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Hanns Ulrich Zeilhofer

Publications and source records attributed to Hanns Ulrich Zeilhofer.

At least 19 recordsLinked to original sources
PubMed2006

UFP-101 antagonizes the spinal antinociceptive effects of nociceptin/orphanin FQ: behavioral and electrophysiological studies in mice.

Nociceptin/orphanin FQ (N/OFQ) modulates various biological functions, including nociception, via selective stimulation of the N/OFQ peptide receptor (NOP). Here we used the NOP selective antagonist UFP-101 to characterize the receptor involved in the spinal antinociceptive effects of N/OFQ evaluated in the mouse tail withdrawal assay and to investigate the mechanism underlying this action by assessing excitatory postsynaptic currents (EPSC) in laminas I and II of the mouse spinal cord dorsal horn with patch-clamp techniques. Intrathecal (i.t.) injection of N/OFQ in the range of 0.1-10 nmol produced a dose dependent antinociceptive effect, which was prevented by UFP-101, but not by naloxone. In contrast the antinociceptive effect of the mu-opioid peptide receptor agonist endomorphin-1 was blocked by naloxone but not by UFP-101. Moreover, N/OFQ and endomorphin-1 induced a significant antinociceptive effect in wild type mice while in mice knockout for the NOP receptor gene only endomorphin-1 was found to be active. In mouse spinal cord slices 1 microM N/OFQ reduced EPSC to 60+/-4% of control values. This inhibitory effect was reversed in a concentration dependent manner by UFP-101 (pA2 value 6.44). The present results demonstrate that N/OFQ-induced spinal antinociception in vivo and inhibition of spinal excitatory transmission in vitro are mediated by receptors of the NOP type.

Analgesics↗
PubMed2006

Prostanoids in nociception and pain.

Prostaglandins are lipid mediators produced by cyclooxygenases from arachidonic acid, which serve pivotal functions in inflammation and pain. Inhibition of their production is the major analgesic mechanism of action of non-steroidal anti-inflammatory drugs (NSAIDs)-but also the source of most of their unwanted effects. While the development of selective inhibitors of inducible cyclooxygenase (COX)-2 (so called coxibs) has greatly reduced gastrointestinal side effects, the recent disappointment about a potential cardiovascular toxicity of COX-2-selective inhibitors has boosted interest in alternative targets. The discovery of several prostaglandin synthases and of distinct prostaglandin receptors has unraveled an unforeseen diversity within the prostanoid synthetic pathway. Behavioral and electrophysiological work in particular with genetically engineered mice meanwhile provides new clues to the role of different prostaglandins, prostaglandin synthases and prostaglandin receptors in pain pathways.

Animals↗
PubMed2006

Analgesic strategies beyond the inhibition of cyclooxygenases.

Blocking the formation of prostaglandins with cyclooxygenase (COX) inhibitors has been the treatment of choice for inflammatory pain for more than a century. Although these agents provide profound pain relief, their long-term use is hampered by severe side-effects, mainly ulceration of the upper gastrointestinal tract. The development of COX-2-selective inhibitors ("coxibs") has significantly reduced gastrointestinal toxicity, but evidence from controlled clinical trials and experimental studies indicates that the use of coxibs has a significant cardiovascular risk. Recently, signalling elements downstream of COX-2 inhibition have been identified, which offer a great diversity of possible targets. This review focuses on prostaglandin E synthases, prostaglandin receptors and downstream effectors of prostaglandins in the PNS and CNS, including transient receptor potential channels, tetrodotoxin-resistant Na(+) channels and inhibitory glycine receptors. These novel targets should enable inflammatory pain to be treated with improved specificity and, possibly, fewer side-effects.

Cyclooxygenase Inhibitors↗
PubMed2006

Spinal prostaglandin E receptors of the EP2 subtype and the glycine receptor alpha3 subunit, which mediate central inflammatory hyperalgesia, do not contribute to pain after peripheral nerve injury or formalin injection.

