Biomedical subjects

Koichi Noguchi

Publications and source records attributed to Koichi Noguchi.

49 records · Page 3Linked to original sources

PubMed2002

Analysis of gene expression following spinal cord injury in rat using complementary DNA microarray.

To identify genes that were altered by spinal cord injury (SCI), we used complementary DNA microarray consisting 1176 rat genes. Rats were subjected to contusive injury of the thoracic spinal cord. Sham animals received only a laminectomy. Twenty-four hours later, spinal cord was dissected out, a 32P labeled probe was prepared and hybridized to the microarray. We identified three genes that showed a greater than 2-fold increase in SCI tissue, heat shock 27-kDa protein, tissue inhibitor of metalloproteinase-1 and epidermal fatty acid-binding protein. Seven genes, lecithin:cholesterol acyltransferase, dipeptidyl aminopeptidase related protein, phospholipase C delta 4, plasma membrane Ca2+-ATPase isoform 2, G-protein GO alpha subunit, GABA transporter 3, and neuroendrocrine protein 7B2 were down-regulated greater than 50% in SCI tissue. Changes in expression of these genes were confirmed by reverse transcription-polymerase chain reaction. These genes may play a role in the response to tissue damage or repair following SCI.

Animals↗

PubMed2002

Involvement of glutamate receptors on hyperexcitability of wide dynamic range neurons in the gracile nucleus of the rats with experimental mononeuropathy.

In order to clarify the functional role of glutamate receptors of the gracile nucleus neurons in rats with nerve injury-induced hyperalgesia, pharmacological, electrophysiological and in situ hybridization techniques were used in rats with chronic constriction nerve injury (CCI) of the sciatic nerve. A total of 54 wide dynamic range neurons were recorded from the gracile nucleus in the rats with CCI. Mechanical evoked responses were significantly depressed following application of AMPA receptor antagonist, CNQX, with noxious and non-noxious responses being similarly affected. AP-5, an NMDA receptor antagonist, induced depression of the pressure-evoked response only after application of the 1-microM concentration of this drug. The size of the receptive fields was significantly decreased after CNQX, but not MK-801 or AP-5, application. Afterdischarge was significantly depressed following the application of CNQX (1000 microM). The expression of ionotropic glutamate receptor subunit mRNAs in the gracile nucleus was studied using the in situ hybridization technique. The signals for NMDA subunits, NR2A, -2B and -2C, in the gracile nucleus neurons were not prominent, suggesting a low level expression of functional NMDA receptor complex. AMPA receptor subunits GluR1, -R2, -R3 and -R4 mRNAs were expressed in a large number of gracile nucleus neurons. These data are consistent with the pharmacological results that AMPA receptor antagonists depressed nociceptive neuronal activity, but NMDA receptor antagonists showed limited effects. These results suggest that the ionotropic glutamate receptors, i.e. the AMPA and NMDA receptors, are differentially involved in modulation of the wide dynamic range neuronal activity in the gracile nucleus following peripheral nerve injury.

Animals↗

PubMed2002

VR1, but not P2X(3), increases in the spared L4 DRG in rats with L5 spinal nerve ligation.

We investigated the expression of two candidate transducers of noxious stimuli in peripheral tissues, the vanilloid receptor subtype 1 (VR1) and the P2X(3), a subunit of the ionotropic P2X receptor for ATP, in spared L4 DRG neurons following L5 spinal nerve ligation, a neuropathic pain model. VR1 mRNA expression increased in the small- and medium-sized DRG neurons from the first to 28th day after injury, and this up-regulation corresponded well with the development and maintenance of thermal hyperalgesia of the hind paw. The increase in VR1-immunoreactive (ir) neurons was confirmed at the third day after surgery. In contrast, there was no change in expression of P2X(3) mRNA over 4 weeks after ligation, or in the percentage of P2X(3)-ir neurons observed 3 days after surgery. Our data suggests that increased VR1 in the spared L4 DRG may contribute to the exaggerated heat response observed in this neuropathic pain model. Taken together with the previous reports that P2X(3) expression increases in the spared DRG neurons in other neuropathic pain models, there appears to be differences in the phenotypic changes and pathomechanisms of the various neuropathic pain models.

