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M Kress

Publications and source records attributed to M Kress.

At least 37 records · Page 2Linked to original sources
PubMed2000

M2-receptor subtype does not mediate muscarine-induced increases in [Ca(2+)](i) in nociceptive neurons of rat dorsal root ganglia.

Multiple muscarinic receptor subtypes are present on sensory neurons that may be involved in the modulation of nociception. In this study we focused on the presence of the muscarinic receptor subtypes, M2 and M3 (M2R, M3R), in adult rat lumbar dorsal root ganglia (DRG) at the functional ([Ca(2+)](i) measurement), transcriptional (RT-PCR), and translational level (immunohistochemistry). After 1 day in culture exposure of dissociated medium-sized neurons (20-35 micrometer diam) to muscarine was followed by rises in [Ca(2+)](i) in 76% of the neurons. The [Ca(2+)](i) increase was absent after removal of extracellular calcium and did not desensitize after repetitive application of the agonist. This rise in [Ca(2+)](i) may be explained by the expression of M3R, which can induce release of calcium from internal stores via inositoltrisphospate. Indeed the effect was antagonized by the muscarinic receptor antagonist atropine as well as by the M3R antagonist, 4-diphenylacetoxy-N-(2 chloroethyl)-piperidine hydrochloride (4-DAMP). The pharmacological identification of M3R was corroborated by RT-PCR of total RNA and single-cell RT-PCR, which revealed the presence of mRNA for M3R in lumbar DRG and in single sensory neurons. In addition, RT-PCR also revealed the expression of M2R, which did not seem to contribute to the calcium changes since it was not prevented by the M2 receptor antagonist, gallamine. Immunohistochemistry demonstrated the presence of M2R and M3R in medium-sized lumbar DRG neurons that also coexpressed binding sites for the lectin I-B4, a marker for mainly cutaneous nociceptors. The occurrence of muscarinic receptors in putative nociceptive I-B4-positive neurons suggests the involvement of these acetylcholine receptors in the modulation of processing of nociceptive stimuli.

Animals↗
PubMed1999

Capsaicin, protons and heat: new excitement about nociceptors.

The past few years have witnessed a remarkable progress in understanding the neurobiology of pain. Important advances have been made particularly in the field of peripheral signal transduction in nociceptors. Membrane receptors have been identified for capsaicin, a pungent ingredient of chilli peppers, protons (i.e. acidic solutions) and for heat, three stimuli that specifically excite nociceptors. Of particular interest appears to be the first cloned capsaicin receptor, VR1, which has been suggested to serve as an integrator of these three nociceptive stimuli. These findings not only give new insights into the molecular machinery of nociceptor activation and sensitization, but can also provide a rational basis for pharmacological research aiming for a new class of peripherally acting analgesics, which should selectively interfere with nociceptor activation.

Analgesics↗
PubMed1999

Heat-induced release of CGRP from isolated rat skin and effects of bradykinin and the protein kinase C activator PMA.

In the skin, noxious heating induces an axon reflex response which is commonly accepted to be due to the release of vasodilatory neuropeptides from polymodal nociceptors. In the present study, the quantitative assessment of calcitonin gene-related peptide (CGRP) release from rat skin serves as an integrative measure of primary afferent activation by noxious heat and the presumed sensitising action of bradykinin and an activator of protein kinase C (PKC). The isolated rat hairy skin of either hind paw was mounted on acrylic rods and exposed for 5 min periods to synthetic interstitial fluid of either 32 degrees C for control or of higher temperatures up to 59 degrees C during stimulation. In addition, experiments were performed in calcium free solution (containing 10 mM EGTA) or the skin was preloaded with the membrane permeant calcium chelator BAPTA-AM (1 mM). To look for modulatory effects on the heat responses, bradykinin or polymyristate-acetate (PMA) were added during heat stimulation in further experiments. Heating the skin induced a temperature-dependent release of CGRP from a threshold of 43 degrees C which was absent in calcium free solution. Only at the highest temperatures (55 and 59 degrees C) was a partially calcium-independent release observed. Inhibition of the release was also obtained with the intracellular calcium buffer BAPTA-AM. Bradykinin 10 but not 1 microM as well as PMA 1 and 10 microM significantly facilitated the heat-induced CGRP release at 47 degrees C whereby BK caused a marginal and PMA a significant CGRP release by itself. Our results indicate that moderate noxious heat induces calcium-dependent CGRP release and this can be facilitated by bradykinin and by the activation of PKC. This suggests the same sensitising mechanism that affects nociceptor heat responses.

Animals↗
PubMed1999

Calcitonin gene-related peptide and prostaglandin E2 but not substance P release induced by antidromic nerve stimulation from rat skin in vitro.