Inflammation, peripheral nerve injury and chemical irritants can cause central sensitization in pain pathways. Prostaglandins produced in the CNS induce central sensitization during inflammation mainly by relieving nociceptive neurons from glycinergic inhibition. We have recently identified spinal prostaglandin E receptors of the EP2 subtype (EP2 receptors) and the glycine receptor alpha3 subunit (GlyR alpha3) as signal transduction elements involved in the generation of central inflammatory hyperalgesia. It is however still unknown to what extent inhibition of glycine receptors by PGE2 contributes to neuropathic or chemically induced pain. To address this question, we have analyzed mice deficient in the EP2 receptor (EP2-/- mice) or in the GlyR alpha3 subunit (GlyR alpha3-/- mice) using the chronic constriction injury (CCI) model of neuropathic pain and the formalin test. We found that EP2-/- mice and GlyR alpha3-/- mice develop thermal and mechanical hyperalgesia in the CCI model indistinguishable from that seen in wild-type mice. In the formalin test, EP2-/- mice, but not GlyR alpha3-/- mice, exhibited reduced nocifensive behavior. The lack of a phenotype in GlyR alpha3-/- mice together with the absence of a facilitating effect of intrathecal PGE2 on formalin-induced nociception in wild-type mice suggests that peripheral rather than spinal EP2 receptors are involved. These results indicate that inhibition of glycinergic neurotransmission by EP2 receptor activation does not contribute to pain following peripheral nerve injury or chemical irritation with formalin. Our results thus provide further evidence that inflammatory hyperalgesia and neuropathic pain involve different mechanisms of central sensitization.

Animals↗
PubMed2006

Endogenous nociceptin/orphanin FQ signalling produces opposite spinal antinociceptive and supraspinal pronociceptive effects in the mouse formalin test: pharmacological and genetic evidences.

Nociceptin/orphanin FQ (N/OFQ) has been demonstrated to modulate nociceptive transmission via selective activation of N/OFQ peptide (NOP) receptors. Despite huge research efforts, the role(s) of the endogenous N/OFQ-NOP receptor system in pain processing remains incompletely understood. In the present study, we investigated the role of endogenous N/OFQ in the processing of tonic nociceptive input. To address this issue the effects of NOP-selective antagonists [Nphe1,Arg14,Lys15]N/OFQ-NH2 (UFP-101) and J-113397 on nociceptive behaviour, and the nociceptive phenotype of NOP receptor-deficient mice were tested in the mouse formalin test. Twenty microliters of 1.5% formalin solution was injected subcutaneously into the right hind paw causing a characteristic pattern of nociceptive behaviours (licking, biting and lifting of the injected paw). In control mice, the injection of formalin resulted in a classical biphasic nociceptive response with the first phase lasting from 0 to 10 min and the second phase from 15 to 45 min. UFP-101 at 10 nmol/mouse (but not at 1 nmol/mouse) produced antinociceptive action when injected intracerebroventricularly and a pronociceptive action when given intrathecally. Systemic administration of J-113397 (10 mg/kg, intravenously) and the genetic ablation of the NOP receptor gene both produced a significant increase of mouse nociceptive behaviour. Collectively, these results demonstrate that endogenous N/OFQ-NOP receptor signalling is activated during the mouse formalin test producing spinal antinociceptive and supraspinal pronociceptive effects. The overall effect of blocking NOP receptor signalling, by either systemic pharmacological antagonism or genetic ablation, indicates that the spinal antinociceptive action prevails over supraspinal pronociceptive effects.

Analgesics↗
PubMed2006

Imaging of hyperalgesia in rats by functional MRI.