Animals↗

PubMed2002

Expression of neurotrophic factors in the dorsal root ganglion in a rat model of lumbar disc herniation.

A variety of molecules released by inflammatory reactions in the dorsal root and dorsal root ganglion (DRG) may play important roles in the pathology of neuronal abnormalities in lumbar disc herniation. In order to elucidate the pathophysiological mechanisms of painful radiculopathy, secondary to lumbar disc herniation, we evaluated pain-related behavior and the change of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) expression in the DRG and dorsal root using a rat model of lumbar disc herniation. In the nucleus pulposus (NP) group, the left L4/5 nerve roots were exposed after hemilaminectomies and autologous intervertebral discs, which were obtained from coccygeal intervertebral discs, were implanted on each of the exposed nerve roots without mechanical compression. Rats in the NP group, but not the sham-operated rats, developed mechanical allodynia on the ipsilateral hind paw for 1 day after surgery and showed a significant increase in the number of NGF-immunoreactive (IR) cells in the nerve root and DRG. NGF-IR cells in the nerve root and DRG included macrophages and Schwann cells, because these cells were labeled for NGF and ED-1 or glial fibrillary acid protein by dual immunostaining. A significant increase in the percentage of BDNF-IR neurons in the DRG was observed in the NP group at 3 days after surgery and the increase in BDNF mRNA expression was confirmed using in situ hybridization histochemistry and reverse transcription-polymerase chain reaction. We also injected NGF into the endoneurial space of the normal rat spinal nerve root and found that the NGF injection produced dose-dependent mechanical allodynia on the ipsilateral hind paw at 1 day after surgery and an increase in the percentage of BDNF-IR neurons in the DRG at 3 days after surgery compared to the group receiving saline injection. These findings suggest that in the lumbar disc herniation model, i.e. neuritis of the nerve root, increased NGF produced by the inflammatory responses in the dorsal root and DRG tissues may affect the production of BDNF in the DRG and may play important roles in the modulation of the dorsal horn neurons. These changes in neurotrophic factors in the primary afferents may be involved in the pathophysiological mechanisms of neuropathic pain produced by lumbar disc herniation.

Animals↗

PubMed2002

Expression of Apc2 during mouse development.

APC2 (previously known as APCL), a molecule closely related to the adenomatous polyposis coli (APC) tumor suppressor, can deplete cytoplasmic beta-catenin, like APC itself. Recently, it has been shown that APC2 may regulate the localization of p53 and the microtubule stability and/or extension. Although it has been reported that APC2 mRNA is expressed in human brain, the anatomical and ontogenic expression patterns remain unclear. The purpose of this study was to investigate the distribution of mouse Apc2 during mouse development. In the adult brain, Apc2 is expressed predominantly in neurons and throughout the brain. Northern blot analysis demonstrated a high level of Apc2 expression in embryonic and early postnatal brain. Ontogenic analysis has indicated that Apc2 is expressed in neural tissue, including the peripheral nervous system. During development of cortex, retina and cerebellum, Apc2 is expressed in post-mitotic cells. These findings suggest that Apc2 may contribute to the development of neuronal cells.

Animals↗

PubMed2002

Expression of activating transcription factor 3 and growth-associated protein 43 in the rat geniculate ganglion neurons after chorda tympani injury.

The purpose of this study was to evaluate the degree of damage in the geniculate ganglion and its target organ as a result of chorda tympani (CT) injury. We performed unilateral transection of the rat CT and examined expression of the activating transcription factor 3 (ATF3), a neuronal injury marker, and the growth-associated protein 43 (GAP-43), a regeneration-associated molecule. The mean proportion of ATF3-immunoreactive (ir) neurons in the geniculate ganglion was approximately 32% at 3 days after CT injury, but these neurons were never detected in the naive ganglion. Using in situ hybridization, the mean percentage of GAP-43 mRNA-labeled neurons (signal : noise ratio > or = 10) was observed to have increased significantly to approximately 60% for 1-7 days after CT injury, while that in the naive ganglion was < 15%. The results of morphological studies using scanning electron microscopy and immunohistochemistry indicated that atrophic change and reduction of protein gene-product 9.5-ir fibers in the denervated papillae, mainly in the intragemmal region, were observed after CT injury. Increase in GAP-43 mRNA, suggesting CT axonal regeneration, may have a role in recovery from taste disorders. However, this regenerative process may be involved in abnormal activity in the axotomized neurons or the adjacent intact neurons and so one must not disregard the existence of injured geniculate ganglions when considering the treatment of diseases that cause CT injury.

