated by ischemic preconditioning and moderately reduced by cycloheximide. These results indicate that the loss of cytochrome c from mitochondria correlates with hippocampal CA1 neuronal death after transient cerebral ischemia in relation to both caspase-dependent and -independent pathways. The amount of mitochondrial cytochrome c regained may determine whether ischemic hippocampal CA1 neurons survive or succumb to late-phase death.

Functional reorganization of sensory pathways in the rat spinal dorsal horn following peripheral nerve injury

Functional reorganization of sensory pathways in the rat spinal dorsal horn following sciatic nerve transection was examined using spinal cord slices with an attached dorsal root. Slices were obtained from animals whose sciatic nerve had been transected 2-4 weeks previously and compared to sham-operated controls. Whole-cell recordings from substantia gelatinosa neurones in sham-operated rats, to which nociceptive information was preferentially transmitted, revealed that dorsal root stimulation sufficient to activate A afferent fibres evoked a mono- and/or polysynaptic EPSC in 111 of 131 (approximately 85%) neurones. This is in contrast to the response following A fibre stimulation, where monosynaptic EPSCs were observed in 2 of 131 (approximately 2%) neurones and polysynaptic EPSCs were observed in 18 of 131 (approximately 14%) neurones. In sciatic nerve-transected rats, however, a polysynaptic EPSC following stimulation of A afferents was elicited in 30 of 37 (81%) neurones and a monosynaptic EPSC evoked by A afferent stimulation was detected in a subset of neurones (4 of 37, approximately 11%). These observations suggest that, following sciatic nerve transection, large myelinated A afferent fibres establish synaptic contact with interneurones and transmit innocuous information to substantia gelatinosa. This functional reorganization of the sensory circuitry may constitute an underlying mechanism, at least in part, for sensory abnormalities following peripheral nerve injuries.

Intravenous anesthetics differentially reduce neurotransmission damage caused by oxygen-glucose deprivation in rat hippocampal slices in correlation with N-methyl-d-aspartate receptor inhibition

OBJECTIVE

To examine the relation between the effect of intravenous anesthetics on ischemic neurotransmission damage and their actions on N-methyl-d-aspartate (NMDA) receptors in an in vitro cerebral ischemic model.

DESIGN

Prospective, randomized study in freshly prepared rat hippocampal slices.

SETTING

University research laboratory.

SUBJECTS

Hippocampal slices were prepared from male Wistar rats (4-5 wks old).

INTERVENTIONS AND MEASUREMENTS

In vitro ischemia was induced by exposing slices to glucose-free Krebs solution gassed with 95% N2 /5% CO2 at 37.1-37.3 degrees C. Ischemic neurotransmission damage was indicated by the amplitudes of population spikes (PS) recorded from the CA1 pyramidal layer after stimulation of the Schaffer collaterals. The effect of anesthetics on NMDA receptors was determined by measuring the NMDA-mediated changes in intracellular calcium in the CA1 pyramidal layer with a calcium indicator, fura-2.

RESULTS

Following 4, 6, and 7.5 mins ischemia in vitro, the recoveries of PS (% control) were 100%, 17.5 +/- 21.8%, and 5.4 +/- 2.1%, respectively. 3-(R)-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP, 5 microM), an NMDA receptor antagonist, increased the recovery of PS to 88.3 +/- 24.5% after 6 mins ischemia, and to 42.1 +/- 18.7% after 7.5 mins ischemia. Thiopental (400 microM), thiamylal (400 microM), and ketamine (100 microM), but not propofol (100 microM) and etomidate (10 microM), improved the recovery of PS after 6 and 7.5 mins ischemia; the degrees of their protection were comparable to that of 5 microM CPP. The NMDA-mediated increases in intracellular calcium were almost completely inhibited by thiamylal, reduced to half by ketamine and thiopental, augmented by propofol, and not affected by etomidate.

CONCLUSIONS

The results indicate that the efficacy of intravenous anesthetics in attenuating ischemic neuronal damage varies among agents, relating to their effects on NMDA receptors.

Naloxone improves arterial blood pressure and hypoxic ventilatory depression, but not survival, of rats during acute hypoxia

OBJECTIVE

To investigate the effects of naloxone and morphine during acute hypoxia.

DESIGN

Prospective, randomized animal study.

SETTING

University laboratory.

SUBJECTS

Twenty-eight adult male Sprague Dawley rats, weighing 300-350 g.

INTERVENTIONS

The rats were implanted with a femoral catheter and subcutaneous electrodes for electrocardiogram recording and were randomly assigned to receive morphine (5 mg/kg), naloxone (5 mg and 10 mg/kg), or normal saline (control) (n = 7 in each). Fifteen minutes after intraperitoneal injection of the drug, each rat was exposed to hypoxic gas (5% oxygen, 95% N2) for 70 mins. Hypoxic survival time was measured. Mean arterial pressure (MAP), arterial pH, Paco2, Pao2, and base excess were measured before injection (baseline), 14 mins after injection (H0), and 6 mins (H1), 33 mins (H2), and 48 mins (H3) after exposure to hypoxia.

