ArticlePDF Available
100 3/07
ARTIKEL DES QUARTALS
ARTIKEL DES QUARTALS
Vorgestellt von Peter Grafe, Ludwig-Maximilians-Universität München, Institut für
Physiologie – Physiologische Genomik, Schillerstr. 46, 80336 München
Sensory neuron sodium channel
Nav1.8 is essential for pain at low
temperatures
Katharina Zimmermann, Andreas Leffler, Alexandru Babes, Cruz Miguel Cendan, Richard
W. Carr, Jin-ichi Kobayashi, Carla Nau, John N. Wood und Peter W. Reeh
Erschienen in Nature 2007 June 14, 447: 855-858
„Mit steifgefrorenen Fingern einen Knoten
im Schnürsenkel zu lösen ist schwierig. Das
Gefühl fehlt und Nerven wie Muskeln ver-
richten ihren Dienst nur widerwillig. Weh tun
die eiskalten Finger trotzdem - umso mehr,
wenn man sie noch einklemmt. So unange-
nehm das ist, es schützt uns vor unbemerkter
Erfrierung.“ Mit dieser uns vertrauten Situa-
tion beschreiben die Autoren ihr Forschungs-
thema. Jetzt haben sie eine neurobiologische
Bedingung des Kälteschmerzes entdeckt.
Das Aktionspotenzial ist ein bioelektrisches
Phänomen von erregbaren Zellmembranen.
Ein typisches Kennzeichen dieses Signals,
nämlich eine Änderung des Membranpoten-
zials um etwa 100 mV in nur 1 Millisekunde,
wird durch das Öffnen von spannungsgesteu-
erten, Na+-permeablen Ionenkanalproteinen
(Nav) verursacht. Zurzeit kennen wir min-
destens neun verschiedene Arten von Nav
(Nav1.1-Nav1.9), die organspezifisch zur
Erregbarkeit von unterschiedlichen Zellarten
beitragen. Mutationen in den Genen für Nav
konnten identifiziert werden und haben das
Verständnis von Errregbarkeitsstörungen der
Skelettmuskulatur (Nav1.4), der Herzmusku-
latur (Nav1.5) und des Zentralnervensystems
(Nav1.1, Nav1.2) entscheidend verbessert.
In den Untersuchungen von Zimmermann
et al. geht es um die Funktion von Nav1.8,
einem der spannungsgesteuerten, Na+-per-
meablen Ionenkanalproteine in nozizeptiven
(d.h. an der Schmerzempfindung beteiligten)
Nervenzellen des peripheren Nervensystems.
Beobachtungen in den letzten Jahren haben
ergeben, dass in peripheren nozizeptiven
Neuronen verschiedene Arten von Nav ex-
primiert werden. Dazu gehören Nav1.3,
Nav1.7, Nav1.8 und Nav1.9. Die Frage nach
der spezifischen Funktion dieser Proteine
bei den verschiedenen Arten von Schmerz
ist ein wichtiges Forschungsthema. Damit
verbunden ist die Hoffnung, dass die selektive
pharmakologische Blockade einer Unterart
von Nav die Unterdrückung von unerwünsch-
ten Schmerzformen ermöglicht, während z.B.
die notwendigen nützlichen Schmerzreize für
Schutzreaktionen unbeeinflusst bleiben. Sehr
wichtige Erkenntnisse ergaben sich dabei
in jüngster Zeit durch Untersuchungen von
familiär gehäuft auftretenden pathologischen
Schmerzformen. Bei vielen Patienten waren
Mutationen im Gen für Nav1.7 nachweisbar.
Diese Beobachtung war aber für Schmerz-
forscher eine unerwartete Überraschung. Für
viele Jahre wurde nämlich dem Ionenkanal-
protein Nav1.8 eine entscheidende Funktion in
peripheren nozizeptiven Nervenzellen zuge-
sprochen. Diese Annahme war insbesondere
deshalb naheliegend, weil Nav1.8 - Proteine
nur in nozizeptiven Nervenzellen des peri-
pheren Nervensystems und nicht in anderen
Neuronen des peripheren oder zentralen
Nervensystems gefunden wurden. Die Unter-
suchungen von Zimmermann et. al. haben nun
erstmalig die spezifische Funktion von Nav1.8
für nozizeptive Neurone aufgezeigt. Entschei-
dend für diese Entdeckung war die besondere
experimentelle Untersuchungsbedingung:
Wie funktionieren periphere nozizeptive
Neurone bei sehr tiefen Temperaturen? Wie
wird der Kälteschmerzreiz in Nervenfasern
fortgeleitet?
In einer ersten Serie von Experimenten
wurden in einem isolierten Haut-Nerven-
präparat der Ratte und der Maus einzelne
unmyelinisierte Nervenfasern gesucht, die
durch Kälte und mechanische Reize erregt
werden. Dann wurden diese Nervenfasern
auch durch elektrische Reizpulse in der Haut
stimuliert und die Wirkung von Tetrodotoxin
(TTX) auf die Bildung von Aktionspoten-
zialen in den Nervenendigungen getestet.