Activating Transcription Factor 3↗

PubMed2002

Heme oxygenase-1 expression after spinal cord injury: the induction in activated neutrophils.

Tissue damage and neurological dysfunction after spinal cord injury may result, in part, from delayed or secondary mechanisms that appear to involve several endogenous factors. Among them, neutrophils are known to play important roles in the pathomechanisms of the secondary injury, that is, neutrophils are activated by an interaction with the endothelial cells, migrate into the damaged tissue and release several kinds of proteases or oxygen radicals. In the present study, we examined heme oxygenase-1 expression in the damaged spinal cord. The administration of an inhibitor of heme oxygenase-1 in vivo produced a delayed recovery of motor function after spinal cord injury, suggesting that heme oxygenase-1 may play roles as an endogenous anti-inflammatory enzyme and protective gene in the damaged and inflammatory tissue. We found that many neutrophils expressing heme oxygenase-1 mRNA and protein were recruited into the damaged spinal cord with extensive hemorrhages during early stage of spinal cord injury. In an in vitro study, neutrophils incubated with proinflammatory cytokines, such as interleukin-1, 6 or interferon-gamma, expressed heme oxygenase-1 mRNA and protein. Based on these findings we conclude that the activated neutrophils can express heme oxygenase-1 in the injured spinal cord tissue, perhaps expecting modulatory and neuroprotective actions in the inflammatory response to spinal cord injury.

Animals↗

PubMed2002

Plastic changes in nociceptive transmission of the rat spinal cord with advancing age.

To understand characteristics of the pain system in the elderly, we investigated the electrophysiological properties of nociceptive neurons in the lumbar spinal dorsal horn of aged (29-34-mo old) and adult (7-13-mo old) rats. The responses of nociceptive neurons to noxious thermal stimulation, as well as the spontaneous firing rate, were significantly higher in the aged as compared with adult rats. Furthermore, the size of the high-threshold receptive field area of wide dynamic range neurons was larger (P < 0.01) and that of the low-threshold area was smaller (P < 0.05) in aged rats than in adult rats. The increased nociceptive neuronal activity in the aged rats correlated with the finding that the paw withdrawal latency was significantly shorter in the aged rats than those of the adult rats following heat stimulation of the hind paw (P < 0.05). Reversible local anesthetic block of descending pathways resulted in a dramatic increase in neuronal activity in adult rats but had little effect in aged rats. There was also a significant loss of serotoninergic and noradrenergic fibers in the spinal dorsal horn of the aged rats. These results demonstrate an age-related plasticity in spinal nociceptive processing that is related to impairment of descending modulatory pathways.

Aging↗

PubMed2002

Contribution of the spared primary afferent neurons to the pathomechanisms of neuropathic pain.

Neuropathic pain is caused by nervous-system lesions. Early studies on the pathomechanisms of this abnormal pain state have focused on the directly injured fibers and neurons. Here, we present recently accumulating data about the contribution of the primary afferent neurons spared from direct injury to the pathomechanisms of neuropathic pain. The phenotypic changes in the spared neurons are similar to those in the neurons in peripheral inflammation models, as opposed to those in the directly injured neurons. Electrophysiological changes and behavioral data also favor the contribution of the spared neurons. These attractive targets of study will give us new approaches for understanding the abnormal pain.

Afferent Pathways↗

PubMed2001

A selective increase in Fos expression in spinal dorsal horn neurons following graded thermal stimulation in rats with experimental mononeuropathy.

