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R Munglani

Publications and source records attributed to R Munglani.

At least 19 recordsLinked to original sources
PubMed2001

Cell death in the superficial dorsal horn in a model of neuropathic pain.

The aims of this study were to investigate the occurrence of apoptotic cell death in the dorsal horn of the adult rat spinal cord following chronic constriction injury (CCI) to the sciatic nerve and to correlate this with behavioural responses. Six groups of six rats were used as follows: 1) CCI, 2) CCI, 3) MK801 + CCI, 4) axotomy, 5) sham, and 6) naive. Group 1 animals were behaviourally tested for thermal hyperalgesia 8 days following surgery and sacrificed and the spinal cords removed and frozen. The rest of the groups underwent the same procedure 14 days following surgery. The lumbar region of the spinal cord was cryosectioned and the incidence of apoptotic cells investigated using the TUNEL technique plus Hoechst double labelling. By 8 days post-CCI, hyperalgesia had developed in the ipsilateral paw, which was still present 14 days after the injury compared to the contralateral paw and naive and sham animals. Preemptive MK-801 prevented the onset of hyperalgesia. Significant numbers of apoptotic cells were present in the ipsilateral dorsal horn of the spinal cord 8 and 14 days following CCI compared to the contralateral side and to naive and sham animals. Preemptive treatment with MK-801 reduced the extent of apoptosis resulting from CCI to the level seen in control animals. This study demonstrates that cells undergo apoptosis as a result of CCI simultaneous with the occurrence of hyperalgesia. Furthermore, MK-801 prevents the onset of hyperalgesia and reduces the extent of apoptotic cell death, suggesting, perhaps, that apoptosis contributes to the initiation/maintenance of hyperalgesia.

Animals↗
PubMed1999

Effect of pre-emptive NMDA antagonist treatment on long-term Fos expression and hyperalgesia in a model of chronic neuropathic pain.

The unilateral sciatic nerve chronic constriction injury (CCI) model of Bennett and Xie [G.J. Bennett, Y.-K. Xie, A peripheral neuropathy in rat that produces disorders of pain sensation like those seen in man, Pain, 33 (1988) 87-108] shows features of a neuropathic pain state. We examined mechanical hyperalgesia and Fos protein staining in the lumbar spinal cord 1, 7, 14 and 28 days after unilateral CCI to the sciatic nerve or sham operation. In addition, we examined the effect of the NMDA antagonist MK-801 (0.3 mg/kg s.c. administered 30 min prior to and 6 h following operation) on Fos expression and hyperalgesia at 28 days. CCI animals were hyperalgesic compared to the sham operated animals at 14 and 28 days post injury. MK-801 reduced hyperalgesia by 68% in CCI animals on day 28 (p=0.0001). In the spinal cord, Fos positive cells were present bilaterally in deeper laminae in both sham and CCI animals at all time points examined. Relatively few Fos positive cells were present in laminae 1-2 at any time point examined. At days 1 and 7, there were increased numbers of Fos positive cells ipsilaterally in the deeper laminae of the spinal cord in CCI animals compared to sham animals, but by 14 and 28 days Fos counts were similar in sham and CCI despite the obvious behavioural differences between the two groups. Fos counts ipsilateral to the injury in laminae 3-10 correlated with hyperalgesia scores in the CCI but not sham animals. Analysis at the 28-day time point showed that MK-801 differentially affected Fos expression: MK-801 significantly reduced the Fos count bilaterally in laminae 3-10 in the CCI but not in the sham group animals. These results indicate that Fos expression is initiated by different peripheral and central mechanisms following nerve injury or sham operation.

Animals↗
PubMed1999

Effect of post-injury NMDA antagonist treatment on long-term Fos expression and hyperalgesia in a model of chronic neuropathic pain.