Nav1.8-Kanalproteine sind, im Unterschied
zu anderen Nav, nicht durch TTX funktionell
blockierbar. In der Gegenwart von TTX waren
die Fasern zunächst nicht mehr erregbar, bei
Abkühlung unter 25 ± 2°C konnten jedoch in
vielen unmyelinisierten Nervenfasern wieder
Aktionspotenziale durch stärkere Kälte, me-
chanische Reize und durch elektrische Stimu-
lation ausgelöst werden. Dies bedeutet also,
dass Nav1.8-Ionenkanalproteine bei diesen
Bedingungen zur Bildung von Aktionspoten-
zialen in spezifischen Nervenendigungen und
zu deren Fortleitung beitragen.
Die NaV1.8-/--Maus friert offensichtlich auf der kalten Eisplatte, zeigt aber nicht das Kälte-
schmerzverhalten ihrer „wildtype“-Artgenossen im Cold Plate Test (Säulendiagramm). Der
TTX-resistente Natriumkanal Nav1.8 kann auch bei Kälte noch Aktionspotenziale generie-
ren, wenn andere spannungsgesteuerte Natriumkanäle blockieren.
3/07 101
Diese besondere Bedeutung von Nav1.8
für die Erregbarkeit von Nervenzellen bei
niedrigen Temperaturen wird auch durch
sorgfältige vergleichende Untersuchungen der
elektrophysiologischen Eigenschaften von
Nav1.7 und Nav1.8 deutlich. Diese Studien
erfolgten sowohl an einzelnen Hinterwurzel-
ganglienzellen als auch an Modellzellen mit
künstlich exprimierten Kanälen. Insbesondere
konnte als wichtigster Unterschied zwischen
beiden Arten von Ionenkanälen beobachtet
werden, dass Kälte keinen Einfluss auf die
langsame Inaktivierung von Nav1.8, wohl
aber von Nav1.7 hat. Der Begriff „langsame
Inaktivierung“ beschreibt das langsame Ab-
nehmen von aktivierbaren Nav-Ionenkanälen
bei Membrandepolarisationen von mehreren
Sekunden. Es ist deshalb plausibel, dass eine
langdauernde Depolarisation der Nervenendi-
gung in der Kälte zu einer Inaktivierung von
TTX-sensitiven Na+-Kanälen (z.B. Nav1.7)
führt, während Nav1.8-Kanalproteine weiter-
hin für die Bildung von Aktionspotenzialen
zur Verfügung stehen.
Die entscheidenden Hinweise zur funktio-
nellen Bedeutung von Nav1.8 erhielten die
Autoren dann durch Beobachtungen von
Mäusen, in denen dieses Protein nicht mehr
exprimiert wird (Nav1.8-/--Mäuse):
(a) In Hinterwurzelganglienzellen dieser Tiere
konnten Aktionspotenziale bei 30 °C, aber
nicht bei 10 °C ausgelöst werden.
(b) Es war keine Erregbarkeit der nozizep-
tiven Nervenendigungen durch starke
mechanische Reizung während Kälte bei
Mäusen ohne Nav1.8-Kanalproteine zu
beobachten.
(c) Die Wirkung von schmerzhafter Kälte,
gesteigert durch Menthol, das die unmye-
linisierten Fasern sensibilisiert, war in den
Nav1.8-/--Mäusen deutlich abgeschwächt.
(d) Sehr eindrucksvoll war das Verhalten
der Nav1.8-/--Mäuse bei Testung auf einer
Kälteplatte. Normalerweise führt der
dabei ausgelöste Kälteschmerz dazu, dass
die Mäuse die Pfoten anheben oder sogar
hochspringen. Dieses Verhalten war ohne
das Nav1.8-Kanalprotein nicht zu beobach-
ten (siehe Abbildung). Trotz der fehlenden
Schmerzempfindung scheinen die Mäuse
aber zu frieren, denn sie sträuben das Fell
und kauern sich zusammen.
Zusammengefasst zeigen uns die in der Arbeit
von Zimmermann et al. beschriebenen Befun-
de, dass eines der Proteine aus der Gruppe von
spannungsabhängigen Natriumkanälen (Nav)
sich von den anderen in einer spezifischen
Funktion unterscheidet. Die in der Einleitung
genannten Vorgänge können damit erklärt
werden. Viele der Nav-Proteine werden durch
Kälte inaktiviert und führen zu einer Funk-
tionsminderung. Im Gegensatz dazu ist der
spannungsabhängige Natriumkanal Nav1.8
aber auch bei Kälte noch funktionsfähig. Aus
diesem Wissen ergeben sich auch neue the-
rapeutische Ansätze. Die spezifische medika-
mentöse Blockade von Nav1.8 könnte z.B. die
„Kälteallodynie“ beheben, eine schmerzhafte
Überempfindlichkeit, die manche Erkrankun-
gen peripherer Nerven begleitet.