In order to clarify the central mechanisms of thermal hyperalgesia produced by peripheral nerve injury, Fos protein-like immunoreactive (Fos-LI) cells in spinal dorsal horn neurons were studied in rats with chronic constriction nerve injury (CCI) following graded thermal stimulation of the hind paw. The graded thermal stimuli (cold: 5, 10 and 15 degrees C, heat: 42, 46 and 54 degrees C) were applied to the plantar surface of the operated hind paw 14 days after CCI or sham operation, and the number of Fos-LI cells in the spinal dorsal horn was quantified. Many Fos-LI cells were expressed in the superficial laminae of the spinal dorsal horn both in sham-operated and CCI rats following thermal stimulation. Fos-LI cells were mainly restricted to the medial half of the superficial laminae of the spinal dorsal horn, and were sparsely distributed in the deeper laminae. The number of Fos-LI cells in the superficial laminae (laminae I--II) of the dorsal horn was significantly higher in CCI rats after stimulation at 10 and 46 degrees C, but not at the other stimulating temperatures (5, 15, 42, and 54 degrees C) as compared to that in sham-operated rats. In laminae III-IV, the number of Fos-LI cells was significantly higher at all stimulus temperatures in CCI rats when compared to the sham-operated rats. No distribution difference of Fos-LI cells was observed between CCI and sham-operated rats in laminae V--VI. Thus, in the spinal dorsal horn of the CCI rats, there was a selective increase in thermal stimulus-induced Fos-LI cells in the superficial dorsal horn after stimulating at near noxious threshold intensities and a non-selective increase in Fos-LI cells in laminae III--IV after both noxious and innocuous thermal stimuli. The increase of Fos-LI cells in the superficial laminae may be related to hypersensitivity to noxious stimuli while the increase of Fos-LI cells in laminae III--IV may be related to an increased sensitivity to both noxious and innocuous stimuli that leads to increased reflex activity following nerve injury.

Animals↗

PubMed2001

Differential regulation of P2X(3) mRNA expression by peripheral nerve injury in intact and injured neurons in the rat sensory ganglia.

The P2X(3) receptor is a ligand-gated cation channel activated by the binding of extracellular adenosine 5'-triphosphate (ATP), an agent that has been suggested to have a role in the nociceptive pathway after tissue and nerve injury. After peripheral nerve injury, both down regulation and up regulation of the P2X(3) receptor in sensory ganglion neurons have been observed. The purpose of this study was to examine the precise regulation of P2X(3) mRNA expression in primary sensory neurons after nerve injury. We used two nerve injury models in the rat, the transection of the tibial and common peroneal nerves and the transection of the infraorbital nerve, and observed dorsal root ganglion (DRG) and trigeminal ganglion neurons, respectively. P2X(3) mRNA in both neuron populations was detected by in situ hybridization with an oligonucleotide probe that was confirmed by Northern blot analysis. To identify axotomized neurons, we examined the expression of activating transcription factor 3 (ATF3), which is regarded as a neuronal-injury marker, using immunohistochemistry. In the DRG, the mean percentage of P2X(3) mRNA-labeled neurons relative to the total number of neurons increased from 32.7% in the naive rats to 42.7% at 3 days after injury. The mean percentage of P2X(3) mRNA-labeled neurons in ATF3 immunoreactive (ir) neurons was 29.5% at 3 postoperative days, which gradually decreased to 11.2% at 28 days after injury. In the trigeminal ganglion, the mean percentage of P2X(3) mRNA-labeled neurons was 36.9% at 3 days after injury, versus 26.0% in the naive rats. In the ATF3-ir neurons, the mean percentage of P2X(3) mRNA-labeled neurons was 25.3% at 1 postoperative day and was reduced to 6.1% at 28 postoperative days. The finding that P2X(3) mRNA in ATF3-ir neurons decreased significantly after injury indicates that axotomized neurons decreased the expression of P2X(3) mRNA, despite the increase in P2X(3) mRNA relative to the total number of sensory ganglion neurons. These data strongly suggest that P2X(3) mRNA expression increases in intact neurons and that P2X(3) mRNA in intact neurons may play a role in the pathomechanism of post-nerve injury in primary sensory neurons.

Activating Transcription Factor 3↗

PubMed1998

Responses of dorsal column nuclei neurons in rats with experimental mononeuropathy.