MEASUREMENTS AND MAIN RESULTS

Hypoxic survival was similar between the naloxone 5 mg/kg and control groups (p = .183), significantly lower in the naloxone 10 mg/kg group (p < .01), and significantly higher in the morphine 5 mg/kg group (p < .05) compared with controls. MAP significantly decreased in all groups. However, at H2-H3, MAP was better preserved in both naloxone groups and was lower in the morphine group compared with controls. Paco2 was maintained higher at H0-H3 in the morphine group and lower at H2-H3 in both naloxone groups compared with controls.

CONCLUSION

During acute hypoxia, naloxone preserves arterial blood pressure and attenuates hypoxic ventilatory depression by antagonizing endogenous opiates, but it does not improve hypoxic survival. In contrast, morphine, which enhances the action of endogenous opiates, does improve hypoxic survival. The acute hypoxic tolerance of morphine may be partly attributable to a depression of oxygen consumption, increased cerebral blood flow secondary to high Paco2, and protective actions mediated by delta-opioid receptors.

The effects of anesthetics on cortical spreading depression elicitation and c-fos expression in rats

The effects of anesthetics on the generation of cortical spreading depression (CSD) were investigated. Volatile anesthetics halothane, isoflurane, sevoflurane (0.5, 1.0, and 2.0 MAC), and the intravenous anesthetic pentobarbital were studied. Cortical spreading depression was induced by 3M-KCl applied to a surface of brain cortex for 30 minutes. Direct current (DC) potential was recorded, and the number, amplitude, and duration of CSDs were observed. With increasing concentrations of each volatile anesthetic, there was a dose-related reduction in CSD frequency but not in CSD amplitude. At 2.0 MAC of sevoflurane the suppression of CSD was less than with the other volatile anesthetics. In addition, the influence of anesthetics on expression of c-fos mRNA was investigated. Additional animals anesthetized by isoflurane or sevoflurane were studied. Five CSDs were elicited by electric stimulation (0.5 mV, 1 second) in each animal. In situ hybridization with 35S-labeled oligonucleotides was used to evaluate the level of c-fos mRNA. The expression of c-fos was observed in the hemisphere in which CSD was elicited, but there was no difference in expression of c-fos among the groups. We conclude that volatile anesthetics can induce suppression of CSD elicitation in a dose dependent manner, but that at high concentrations sevoflurane is significantly less effective than other volatile agents. Pentobarbital has the least effect on KCl-induced CSD. These data suggest that the choice of anesthetics can impact the results of studies examining membrane depolarization and the ionic changes initiated by CSD.

[Anesthetic management with veno-venous extracorporeal membrane oxygenator (VV-ECMO) in a patient with severe tracheobronchial stenosis]

We conducted an anesthetic management to perform tracheostomy and tracheolysis in a 33 year-old female with severe stenosis extending to the lower trachea and right main bronchus. The minimal diameter of the stenotic lesion of the trachea was 3 mm according to the preoperative examinations including tomography, CT scan and magnetic resonance imaging. Since there was a high risk of airway collapse during anesthetic induction that could have made ventilation impossible, we decided to apply VV-ECMO to support gas-exchange prior to anesthetic induction. Blood gas analysis showed good results, and sufficient oxygenation and stable circulation were achieved during surgical procedures. Total intravenous anesthesia with propofol and fentanyl could provide adequate depth of anesthesia during surgery and rapid recovery with good spontaneous respiration after the termination of the infusion. VV-ECMO was a useful method to support gas-exchange in a case not requiring circulatory assistance without uneven oxygenation sometimes observed in VA-ECMO.

Complete recovery of consciousness in a patient with decorticate rigidity following cardiac arrest after thoracic epidural injection

A 46-yr-old man with dysaesthesia (burning sensation) following herpes zoster in the left upper chest region was treated with a single thoracic (T2/T3) epidural injection (1.0% lidocaine 3 ml + 0.125% bupivacaine 3 ml) as an outpatient. Twenty minutes after the injection, a nurse noticed the patient to be unconscious with dilated pupils, apnoea and cardiac arrest. Following immediate cardiopulmonary resuscitation, the patient was treated with an i.v. infusion of thiamylal sodium 2-4 mg kg-1 h-1 and his lungs were mechanically ventilated. When the patient developed a characteristic decorticate posture, mild hypothermia (oesophageal temperature, 33-34 degrees C) was induced. On the 17th day of this treatment, after rewarming (35.5 degrees C) and discontinuation of the barbiturate, the patient responded to command. Weaning from the ventilator was successful on the 18th day. About 4 months after the incident, the patient was discharged with no apparent mental or motor disturbances. We suggest that mild hypothermia with barbiturate therapy may have contributed to the successful outcome in this case.