Kurzbiografien
Katharina Zimmermann: 1996-2002 Medi-
zinstudium in Erlangen. Auslandsstudienjahr
an der Nagoya University, Nagoya, Japan
und an der McGill-University in Montreal,
Kanada. Bis 2003 Graduiertenstipendium und
Doktorarbeit am Institut für Physiologie und
Pathophysiologie der Universität Erlangen;
Dissertation über die Wirkung von Purinen,
Protonen, Nichtsteroidalen Antiphlogistika
und Triptanen auf die CGRP-Freisetzung
in der Dura Mater, ausgezeichnet mit dem
Promotionspreis der Staedtler-Stiftung 2004.
2003 Ärztin im Praktikum in der Klinik für
Anästhesiologie der Universiät Erlangen.
2004-2005 Postdoktorandin am Institut für
und Doktorarbeit am Institut für Physiologie
und Biokybernetik, Universität Erlangen;
Dissertation über Zahnschmerz evozierte
kortikale Potenziale beim Menschen. 1979-
1982 Postdoktorand bei Michael Illert und
Gerrit ten Bruggencate am Physiologischen
Institut der LMU nchen; Arbeiten über
Ia-Konvergenzmuster an zervikalen Moto-
neuronen und über Elektroakupunktur. 1982
bei Klaus Schaffler, „contract research lab“
in München; Entwicklung eines Tiermodells
der diabetischen Neuropathie.1982-1987
Hochschulassistent am Physiologischen Ins-
titut der Universität Heidelberg bei Hermann
Handwerker, Arbeiten über inflammatorische
Sensibilisierung primärer nozizeptiver Affe-
renzen und Entwicklung/Validierung einer
isolierten Haut-Nervenpräparation; dort 1986
Habilitation im Fach Physiologie. Seit 1987
Professor für Physiolgie an der Universität
Erlangen und Leiter der Arbeitsgruppe für
Primäre Nozizeptive Neurone im Institut für
Physiologie und Pathophysiologie, dort 1992-
2004 Projektleiter im SFB353 (Schmerz-Pa-
thobiologie), Arbeiten über Chemo- und H+-
Sensibilität, GPCR und Signaltransduktion,
Neuropeptidsekretion und Genexpression,
sensorische Transduktion und TRP-Kanäle,
sowie über K+- und Na+-Kanäle, die Sensibi-
lität und Erregbarkeit von Nervenendigungen
bestimmen.
Korrespondenzadresse
Prof. Dr. Peter W. Reeh
Universität Erlangen-Nürnberg
Institut für Physiologie und
Exp. Pathophysiologie
Universitätsstraße 17, 91054 Erlangen
Tel.: + 49 (0) 9131 852 2228
Fax: + 49 (0) 9131 852 2497
E-Mail: reeh@physiologie1.uni-erlangen.de
Peter W. Reeh
Katharina Zimmermann
Physiologie und Pathophysiologie bei Peter
Reeh und Clemens Forster. Arbeiten über die
Funktionen von TRP-, Na+- und K+-Kanälen
in der thermischen und nozizeptiven Trans-
duktion und in der Erregbarkeit von Nerven-
endigungen sowie über die cerebrale Aktivie-
rung durch Muskelkater beim Menschen. Seit
2006 Postdoktorandin bei David Clapham im
Department of Neurobiology der Harvard
Medical School in Boston, gefördert von der
Deutschen Forschungsgemeinschaft.
Peter Reeh: 1968-1975 Studium generale
und Medizinstudium in Hamburg und Er-
langen. Bis 1979 Graduiertenstipendium
ARTIKEL DES QUARTALS
102 3/07
FORSCHUNGSFÖRDERUNG
July 12–16, 2008
Geneva | Switzerland
Palexpo
 


6
th
FENS
Organized by the Federation of European
Neuroscience Societies | FENS
http://www.fens.org
Hosted by the Swiss Society for Neuroscience | SSN
Full details of the programme and
instructions for registration and abstract
submission can be obtained from
http://forum.fens.org/2008.
Deadline for early registration and
abstract submission: January 31, 2008.
The website for abstract submission
opens on December 1, 2007.
Call for Abstracts
A must in Europe for
neuroscientists all over
the world.
PLENARY LECTURES
David Attwell, London, UK
Elena Cattaneo, Milan, Italy
Barry Dickson, Vienna, Austria
Barry Everitt, Cambridge, UK
Magdalena Götz, Munich, Germany
Riitta Hari, Helsinki, Finland
Thomas M. Jessell, New York, USA
Bert Sakmann, Heidelberg/Munich,
Germany
Daniel Schacter, Cambridge MA,
USA
SYMPOSIA
DEVELOPMENT
Cell adhesion molecules: from
neural recognition to connectivity.
Emerging functions of neuronal mi-
gration during brain development.
Endocannabinoids in the developing
brain.
GABA and adult neurogenesis:
from cell fate to synaptic plasticity.
Genetic control of neuronal circuit
assembly.
Mitochondrial transport and its
emerging impact on synaptic trans-
mission and neurodegeneration.
Molecular mechanisms of synaptic
formation and function: insight for
cognitive dysfunction.
SYNAPTIC TRANSMISSION
AND EXCITABILITY
Actin dynamics in synaptic trans-
mission.