Chronic constriction injury (CCI) of the sciatic nerve results in persistent mechanical hyperalgesia together with Fos protein expression in the lumbar spinal cord. We have examined the relationship between mechanical hyperalgesia and Fos expression within the lumbar spinal cord on days 14, 35 and 55 after either CCI or sham operation. To determine the role of NMDA receptor mechanisms in the maintenance of hyperalgesia and Fos expression, the NMDA antagonist MK-801 (0.3 mg kg-1 s.c.) was administered daily on days 28 to 34 after operation. CCI animals developed unilateral hind limb hyperalgesia that persisted unchanged from days 14 to 55 of the study. MK-801 treatment reduced hyperalgesia by 57% (p=0.02) on day 35 in CCI animals but did influence hyperalgesia at day 55. In the spinal cord, Fos positive cells were present bilaterally throughout laminae 3-10 at all time points examined in both CCI and sham group animals. Fos counts ipsilateral to the side of injury in laminae 3-10 correlated significantly with hyperalgesia scores in the CCI but not sham animals. MK-801 treatment resulted in a suppression of Fos expression in ipsilateral laminae 3-4 (p=0.0017) and laminae 5-10 (p=0.0026) of CCI animals on day 35. Fos expression in sham group animals was not inhibited by MK-801 treatment at day 35. These results indicate that Fos expression is maintained by differing mechanisms following nerve injury or sham operation. The functional consequences of Fos expression following nerve injury and sham operation are discussed.

Animals↗
PubMed1999

Effect of colchicine on neuropeptide Y expression in rat dorsal root ganglia and spinal cord.

Neuropeptide Y (NPY) expression in the spinal cord and dorsal root ganglia (DRG) was examined after application of colchicine, an axonal transport blocker, on the intact sciatic nerve or prior to axotomy or chronic constriction injury (CCI). Rats that underwent topical application of colchicine on the sciatic nerve showed decreased responsiveness to heat stimulation, ipsilaterally. CCI-induced hyperalgesia was prevented by prior application of colchicine. However, colchicine did not block axotomy-induced NPY increase when applied proximally to the injury. In fact, colchicine induced the expression of NPY in the DRG and spinal cord in an identical manner to axotomy. The present data indicates that the increase in NPY observed after nerve injury could be initiated by the suppression of retrograde transport of factors, possibly neurotrophins, rather than by the production of an active factor at the site of injury.

Animals↗
PubMed1999

The longer term effect of pulsed radiofrequency for neuropathic pain.

Pulse radiofrequency has been recently described as a technique to apply a relatively high voltage near a nerve but without the usual effects of a rise in temperature or subsequent nerve injury. In this set of case reports, the effect of pulsed radiofrequency (PRF) is described in patients with neuropathic pain syndromes which have been poorly controlled with other oral and invasive treatments. Whilst anecdotal, the results have been remarkable and should encourage further research into this technique. Observations from the basic science tend to support the concept that PRF may induce some sort of long-term depression in the spinal cord.

Adult↗
PubMed1998

An improved method for detection of apoptosis in tissue sections and cell culture, using the TUNEL technique combined with Hoechst stain.

We describe a novel procedure for combining a fluorescent variant of the TUNEL technique with Hoechst 33342 stain (bis-benzimide) to identify apoptosis in tissue sections and cell culture. The biochemical hallmark of apoptosis is internucleosomal DNA cleavage, which gives rise to oligonucleosome-sized fragments (multiples of approximately 180 bp) that can be directly visualised by labelling with biotinylated or digoxygenin-conjugated nucleosides in a reaction that employs terminal deoxynucleotide transferase (TUNEL). TUNEL and Hoechst 33342 have been used separately to identify apoptosis. TUNEL specifically labels dying cells, yet a low background makes comparison of labelled cells with surrounding normal cells difficult and causes disorientation in tissue sections. Hoechst 33342 binds all DNA therefore staining all nuclear material, allowing identification of apoptotic nuclei, but the analysis is laborious. Combining the two fluorescent labels allows the initial recognition of apoptotic cells using the TUNEL technique then, by simply changing the filter, the TUNEL positive nuclei can be compared to surrounding normal nuclei to assess changes in morphology and size. Hoechst 33342 acts as a counterstain, allowing identification of anatomical structures, and permits quantitative comparison between TUNEL positive versus normal cells. We have evaluated the technique using sections of rat embryo, post-axotomy neonatal dorsal root ganglia and adult dorsal root ganglia cell culture.

Animals↗
PubMed1998

TUNEL, Hoechst and immunohistochemistry triple-labelling: an improved method for detection of apoptosis in tissue sections--an update.