Ischemic tolerance preserves propagation of membrane depolarization

The functional integrity of the synaptic connections within the hippocampus in gerbils that had acquired ischemic tolerance was investigated. The propagation of membrane depolarization across the hippocampus in response to electrical stimulation of CA1 was monitored with the use of a high speed optical recording technique. In comparison to control slices, propagation was significantly depressed and depolarization was shortened in slices from gerbils subjected to 5 min of ischemia. Hippocampal slices from gerbils who were preconditioned with prior sublethal ischemia demonstrated only a slight reduction in propagation. The duration of depolarization was longer than that of ischemia group. These findings suggest that ischemia induces a functional disturbance of synaptic transmission and membrane depolarization. Ischemic preconditioning significantly reduced the extent of this functional disturbance.

The effects of nicardipine on dynamic cerebral autoregulation in patients anesthetized with propofol and fentanyl

We investigated the effects of nicardipine on dynamic cerebral pressure autoregulation in 13 normal adult patients undergoing gynecologic or orthopedic surgery. Anesthesia was induced and maintained with propofol and fentanyl. Hypotension to a mean arterial pressure of 60-65 mm Hg was induced and maintained with a continuous infusion of nicardipine. Time-averaged mean blood flow velocity in the right middle cerebral artery was measured continuously by using transcranial Doppler ultrasonography. The cerebral autoregulatory responses were activated by releasing thigh cuffs. The actual blood flow velocity in the right middle cerebral artery response to acute change in mean arterial pressure was fitted to 1 of 10 computer-generated curves to determine the dynamic rate of cerebral autoregulation (dRoR), and the best fitting curve was used. The autoregulation test was repeated until two values of dRoR were obtained at baseline and during induced hypotension. Nicardipine significantly reduced dRoR values of 13.1% +/- 3.6%/s at baseline to 8.3% +/- 2.6%/s during hypotension (P: < 0.01). During deliberate hypotension induced by nicardipine, the cerebral dynamic autoregulatory response is impaired in normal adult patients.

IMPLICATIONS

During deliberate hypotension induced by nicardipine, the cerebral dynamic autoregulatory response is impaired in normal adult patients.

The stereoselective effects of ketamine isomers on heteromeric N-methyl-D-aspartate receptor channels

The effects of S(+)- and R(-)-ketamine on heteromeric N-methyl-D-aspartate receptor channels were investigated on the epsilon1/zeta1, epsilon2/zeta1, epsilon3/zeta1, and epsilon4/zeta1 channels expressed in Xenopus oocytes. S(+)-ketamine inhibited all four epsilon/zeta channels more effectively than R(-)-ketamine. The inhibitor concentrations for half-control response for S(+)-ketamine were quite similar among the four channels with 0.44-0.56 microM. However, the inhibitor concentrations for half-control response for R(-)-ketamine varied slightly among the four channels with 1.0 microM for epsilon2/zeta1 and epsilon3/zeta1 channels and 1.9-2.0 microM for epsilon1/zeta1 and epsilon4/zeta1 channels. Thus, the potency ratio of S(+)- and R(-)-ketamine for heteromeric channels was only slightly different among the epsilon/zeta channels.

IMPLICATIONS

The potency order and ratio of ketamine isomers for inhibition of N-methyl-D-aspartate receptor channels may not be so different between the brain region and the developmental stage.

[Anesthetic management of thrombectomy for left ventricular huge mobile thrombus]

A 45 year-old male underwent thrombectomy for huge mobile thrombus and aneurysmectomy in the left ventricle. Despite of the patient's preoperative poor cardiac function and difficulties in weaning from cardiopulmonary bypass, he could recover with the aid of left ventricular bypass for 6 days without complications such as thromboembolism. Intraoperative transesophageal echocardiography was useful in observation of thrombus, decision making in the adaptation and type-selection of mechanical ventricular support, and evaluation of its efficacy.

Preemptive analgesia by intravenous low-dose ketamine and epidural morphine in gastrectomy: a randomized double-blind study

BACKGROUND

Morphine and ketamine may prevent central sensitization during surgery and result in preemptive analgesia. The reliability of preemptive analgesia, however, is controversial.

METHODS

Gastrectomy patients were given preemptive analgesia consisting of epidural morphine, intravenous low-dose ketamine, and combinations of these in a randomized, double-blind manner. Postsurgical pain intensity was rated by a visual analog scale, a categoric pain evaluation, and cumulative morphine consumption.

