Tapentadol potentiates descending pain inhibition in chronic pain patients with diabetic polyneuropathy.

BACKGROUND: Tapentadol is an analgesic agent for treatment of acute and chronic pain that activates the µ-opioid receptor combined with inhibition of neuronal norepinephrine reuptake. Both mechanisms are implicated in activation of descending inhibitory pain pathways. In this study, we investigated the influence of tapentadol on conditioned pain modulation (CPM, an experimental measure of endogenous pain inhibition that gates incoming pain signals as a consequence of a preceding tonic painful stimulus) and offset analgesia (OA, a test in which a disproportionally large amount of analgesia becomes apparent upon a slight decrease in noxious heat stimulation). METHODS: Twenty-four patients with diabetic polyneuropathy (DPN) were randomized to receive daily treatment with tapentadol sustained-release (SR) [average daily dose 433 (31) mg] or placebo for 4 weeks. CPM and OA were measured before and on the last day of treatment. RESULTS: Before treatment, none of the patients had significant CPM or OA responses. At week 4 of treatment, CPM was significantly activated by tapentadol SR and coincided with significant analgesic responses. CPM increased from 9.1 (5.4)% (baseline) to 14.3 (7.2)% (placebo) and 24.2 (7.7)% (tapentadol SR, P<0.001 vs placebo); relief of DPN pain was also greater in patients treated with tapentadol than placebo (P=0.028). Neither placebo nor tapentadol SR treatment had an effect on the magnitude of the OA responses (P=0.78). CONCLUSIONS: Tapentadol's analgesic effect in chronic pain patients with DPN is dependent on activation of descending inhibitory pain pathways as observed by CPM responses. CLINICAL TRIAL REGISTRATION: The study was registered at trialregister.nl under number NTR2716.

Equine pericardium for dural grafts: clinical results in 200 patients.

AIM: Serous sheets are currently used in Neurosurgery as dural substitute. The aim of this study is to demonstrate that the horse pericardium, which has the essential charasteristics of reabsorbable membranes and moreover is BSE-free, is an excellent dural substitute. METHODS: 200 patients, 53 suffering from cranial traumatic conditions and 97 from cranial and craniospinal neoplastic pathologies, underwent a surgical procedure with the application of horse pericardium as a dural prosthesis. RESULTS: The follow-up controls of the patients included a neurosurgical visit and advanced diagnostic imaging (CT or MR). In the first 3 cases, an accumulation of CSF occurred under the surgical edge. Lumbar 7-days drainage was required in just one case. The use of Zero 5 suture seems to have obviated this problem, as it was never observed again in subsequent cases. The diagnostic imaging showed no alterated images and no clinical-neurological sequelae regarding the prosthesis in question were recorded. CONCLUSIONS: The Audiomesh Neuro prosthesis has all the characteristics of reabsorbable membranes: they are free from antigenic effects and do not produce any toxic catabolites. The membrane proved to be resistant to surgical suture, impermeable to CSF and is transparent. Yet the suture must be carried out carefully through a small non-traumatic needle. Audiomesh Neuro does not adhere to the underlying cerebral cortex and does not cause any clinical evidence or radiological artifacts.

A randomized controlled trial and novel mathematical analysis of the analgesic effect of oxycodone versus paracetamol orodispersible tablets.

BACKGROUND: For effective treatment of acute pain, a rapid onset of action is important. Here we quantify the antinociceptive profile of an orodispersible oxycodone tablet (OOT) in a randomized, double-blind, active comparator (paracetamol orodispersible tablet, POT), crossover study design in a population of healthy volunteers. METHODS: Twelve female volunteers were randomized to receive 20 mg OOT and 500 mg POT sublingually on two occasions. The electrical pain threshold (EPTh), electrical pain tolerance (EPTol) and pressure pain threshold (PPT) were obtained at regular intervals for 5 h. Time-response data were analysed with a longitudinal pharmacodynamic model characterized by rate constants for analgesia onset (kON ), offset (kOFF ), potency parameter (EFF) and validated with a bootstrap analysis. Values are the median (95% CI) as derived from the bootstrap analysis. RESULTS: OOT produced a rapid increase in response values. For electrical pain analgesia onset, t½kON , 44 (25-67) versus analgesia offset, t½kOFF , 156 (63-552) min, p < 0.01. For pressure pain, t½kON equalled t½kOFF : 30 (16-48) min. OOT was most potent on EPTol: EFF 0.95 (0.39-1.71), p < 0.01, with similar potencies on EPTh, 0.43 (0.19-0.87) and PPT, 0.40 (0.21-0.67). Paracetamol displayed 14% of the analgesic efficacy of oxycodone. CONCLUSIONS: The analgesic effect of orodispersible oxycodone was successfully quantified using a mathematical model of analgesia evolution. This method allows quantification of a variety of responses times from sparse data sets. Response times as defined by a 30% increase in response thresholds varied significantly among end points: EPTol 15 min, PPTh 18 min and EPTh 41 min.