Cerebral activation in response to sequences of temperature boosts at the hindpaw was observed in functional magnetic resonance imaging (fMRI) experiments in isoflurane anesthetized rats. Cingulate, retrosplenial, sensory-motor and insular cortex, medial and lateral posterior thalamic nuclei, pretectal area, hypothalamus and periaqueductal gray were the most consistently, often bilaterally activated regions. With the same experimental paradigm, activity changes in the brain following subcutaneous zymosan injection into one hindpaw were detected. These changes developed over time (up to 4h) in parallel with the temporal development of hyperalgesia shown by a modified Hargreaves test, thus reflecting processes of peripheral and central sensitization. When the heat stimuli were applied to the inflamed paw, the hyperalgesia manifested itself as a volume increase of the activated areas and/or an enhanced functional blood oxygenation level dependent (BOLD) signal in all the above-mentioned brain regions. Enhanced BOLD signals were also observed in response to stimulation of the contralateral non-injected paw. They were significant in higher associative regions and more pronounced in output-related than in input-related brain structures. This indicates additional sensitization processes in the brain, which we named cerebral sensitization. Long lasting zymosan-induced hyperalgesia could be monitored with high resolution fMRI in rats under isoflurane anaesthesia. This technique may provide an effective method for testing new analgesics and studying structure specific pain processing.

Afferent Pathways↗
PubMed2005

Glycinergic neurons expressing enhanced green fluorescent protein in bacterial artificial chromosome transgenic mice.

Although glycine is a major inhibitory transmitter in the mammalian CNS, the role of glycinergic neurons in defined neuronal circuits remains ill defined. This is due in part to difficulties in identifying these cells in living slice preparations for electrophysiological recordings and visualizing their axonal projections. To facilitate the morphological and functional analysis of glycinergic neurons, we generated bacterial artificial chromosome (BAC) transgenic mice, which specifically express enhanced green fluorescent protein (EGFP) under the control of the promotor of the glycine transporter (GlyT) 2 gene, which is a reliable marker for glycinergic neurons. Neurons expressing GlyT2-EGFP were intensely fluorescent, and their dendrites and axons could be visualized in great detail. Numerous positive neurons were detected in the spinal cord, brainstem, and cerebellum. The hypothalamus, intralaminar nuclei of the thalamus, and basal forebrain also received a dense GlyT2-EGFP innervation, whereas in the olfactory bulb, striatum, neocortex, hippocampus, and amygdala positive fibers were much less abundant. No GlyT2-EGFP-positive cell bodies were seen in the forebrain. On the subcellular level, GlyT2-EGFP fluorescence was colocalized extensively with glycine immunoreactivity in somata and dendrites and with both glycine and GlyT2 immunoreactivity in axon terminals, as shown by triple staining at all levels of the neuraxis, confirming the selective expression of the transgene in glycinergic neurons. In slice preparations of the spinal cord, no difference between the functional properties of EGFP-positive and negative neurons could be detected, confirming the utility of visually identifying glycinergic neurons to investigate their functional role in electrophysiological studies.

Amino Acid Transport Systems, Neutral↗
PubMed2005

Synaptic modulation in pain pathways.

All higher organisms possess a sensory system that allows them to detect potentially tissue-damaging (or noxious) stimuli. The proper functioning of this system is essential to protect their bodies from tissue damage. However, under pathological conditions after severe tissue injury and in inflammatory or neuropathic diseases, this system can become sensitized, and pain can then turn into a disease. Such exaggerated pain sensation (or hyperalgesia) can arise at different levels of integration. It can originate from an increased responsiveness of primary nociceptors, specialized nerve cells, which sense noxious stimuli, or from changes in the central processing of nociceptive input. Like other sensory input, nociceptive signals are relayed in the central nervous system by neurons, which communicate with each other mainly through chemical synapses. Changes in the excitability of these neurons or in the strength of their synaptic coupling provide the cellular basis for many forms of pathological pain. This review focuses on the synaptic processing of pain-related signals in the spinal cord dorsal horn, the first site of synaptic integration in the pain pathway. Particular emphasis is paid to synaptic processes underlying the generation of pathological pain evoked by inflammation or neuropathic diseases.