RESULTS

Preemptive analgesia by epidural morphine and by intravenous low-dose ketamine were significantly effective but not definitive. With epidural morphine, a significant reduction in visual analog scale scores at rest was observed at 24 and 48 h, and morphine consumption was significantly lower at 6 and 12 h, compared with control values. With intravenous ketamine, visual analog scale scores at rest and morphine consumption were significantly lower at 6, 12, 24, and 48 h than those in control subjects. The combination of epidural morphine and intravenous ketamine provided definitive preemptive analgesia: Visual analog scale scores at rest and morphine consumption were significantly the lowest at 6, 12, 24, and 48 h, and the visual analog scale score during movement and the categoric pain score also were significantly the lowest among the groups.

CONCLUSION

The results suggest that for definitive preemptive analgesia, blockade of opioid and N-methyl-d-aspartate receptors is necessary for upper abdominal surgery such as gastrectomy; singly, either treatment provided significant, but not definitive, postsurgical pain relief. Epidural morphine may affect the spinal cord segmentally, whereas intravenous ketamine may block brain stem sensitization via the vagus nerve during upper abdominal surgery.

Intraoperative Doppler color flow imaging combined with regulation of arterial inflow during surgery for intrahepatic arterioportal fistula

Large fistulas associated with impaired liver function should be treated by direct obliteration or removal of the shunt orifice. In a large shunt with the portal branch lying on the arterial branch, identification of the exact site of the fistula can be a challenge. We report a case of impaired liver function due to a large intrahepatic arterioportal fistula. The site of the shunt orifice could not be located accurately by preoperative imaging. However, intraoperative color Doppler ultrasonography and the simple regulation of arterial inflow clearly demonstrated the shunt orifice. This original technique has allowed the precise definition of the problem and has optimized the surgical treatment for this critical condition. Consequently, it should be considered a new option for the definition and management of large intrahepatic arterioportal fistulas.

N-methyl-D-aspartate receptor channel block by meperidine is dependent on extracellular pH

Large concentrations of meperidine inhibit N-methyl-D-aspartate-(NMDA) receptor channels by channel block mechanisms. Extracellular pH regulates the activity and drug sensitivity of NMDA-receptor channels. We examined the influence of extracellular pH on sensitivity to meperidine of epsilon/zeta heteromeric NMDA-receptor channels expressed in Xenopus oocytes. Inhibition of epsilon1/zeta1, epsilon2/zeta1, epsilon3/zeta1, and epsilon4/zeta1 channels by meperidine was dependent on pH, with more inhibition at acidic pH and less inhibition at alkaline pH. The degree of voltage-dependence of meperidine block was only slightly affected by changes in pH, whereas affinity for meperidine was greatly reduced at alkaline pH. Furthermore, interaction of meperidine with Mg(2+) block was reduced at alkaline pH. Because the percentage of the protonated form of meperidine is only slightly affected by pH, changes in properties of the meperidine binding site may be involved in mechanisms of alteration of meperidine potency by pH.

IMPLICATIONS

At acidic pH the potency of meperidine for N-methyl-D-aspartate-receptor channels was increased. Any antinociceptive and neuroprotective benefit from the N-methyl-D-aspartate-receptor antagonist property of meperidine may be pH dependent.

Actions of midazolam on GABAergic transmission in substantia gelatinosa neurons of adult rat spinal cord slices

BACKGROUND

Although intrathecal administration of midazolam has been found to produce analgesia, how midazolam exerts this effect is not understood fully at the neuronal level in the spinal cord.

METHODS

The effects of midazolam on either electrically evoked or spontaneous inhibitory transmission and on a response to exogenous gamma-aminobutyric acid (GABA), a GABA(A)-receptor agonist, muscimol, or glycine were evaluated in substantia gelatinosa neurons of adult rat spinal cord slices by using the whole-cell patch-clamp technique.

RESULTS

Bath-applied midazolam (1 microM) prolonged the decay phase of evoked and miniature inhibitory postsynaptic currents (IPSCs), mediated by GABA(A) receptors, without a change in amplitudes, while not affecting glycine receptor-mediated miniature inhibitory postsynaptic currents in both the decay phase and the amplitude. Either GABA- or muscimol-induced currents were enhanced in amplitude by midazolam (0.1 microM) in a manner sensitive to a benzodiazepine receptor antagonist, flumazenil (1 microM); glycine currents were, however, unaltered by midazolam.

CONCLUSIONS

Midazolam augmented both the duration of GABA-mediated synaptic current and the amplitude of GABA-induced current by acting on the GABA(A)-benzodiazepine receptor in substantia gelatinosa neurons; this would increase the inhibitory GABAergic transmission. This may be a possible mechanism for antinociception by midazolam.