Neutrophil hyperpolarization in response to a chemotactic peptide.

The chemotactic peptide formylmethionyl-leucyl-phenylalanine (fMLP), at concentrations below 10(-9) M, elicits a sustained increase in the human neutrophil's membrane potential within 10 s of its addition. This hyperpolarization, detected with the fluorescent cationic potentiometric probes, 3,3'-dipentyloxacarbocyanine (diO-C5-(3)), and 1,1'-dipropyl-3,3,3',3'-tetramethylindocarbocyanine iodide (diI-C3-(3)), and with the anionic probe bis-(1,3-diethylthiobarbituric)trimethine oxonol (bis-oxonol), is immediately followed by a large depolarization when [fMLP] greater than 10(-9) M. By extracellular substitution of sodium ions with potassium ions or choline or by pretreatment of the cells with ionophores, we report here that the hyperpolarization is primarily dependent on an intact potassium ion gradient and is accompanied by a concurrent acidification of the cytoplasm (approximately 0.05 pH unit) Although the latter occurs simultaneously with a large, transient increase in cytosolic Ca2+ at [fMLP] greater than 10(-10) M, it occurs without a detectable increase in cytosolic Ca2+ at [fMLP] less than 10(-10) M. The hyperpolarization is neither affected nor initiated by the chemotactic peptide antagonist tert-butyloxycarbonyl-methionyl-leucyl-phenylalanine, whereas the depolarization is completely inhibited. Neutrophils isolated from patients with X-linked chronic granulomatous disease exhibit normal hyperpolarizations and cytosolic Ca2+ increases in response to chemotactic peptides but exhibit no depolarization or oxidative burst. The hyperpolarization appears earlier in the ontogeny of differentiating myeloid precursor cells than either the rise in cytosolic Ca2+ or the depolarization response. Together, these findings indicate that an increase in transmembrane potential is one of the earliest events in the neutrophil response to chemotactic peptides, coinciding temporally with increases in cytoplasmic Ca2+ and H+ concentrations but preceding detectable oxidative burst activity.

Simultaneous measurement of stimulus-induced changes in cytoplasmic Ca2+ and in membrane potential of human neutrophils.

The activation of human neutrophils by chemotactic peptides evokes a rapid change in membrane potential and an increase in cytoplasmic Ca2+ levels. These events are followed up to a minute later by detectable levels of microbicidal agents formed by the oxidative burst. Except for the latter, the sequence of events has remained unclear. We report here that a new fluorescent Ca2+ indicator developed by R. Tsien, Indo-1, has allowed us to resolve the temporal relationship between the rapid and transient cytoplasmic Ca2+ rise and the membrane potential change and to do so on very small samples by using a fluorescence-activated cell sorter. We have adapted a FACS 440 for simultaneous single cell membrane depolarization and cytoplasmic [Ca2+] detection in human neutrophils upon stimulation with formyl-methionyl-leucyl-phenylalanine (fMLP). A membrane potential probe, dipentyloxacarbocyanine, allows us to determine that the membrane potential change is fMLP dose-dependent and apparently biphasic. The depolarization is maximal 40 s after stimulation. In contrast, cytosolic [Ca2+], while fMLP-dose dependent, is maximal at 10 s and already decreasing rapidly when the cell has reached its lowest potential. It can be measured with Indo-1 which has a fluorescence emission (lambda ex = 357 nm) maximum at 485 nm when Ca2+-free and 405 nm when Ca2+-liganded. The ratio of these fluorescences may then be calibrated in terms of cytoplasmic Ca2+ levels. Thus, Ca2+ release into the cytoplasm becomes the earliest evidence of neutrophil stimulation by fMLP and occurs in close association with an apparent membrane hyperpolarization.

Calcium modulation and chemotactic response: divergent stimulation of neutrophil chemotaxis and cytosolic calcium response by the chemotactic peptide receptor.