G protein coupled inwardly rectify-
ing
K+ channels: from structure to
function.
Glia-mediated synaptic plasticity.
Glycogen synthase kinase 3 (GSK3)
in
synaptic plasticity, memory and
disease.
Metabotropic glutamate recep-
tor plasticity: roles in normal and
abnormal brain function.
Metaplasticity from molecules to
behaviour.
Molecular probes and switches for
functional analysis of receptors,
ionic channels and synaptic net-
works.
Neuronal network oscillations in
health and disease.
Nicotinic receptor signaling in the
brain: from molecules to cognition.
Presynaptic terminals: structural
constraints and molecular dynamics.
Recent advances in neurotrophin
signaling at central synapses.
Regulation of neurotransmission
by cytoskeletal dynamics.
Structure, dynamics and in vivo
func
tions of neurotransmitter trans-
porters.
Subunit-specific NMDA receptor
regulation.
SENSORY SYSTEMS
Imaging development and plasticity
in the visual cortex: from synapses
to functional networks.
Molecular mechanims of whisker-
to-barrel system development.
Neuronal information processing in
drosophila: genetics meets physio-
logy.
Neuronal network architecture and
graphical processing in the neo-
cortex.
New TRPips in mammalian thermo-
sensation.
Pain: mechanisms and persistent
symptoms.
Spontaneous activity in cortical
networks.
MOTOR SYSTE MS
Cerebellar network function: new
imaging and modeling approaches.
Computational and neural mecha-
nisms for the control of goal directed
movement in primates.
Modulation and metamodulation
of motor control networks.
AUTONOMIC, LIMBIC AND
OTHER SYSTEMS
Stress-protective effects of brain
oxytocin: from animal to human
studies.
COGNITION AND BEHAVIOUR
Entorhinal grid cells, navigation
and memory.
Epigenetic regulation of cognitive
function and behaviour.
Localizing memory traces con-
cepts, methods and organisms.
Molecular, cellular and circuit
contributions to cognitive decline in
normal aging.
Multiple hippocampi in one?
Memory
and
beyond along the septo-temporal
axis.
Neuronal circuits of fear extinction.
Sleep, off-line reactivation and
memory consolidation.
Social brains: how we perceive and
understand intentions and feelings
in other people.
The neurobiology of choice and
decision-making.
Tracing mental images in the brain.
Translation regulation subserving
memory and synaptic plasticity
consolidation.
Wiring the developing brain:
genes and activity in songbirds.
Zebrafish: a new model organism
for behavioural neuroscience.
NEUROLOGICAL AND
PSYCHIATRIC CONDITIONS
Adaptive changes within the mam-
malian nervous system and func-
tional recovery following injuries.
Antigen drainage out of the brain:
a new role for microglia?
Compartmental degeneration in
Motor Neuron Disease: where does
the end begin?
Gene transfer for neurodegene-
rative diseases.
Molecular mechanisms in Parkin-
son’s disease and other synuclein-
opathies.
Neurogenesis and gliogenesis in
brain repair.
New insights into cortico-amygdala
interactions: implications for dis-
orders of emotion.
Novel molecular mechanisms
mediating cocaine addiction and
its behavioural effects.
Role of sodium channels in idiopa-
thic and chronic focal epilepsies.
Stress: a neural disconnection
syndrome, towards new molecular
targets.
Synapse recycling, memory impair-
ment and Alzheimer’s disease.
WORKSHOPS
Investigating dendritic membrane
potential with voltage sensitive
dyes.
Integrated open-source solutions
for data acquisition, management
and dynamic analysis of cell struc-
tures in the nervous system.
Pre-clinical evaluation of stem cell
therapy in stroke.
Emerging high-resolution in vivo
technologies.
SPECIAL LECTURES
EBBS Lecture
Angela Friederici, Leipzig, Germany
Hertie Foundation Lecture
Paul Greengard, New York, USA
Human Frontier Science Program
lecture
Nobutaka Hirokawa, Tokyo, Japan
Reemtsma Foundation
Zuelch Lecture
John P. Donoghue, Providence, USA
Academia Europaea
(Physiology & Medicine)
Alexei Verkhratsky, Manchester,
United Kingdom
Max Cowan Lecture
James Fawcett, Cambridge,
United Kingdom
Kemali Prize Lecture
Massimo Scanziani, La Jolla, USA
Fondation IPSEN Neuronal Plasticity
awarding lectures
GlaxoSmithKline Neural Stem Cell
FENS Research Award
Boehringer Ingelheim
FENS Research Award
FENS EJN Awards
SPECIAL EVENTS
NEURON-CELL-Press Symposium
EDAB BAW Reception/
Social program
EU-driven funding opportunities
in brain research
NENS Symposium
EDAB symposium Music and the
Brain: Perception to Emotion
Swiss Academy of Medical
Sciences Théodore Ott Prize 2008
Award Ceremony
FENS / European Brain Council
symposium
Breaking news in neuroscience
Blue Brain Project Phase I:
The neocortical column model.
