Naoshi Fujiwara

Reduced Sensitivity to Ketamine and Pentobarbital in Mice Lacking the N-Methyl-d-Aspartate Receptor GluRε1 Subunit

Ketamine is an IV anesthetic with N-methyl-d-aspartate receptor (NMDAR)-blocking properties. However, it is still unclear whether ketamine’s general anesthetic actions are mediated primarily via blockade of NMDAR. Functional NMDARs are composed by the assembly of a GluR&zgr;1 (NR1) subunit with GluR&egr; (GluR&egr;1–4; NR2A–D) subunits, which confer unique properties on native NMDARs. We hypothesized that animals deficient in GluR&egr;1, an abundant and ubiquitously postnatally expressed NMDAR subunit, might be resistant to the effects of ketamine. Here, we evaluated a righting reflex to determine the general anesthetic/hypnotic potency of ketamine administered intraperitoneally to GluR&egr;1 knockout mice and compared these results with those for wild-type mice. Mutant mice were more resistant to ketamine than control mice. Unexpectedly, mutant mice were also more resistant to pentobarbital, which is thought not to interact with NMDAR at clinically relevant concentrations. Although these data in no way eliminate the possibility of the involvement of the NMDAR GluR&egr;1 subunit in mediation of ketamine anesthesia/hypnosis, they suggest the difficulties with interpretation of altered anesthetic sensitivity in knockout animal models.

Management of intractable pain with percutaneous epidural spinal cord stimulation : differences in pain-relieving effects among diseases and sites of pain

This study is a survey of the overall clinical results achieved with our pain treatment method, percutaneous epidural low-frequency (1.6-8.0 Hz) spinal cord stimulation. It examines the relationship between the effectiveness of epidural spinal cord stimulation (ESCS) and diseases or sites of pain. Continuous indwelling of the catheter electrodes in the posterior epidural space ranged from 3 to 67 days, and the duration of percutaneous ESCS varied from less than 1 wk to more than 1 yr. Complete pain relief (100%) was achieved during stimulation in 11.5% of the patients (52 of 454). Complete (100%) to partial (more than 30%) pain relief occurred in 71.1% of the patients. In six (1.3%) patients pain was aggravated by stimulation. Analgesics and/or sedatives were discontinued completely after treatment in 52 patients (11.5%) and reduced in 263 patients (57.9%). The number of patients who rated pain relief better than 50% was significantly more in carcinoma/sarcoma and causalgia (P < 0.001), and significantly less in postherpetic neuralgia and thromboangitis obliterans/arterial sclerosis obliterans (P < 0.001) than the average in all diseases. There was a significantly high responsiveness to ESCS in female patients in comparison to male patients (P < 0.05). Pain in the head/face, neck/upper extremities, and trunk responded more to ESCS than pain in the lower extremities. Alleviation of pain by ESCS was lower when the verbal pain score was high. There were no major complications in percutaneous ESCS. Thus, we have demonstrated that pain-alleviating effects of ESCS varies significantly by disease and site of pain, and that this simple percutaneous method can be used for a relatively long period.

Observation of spinal canal and cisternae with the newly developed small-diameter, flexible fiberscopes

Small-diameter (0.5-, 0.9-, and 1.4-mm) flexible fiberscopes were developed for visual diagnosis of spinal canal diseases. The fiberscopes were introduced via a Tuohy needle into the subarachnoid and epidural spaces of ten patients with various pain syndromes. Clear visualization of the subarachnoid space was achieved using the fiberscopes. The epidural space could be visualized only during withdrawal of the fiberscope. In five cases, the fiberscope could be advanced up to the level of the cisternae without causing the patient any discomfort. A slight headache and transient fever were noted after the examination in five and two cases, respectively, but no other complications occurred. Interestingly, preexisting pain diminished (two cases) or disappeared (one case) after the myeloscopy in three of five cases in which the myeloscopy revealed aseptic adhesive arachnoiditis. Further studies should be carried out to evaluate the usefulness of this technique.

Effects of Isoflurane on Spinal Inhibitory Potentials

The effects of isoflurane on segmental spinal cord potentials and heterosegmental slow positive potentials in response to fore- and hindpaw stimulation were studied in the rat. The heterosegmental slow positive potential and late (second) component of the slow positive wave (P2) of segmental spinal cord potential, thought to be primary afferent depolarization, an agent of presynaptic inhibition activated by a feedback loop via supraspinal structures, were greatly suppressed by the anesthetic. In contrast the negative wave (N1) of segmental spinal cord potential, believed to be synchronized activity of dorsal horn neurons, was only minimally affected. No differential effects of isoflurane on spinal cord potentials activated by fore- and hindpaws were found. Thus, the inhibitory activities of the spinal cord, particularly those produced by a feedback loop via supraspinal structures, are suggested to be highly vulnerable to isoflurane.

