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S Bramwell

Publications and source records attributed to S Bramwell.

15 recordsLinked to original sources
PubMed2003

Identification of MEK1 as a novel target for the treatment of neuropathic pain.

(1) In the present study we have attempted to identify changes in gene expression which are associated with neuropathic pain using subtractive suppression hybridization analysis of the lumbar spinal cord of animals suffering streptozocin induced diabetic neuropathy. (2) Using this approach, we found a significant up-regulation of several key components of the extracellular signal-regulated kinase (ERK) cascade. These findings were confirmed by Western blot analysis, which demonstrated that the levels of active ERK1 and 2 correlated with the onset of streptozocin-induced hyperalgesia. (3) Intrathecal administration of the selective MAPK/ERK-kinase (MEK) inhibitor PD 198306 dose-dependently (1-30 micro g) blocked static allodynia in both the streptozocin and the chronic constriction injury (CCI) models of neuropathic pain. (4) The antihyperalgesic effects of PD 198306, in both the streptozocin and CCI models of neuropathic pain, correlated with a reduction in the elevated levels of active ERK1 and 2 in lumbar spinal cord. (5) Intraplantar administration of PD 198306 had no effect in either model of hyperalgesia, indicating that changes in the activation of ERKs and the effect of MEK inhibition are localized to the central nervous system. (6) In summary, we have demonstrated for the first time that the development of neuropathic pain is associated with an increase in the activity of the MAPK/ERK-kinase cascade within the spinal cord and that enzymes in this pathway represent potential targets for the treatment of this condition.

Animals↗
PubMed2001

Streptozocin-induced neuropathy is associated with altered expression of voltage-gated calcium channel subunit mRNAs in rat dorsal root ganglion neurones.

Voltage-gated calcium channels (VGCCs) within sensory neurones are believed to perform an important role in neuropathic pain. In the present study we examine the changes in VGCC mRNA which occur following streptozocin- (STZ) induced diabetic neuropathy using in situ hybridization. STZ caused a significant increase in alpha(2)delta(1), alpha(2)delta(2), and alpha(2)delta(3) mRNA levels in all neuronal cell types. Similarly, mRNA levels of alpha(1F), alpha(1I), and alpha(1S) were increased in all cell types studied whilst alpha(1A) and alpha(1G) mRNAs were specifically upregulated in medium and large diameter neurones. In conclusion, we demonstrate that the induction of diabetic neuropathy is associated with dramatic changes in the expression of VGCCs.

Animals↗
PubMed2001

Beta3, a novel auxiliary subunit for the voltage gated sodium channel is upregulated in sensory neurones following streptozocin induced diabetic neuropathy in rat.

In the present study we have used in situ hybridization to examine the changes in mRNA expression of the voltage gated sodium channel subunits beta1 and beta3, which occur in response to streptozocin induced diabetic neuropathy. Under control conditions beta1 mRNA was detected throughout the spinal cord and in large dorsal root ganglion (DRG) Abeta fibres whilst beta3 mRNA was expressed exclusively in the layers I/II and X of the spinal cord and in small DRG c-fibres. Following streptozocin treatment, the expression of beta1 mRNA remained unchanged in both the spinal cord and DRG whilst beta3 message was significantly increased in both the spinal cord and in medium diameter Adelta type DRG neurones. In conclusion, the present study illustrates that the development of the neuropathic pain state is associated with distinct changes in the pattern of beta3 subunit expression and that these changes appear to be specific to the neuropathic pain state induced.

Animals↗
PubMed2000

Gabapentin inhibits excitatory synaptic transmission in the hyperalgesic spinal cord.

In the present study we tested the effects of the antihyperalgesic compound gabapentin on dorsal horn neurones in adult spinal cord. Slices were taken from control and hyperalgesic animals suffering from streptozocin-induced diabetic neuropathy. At concentrations up to 100 microM, bath application failed to affect the resting membrane properties of dorsal horn neurones taken from both groups of animal. In contrast, bath application of gabapentin dramatically reduced the magnitude of the excitatory postsynaptic current (EPSC) in neurones taken from hyperalgesic animals without altering the magnitude of the EPSC in control animals. Using a paired pulse stimulation protocol, together with analysis of miniature EPSC's, it was possible to demonstrate that gabapentin mediated these effects via a pre-synaptic site of action.

Acetates↗
PubMed2000

beta3, a novel auxiliary subunit for the voltage-gated sodium channel, is expressed preferentially in sensory neurons and is upregulated in the chronic constriction injury model of neuropathic pain.