The liberation of calcitonin gene-related peptide from rat skin in vitro induced by antidromic electrical stimulation of unmyelinated units is demonstrated. Prostaglandin E2 was released concomitantly during C-fiber stimulation. A dose-dependent increase in prostaglandin E2 content of the eluate was also observed in response to stimulation with substance P (10(-7) to 10(-5) M) and calcitonin gene-related peptide (10(-6) and 10(-5) M). In contrast, prostaglandin E2 did not induce measurable release of neuropeptides. The amount of calcitonin gene-related peptide released during suprathreshold electrical stimulation increased with pulse frequency. Calcitonin gene-related peptide and prostaglandin release were completely inhibited in the presence of EMD 61753, a selective kappa-opioid receptor agonist. No significant release of substance P was observed. The data demonstrate a primary release of calcitonin gene-related peptide from unmyelinated but not myelinated primary afferents in the rat skin, which is accompanied by a secondary liberation of prostaglandin E2, connecting neurogenic inflammation to general mechanisms of inflammation.

Acetamides↗
PubMed1999

Rises in [Ca2+]i mediate capsaicin- and proton-induced heat sensitization of rat primary nociceptive neurons.

Capsaicin (CAPS) as well as acidic pH induces Ca2+ influx in a subset of rat dorsal root ganglion neurons. Here we show that CAPS as well as three different approaches to induce experimental tissue acidification (phosphate buffered solution pH 5.4, CO2-gassed solution pH 6.1 and NPE-caged protons) yielded a transient heat sensitization of peripheral nociceptive terminals in rat skin in vitro. The heat sensitization induced by CAPS (1 microM) could be prevented by preloading the neurons with the neuroprotective calcium chelator BAPTA-AM (1 mM). However, this pretreatment had no effect on the sensitization following exposure to acidic solutions (pH 5.4 and pH 6.1). Therefore, the membrane-permeant proton buffer SNARF-AM (200 microM) was used together with BAPTA-AM in order to prevent changes in intracellular pH. Under these conditions heat sensitization by low pH did not occur. To investigate the underlying membrane mechanisms, current recordings together with simultaneous calcium measurements using FURA-2 were performed in neurons isolated from rat dorsal root ganglia. In a subset of these neurons, an increase in [Ca2+]i and concomitant facilitation of heat-activated ionic currents was observed after application of CAPS as well as pH 5.6. Rises in [Ca2+]i thus appear to play an essential role in plastic changes not only of central neurons but also of peripheral nociceptive terminals which may account for heat hyperalgesia.

Animals↗
PubMed1999

Role of [Ca2+]i in the ATP-induced heat sensitization process of rat nociceptive neurons.

In inflamed tissue, nociceptors show increased sensitivity to noxious heat, which may account for heat hyperalgesia. In unmyelinated nociceptive afferents in rat skin in vitro, a drop of heat threshold and an increase in heat responses were induced by experimental elevation of intracellular calcium ([Ca2+]i) levels with the calcium ionophore ionomycin (10 microM). Similar results were obtained in experiments employing [Ca2+]i release from preloaded "caged calcium" (NITR-5/AM) via UV photolysis. In both cases, sensitization was prevented by preventing rises in [Ca2+]i with the membrane-permeant calcium chelator BAPTA-AM (1 mM). No pronounced change of mechanical sensitivity was observed. Heat-induced membrane currents (Iheat) were investigated with patch-clamp recordings, and simultaneous calcium measurements were performed in small sensory neurons isolated from adult rat dorsal root ganglia (DRG). Ionomycin-induced rises in [Ca2+]i resulted in reversible sensitization of Iheat. In the same subset of DRG neurons, the endogenous algogen ATP (100 microM) was used to elevate [Ca2+]i, which again resulted in significant sensitization of Iheat. In correlative recordings from the skin-nerve preparation, ATP induced heat sensitization of nociceptors, which again could be blocked by preincubation with BAPTA-AM. Rises in [Ca2+]i in response to inflammatory mediators, e.g., ATP, thus appear to play a central role in plastic changes of nociceptors, which may account for hypersensitivity of inflamed tissue.

Adenosine Triphosphate↗
PubMed1998

Expression of the mitotic motor protein Eg5 in postmitotic neurons: implications for neuronal development.