Neuroscience and Human Culture
supported by the Evens Foundation
FENS/IBRO Alumni Symposium
POSTERS
Preliminary Scientific Programme
of the FENS Forum 2008
http://www.fens.org
FENS_Genf_Anz_DopS_RZ.indd 1-2 02.08.2007 18:56:21 Uhr
... NaV1.8 is mainly found in nociceptive C-fibres (Jurcakova et al., 2018;Shields et al., 2012) and produces TTX-resistant current. NaV1.8 is resistant to cooling (Zimmermann, 2007) and enriched in the distal part of axons (Klein et al., 2017;Zimmermann et al., 2007). Inflammatory mediators can slow its fast inactivation kinetics to provoke "resurgent currents" (Tan et al., 2014;Xiao et al., 2019) providing a mechanism for inflammatory and neuropathic pain. ...
... NaV1.8 is mainly found in nociceptive C-fibres (Jurcakova et al., 2018;Shields et al., 2012) and produces TTX-resistant current. NaV1.8 is resistant to cooling (Zimmermann, 2007) and enriched in the distal part of axons (Klein et al., 2017;Zimmermann et al., 2007). Inflammatory mediators can slow its fast inactivation kinetics to provoke "resurgent currents" (Tan et al., 2014;Xiao et al., 2019) providing a mechanism for inflammatory and neuropathic pain. ...
... All of this suggests that slow ramp currents can push sodium channels from close-active state into close-inactive state and keep it in this phase for a long period of time compared to fast inactivation. Concerning sodium channel subtypes, NaV1.7 takes a long time to transition into closed state inactivation and can thus deliver a ramp current (Cummins et al, 1998) but Nav1.7 is also more prone to enter slow inactivation than NaV1.8 during cooling (Zimmermann et al., 2007). ...
Thesis
The main underlying mechanisms of chronic pain are still unclear. In this thesis, two new approaches targeting the excitability of peripheral nociceptive neurons were employed to examine processes leading to ongoing nociceptive discharge. Thereby we aimed to contribute to the understanding of peripherally driven spontaneous pain that leads to suffering in many patients with chronic pain. We used a new model of low extracellular potassium application that induces ongoing nociceptor activity at the sensory endings of skin nociceptors and a slow depolarizing ramp stimulus that preferentially activates C-fibres and is more closely related to the physiologic induction of action potentials in primary afferent neurons. Low potassium solution unexpectedly led to a rapid and transient depolarisation that is probably mediated by a loss of ion selectivity in 2 pore domain potassium channels. However, the dominant effect of low potassium was a massive increase of intracellular sodium mediated primarily by an influx of sodium ions via NaV1.9 channels. Moreover, primary afferents lacking NaV1.9 such as cold sensitive A-fibres of the cornea did not increase their discharge upon stimulation with low potassium. Slow depolarizing ramp stimuli (4 Hz sinusoidal) were found to be more effective at activating C-fibres during cooling whereas traditional rectangular stimulation became less effective. This differential effect could be explained by cold-induced closure of two pore domain potassium channels leading to increased membrane resistance. The increased membrane resistance increases the membrane time constant whereby the same transmembrane current will more effectively change membrane potential. This mechanism has major clinical importance for cold-induced pain. The voltage-sensitive sodium channel NaV1.7 would have the ideal characteristics to mediate the activation upon slow depolarizing ramps as it is known to amplify such stimuli via a “ramp current”. Activation of C-fibres by sinusoidal stimuli was not blocked by TTX suggesting that NaV1.7 is not the only NaV that can respond to slow depolarizing changes in membrane potential. Innovative excitability tests were used to investigate peripheral nerve fibres of rats that had received cisplatin to induce an acute nephropathy and potentially a peripheral neuropathy. In treated animals, unmyelinated fibres were found to be more sensitive to slow depolarizing stimuli suggesting hyper-excitability. However, the number of animals was low and it remains unclear how robust this effect is. In summary, the model of potassium free extracellular solution was used to identify NaV1.9 and 2 pore domain potassium channels as major determinants of small fibre excitability that have already been linked to clinical chronic pain states. Moreover, the cold-induced hyper-excitability of unmyelinated fibres in response to slow depolarizing ramp stimuli found in our study has important mechanistic implications for the generation of cold-induced pain and hypersensitivity in patients with neuropathic pain. It will be of major interest to use the newly developed tests for axonal excitability in pathophysiologic conditions and ultimately in human tissue in order to specify promising molecular targets that can lead to innovative analgesic treatment options in the future.
... There are specific heat nociceptors which express TRP receptors such as TRPV1-4 which are activated when the temperature reaches a specific 'set point'. These set points are 41°C for TRPV1, 52° for TRPV2, 33° for TRPV3 and 27°C for TRPV 4. [65] Cold The menthol sensitive TRPM8 receptors are the main population in cold receptors; but, to differentiate various gradients of cold, it needs supportive presence and activation of additional receptor types such as NaV1.8 and 1.9 as well as potassium channels TRAAK, TREK-1 [66] and TRP channels like TRPA1 [59,67] and TRPC5. [66] Only this diversity of receptors grant the possibility of discrimination between cold and noxious cold. ...