Regionally Different Elevation Of Intracellular Free Calcium In Hippocampus Of Septic Rat Brain

ABSTRACT The effect of sepsis on cellular calcium homeostasis in the central nervous system (CNS) was investigated using hippocampal slices of rats in which sepsis was induced by cecal ligation and puncture (CLP). Hippocampal slices were prepared from septic or sham-operated rats at 24 h after abdominal surgery. The basal intracellular calcium ([Ca2+]i) and its response to oxygen-glucose deprivation in hippocampal slices were measured for assessing cellular calcium homeostasis using fura-2 fluorescent imaging technique. The levels of [Ca2+]i- were estimated by the fluorescence ratio (R340/380). Twenty-four hours after CLP, spontaneous movement was reduced and plasma lactate was increased in the septic rats in comparison with the sham-operated rats in which laparotomy was performed without CLP. Basal level of R34O/380 in the CA4 area (.72 ± .07) was significantly higher (p < .001) in the septic group than that in the sham-operated group (.55 ± .06). The fluorescence ratio of septic vs. sham-operated in other hippocampal regions were .55 ± .09 vs. .48 ± .06 in CA1 (not significant) and .65 ± .10 vs. .59 ± .08 (not significant) in CA3, respectively. Increase in [Ca2+]i- due to oxygen-glucose deprivation was significant in CA1 and CA3 of the septic group and in all hippocampal regions of sham-operated group. However, it was not significantly increased in CA4 of the septic group. These results suggest that regional deregulation of cellular calcium occurs in the CNS following CLP. Cellular calcium deregulation may be one of the pathogeneses occurred in clinically observed septic encephalopathy.

Hypoxia Modifies the Vasodilatory Effects of Nitroglycerin, Prostaglandin E1, and Hydralazine on Isolated Porcine Coronary Arteries

Summary: To evaluate the potency of vasodilatory drugs in hypoxia, we studied the effects of nitroglycerin (NTG), prostaglandin E1 (PGE1), and hydralazine on porcine coronary artery constricted with endothelin-1 (ET-1) in both oxygenated and hypoxic conditions. Removal of endo-thelium potentiated NTG-induced relaxation in oxygenated conditions. Hypoxia potentiated relaxation of endo-thelium-intact arteries induced by NTG, but not relaxation of endothelium-denuded arteries. These findings suggest that hypoxia may modify endothelial function in NTG-induced relaxation. The relaxation of endothelium-intact and -denuded arteries induced by PGE1 in hypoxia was significantly greater than that in the oxygenated condition. PGE, significantly increased the content of cyclic AMP in the hypoxic condition; it was much greater than that in the oxygenated condition, suggesting that hypoxia may enhance PGE1-induced relaxation by increasing cyclic AMP levels. Hypoxia attenuated hydralazine-induced relaxation in both endothelium-intact and denuded arteries. Indomethacin and aspirin attenuated hydralazine-induced relaxation in the oxygenated condition, suggesting that cyclooxygenase-related eicosanoid(s) may be involved in hydralazine-induced relaxation. However, indomethacin did not alter relaxation of hypoxic arteries induced by hydralazine. These findings suggest that hypoxia may inactivate cyclooxygenase in hydralazine-induced relaxation. Hypoxia may greatly modify the action of vasodilators on porcine coronary smooth muscle.

Association of urinary 8-OHdG with lifestyle and body composition in elderly natural disaster victims living in emergency temporary housing.

ObjectivesResidents who lost land and houses due to disasterous heavy rainfall-related events on July 13, 2004 and the Chuetsu Earthquake on October 23, 2004 were moved to emergency temporary housing. The change in life style due to living under such conditions is assumed to increase oxidative stress level. In this study, we investigated the oxidative stress level in elderly residents of emergency temporary housing, and analyzed its association with lifestyle and body composition following these disasters.MethodsA noninvasive oxidative stress marker, urinary 8-hydroxydeoxyguanosine (8-OHdG), and body composition were measured in 73 elderly residents of emergency temporary housing.ResultsIn the elderly female residents, the urinary 8-OHdG level tended to decrease with time after the disasters. 8-OHdG levels were slightly higher in females than males and significantly higher among those who exercised regularly compared to those who did not, particularly in females. A weak correlation was noted between the urinary 8-OHdG level and muscle ratio in females.ConclusionsThe in vivo oxidative stress level in our study cohort of elderly residents of emergency temporary housing changed following the change in life style, but remained within the normal range. The increase in oxidative stress levels of elderly females was related to menopause. A decrease in estrogen levels due to menopause inhibits its antioxidant effects, which increases 8-OHdG levels. Although it is difficult to determine, a decrease in daily stressors over time following the disaster could be a cause of the decrease in oxidative stress levels. We suggest that the close evaluation of the stress level of disaster victims is desirable, in combination with evidence of antioxidative substances and the psychosocial influence of suffering as a consequence of the disaster.