It is well established that the microtubules of the mitotic spindle are organized by a variety of motor proteins, and it appears that the same motors or closely related variants organize microtubules in the postmitotic neuron. Specifically, cytoplasmic dynein and the kinesin-related motor known as CHO1/MKLP1 are used within the mitotic spindle, and recent studies suggest that they are also essential for the establishment of the axonal and dendritic microtubule arrays of the neuron. Other motors are required to tightly regulate microtubule behaviors in the mitotic spindle, and it is attractive to speculate that these motors might also help to regulate microtubule behaviors in the neuron. Here we show that a homolog of the mitotic kinesin-related motor known as Eg5 continues to be expressed in rodent neurons well after their terminal mitotic division. In neurons, Eg5 is directly associated with the microtubule array and is enriched within the distal regions of developing processes. This distal enrichment is transient, and typically lost after a process has been clearly defined as an axon or a dendrite. Strong expression can resume later in development, and if so, the protein concentrates within newly forming sprouts at the distal tips of dendrites. We suggest that Eg5 generates forces that help to regulate microtubule behaviors within the distal tips of developing axons and dendrites.

Animals↗
PubMed1998

A technique for fast application of heated solutions of different composition to cultured neurones.

A technique is described that allows the application of fast temperature changes (time constant approximately 300 ms) of solutions superfusing cultured neurones under whole-cell mode of membrane current recording. Its principle is in heating the common outlet of the manifold which consists of 12 tubes connected to barrels containing test solutions of different composition. The outlet is made from a glass capillary (25 mm length, 620/350 microns outer/inner diameter) coated on the outside wall with platinum for a length of 12 mm. The heating element, a platinum layer, is electrically connected to the probe fixed to the micromanipulator used for positioning the manifold. The solutions, driven by gravity, are applied by opening electronic valves controlled either manually or in programmed sequences. The DC current for heating is controlled either manually or by external voltage command. The advantage of the technique is that the same temperature pattern can be applied to 12 different solutions. The technique is used for classifying sensory neurones in culture with respect to their sensitivity to heat and algogens; however, it is applicable to any study of the effects of increased temperature on the activity of ion channels in cultured cells.

Cell Membrane↗
PubMed1998

Stimulated prostaglandin E2 release from rat skin, in vitro.

The excitatory effect of bradykinin (BK) and of low pH on nociceptors appears to partly depend on secondary release of prostaglandins from the surrounding tissue. Rat skin, in vitro, is introduced as a novel model to measure basal and stimulated release of PGE2 and, in future, other substances relevant to nociception, such as neuropeptides. Flaps of hairy skin (n=57) from the rat saphenous region of the hindpaw were subcutaneously excised and fixed on acrylic rods, the corium side exposed. The preparations were equilibrated in carbogen gassed "synthetic interstitial fluid" (SIF) for 30 minutes. The skin flaps were then immersed for 5 minutes each in 9 consecutive glass tubes, which were mounted in a shaking bath at 32 degrees C. Each tube was filled with 5 ml of gassed SIF, the third tube contained inflammatory mediator(s) dissolved in SIF or solutions of low pH. After passage of the skin flap, the eluates were deep frozen (-70 degrees C) and the PGE2 content measured, off-line, using an enzyme immuno-assay. As stimulants, BK at 10(-5) M (n=9) and 10(-6) M (n=4) and BK in equimolar combination with histamine (HA) and serotonin (5-HT; 10(-5) M: n=8, 10(-6) M: n=6, 10(-7) M: n=6) dose-dependently increased PGE2 release. Considering the total amount of PGE2 secreted the combination of inflammatory mediators caused a significantly greater release of PGE2 at 10(-5) and 10(-6) M (p<0.01, Kruskal-Wallis test) than BK stimulation alone. Racemic flurbiprofen caused a profound depression of basal and stimulated release. Solutions of high proton concentration are known to stimulate and sensitize nociceptors. However, phosphate buffered SIF at pH 6.1 and 6.4 caused a substantial and significant decrease of the PGE2 release, probably due to low-pH block of phospholipases. Thus, algogenic potency of mediators does not necessarily match their pro-inflammatory action.

Animals↗
PubMed1998

Inflammatory mediators at acidic pH activate capsaicin receptors in cultured sensory neurons from newborn rats.