... These set points are 41°C for TRPV1, 52° for TRPV2, 33° for TRPV3 and 27°C for TRPV 4. [65] Cold The menthol sensitive TRPM8 receptors are the main population in cold receptors; but, to differentiate various gradients of cold, it needs supportive presence and activation of additional receptor types such as NaV1.8 and 1.9 as well as potassium channels TRAAK, TREK-1 [66] and TRP channels like TRPA1 [59,67] and TRPC5. [66] Only this diversity of receptors grant the possibility of discrimination between cold and noxious cold. ...
Article
Full-text available
The perception of harmful or near harmful threats is expressed and recognized by a feeling of extreme discomfort that is pain. Starting with simple reflex circuits such as contraction or flight to avoid further harm in primitive organisms, evolution provided higher organisms with a complex structure of receptors, transmitters, hormones and nervous systems in order to not only detect harmful or near harmful threat, but also to discriminate quality and intensity of a threatful event as well as to learn how to avoid further exposure and how to behave in order to allow healing and recovery after getting injured. The variety of receptors and transmitters as well as the transmitting inter-neuronal networks are extremely complex and are still not completely elucidated. What is already known of this“nociceptive networks” on the other hand, allows better understanding of the progress and treatment of pathological pain states. By analyzing structure - action relation a variety of new drugs such as receptor agonists and antagonists as well as ion-channel blockers primarily not designed for pain treatment have been proven to be useful in the control of complex pain syndromes. A better understanding of the mechanisms involved in perception and transmission of nociceptive inputs as well as peripheral and central downregulating feedback may help to create individualize analgesic treatment regimens for complicated pain syndromes.
... However, transcription analysis using single neuron RT-PCR and RNA sequencing have revealed a vast abundance of Na V 1.7, 1.8 and 1.9 in the slow conducting unmyelinated sensory neurons 18,19 . Complementary physiological studies have shown that these channels modulate pain signalling [20][21][22] . For their indispensable role in the generation and propagation of action potentials, www.nature.com/scientificreports ...
... Academic Medical Center, University of Amsterdam, the Netherlands). Movements were classified as scratching based on their frequency (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), the amplitude of the signals (above 300 mV) and a minimum of 4 repetitions. For this methodical approach a positive prediction value of 95% was shown before 9 . ...
Article
Full-text available
Acute pruritus occurs in various disorders. Despite severe repercussions on quality of life treatment options remain limited. Voltage-gated sodium channels (NaV) are indispensable for transformation and propagation of sensory signals implicating them as drug targets. Here, NaV1.7, 1.8 and 1.9 were compared for their contribution to itch by analysing NaV-specific knockout mice. Acute pruritus was induced by a comprehensive panel of pruritogens (C48/80, endothelin, 5-HT, chloroquine, histamine, lysophosphatidic acid, trypsin, SLIGRL, β-alanine, BAM8-22), and scratching was assessed using a magnet-based recording technology. We report an unexpected stimulus-dependent diversity in NaV channel-mediated itch signalling. NaV1.7−/− showed substantial scratch reduction mainly towards strong pruritogens. NaV1.8−/− impaired histamine and 5-HT-induced scratching while NaV1.9 was involved in itch signalling towards 5-HT, C48/80 and SLIGRL. Furthermore, similar microfluorimetric calcium responses of sensory neurons and expression of itch-related TRP channels suggest no change in sensory transduction but in action potential transformation and conduction. The cumulative sum of scratching over all pruritogens confirmed a leading role of NaV1.7 and indicated an overall contribution of NaV1.9. Beside the proposed general role of NaV1.7 and 1.9 in itch signalling, scrutiny of time courses suggested NaV1.8 to sustain prolonged itching. Therefore, NaV1.7 and 1.9 may represent targets in pruritus therapy.
... The respective role to the excitability of small DRG neurons of Nav1.7 and Nav1.8, another Nav subunit strongly expressed in nociceptive neurons (Brock et al. 1998;Strassman and Raymond 1999;Black and Waxman 2002;Zimmermann et al. 2007;Persson et al. 2010), was further examined in a similar model (Choi and Waxman 2011). To this aim, the partial conductance of these currents was changed so that one of them (Nav1.7 or Nav1.8) was set on full level and its counterpart varied or eliminated. ...
... Animal studies report a specialized role for Na v 1.8 in mediating noxious cold pain. While very low temperatures affect responsiveness of TTXs channels, Na v 1.8 still remains responsive (Zimmermann, Leffler et al. 2007). ...