Postnatal development of excitation propagation in the trigeminal subnucleus caudalis evoked by afferent stimulation in mice

The postnatal development of nociceptive afferent activity expansion and its modulation features were examined in mice using an optical imaging technique. Developing mice (1-2 weeks old (N1-2 w), 3-4 weeks old (N3-4 w), 5-6 weeks old (N5-6 w) and 7-8 weeks old (N7-8 w)) and neonatally capsaicin-treated mice were used. The propagation of neuronal excitation was measured by changes in fluorescent intensity in horizontal brain stem slices evoked by electrical stimulation to the trigeminal spinal tract. A single-pulse stimulation evoked excitation propagation in the trigeminal caudalis (Vc). The propagation area was larger in N1-2 w than in N7-8 w, and no differences were observed between capsaicin-treated and naive mice in the same age groups. Repetitive stimulation (100 Hz, 30 pulses) elicited long-lasting and widespread excitation propagation. The excitation propagation area was significantly larger in N7-8 w than in N1-2 w, N3-4 w and N5-6 w. This propagation was suppressed by 5 microM L-703.606, an NK1-receptor antagonist, suggesting that the repetitive stimulation-elicited excitation may require substance-P releases. Morphological observations demonstrated that the neural network in the Vc had grown by postnatal week 5. These results suggest that nociceptive afferent activity co-operatively matures with development of the network structure in the Vc, and that a mechanism for prolonged increase in central excitability is established during a later postnatal period.

Arginine Vasopressin Increases Perinuclear [Ca2+] in Single Cultured Vascular Smooth Muscle Cells of Rat Aorta

The effects of arginine vasopressin (AVP, 10(-7) M) on the spatial dynamics of intracellular [Ca2+] in single cultured smooth muscle cells of the rat aorta were studied by digital imaging microscopy using the fluorescent Ca2+ indicator fura-2. The nuclear and cytosolic regions were distinguished by the fluorescent image excited at 380 nm. Changes in intracellular [Ca2+] were expressed as percent increases in the ratios of fluorescence intensity at 500 nm excited by 340 and 380 nm. AVP increased the nuclear and cytosolic [Ca2+] in Ca(2+)-containing (control) (285 +/- 27 and 172 +/- 22%, respectively) or Ca(2+)-free (203 +/- 26 and 121 +/- 15%, respectively) solutions. However, caffeine (20 mM) and ryanodine (20 microM) greatly attenuated the [Ca2+] increase induced by AVP in both regions (61 +/- 21 and 42 +/- 15%, respectively). On the ratio image, the nuclear region was discriminated from other regions at the peak response to AVP in preparations treated with caffeine and ryanodine, whereas the outline of the nuclear region was indistinct in untreated preparations. The finding implies that caffeine- and ryanodine-responsive Ca2+ storage sites may exist in the region surrounding the nucleus. The results suggest that the region surrounding the nucleus may be one of the important Ca2+ storage sites with regard to the responses of rat aortic smooth muscle cells to AVP.

Genetic reduction of GABAA receptor γ2 subunit expression potentiates the immobilizing action of isoflurane

Potentiation of inhibitory gamma-aminobutyric acid subtype A (GABA(A)) receptor function is involved in the mechanisms of anesthetic action. The present study examined the immobilizing action of the volatile anesthetic isoflurane in mice with double knockout (DKO) of phospholipase C-related inactive protein (PRIP)-1 and -2. Both of these proteins play important roles in the expression of GABA(A) receptors containing the gamma2 subunit on the neuronal cell surface. Immunohistochemistry for GABA(A) receptor subunits demonstrated reduced expression of gamma2 subunits in the spinal cord of the DKO mice. Immunohistochemistry also revealed up-regulation of the alpha1 and beta3 subunits even though there were no apparent differences in the immunoreactivities for the beta2 subunits between wild-type and DKO mice. The tail-clamp method was used to evaluate the anesthetic/immobilizing effect of isoflurane and the minimum alveolar concentration (MAC) was significantly lower in DKO mice compared with wild-type controls (1.07+/-0.01% versus 1.36+/-0.04% atm), indicating an increased sensitivity to isoflurane in DKO mice. These immunohistochemical and pharmacological findings suggest that reduced expression of the GABA(A) receptor gamma2 subunit affects the composition and function of spinal GABA(A) receptors and potentiates the immobilizing action of isoflurane.