Whole cell membrane currents induced by the inflammatory mediators, bradykinin, 5-hydroxytryptamine (5-HT) and prostaglandin E2, were investigated in capsaicin-sensitive dorsal root ganglion (DRG) neurons from newborn rats grown on a monolayer of hippocampal glia without nerve growth factor (NGF). When firmly attached to an underlying cell, the neurons survived >14 days without growing extensive processes. A majority of the small diameter neurons ( approximately 80%) exhibited sensitivity to capsaicin (3-6 muM) and this was enhanced in solution of low pH. In acidic extracellular solution (pH 6.1), the combination of bradykinin (10 microM), 5-HT (10 microM) and prostaglandin E2 (1 microM) induced an inward membrane current in all capsaicin-sensitive DRG neurons (n = 43). The current exceeded the sustained, low pH-induced membrane current by 205 +/- 53 (SE) pA. The combination of acidic inflammatory mediators was ineffective in cells that were insensitive to capsaicin. In capsaicin-sensitive neurons, the inflammatory mediators when applied singly or in any combination of two, induced no membrane currents or small current at pH 7.3 and 6.1. Capsazepine (10 microM), the capsaicin antagonist, completely inhibited the facilitatory action of inflammatory mediator combination but not the sustained inward current induced by acidic extracellular solution (pH 6.1 or 5.5). It is suggested that the inflammatory mediators, bradykinin,5-HT, and prostaglandin E2 together act as endogenous mediators at capsaicin receptors to generate an inward current when the ion channel is protonized.

Animals↗
PubMed1997

Fractional Ca2+ currents through capsaicin- and proton-activated ion channels in rat dorsal root ganglion neurones.

1. Capsaicin and protons cause excitation and sensitization of primary nociceptive afferents. In a subset of dorsal root ganglion (DRG) neurones, which probably represent nociceptive neurones, both capsaicin and protons induce slowly inactivating non-selective cation currents. Whole-cell as well as single channel currents activated by these two stimuli share many biophysical and physiological properties in these neurones. This has lead to the suggestion that protons and capsaicin might activate the same ion channels. 2. In this study we simultaneously measured fluorescence signals and whole-cell currents activated by capsaicin or protons in acutely isolated DRG neurones filled with a high concentration (1 mM) of the Ca2+ indicator dye fura-2. From these measurements the fractional contribution of Ca2+ (Pf; the portion of the whole-cell current carried by Ca2+) to capsaicin- and two types of proton-induced (fast and slowly inactivating) membrane currents was determined. 3. Capsaicin- and slowly inactivating proton-induced currents were accompanied by a change in fluorescence that was dependent on the presence of extracellular Ca2+. With 1.6 mM extracellular Ca2+ and at a holding potential of -80 mV Pf of capsaicin-induced currents (at pH 7.3) was 4.30 +/- 0.17% (mean +/- S.E.M.; no. of experiments, n = 16) and of slowly inactivating proton-induced currents (at pH 5.1) was 1.65 +/- 0.11% (n = 17). Pf of fast inactivating proton-induced currents was negligible. 4. Pf of capsaicin- and slowly inactivating proton-induced currents increased with increasing extracellular Ca2+ concentration (0.5-4.8 mM). 5. Pf of both current types decreased linearly with decreasing extracellular pH by about 0.7% per pH unit over the pH range investigated. When determined at the same extracellular pH Pf values were significantly different for the two current types at all pH values tested. 6. In summary, our results provide evidence that capsaicin and protons activate ion channels which are markedly permeable to Ca2+. The fractional contribution of Ca2+, however, was significantly different for capsaicin- and slowly inactivating proton-induced currents. This strongly suggests that the two stimuli activate different populations of ion channels and supports the possibility that Ca2+ influx through these channels may be important for Ca(2+)-dependent sensitization of primary nociceptive neurones.

Animals↗
PubMed1997

An interaction of inflammatory mediators and protons in small diameter dorsal root ganglion neurons of the rat.

The effects of inflammatory mediators (bradykinin, serotonin, prostaglandin E2 and histamine) and of acidic solutions on dissociated sensory neurons from the adult rat were studied using the whole cell patch-clamp technique and a fast system for drug application. At -60 mV holding potential, a large subpopulation of small neurons responded to acidic pH (6.1) with a sustained inward current whereas none of the inflammatory mediators induced a sustained excitatory conductance. In 3/17 pH-sensitive neurons, a small 130 pA inward current was observed in response to serotonin that exhibited fast inactivation. Addition of 10(-5) M serotonin, prostaglandin E2 or histamine singly did not alter the sustained proton-induced current. However, addition of bradykinin (10(-5) M) resulted in a significant increase of the current which was even more facilitated when all the inflammatory mediators were applied together at pH 6.1. We suggest that inflammatory mediators may act to modulate ionic channels, that are operated by protons, possibly via intracellular second messenger action.

Acids↗
PubMed1997

Methylene blue induces ongoing activity in rat cutaneous primary afferents and depolarization of DRG neurons via a photosensitive mechanism.