Analgesics↗
PubMed2005

Spinal inflammatory hyperalgesia is mediated by prostaglandin E receptors of the EP2 subtype.

Blockade of prostaglandin (PG) production by COX inhibitors is the treatment of choice for inflammatory pain but is also prone to severe side effects. Identification of signaling elements downstream of COX inhibition, particularly of PG receptor subtypes responsible for pain sensitization (hyperalgesia), provides a strategy for better-tolerated analgesics. Here, we have identified PGE2 receptors of the EP2 receptor subtype as key signaling elements in spinal inflammatory hyperalgesia. Mice deficient in EP2 receptors (EP2-/- mice) completely lack spinal PGE2-evoked hyperalgesia. After a peripheral inflammatory stimulus, EP2-/- mice exhibit only short-lasting peripheral hyperalgesia but lack a second sustained hyperalgesic phase of spinal origin. Electrophysiological recordings identify diminished synaptic inhibition of excitatory dorsal horn neurons as the dominant source of EP2 receptor-dependent hyperalgesia. Our results thus demonstrate that inflammatory hyperalgesia can be treated by targeting of a single PG receptor subtype and provide a rational basis for new analgesic strategies going beyond COX inhibition.

Animals↗
PubMed2004

The AMPA receptor subunits GluR-A and GluR-B reciprocally modulate spinal synaptic plasticity and inflammatory pain.

Ca(2+)-permeable AMPA receptors are densely expressed in the spinal dorsal horn, but their functional significance in pain processing is not understood. By disrupting the genes encoding GluR-A or GluR-B, we generated mice exhibiting increased or decreased numbers of Ca(2+)-permeable AMPA receptors, respectively. Here, we demonstrate that AMPA receptors are critical determinants of nociceptive plasticity and inflammatory pain. A reduction in the number of Ca(2+)-permeable AMPA receptors and density of AMPA channel currents in spinal neurons of GluR-A-deficient mice is accompanied by a loss of nociceptive plasticity in vitro and a reduction in acute inflammatory hyperalgesia in vivo. In contrast, an increase in spinal Ca(2+)-permeable AMPA receptors in GluR-B-deficient mice facilitated nociceptive plasticity and enhanced long-lasting inflammatory hyperalgesia. Thus, AMPA receptors are not mere determinants of fast synaptic transmission underlying basal pain sensitivity as previously thought, but are critically involved in activity-dependent changes in synaptic processing of nociceptive inputs.

Animals↗
PubMed2004

GlyR alpha3: an essential target for spinal PGE2-mediated inflammatory pain sensitization.

Prostaglandin E2 (PGE2) is a crucial mediator of inflammatory pain sensitization. Here, we demonstrate that inhibition of a specific glycine receptor subtype (GlyR alpha3) by PGE2-induced receptor phosphorylation underlies central inflammatory pain sensitization. We show that GlyR alpha3 is distinctly expressed in superficial layers of the spinal cord dorsal horn. Mice deficient in GlyR alpha3 not only lack the inhibition of glycinergic neurotransmission by PGE2 seen in wild-type mice but also show a reduction in pain sensitization induced by spinal PGE2 injection or peripheral inflammation. Thus, GlyR alpha3 may provide a previously unrecognized molecular target in pain therapy.

Amino Acid Sequence↗
PubMed2004

Gabapentin may inhibit synaptic transmission in the mouse spinal cord dorsal horn through a preferential block of P/Q-type Ca2+ channels.