We describe an updated protocol which allows the combination of the previously described TUNEL and Hoechst 33342 double-labelling (G. Whiteside, N. Cougnon, S.P. Hunt, R. Munglani, An improved method for the detection of apoptosis in tissue sections and cell culture, using the TUNEL technique combined with Hoechst stain, Brain Res. Protocols, 2, 1998, 160-164 [3]), with immunohistochemistry. The inclusion of the immunohistochemistry step allows identification of apoptosis in distinct cell types by using cell specific markers. It also permits investigation into the proteins expressed in cells undergoing apoptotic cell death. We have evaluated the triple staining in sections of post-axotomy neonatal dorsal root ganglia.

Animals↗
PubMed1998

Differential time course of neuronal and glial apoptosis in neonatal rat dorsal root ganglia after sciatic nerve axotomy.

Sensory neurons in neonatal rat lumbar dorsal root ganglia die after sciatic nerve axotomy, and previous studies have estimated the total cell loss to be 40-95%. We have used the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) technique, combined with immunohistochemistry, to investigate the contribution of apoptosis to the cell loss that occurs after unilaterally transecting the sciatic nerve of new-born rats. TUNEL-positive cells were detected 1 day post-lesion, and their number peaked 3 days after the injury. Combining TUNEL labelling with immunohistochemistry, for neuron-specific neurofilament 150 kDa, or glial-specific S-100beta, enabled us to identify dying neurons and dying glia. One day after axotomy, most of the TUNEL-positive cells (58%) were neurons, whereas 3 days post-injury, only a small number of dying cells (6%) were neuronal. This lower incidence was due to a decrease in neuronal death and an increase in glial death. The glia in the dorsal root ganglia therefore die subsequent to the neurons. The apoptotic nature of the cell death was confirmed by electron microscopy, with fine structural features of apoptotic cell death, e.g. chromatin compaction and membrane blebbing, being observed in both glia and neurons. Our results confirm that extensive apoptosis occurs in the neonatal lumbar dorsal root ganglia after sciatic nerve section, and show that neurons and glial cells die with different time-courses. The results suggest a neuron-glia trophic interdependence in the dorsal root ganglia.

Animals↗
PubMed1997

The therapeutic potential of neuropeptide Y in cardiovascular disease.

Neuropeptide Y (NPY), a widely distributed peptide neurotransmitter, is implicated in both the central and peripheral control of the cardiovascular system. Pathological changes in endogenous NPY release and receptor function may contribute to the development and maintenance of hypertension, myocardial ischaemia and cardiac failure. At least six NPY receptor subtypes are known to exist, and the activation of a certain number of these results in complex central and peripheral changes in cardiovascular function. The cloning and sequencing of NPY receptor subtypes has led to the possibility of developing subtype-specific ligands targeted at NPY receptors, and this article will consider their therapeutic potential in cardiovascular disease.

Journal Article↗
PubMed1997

The therapeutic potential of neuropeptide Y in central nervous system disorders with special reference to pain and sympathetically maintained pain.

Neuropeptide Y (NPY), a widely distributed peptide, has been shown to have numerous effects in both the central and peripheral nervous systems. In particular, NPY has an important role in mediating analgesia and hyperalgesia by distinct central and peripheral mechanisms. At least six NPY receptor subtypes are known to exist and the development of subtype-specific ligands targeted at NPY receptors will offer novel therapeutic agents. This article will review the involvement of NPY in diverse pathologies of the nervous system, including pain, and will propose a role for NPY in the maintenance of sympathetically maintained pain.

Journal Article↗
PubMed1996

Neuropeptide changes persist in spinal cord despite resolving hyperalgesia in a rat model of mononeuropathy.