Norepinephrine facilitates inhibitory transmission in substantia gelatinosa of adult rat spinal cord (part 1): effects on axon terminals of GABAergic and glycinergic neurons

BACKGROUND

The activation of descending norepinephrine-containing fibers from the brain stem inhibits nociceptive transmission at the spinal level. How these descending noradrenergic pathways exert the analgesic effect is not understood fully. Membrane hyperpolarization of substantia gelatinosa (Rexed lamina II) neurons by the activation of alpha2 receptors may account for depression of pain transmission. In addition, it is possible that norepinephrine affects transmitter release in the substantia gelatinosa.

METHODS

Adult male Sprague-Dawley rats (9-10 weeks of age, 250-300 g) were used in this study. Transverse spinal cord slices were cut from the isolated lumbar cord. The blind whole-cell patch-clamp technique was used to record from neurons. The effects of norepinephrine on the frequency and amplitude of miniature excitatory and inhibitory postsynaptic currents were evaluated.

RESULTS

In the majority of substantia gelatinosa neurons tested, norepinephrine (10-100 microM) dose-dependently increased the frequency of gamma-aminobutyric acid (GABA)ergic and glycinergic miniature inhibitory postsynaptic currents; miniature excitatory postsynaptic currents were unaffected. This augmentation was mimicked by an alpha1-receptor agonist, phenylephrine (10-60 microM), and inhibited by alpha1-receptor antagonists prazosin (0.5 microM) and 2-(2,6-dimethoxyphenoxyethyl) amino-methyl-1,4-benzodioxane (0.5 microM). Neither postsynaptic responsiveness to exogenously applied GABA and glycine nor the kinetics of GABAergic and glycinergic inhibitory postsynaptic currents were affected by norepinephrine.

CONCLUSION

These results suggest that norepinephrine enhances inhibitory synaptic transmission in the substantia gelatinosa through activation of presynaptic alpha1 receptors, thus providing a mechanism underlying the clinical use of alpha1 agonists with local anesthetics in spinal anesthesia.

Involvement of presurgical pain in preemptive analgesia for orthopedic surgery: a randomized double blind study

Preemptive analgesia (PA) is effective in animal models but its clinical effectiveness remains controversial. We examined the effect of preexisting pain on PA. Subjects were recruited from patients needing orthopedic surgery. Some had presurgical pain (fracture surgery and arthritic surgery), while others had no presurgical pain (removal surgery for a tumor, nail or plate). Epidural morphine or a saline control was given preemptively before surgery and maintained until skin closure. Following skin closure, naloxone or placebo was injected intravenously to erase the aftereffects of the morphine. After total recovery, the PCA pump was set to inject epidural morphine. Pain intensity after surgery was measured by a visual analogue scale (VAS), and the amount of morphine used within 48h after surgery. PA was significantly effective for removal surgery, but ineffective for fracture or arthritic surgery. For the fracture and arthritic surgery PA treatment groups, there was a significant correlation between pre- and postsurgical (6h) spontaneous pain, while the corresponding control groups showed no significant correlation. Postsurgical VAS values in the fracture and arthritic surgery control groups increased significantly compared with presurgical VAS values. PA was effective when presurgical pain was absent, but ineffective when presurgical pain was present. We propose that central sensitization is already established by presurgical pain, and preserved until the termination of surgery. The ineffectiveness of PA did not depend on whether the pain was acute (fracture surgery) or chronic (arthritic surgery).

Norepinephrine facilitates inhibitory transmission in substantia gelatinosa of adult rat spinal cord (part 2): effects on somatodendritic sites of GABAergic neurons

BACKGROUND

It has been reported previously that norepinephrine, when applied to the spinal cord dorsal horn, excites a subpopulation of dorsal horn neurons, presumably inhibitory interneurons. In the current study, the authors tested whether norepinephrine could activate inhibitory interneurons, specifically those that are "GABAergic."

METHODS

A transverse slice was obtained from a segment of the lumbar spinal cord isolated from adult male Sprague-Dawley rats. Whole-cell patch-clamp recordings were made from substantia gelatinosa neurons using the blind patch-clamp technique. The effects of norepinephrine on spontaneous GABAergic inhibitory postsynaptic currents were studied.

RESULTS

In the majority of substantia gelatinosa neurons tested, norepinephrine (10-60 microM) significantly increased both the frequency and the amplitude of GABAergic inhibitory postsynaptic currents. These increases were blocked by tetrodotoxin (1 microM). The effects of norepinephrine were mimicked by the alpha1-receptor agonist phenylephrine (10-80 microM) and inhibited by the alpha1-receptor-antagonist WB-4101 (0.5 microM). Primary-afferent-evoked polysynaptic excitatory postsynaptic potentials or excitatory postsynaptic currents in wide-dynamic-range neurons of the deep dorsal horn were also attenuated by phenylephrine (40 microM).