Gabapentin is a lipophilic analog of gamma-amino butyric acid (GABA) with therapeutic activity against certain forms of epilepsy and neuropathic pain. Despite its structural similarity to GABA, it does not bind GABAA or GABAB receptors and the mechanism, especially of its analgesic action, has remained elusive. Here, we have studied its effects on synaptic transmission mediated by the major spinal fast excitatory and inhibitory neurotransmitters, L-glutamate and glycine, in the superficial layers of the spinal cord dorsal horn, a CNS area, which is critically involved in nociception. Gabapentin reversibly reduced evoked excitatory postsynaptic currents mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA-EPSCs) and inhibitory postsynaptic currents mediated by glycine (gly-IPSCs). Inhibition of AMPA-EPSCs and gly-IPSCs occurred with similar potencies (approximately 10-50 nM) and by about the same degree (approximately 40% at 1 microM). Gabapentin did not affect membrane currents elicited by exogenously applied glutamate or glycine arguing against a postsynaptic site of action. Selective blockade of N-type Ca2+ channels with omega-conotoxin GVIA dramatically increased and blockade of P/Q-type channels with omega-agatoxin IVA strongly attenuated inhibition of evoked synaptic transmission by gabapentin. These results show that gabapentin affects both excitatory and inhibitory spinal neurotransmission via a presynaptic mechanism which preferentially involves P/Q-type Ca2+ channels.

Acetates↗
PubMed2004

The spinal antinociceptive effect of nocistatin in neuropathic rats is blocked by D-serine.

BACKGROUND: The neuropeptide nocistatin (NST) has been implicated in the modulation of nociceptive responses in the spinal cord. Depending on the dose, both pronociceptive and antinociceptive effects have repeatedly been reported. The pronociceptive effect is most likely attributable to inhibition of synaptic glycine and gamma-aminobutyric acid release and a subsequent reduction in the activation of inhibitory glycine and gamma-aminobutyric acid receptors, but the mechanisms of its antinociceptive action have hitherto remained elusive. It has recently been demonstrated that synaptically released glycine contributes to N-methyl-D-aspartate receptor activation. The authors therefore investigated whether a reduction in glycine release might also account for the antinociceptive action of NST in neuropathic rats. METHODS: The authors analyzed the effects of spinally applied NST in the chronic constriction injury model of neuropathic pain. NST was injected intrathecally from nanomolar to picomolar doses and its effects on thermal paw withdrawal latencies were monitored. Furthermore, we tested whether D-serine (100 microg per rat), a full agonist at the glycine binding site of the N-methyl-D-aspartate receptor, would interfere with the effects of NST. RESULTS: At high doses (10 nmol/rat), intrathecally injected NST was pronociceptive, whereas lower doses (1 pmol/rat) elicited antinociception. The antinociceptive, but not the pronociceptive, action was occluded by intrathecal pretreatment with D-serine. L-serine, which does not bind to N-methyl-D-aspartate receptors, affected neither the pronociceptive nor the antinociceptive effect. CONCLUSIONS: These results demonstrate that NST produces a biphasic dose-dependent effect on neuropathic pain. The spinal antinociception by NST is most likely attributable to inhibition of glycine-dependent N-methyl-D-aspartate receptor activation.

Analgesics, Opioid↗
PubMed2003

Facilitation of spinal NMDA receptor currents by spillover of synaptically released glycine.

In the mammalian CNS, N-methyl-D-aspartate (NMDA) receptors serve prominent roles in many physiological and pathophysiological processes including pain transmission. For full activation, NMDA receptors require the binding of glycine. It is not known whether the brain uses changes in extracellular glycine to modulate synaptic NMDA responses. Here, we show that synaptically released glycine facilitates NMDA receptor currents in the superficial dorsal horn, an area critically involved in pain processing. During high presynaptic activity, glycine released from inhibitory interneurons escapes the synaptic cleft and reaches nearby NMDA receptors by so-called spillover. In vivo, this process may contribute to the development of inflammatory hyperalgesia.

Analgesics↗
PubMed2003

Nociceptin/orphanin FQ and its receptor--potential targets for pain therapy?