Conference Paper
In mammals, ten isoforms of Nav channels (Nav1.1-1.9 and Nax) are known that exhibit specific spatial and temporal expression patterns. Human genetics and transgenic mouse studies have revealed a pivotal role for voltage-gated sodium channel Nav1.7 in both acute and chronic pain. Therefore Nav1.7 is a promising analgesic drug target as individuals with loss of function mutations are normal except for a complete inability to perceive pain and having anosmia. As Nav family members share high sequence homology, potential Nav1.7 blockers need to be highly selective. The aim of this thesis was to gain a greater understanding of Nav1.7. Firstly, I examined the regulation of the SCN9A gene, which encodes Nav1.7, through cloning and analysis of a natural antisense transcript (NAT). The complementary NAT overlaps tail-to-tail with the SCN9A/Scn9a sense transcript in both human and mouse genomes. Overexpression of the NAT in vitro specifically decreases the level of mRNA, protein and peak current of Nav1.7. Therefore the NAT may play an important role in regulating human pain thresholds and is a potential candidate gene for individuals with chronic pain disorders that map to the SCN9A locus. Secondly, I investigated the protein-interaction network of Nav1.7 through analysis of a newly developed Nav1.7 TAP tagged mouse. Here, I aimed to identify subtype specific interaction partners of Nav1.7 and found that Nav1.7 is associated with β3 and β4 subunits (Navβ) as well as functional molecules that play a crucial role in protein synthesis, intracellular trafficking and pain processing. Finally, I studied a newly developed mouse model of inherited Primary Erythromelalgia (PE, hNav1.7 L858F), a human pain disorder caused by a mutation in SCN9A. This hNav1.7 L858F TAP tag mouse line recapitulated the human PE phenotype and will potentially be useful in preclinical screening of candidate Nav1.7 blockers.
Article
Full-text available
The effects during healthy aging of the tetrodotoxin-resistant voltage-gated sodium channel 1.8 (Nav1.8), the acid-sensing ion channel-3 (ASIC3), the purinergic-receptor 2X3 (P2X3) and transient receptor potential of melastatin-8 (TRPM8) on responses to non-noxious stimuli are poorly understood. These effects will influence the transferability to geriatric subjects of findings obtained using young animals. To evaluate the involvement of these functional markers in mechanical and cold sensitivity to non-noxious stimuli and their underlying mechanisms, we used a combination of immunohistochemistry and quantitation of immunostaining in sub-populations of neurons of the dorsal root ganglia (DRG), behavioral tests, pharmacological interventions and Western-blot in healthy male Wistar rats from 3 to 24 months of age. We found significantly decreased sensitivity to mechanical and cold stimuli in geriatric rats. These behavioural alterations occurred simultaneously with differing changes in the expression of Nav1.8, ASIC3, P2X3 and TRPM8 in the DRG at different ages. Using pharmacological blockade in vivo we demonstrated the involvement of ASIC3 and P2X3 in normal mechanosensation and of Nav1.8 and ASIC3 in cold sensitivity. Geriatric rats also exhibited reductions in the number of A-like large neurons and in the proportion of peptidergic to non-peptidergic neurons. The changes in normal sensory physiology in geriatric rats we report here strongly support the inclusion of aged rodents as an important group in the design of pre-clinical studies evaluating pain treatments.
Article
Full-text available
Key points C‐nociceptors are generally assumed to have a low maximum discharge frequency of 10–30 Hz. However, only mechano‐insensitive ‘silent’ C‐nociceptors cannot follow electrical stimulation at 5 Hz (75 pulses) whereas polymodal C‐nociceptors in the pig follow stimulation at up to 100 Hz without conduction failure. Sensitization by nerve growth factor increases the maximum following frequency of ‘silent’ nociceptors in pig skin and might thereby contribute in particular to intense pain sensations in chronic inflammation. A distinct class of C‐nociceptors with mechanical thresholds >150 mN resembles ‘silent’ nociceptors at low stimulation frequencies in pigs and humans, but is capable of 100 Hz discharge and thus is suited to encode painfulness of noxious mechanical stimuli. Abstract Using extracellular single‐fibre recordings from the saphenous nerve in pig in vivo, we investigated peak following frequencies (5–100 Hz) in different classes of C‐nociceptors and their modulation by nerve growth factor. Classes were defined by sensory (mechano‐sensitivity) and axonal characteristics (activity dependent slowing of conduction, ADS). Mechano‐insensitive C‐nociceptors (CMi) showed the highest ADS (34% ± 8%), followed only 66% ± 27% of 75 pulses at 5 Hz and increasingly blocked conduction at higher frequencies. Three weeks following intradermal injections of nerve growth factor, peak following frequency increased specifically in the sensitized mechano‐insensitive nociceptors (20% ± 16% to 38% ± 23% response rate after 72 pulses at 100 Hz). In contrast, untreated polymodal nociceptors with moderate ADS (15.2% ± 10.2%) followed stimulation frequencies of 100 Hz without conduction failure (98.5% ± 6%). A distinct class of C‐nociceptors was exclusively sensitive to strong forces above 150 mN. This class had a high ADS (27.2% ± 7.6%), but displayed almost no propagation failure even at 100 Hz stimulation (84.7% ± 17%). Also, among human mechanosensitive nociceptors (n = 153) those with thresholds above 150 mN (n = 5) showed ADS typical of silent nociceptors. C‐fibres with particularly high mechanical thresholds and high following frequency form a distinct nociceptor class ideally suited to encode noxious mechanical stimulation under normal conditions when regular silent nociceptors are inactive. Sensitization by nerve growth factor increases maximum discharge frequency of silent nociceptors, thereby increasing the frequency range beyond their physiological limit, which possibly contributes to excruciating pain under inflammatory conditions.