To examine the functional role of dorsal column nuclei in neuropathic pain, electrophysiological properties of low- and high-threshold dorsal column nuclei neurons in neuropathic and normal rats were examined. Single-neuronal activities were recorded from the gracile nucleus (GN) in rats at 10-14 days after application of four loose ligatures around the sciatic nerve (chronic constriction nerve injury; CCI). A total of 190 units were recorded from the GN in naive and CCI rats. The largest population of low-threshold mechanoreceptive (LTM) neurons recorded from the GN of naive rats were classified as rapidly-adapting (RA) LTM neurons, whereas those from CCI rats were slowly-adapting (SA) neurons. Mean orthodromic latencies of GN neurons ipsilateral to the CCI after sciatic nerve stimulation were significantly longer than those of naive animals and those of GN neurons without receptive fields were significantly longer than any other type of neurons. One hundred and eight of 190 GN neurons were also antidromically activated following electrical stimulation of the ventro-lateral posterior nucleus of the thalamus. Furthermore, when stronger stimuli were applied to the sciatic nerve, some GN neurons also responded with long latencies. GN neurons of sham-operated naive rats and those contralateral to the CCI had mechanical receptive fields on the paw, whereas 8.0% of the GN neurons in the CCI side did not have any detectable mechanical receptive field. Receptive field size was not significantly different between neurons ipsilateral or contralateral to the CCI and those of naive rats. Spontaneous activity of GN neurons from the ipsilateral side was significantly higher than those from the contralateral side. On the other hand, spontaneous activity of GN neurons both ipsilateral and contralateral to the CCI were significantly higher than those from naive rats. Furthermore, afterdischarges of GN neurons ipsilateral and contralateral to the CCI were significantly higher than those of naive rats. The present data suggest that the dorsal column pathway is involved in CCI-produced sensory abnormalities by conveying their hyperactivity to thalamic neurons.

Animals↗

PubMed1998

Change in mRNAs for neuropeptides and the GABA(A) receptor in dorsal root ganglion neurons in a rat experimental neuropathic pain model.

We examined two possible mechanisms of neuropathic pain: contribution of adjacent intact nerves and decrease in presynaptic inhibition at the central terminal of the injured primary afferent. To this end, we examined the effects of unilateral L5 spinal nerve ligation, which causes mechanical allodynia and heat hyperalgesia in the ipsilateral hind paw, on gene expression in L4 and L5 dorsal root ganglion (DRG) neurons using in situ hybridization (ISH). Specifically, we examined changes in the expression of messenger RNAs (mRNAs) for neuropeptides which have been reported to be up- or down-regulated in the axotomized DRG neurons and for gamma-aminobutyric acid (GABA)A receptor (GABA(A)-R) subunits which contribute to presynaptic inhibition at the primary afferent terminals. Seven days following ligation, ISH demonstrated an increase in signal intensity for calcitonin gene-related peptide (CGRP) mRNA in the subpopulation of small-to medium-sized L4 DRG neurons ipsilateral to the ligation which were not directly injured as compared to the contralateral side, although the overall percentages and the size distribution of positively labelled neurons for CGRP mRNA were not different between the bilateral L4 DRGs. This suggests that the L4 DRG neurons which express CGRP mRNA constitutively up-regulated the gene expression and the functional importance of these neurons has increased following L5 spinal nerve ligation. However, the mRNAs for other neuropeptides such as preprotachykinin (PPT), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), and galanin (GAL), were not different between the bilateral L4 DRGs. The mRNA for the GABA(A)-Rgamma2 subunit was significantly down-regulated in the medium- to large-sized L5 DRG neurons ipsilateral to the ligation as compared to the contralateral side. GABA(A)-Ralpha2 subunit mRNA also decreased in the ipsilateral L5 DRG neurons but did not reach statistical significance. There was no difference in mRNAs between the bilateral L4 DRGs. These data suggest that the presynaptic disinhibition of the ipsilateral L5 primary afferent terminals may be explained at least partly by the down-regulation of GABA(A)-R following L5 spinal nerve ligation. Thus, both the up-regulation of CGRP in adjacent intact nerves and the decrease in presynaptic inhibition at the central terminal of the injured primary afferent could cause the hyper-excitability of dorsal horn neurons and contribute to the molecular mechanisms of this neuropathic pain model.

Animals↗