Adult dorsal root ganglia (DRG) have been shown to express a wide range of voltage-gated sodium channel alpha-subunits. However, of the auxiliary subunits, beta1 is expressed preferentially in only large- and medium-diameter neurons of the DRG while beta2 is absent in all DRG cells. In view of this, we have compared the distribution of beta1 in rat DRG and spinal cord with a novel, recently cloned beta1-like subunit, beta3. In situ hybridization studies demonstrated high levels of beta3 mRNA in small-diameter c-fibres, while beta1 mRNA was virtually absent in these cell types but was expressed in 100% of large-diameter neurons. In the spinal cord, beta3 transcript was present specifically in layers I/II (substantia gelatinosa) and layer X, while beta1 mRNA was expressed in all laminae throughout the grey matter. Since the pattern of beta3 expression in DRG appears to correlate with the TTX-resistant voltage-gated sodium channel subunit PN3, we co-expressed the two subunits in Xenopus oocytes. In this system, beta3 caused a 5-mV hyperpolarizing shift in the threshold of activation of PN3, and a threefold increase in the peak current amplitude when compared with PN3 expressed alone. On the basis of these results, we examined the expression of beta-subunits in the chronic constriction injury model of neuropathic pain. Results revealed a significant increase in beta3 mRNA expression in small-diameter sensory neurons of the ipsilateral DRG. These results show that beta3 is the dominant auxiliary sodium channel subunit in small-diameter neurons of the rat DRG and that it is significantly upregulated in a model of neuropathic pain.

Animals↗
PubMed1999

Detection of static and dynamic components of mechanical allodynia in rat models of neuropathic pain: are they signalled by distinct primary sensory neurones?

In the present study, chronic constrictive injury (CCI model) of the sciatic nerve or tight ligation of L5 and L6 spinal nerves (Chung model) produced both dynamic and static components of mechanical allodynia in rats. The two responses were detected, respectively, by lightly stroking the hind paw with cotton wool or application of pressure using von Frey hairs. Animals with spinal nerve ligation developed both types of responses at a faster rate compared to animals with the CCI. Morphine (1-3 mg/kg, s.c.) dose-dependently blocked static but not dynamic allodynia. In contrast, pregabalin (previously S-isobutylgaba and CI-1008) dose-dependently (3-30 mg/kg, p.o.) blocked both types of allodynia. In CCI animals, two administrations of capsaicin (100 microg/50 microl) into the plantar surface of the ipsilateral paw at 1-h intervals blocked the maintenance of thermal hyperalgesia without affecting either static or dynamic allodynia. The similar administration of a further two doses of capsaicin into the same animals blocked the maintenance of static allodynia without affecting the dynamic response. These data indicate that thermal hyperalgesia, static and dynamic allodynia are respectively signalled by C-, Adelta- and Abeta/capsaicin insensitive Adelta- primary sensory neurones. It is suggested that pregabalin possesses a superior antiallodynic profile than morphine and may represent a novel class of therapeutic agents for the treatment of neuropathic pain.

Animals↗
PubMed1997

An antiserum to idazoxan recognizes an immunoreactive substance in human serum and cerebral spinal fluid which is not agmatine.

A polyclonal antibody was generated in rabbits to an idazoxan-albumin antigen. The anti-idazoxan antiserum had high affinity for unconjugated 3H-idazoxan (Kd of 19.8 nM) in a radio-immunoassay (RIA). Of various drugs and native molecules only idazoxan potently (Ki of 24 nM) inhibited 3H-idazoxan binding to the anti-idazoxan antibody. A few drugs weakly inhibited 3H-idazoxan binding (IC50 > 605 microM) with rank order of UK 14304 > guanabenz > cirazoline > amiloride > naphazoline. Neither agmatine, an endogenous clonidine displacing substance (CDS), catecholamines or imidazoles inhibited the binding of 3H-idazoxan to the anti-idazoxan antibody. The anti-idazoxan RIA was 4-6 fold more sensitive than an antibody to para-amino clonidine. The CDS detected by ligand displacement from bovine brain dose-dependently inhibited 3H-idazoxan binding. This immunoreactive (ir-) CDS activity was present in human (0.9-4.1 U/ml) and rat sera (1-2 U/ml) and in the cerebro-spinal fluid of eight patients with serious disease of the central nervous system, but not in controls. We conclude: (1) an anti-idazoxan RIA is a sensitive, selective and clinically applicable RIA for measuring ir-CDS; (2) ir-CDS is not agmatine; (3) CDS represents a family of endogenous ligands for imidazoline receptors including ir-CDS and agmatine.

Agmatine↗
PubMed1995

An antibody to agmatine localizes the amine in bovine adrenal chromaffin cells.

Agmatine, a newly identified amine in mammalian brain, is an endogenous ligand for imidazoline and alpha 2-adrenergic receptors. We sought to develop a polyclonal antibody to agmatine suitable for immunocytochemistry. Agmatine was conjugated to keyhole limpet hemocyanin and injected into rabbits. The polyclonal antiserum so generated dose-dependently recognized the agmatine conjugate but not carrier protein by dot blot. Its reaction with the conjugate was selectively antagonized by agmatine but not related compounds. The antiserum, but not pre-immune or pre-adsorbed antiserum, selectively stained cultured adrenal chromaffin cells. Our results indicate that agmatine immunoreactivity is contained in a sub-population of adrenal chromaffin cells and, thus, these antibodies are useful for immunocytochemical localization of the amine in mammalian tissues.