Article
Full-text available
The voltage-gated sodium channel Nav1.8 mediates the tetrodotoxin-resistant (TTX-R) Na⁺ current in nociceptive primary sensory neurons, which has an important role in the transmission of painful stimuli. Here, we describe the functional modulation of the human Nav1.8 α-subunit in Xenopus oocytes by auxiliary β subunits. We found that the β3 subunit down-regulated the maximal Na⁺ current amplitude and decelerated recovery from inactivation of hNav1.8, whereas the β1 and β2 subunits had no such effects. The specific regulation of Nav1.8 by the β3 subunit constitutes a potential novel regulatory mechanism of the TTX-R Na⁺ current in primary sensory neurons with potential implications in chronic pain states. In particular, neuropathic pain states are characterized by a down-regulation of Nav1.8 accompanied by increased expression of the β3 subunit. Our results suggest that these two phenomena may be correlated, and that increased levels of the β3 subunit may directly contribute to the down-regulation of Nav1.8. To determine which domain of the β3 subunit is responsible for the specific regulation of hNav1.8, we created chimeras of the β1 and β3 subunits and co-expressed them with the hNav1.8 α-subunit in Xenopus oocytes. The intracellular domain of the β3 subunit was shown to be responsible for the down-regulation of maximal Nav1.8 current amplitudes. In contrast, the extracellular domain mediated the effect of the β3 subunit on hNav1.8 recovery kinetics.
Thesis
Hintergrund und Ziele: Bei der Applikation des Muskelrelaxans Rocuronium (Esmeron®) im Rahmen der Einleitung einer Allgemeinanästhesie wird sehr häufig ein Injektionsschmerz beobachtet. Eine mögliche Erklärung hierfür ist die direkte Aktivierung nozizeptiver C-Fasern. Diese Arbeit soll untersuchen, ob Rocuronium und die chemisch-verwandten Muskelrelaxanzien Pancuronium und Vecuronium sowie die strukturell unterschiedlichen Wirkstoffe Atracurium und Succinylcholin Agonisten an nozizeptiven TRP-Kanälen - und hier insbesondere am Irritanzienrezeptor TRPA1 und am Capsaicinrezeptor TRPV1 - sind und über diesen Mechanismus nozizeptive Nervenfasern aktivieren können. Methoden: Human embryonic kidney (HEK) 293t-Zellen wurden mit Wildtyp- und Mutanten-cDNAs von TRPA1, TRPV1, TRPV2, TRPV3, TRPV4 und TRPM8 mit Hilfe des Nanofectin Kits transient transfiziert. Zusätzlich wurde CD8-pih3m cotransfiziert um Zellen, die das gewünschte Protein exprimieren, mittels anti-CD8-Immunobeads identifizieren zu können. Zur Messung wurden die Zellen in ein Bad aus calciumfreier Extrazellularlösung eingebracht und aus Borosilikat gezogene Pipetten zur Hälfte mit Intrazellularlösung gefüllt. Die Patch-Clamp-Experimente wurden in der Whole-Cell-Konfiguration bei Zimmertemperatur durchgeführt. Das Haltepotential wurde auf -60 mV eingestellt. Ergebnisse und Beobachtungen: Rocuronium aktiviert hTRPA1 dosisabhängig ab einer Konzentration von 10 nM, hTRPV1 ab einer Konzentration von 1 nM. In hohen Konzentrationen verringert sich die Stromamplitude bei beiden Kanälen wieder, was auf eine zusätzlich blockierende Eigenschaft von Rocuronium in hohen Konzentrationen an beiden Kanälen hinweisen kann. Dazu konnte gezeigt werden, dass Rocuronium Carvacrol-induzierte Ströme in hTRPA1-exprimierende Zellen und Capsaicin-induzierte Ströme in hTRPV1-exprimierende Zellen anteilig blockiert. Die Mutante hTRPA1-3C zeigt im Vergleich zum Wildtyp stark verminderte und die Mutante hTRPA1-3CK keine Einwärtsströme durch Rocuronium. Ein niedriger pH sensibilisiert hTRPV1 für die Aktivierung durch Rocuronium nicht, es zeigte sich tendenziell eine Blockade von hTRPV1. Vecuronium, Pancuronium, Atracurium und Succinylcholin induzieren ebenfalls deutliche Einwärtsströme in hTRPA1-exprimierende Zellen. Schlussfolgerung: Rocuronium aktiviert hTRPA1 und hTRPV1 im heterologen Expressionssystem in klinisch-relevanten Konzentrationen. In höheren Konzentrationen werden beide Kanäle durch Rocuronium blockiert. Die Aktivierung von hTRPA1 wird über bestimmte Aminosäuren im N-terminalen Rest vermittelt. Die Aktivierung beider Kanäle in nozizeptiven Neuronen könnte mit verantwortlich sein für den klinisch-beobachteten Brennschmerz durch Rocuronium.
ResearchGate has not been able to resolve any references for this publication.