CONCLUSION

The observations suggest that GABAergic interneurons possess somatodendritic alpha1 receptors, and activation of these receptors excites inhibitory interneurons. The alpha1 actions reported herein may contribute to the analgesic action of intrathecally administered phenylephrine.

Unique radiological appearance of a microcystic meningioma

A 35-year-old female presented with partial complex seizures. Computed tomography (CT) showed a slightly high density mass over the right frontal convexity, with heterogeneous contrast enhancement. T1-weighted magnetic resonance (MR) imaging showed the tumour as a hypo-intense lesion, with faint reticular enhancement after intravenous injection of gadolinium-diethylenetriaminepenta-acetic acid. The tumour was totally removed. The specimen was extremely soft and moist. The histological diagnosis was microcystic meningioma. The tumour cells were composed of typical meningothelial cells and stellate cells. The degenerative character of the tumour may be reflected in the poor enhancement on CT and MR imaging. This faint enhancement effect may be a neuro-imaging characteristic indication of this rare microcystic variant of meningioma.

Effects of nicardipine-, nitroglycerin-, and prostaglandin E1-induced hypotension on human cerebrovascular carbon dioxide reactivity during propofol-fentanyl anesthesia

STUDY OBJECTIVE

To investigate the effects of nicardipine-, nitroglycerin-, and prostaglandine E1-induced hypotension on cerebrovascular carbon dioxide (CO2) reactivity over a wide range of arterial CO2 tension (PaCO2) (PaCO2; range 25 to 50 mmHg).

DESIGN

Prospective, randomized study.

SETTING

Operating room of a university-affiliated hospital.

PATIENTS

36 ASA physical status I and II patients without cerebrovascular disease, hypertension, or diabetes mellitus, undergoing an elective abdominal surgery.

INTERVENTIONS

Patients were randomly allocated to one of three groups (nicardipine-, nitroglycerin-, or prostaglandin E1-induced hypotension group; 12 in each group). Anesthesia was induced and maintained with a bolus dose, followed by a continuous infusion of propofol (6.7 +/- 1.5 mg/kg/hr) and fentanyl (1.68 +/- 0.4 micrograms/kg/hr). Deliberate hypotension of mean arterial pressure 55 to 60 mmHg was induced and maintained with a bolus dose, followed by a continuous infusion of nicardipine (6.80 +/- 0.75 micrograms/kg/min), nitroglycerin (3.20 +/- 1.10 micrograms/kg/min), or prostaglandin E1 (0.103 +/- 0.052 microgram/kg/min).

MEASUREMENTS AND MAIN RESULTS

Time-averaged mean red blood cell velocity in the right middle cerebral artery (Vmca) at PaCO2 ranging from 25 to 50 mmHg was measured with transcranial Doppler ultrasonography. A minimum of six simultaneous measurements of Vmca and PaCO2 were obtained during baseline and deliberate hypotension in each patient. Absolute slope between Vmca and PaCO2 during baseline and deliberate hypotension was determined individually by linear regression analysis. Absolute slope was treated as the variable, because it yielded a significant close correlation coefficient (r > 0.95; p < 0.05). Comparisons between baseline and deliberate hypotension were made by analysis of variance for repeated measures. Mean absolute slope was significantly reduced from 1.88 +/- 0.57 cm/sec/mmHg (mean +/- SD) to 1.21 +/- 0.46 in the nicardipine group (p < 0.05), from 1.75 +/- 0.69 to 1.35 +/- 0.47 in the nitroglycerin group (p < 0.05), and from 1.95 +/- 0.89 to 1.33 +/- 0.70 (p < 0.05) in the prostaglandin E1 group, respectively.

CONCLUSION

Nicardipine-, nitroglycerin-, and prostaglandin E1-induced hypotension attenuate the human cerebrovascular CO2 reactivity during propofol-fentanyl anesthesia.

Direct inhibition of the N-methyl-D-aspartate receptor channel by high concentrations of opioids

BACKGROUND

Electrophysiologic and receptor binding studies showed that some opioids have noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist properties.

METHODS

The effects and mechanisms of action of various opioid compounds were examined on four kinds of heteromeric NMDA receptor channels, namely the epsilon1/zeta1, epsilon2/zeta1, epsilon3/zeta1, and epsilon4/zeta1 channels, expressed in Xenopus oocytes. Furthermore, the action sites of opioids on NMDA receptor channels were investigated by site-directed mutagenesis.

RESULTS

Meperidine inhibited four kinds of channels to a similar extent with inhibitor concentrations for half-control response (IC50s) of 210-270 microM. Morphine, fentanyl, codeine, and naloxone also inhibited NMDA receptor channels with affinities comparable to meperidine. Opioid inhibition exhibited voltage dependence and was quite effective at negative potentials. Opioids also shifted the inhibition curve of Mg2+ to the right. Furthermore, replacement of the conserved asparagine residue with glutamine in the channel-lining segment M2 of the zeta1 subunit, which constitutes the block sites of Mg2+ and ketamine, reduced the sensitivity to opioids, whereas that of the epsilon2 subunit barely affected the opioid sensitivity.