Adrenal Medulla↗
PubMed1993

Effect of acute and repeated administration of 5-HT1A receptor agonists on 5-HT release in rat brain in vivo.

1. Electrophysiological measurements of 5-HT neuronal activity report that repeated administration of 5-HT1A receptor agonists leads to desensitization of the 5-HT1A autoreceptor but this has not yet been detected in measurements of brain 5-HT synthesis or metabolism. Here we have determined the effect of repeated administration of 5-HT1A receptor agonists on brain 5-HT release using microdialysis. 2. Acute administration of the 5-HT1A receptor agonists buspirone (0.1-5 mg/kg s.c.) and ipsapirone (0.03-3 mg/kg s.c.) caused a dose-dependent decrease in 5-HT output in ventral hippocampus of the chloral hydrate anaesthetized rat. 3. The 5-HT response to buspirone (0.1 and 0.5 mg/kg s.c.) and ipsapirone (0.3 mg/kg s.c.) was significantly inhibited by pre-treatment with the 5-HT1/beta-adrenoceptor antagonist pindolol (8-16 mg/kg s.c.). The 5-HT response to buspirone (0.1 mg/kg s.c.) and ipsapirone (0.3 mg/kg s.c.) was not blocked by pretreatment with a combination of the beta 1 and beta 2-adrenoceptor antagonists metoprolol and ICI 118,551 (4 mg/kg s.c.). 4. The effect of an acute challenge of buspirone (0.5 mg/kg s.c.) on 5-HT output in ventral hippocampus was not attenuated in rats treated twice daily for 14 days with 0.5 or 5 mg/kg s.c. buspirone compared to saline-injected controls. Similarly, the decrease in 5-HT induced by an acute challenge of ipsapirone (0.5 mg/kg s.c.) was not attenuated in rats treated twice daily for 14 days with 5 mg/kg s.c. ipsapirone.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1993

Haemophilia A in the highlands: the investigation and management of two families in Tari.

A 12-year-old boy from Tari in the Southern Highlands of Papua New Guinea presented with prolonged bleeding from a minor injury to the lip. He had a history of profuse bleeding and joint swelling following minor trauma. He has two younger brothers with a similar history. It was demonstrated that they had a coagulation profile compatible with factor VIII deficiency and a family tree suggestive of haemophilia A. A further case was investigated some months later. Despite the neighbouring places of residence of the two families no familial connection could be established by involved discussions between family members. This was confirmed by reviewing the data held on the demographic surveillance system of the Tari Unit of the Papua New Guinea Institute of Medical Research. These families are considered against a background of the diagnosis and management of this condition in a rural part of Papua New Guinea. The long-term support of these patients and other similarly affected individuals presents difficult clinical and ethical problems for rural health services.

Child↗
PubMed1985

Development of a mouse antiperoxidase secreting hybridoma for use in the production of a mouse PAP complex for immunocytochemistry and as a parent cell line in the development of hybrid hybridomas.

Mouse antibodies are increasingly used as primary antibodies for immunocytochemistry as more mouse monoclonal antibodies are being produced. The localisation of these antibodies by the PAP technique requires mouse antiperoxidase antibody. A monoclonal antiperoxidase would obviate the limitations of production of a polyclonal mouse antiperoxidase. This paper describes the development of a mouse hybridoma producing such an antibody (MAP A6-2) and the use of this antibody to localise a number of mouse primary antibodies by the PAP technique for both light and electron microscopy. The antibodies localised include monoclonal antienkephalin and antityrosine hydroxylase. MAP A6-2 had a higher affinity in immuno-diffusion experiments and gives slightly better staining with an horse radish peroxidase of a different type from that used for immunisation. Staining was optimum with horse radish peroxidase type X whereas horse radish peroxidase type VI was used for immunisation. Also described is the production of a HAT sensitive variant cell line allowing the possibility of using this hybridoma as a parent cell line for the production of hybrid hybridomas secreting bi-specific antibodies.

Animals↗
PubMed1984

Development and application of a monoclonal rat peroxidase antiperoxidase (PAP) immunocytochemical reagent.

Monoclonal antibodies are being increasingly used in immunocytochemistry but their localisation by the peroxidase antiperoxidase (PAP) procedure requires the use of rat or mouse PAP. In this paper we describe the development and application of a monoclonal rat PAP. This reagent has been used successfully for immunocytochemistry at light and electron microscopy level in combination with rat monoclonal antibodies against serotonin (5-HT), substance P and somatostatin. The monoclonal rat PAP has several advantages over conventional polyclonal rat PAP and is likely to be a valuable developing reagent in immunocytochemistry using rat monoclonal antibodies.

Animals↗