We have previously described the changes in spinal cord neuropeptides in the unilateral sciatic chronic constriction injury (CCI) model of Bennett and Xie [Pain, 33 (1988) 87-108] at 28 days, a time of maximum mechanical hyperalgesia. In this study we examine the same model 100-120 days post injury by which time resolution of the hyperalgesia and peripheral nerve injury has occurred according to previous studies. Rats underwent either CCI of the sciatic nerve (n = 12) or else sham operation (n = 8) which involved exposure but no ligation of the nerve. Mechanical hyperalgesia was assessed with a Ugo-Basile analgesymeter and immunohistochemistry performed on the spinal cord sections of the animals and quantified using a confocal microscope. At this late time point CCI rats were no longer significantly mechanically hyperalgesic compared to the sham animals (P > or = 0.09). However, examination of the lumbar spinal cord revealed the following changes. (i) The neuropeptides substance P (SP) (P < 0.0001) and galanin (P < 0.003) both showed decreases of about 30% ipsilaterally in immunoreactivity in laminae 1 and 2 of the dorsal horn compared to the sham operated animals. (ii) Calcitonin gene-related peptide (CGRP) and neuropeptide Y (NPY) in laminae 1 and 2 showed no significant changes compared to sham animals. (iii) NPY levels in laminae 3 and 4 of the spinal cord showed a 15% increase in immunoreactivity compared to sham animals (P = 0.008). These results indicate that changes in neuronal markers in the spinal cord can persist after apparent resolution of a peripheral nerve injury. We suggest that these changes may form a substrate for subsequent development of abnormal pain states.

Animals↗
PubMed1996

The therapeutic potential of neuropeptide Y. Analgesic, anxiolytic and antihypertensive.

Since its discovery in 1982, neuropeptide Y (NPY) has been shown to have numerous effects mediated by a growing number of NPY receptors in both the CNS and peripheral nervous system. Perhaps best appreciated is the role of NPY in the control of systemic blood pressure, together with its effects on feeding, anxiety and memory. However, recent evidence increasingly supports an important role for NPY in mediating analgesia and hyperalgesia by distinct central and peripheral mechanisms. In this review we concentrate on this important aspect of NPY pharmacology and consider mechanisms controlling the expression of NPY and its receptors. In addition, we also present the more recent data describing the other possible roles for NPY-NPY agonists and antagonists may be useful in the treatment of conditions as varied as anorexia, epilepsy, anxiety, depression, hypertension and heart failure.

Analgesics↗
PubMed1995

Changes in neuronal markers in a mononeuropathic rat model relationship between neuropeptide Y, pre-emptive drug treatment and long-term mechanical hyperalgesia.

Using the chronic constriction model (CCI) of Bennett and Xie (1988), changes in the lumbar spinal cord in neuropeptides and lectin IB4 were examined at 28 days post-nerve constriction and were compared with the degree of mechanical hyperalgesia. Animals following nerve ligation were significantly more hyperalgesic than sham-operated animals (P < 0.0001). Lectin IB4, a marker of primary afferent C fibres, showed a qualitative decrease in staining intensity in laminae 1-2 with ligation compared with both the unoperated contralateral side and with sham animals. Using fluorescent immunohistochemistry to quantify changes in neuropeptides in the dorsal horn we found that substance P showed significant decreases with ligation compared to sham operation (P < 0.002). CGRP and galanin showed no significant changes in laminae 1-2 compared to sham-operated animals. Neuropeptide Y (NPY) showed no significant changes in intensity in laminae 1-2; however, in laminae 3-4 there was a significant increase with nerve ligation compared to sham (P < 0.005). We examined how pre-emptive drug treatment affected these neuronal markers at 28 days. We used (1) clonidine, an alpha 2-adrenoreceptor agonist (1 mg/kg, i.p.), (2) morphine, a mu-opioid agonist (5 mg/kg, i.p.) or (3) MK-801, an N-methyl-D-aspartate (NMDA) receptor antagonist (0.3 mg/kg, s.c.) administered 30 min prior and 6 h following nerve ligation or sham-operation. Hyperalgesia in the ligated group at 28 days was suppressed by treatment with pre-emptive clonidine (P = 0.003) or MK-801 (P = 0.003) but not morphine. With the exception of NPY there was no effect of pre-emptive drug treatment on any neuronal marker examined. Pre-emptive MK-801 reduced the magnitude of the increase in NPY in laminae 3-4 in the ligated group (P < 0.005) and clonidine showed a similar trend but this did not reach significance. Morphine had no effect on NPY staining. There was a significant correlation between the increase in NPY staining in laminae 3-4 and the degree of hyperalgesia (r = 0.6, P < 0.001). These results suggest that the increased NPY expression in laminae 3-4 of the spinal cord (the territory of the myelinated sensory input) may be crucial to the development of hyperalgesia in this model.

Analgesics↗