CONCLUSIONS

These results, together with previous findings, suggest that the low-affinity NMDA receptor antagonist activity is a common characteristic of various opioid compounds, and that the inhibition is a result of channel-block mechanisms at the site, which partially overlaps with those of Mg2+ and ketamine. This antagonist property of opioids may be clinically significant in the spinal cord following epidural or intrathecal administration, after which the cerebrospinal fluid concentrations of some opioids reach the high micromolar level.

Subunit- and site-specific pharmacology of the NMDA receptor channel

N-Methyl-D-aspartate (NMDA) receptor channels play important roles in various physiological functions such as synaptic plasticity and synapse formation underlying memory, learning and formation of neural networks during development. They are also important for a variety of pathological states including acute and chronic neurological disorders, psychiatric disorders, and neuropathic pain syndromes. cDNA cloning has revealed the molecular diversity of NMDA receptor channels. The identification of multiple subunits with distinct distributions, properties and regulation, implies that NMDA receptor channels are heterogeneous in their pharmacological properties, depending on the brain region and the developmental stage. Furthermore, mutation studies have revealed a critical role for specific amino acid residues in certain subunits in determining the pharmacological properties of NMDA receptor channels. The molecular heterogeneity of NMDA receptor channels as well as their dual role in physiological and pathological functions makes it necessary to develop subunit- and site-specific drugs for precise and selective therapeutic intervention. This review summarizes from a molecular perspective the recent advances in our understanding of the pharmacological properties of NMDA receptor channels with specific references to agonists binding sites, channel pore regions, allosteric modulation sites for protons, polyamines, redox agents, Zn2+ and protein kinases, phosphatases.

Enhanced beta-receptor-mediated vasorelaxation in hypoxic porcine coronary artery

To investigate the beta-adrenoceptor-mediated responses in hypoxic coronary arteries, we studied the effect of isoproterenol (Iso) on isolated porcine coronary arteries contracted with endothelin-1 in media aerated with 0, 5, 7.5, and 95% O(2). The concentration-response curve of Iso was significantly shifted to the left by hypoxia (0 and 5% O(2)). In oxygenated and hypoxic arteries, 3 x 10(-8), 10(-6), and 10(-5) M Iso significantly increased the contents of cAMP. However, there was no difference in the increases of cAMP content induced by 3 x 10(-8) M Iso between oxygenated and hypoxic arteries. The content of cAMP induced by high concentrations of Iso (10(-6) and 10(-5) M) was significantly larger in hypoxic than in oxygenated arteries. Furthermore, the potentiation by hypoxia of the Iso-induced vasorelaxation was inhibited by glibenclamide and depolarization by KCl, but not by removal of endothelium and indomethacin. The vasodilatory response to forskolin and dibutyryl cAMP was unaffected by hypoxia. We conclude that activation of the ATP-sensitive K(+) channel may account for the potentiation of the response to Iso in hypoxic coronary arteries.

The effectiveness of preemptive analgesia varies according to the type of surgery: a randomized, double-blind study

The reliability of preemptive analgesia is controversial. Its effectiveness may vary among anatomical areas or surgical types. We evaluated preemptive analgesia by epidural morphine in six surgery types in a randomized, double-blind manner. Pain intensity was rated using a visual analog scale, a verbal report, and a measurement of postsurgical morphine consumption. Preemptive analgesia was effective in limb surgery and mastectomy, but ineffective for gastrectomy, hysterectomy, herniorrhaphy, and appendectomy. Relief of postsurgical pain in hemiorrhaphy was more rapid than that in the other surgery types. Preemptive analgesia was effective in limb surgery and mastectomy, but not in surgeries involving laparotomy, regardless of whether the surgery was major (gastrectomy and hysterectomy) or minor (herniorrhaphy and appendectomy). These results suggest that viscero-peritoneal nociception is involved in postsurgical pain. The abdominal viscera and peritoneum are innervated both heterosegmentally (in duplicate or triplicate by the vagus and/or phrenic nerves) and segmentally (by the spinal nerves). Therefore, supraspinal and/or cervical spinal neurons might be sensitized, despite the blockade of the segmental nerves with epidural morphine. The rapid retreat of the pain after hemiorrhaphy suggests that central sensitization remits soon after minor surgery, but that in appendicitis, it may be protracted by additional noxious stimuli, such as infection.

IMPLICATIONS

Epidural preemptive analgesia was reliably effective in limb and breast surgeries but ineffective in abdominal surgery, suggesting involvement of the brainstem and cervical spinal cord via the vagus and phlenic nerves.