The neuropeptide nociceptin, also called orphanin FQ (N/OFQ), is the endogenous agonist of the N/OFQ peptide receptor (NOP receptor). Both N/OFQ and the NOP receptor share a high degree of homology with classical opioid peptides and opioid receptors, respectively, and use similar signal transduction pathways as classical opioids. The NOP receptor has thus been regarded as the fourth member of the opioid receptor family. Despite this close relationship, 7 years of research have demonstrated that the N/OFQ system has a distinct pharmacological profile and serves different physiological functions. In particular, its role in the control of pain and analgesia at different levels of integration appears quite different from that of classical opioids. The recent development of specific antagonists at the NOP receptor and of NOP receptor or N/OFQ precursor knock-out mice have generated new insights into the role of N/OFQ in pain processing and help to evaluate the N/OFQ-NOP system as a potential target for new analgesic drugs.

Animals↗
PubMed2003

Normal sensitivity to acute pain, but increased inflammatory hyperalgesia in mice lacking the nociceptin precursor polypeptide or the nociceptin receptor.

Nociceptin/orphanin FQ (N/OFQ) is the endogenous agonist of the N/OFQ peptide receptor (NOP receptor). It is released from a larger precursor polypeptide, called prepro-nociceptin (ppN/OFQ) from which, in addition to N/OFQ, other biologically active neuropeptides may be derived. Increasing evidence indicates that exogenous application of N/OFQ to the central nervous system of mice and rats induces pro- and antinociceptive effects depending on the dose and site of administration. Much less is known about a potential contribution of endogenous N/OFQ to pain control. Here, we have used a genetic approach to address this topic. Mice deficient in either the NOP receptor (NOP-R-/- mice) or the N/OFQ precursor polypeptide (ppN/OFQ-/- mice) or both (double knockout mice) were compared with wild-type littermates in animal models of acute and tonic pain. Nociceptive responses to acute noxious heat of all three types of mutant mice were indistinguishable from those of wild-type mice. Accordingly, nociceptive behaviour was very similar in the early phase of the formalin test. However, NOP-R-/-, ppN/OFQ-/- and double knockout mice showed markedly stronger nociceptive responses during prolonged nociceptive stimulation in the second phase of the formalin test and significantly lower thermal pain thresholds in inflamed tissue after zymosan A injection. These results indicate that N/OFQ contributes significantly to endogenous pain control during prolonged nociceptive stimulation but does not affect acute pain sensitivity. Among the three types of mutant mice nociceptive behaviour was nearly identical, indicating that the lack of other potential ppN/OFQ products in the ppN/OFQ-/- mice was apparently without effect on the nociceptive phenotype.

Animals↗
PubMedDate not supplied

Ionotropic glutamate receptors of amacrine cells of the mouse retina.

The mammalian retina contains approximately 30 different morphological types of amacrine cells, receiving glutamatergic input from bipolar cells. In this study, we combined electrophysiological and pharmacological techniques in order to study the glutamate receptors expressed by different types of amacrine cells. Whole-cell currents were recorded from amacrine cells in vertical slices of the mouse retina. During the recordings the cells were filled with Lucifer Yellow/Neurobiotin allowing classification as wide-field or narrow-field amacrine cells. Amacrine cell recordings were also carried out in a transgenic mouse line whose glycinergic amacrine cells express enhanced green fluorescent protein (EGFP). Agonist-induced currents were elicited by exogenous application of NMDA, AMPA, and kainate (KA) while holding cells at -75 mV. Using a variety of specific agonists and antagonists (NBQX, AP5, cyclothiazide, GYKI 52466, GYKI 53655, SYM 2081) responses mediated by AMPA, KA, and NMDA receptors could be dissected. All cells (n = 300) showed prominent responses to non-NMDA agonists. Some cells expressed AMPA receptors exclusively and some cells expressed KA receptors exclusively. In the majority of cells both receptor types could be identified. NMDA receptors were observed in about 75% of the wide-field amacrine cells and in less than half of the narrow-field amacrine cells. Our results confirm that different amacrine cell types express distinct sets of ionotropic glutamate receptors, which may be critical in conferring their unique temporal responses to this diverse neuronal class.

Amacrine Cells↗