The dye methylene blue is known as a blocker of guanylyl cyclase and it has been widely used to deplete cells of internal cyclic GMP. The data presented demonstrate an activation of adult rat sensory neurons by methylene blue via a photosensitive mechanism. In single fiber recordings from primary afferents of the rat skin in vitro, methylene blue, applied to the receptive field, induced discharge activity: 2/2 A beta-, 2/4 A delta- and 5/7 C-fibers showed significantly enhanced firing upon 10 microM methylene blue in the presence of light, whereas the dye was ineffective when illumination was prevented. In whole cell current clamp experiments with dissociated dorsal root ganglion neurons, 100 microM methylene blue was ineffective in the dark but evoked a membrane depolarization of 15.3 +/- 3.5 mV (n = 5) accompanied by discharge activity upon illumination. In whole cell voltage clamp experiments, methylene blue (100 microM) caused a significant slowing of the inactivation of voltage-dependent sodium currents. In addition, an inhibition of fast and slow outward currents was observed with prolonged exposure. The impeded sodium inactivation together with the blockade of potassium currents may contribute to the depolarization and discharge activity observed in primary afferents in vitro as well as in dissociated sensory neurons in culture. We therefore suggest that methylene blue studies with excitable cells or tissues need to be interpreted with caution.

Action Potentials↗
PubMed1997

Expression of the release factor eRF1 (Sup45p) gene of higher eukaryotes in yeast and mammalian tissues.

Polypeptide chain termination in eukaryotic cells is mediated in part by the release factor eRF1 (Sup45p). We have isolated and characterised cDNAs encoding this translation factor from Syrian hamster (Mesocricetus auratus) and human (Homo sapiens) Daudi cells. Comparison of the deduced amino acid sequence of these new eRF1 (Sup45p) sequences with those published for Saccharomyces cerevisiae, Arabidopsis thaliana, Xenopus laevis and human indicates a high degree of amino acid identity across a broad evolutionary range of species. Both the 5' and 3' UTRs of the mammalian eRF1 (Sup45p)-encoding cDNAs show an unusually high degree of conservation for non-coding regions. In addition, the presence of two different lengths of 3' UTR sequences in the mammalian eRF1 (Sup45p) cDNAs indicated that alternative polyadenylation sites might be used in vivo. Northern blot analysis demonstrated that eRF1 (Sup45p) transcripts of differing length, consistent with the use of alternative polyadenylation sites, were detectable in a wide range of mammalian tissues. The Xenopus, human and Syrian hamster eRF1 (Sup45p) cDNAs were shown to support the viability of a strain of S cerevisiae carrying an otherwise lethal sup45::HIS3 gene disruption indicating evolutionary conservation of function. However, the yeast strains expressing the heterogenous eRF1 (Sup45p) showed a defect in translation termination as defined by an enhancement of nonsense suppressor tRNA activity in vivo. Western blot analysis confirmed that Xenopus eRF1 (Sup45p) was primarily ribosome-associated when expressed in yeast indicating that the ribosome-binding domain of eRF1 (Sup45p) is also conserved.

Animals↗
PubMed1997

Human and mouse MOK2 proteins are associated with nuclear ribonucleoprotein components and bind specifically to RNA and DNA through their zinc finger domains.

The human and murine MOK2 ortholog genes that are preferentially expressed in brain and testis tissues encode two different Krüppel-like zinc finger proteins. In this paper, we show that the MOK2 proteins are mainly associated with nuclear ribonucleoprotein components, including the nucleoli and extranucleolar structures, and exhibit specific RNA homopolymer binding activities. Moreover, we have identified an identical 18-bp specific DNA binding sequence for both MOK2 proteins using a pool of random sequence oligonucleotides. The DNA binding domain is localized in the seven adjacent zinc finger motifs, which show 94% identity between human and murine proteins. Taken together, these results establish that the MOK2 proteins are able to recognize both DNA and RNA through their zinc fingers. This dual affinity and the subnuclear localization suggest that MOK2 may play roles in transcription, as well as in the posttranscriptional regulation processes of specific genes.

Animals↗
PubMed1996

Topical acetylsalicylate attenuates capsaicin induced pain, flare and allodynia but not thermal hyperalgesia.

The effect of acetylsalicylic acid (ASA) on capsaicin-evoked activation of cutaneous nociceptors was tested in a double blind study in 10 volunteers. Capsaicin (2% in ethanol) was applied topically for 30 min. Topical ASA (0.25 g/ml) reduced pain intensity and axon reflex flare size. Also, areas of secondary hyperalgesia to light touch and pin-prick were diminished. In contrast, capsaicin-induced heat hyperalgesia was unaffected by ASA. It is concluded that ASA counteracts the excitatory effects of capsaicin on nociceptors and mechanical hyperalgesia but not its sensitizing action to heat.

Administration, Topical↗