Effects of naloxone and morphine on acute hypoxic survival in mice

OBJECTIVE

To investigate a role of the opiate system during acute hypoxic hypoxia, the effects of naloxone and morphine on hypoxic survival rate were investigated in awake adult mice.

DESIGN

Prospective, randomized, animal trial.

SETTING

University research laboratory.

SUBJECTS

Male dd-Y mice (n = 864 in experiment I, n = 144 in experiment II, n = 30 in experiment III).

INTERVENTIONS

The animals were placed in an airtight plastic chamber into which a continuous flow of 8 L/min 5% oxygen-95% nitrogen was passed.

MEASUREMENTS AND MAIN RESULTS

One and 5 mg/kg naloxone had no significant effect on the survival rate of mice subjected to acute hypoxic hypoxia, whereas 10 mg/kg naloxone decreased the survival rate. On the other hand, 2 and 5 mg/kg morphine was shown to have a protective action against acute hypoxic hypoxia. The protective effects of 5 mg/kg morphine against hypoxia was even antagonized by 5 mg/kg naloxone, which did not itself show any significant effect on the survival rate. The oxygen consumption in the morphine-treated (5 mg/kg) mice was significantly (p < .05) lower (87.0% +/- 4.6%; mean +/- SE) than that in the saline-treated animals.

CONCLUSIONS

The present study suggests that the endogenous opiate system does not play a significant role on the pathophysiology caused by acute hypoxic hypoxia and that the improved survival of the hypoxic animals by morphine is at least partly attributable to its depressant effect on oxygen consumption.

Actions of opioids on excitatory and inhibitory transmission in substantia gelatinosa of adult rat spinal cord

1. The actions of opioid receptor agonists on synaptic transmission in substantia gelatinosa (SG) neurones in adult (6- to 10-week-old) rat spinal cord slices were examined by use of the blind whole-cell patch-clamp technique. 2. Both the mu-receptor agonist DAMGO (1 microM) and the delta-receptor agonist DPDPE (1 microM) reduced the amplitude of glutamatergic excitatory postsynaptic currents (EPSCs) which were monosynaptically evoked by stimulating Adelta afferent fibres. Both also decreased the frequency of miniature EPSCs without affecting their amplitude. 3. In contrast, the kappa-receptor agonist U-69593 (1 microM) had little effect on the evoked and miniature EPSCs. 4. The effects of DAMGO and DPDPE were not seen in the presence of the mu-receptor antagonist CTAP (1 microM) and the delta-receptor antagonist naltrindole (1 microM), respectively. 5. Neither DAMGO nor DPDPE at 1 microM affected the responses of SG neurones to bath-applied AMPA (10 microM). 6. Evoked and miniature inhibitory postsynaptic currents (IPSCs), mediated by either the GABAA or the glycine receptor, were unaffected by the mu-, delta- and kappa-receptor agonists. Similar results were also obtained in SG neurones in young adult (3- to 4-week-old) rat spinal cord slices. 7. These results indicate that opioids suppress excitatory but not inhibitory synaptic transmission, possibly through the activation of mu- and delta- but not kappa-receptors in adult rat spinal cord SG neurones; these actions are presynaptic in origin. Such an action of opioids may be a possible mechanism for the antinociception produced by their intrathecal administration.

[Anesthetic management for mitral valve replacement in a patient with mitral stenosis and dilated cardiomyopathy]

A 42-year-old man with dilated cardiomyopathy and rheumatic mitral stenosis underwent mitral valve replacement. Prior intravascular fluid administration and infusion of dopamine and dobutamine stabilized hemodynamics during the induction of anesthesia. High-dose fentanyl at pre-cardiopulmonary bypass period and circulatory assist with milrinone and intraaortic balloon pumping after the bypass enabled us to obtain stable hemodynamics. Preoperative dobutamine stress test provided us the effective information for circulatory management in this patient.

[Anesthetic management of an infant with pulmonary atresia and ventricular septal defect accompanied by excess pulmonary blood flow for systemic-pulmonary shunt operation]

A 6-month-old infant had pulmonary atresia with ventricular septal defect (PA + VSD) accompanied by excess pulmonary artery flow via major aortopulmonary collateral artery, underwent aortopulmonary shunt with artificial graft under midazolam-fentanyl anesthesia. After the administration of protamine, arterial oxygen saturation gradually decreased. We suspected that hypotension and decrease in cardiac output induced by protamine caused the decrease in pulmonary blood flow via central shunt. It is suggested that pulmonary blood flow should be maintained by using an inotropic agent and a selective pulmonary arterial dilator such as prostaglandin E1 in a patient with PA + VSD after the institution of aorto-pulmonary shunt, because the patient with excess pulmonary flow has been reported to have high pulmonary resistance due to pulmonary abnormalities such as stenosis and thrombosis.