Stimulation of neutrophils by chemoattractants is followed by a rapid, transient rise in cytosolic calcium concentration. The role of calcium in activation of cell movement and related responses was examined by selectively chelating extracellular or both extra- and intracellular calcium. Removal of calcium from the extracellular medium did not alter the cytosolic calcium concentration (Quin 2 fluorescence, 110 to 120 nM) of unstimulated neutrophils and did not dramatically affect the rise induced by formyl peptide. Despite the intact Quin 2 response, depletion of extracellular calcium partially inhibited chemotaxis, adherence to substrate, and polarization (increased forward light scatter) in response to formyl peptide. Loading neutrophils with Quin 2 in the absence of calcium depressed cytosolic Ca2+ to 10 to 20 nM and abrogated a detectable rise with formyl peptide stimulation. Depletion of intracellular calcium further inhibited chemotaxis and polarization, although neutrophils still demonstrated significant directed migration and shape change to formyl peptide (30 to 40% of control) without an increase in Quin 2 fluorescence. Other neutrophil responses related to chemotaxis (decreased right-angle light scatter, actin polymerization) were minimally affected by depletion of calcium from either site. The data indicate that neutrophil chemotaxis and related responses to formyl peptide may be activated by intracellular signals not detectable with Quin 2.

Neutrophil defect associated with malignant infantile osteopetrosis.

We studied the phagocytes from three infants with malignant osteopetrosis and from their families in an attempt to define further the phagocyte abnormalities associated with this disorder. The rapid membrane potential depolarization in response to the soluble stimuli formylmethionylleucylphenylalanine (FMLP) and phorbol myristate acetate (PMA) served as a measure of neutrophil activation, with 3,3-dipentyloxacarbocyanine (diOC5 [3]) used as the probe. A fluorescence-activated cell sorter (FACS) allowed us to use small volumes of blood in a new quantitative evaluation of neutrophil response. The neutrophils from the infants with malignant osteopetrosis were very minimally activated with either stimulus, as demonstrated by incomplete membrane potential depolarization (10% to 15% of normal controls). This finding indicates that malignant osteopetrosis is accompanied by a significantly reduced neutrophil response to stimulation. The abnormal activation process was also reflected in the respiratory burst response of the patients' neutrophils and monocytes. Fifty percent to 60% of the infants' neutrophils totally failed to reduce nitro blue tetrazolium dye (NBT), 30% to 40% of the cells showed only slight reduction after PMA or FMLP stimulation, and only 5% to 10% demonstrated normal reduction. Peripheral blood monocytes failed to reduce NBT in 35% to 70% of the cells tested. Similar testing of granulocyte-macrophage colonies grown in vitro from circulating progenitor cells also showed an abnormal distribution of response to PMA, with a majority of colonies showing a decrease or absence of NBT reduction. Thus control of expression of the osteopetrotic defect occurs at or before the progenitor cell level.

The effects of phorbol myristate acetate and chemotactic peptide on transmembrane potentials and cytosolic free calcium in mature granulocytes evolve sequentially as the cells differentiate.

We isolated myeloid precursors from human marrow and studied the effects of phorbol myristate acetate (PMA) and N-formyl-methionyl-leucyl-phenylalanine (fMLP) upon transmembrane potentials and cytosolic calcium ([Ca2+]i) as the cells matured. Using a panel of fluorescent probes, we found that membrane depolarization induced by PMA and fMLP in granulocytes, and elevation in [Ca2+]i stimulated by fMLP, were absent in myeloblasts. When we induced differentiation with granulocyte-macrophage colony-stimulating factors, we found that both ionic responses appeared at approximately the promyelocyte stage. By using di-O-C5(3), we detected an initial phase of fMLP-induced hyperpolarization which appeared ontogenetically earlier than depolarization and which could be evoked in mature granulocytes with lower concentrations of the ligand. Hyperpolarization was partially dependent on extracellular Na+, was abrogated by increasing the external K+ concentration, and was accompanied by mild acidification of the cytoplasm. Bordetella pertussis toxin abolished both hyperpolarization and depolarization. Our findings indicate that shifts in [Ca2+]i and membrane potential changes in response to PMA and fMLP evolve as granulocytes mature. In addition, transmembrane ionic fluxes induced by fMLP appear to be more complex than previously considered, involving at least two separable phases of membrane potential change.