Biomedical subjects

Tsutomu Suzuki

Publications and source records attributed to Tsutomu Suzuki.

At least 19 recordsLinked to original sources

PubMed2004

Involvement of histaminergic system in the discriminative stimulus effects of morphine.

The interactions between morphine and the histaminergic system are not yet fully clarified. More especially, the involvement of the histaminergic system in the discriminative stimulus effects of morphine has not been determined. Therefore, the effects of histamine-related compounds on the discriminative stimulus effects of morphine were examined in rats. Combination tests using histamine-related compounds with morphine were initiated in rats trained to discriminate between 3.0 mg/kg morphine and saline. Zolantidine (central histamine H2-receptor antagonist), but not pyrilamine (central histamine H1-receptor antagonist) or ranitidine (peripheral histamine H2-receptor antagonist), significantly attenuated the discriminative stimulus effects of morphine. The histamine precursor L-histidine significantly potentiated the discriminative stimulus effects of morphine. These results suggest that the discriminative stimulus effects of morphine are, at least in part, mediated through the central activation of histamine H2-receptors in rats.

Animals↗

PubMed2004

Deltorphin II enhances extracellular levels of dopamine in the nucleus accumbens via opioid receptor-independent mechanisms.

The effects of the delta2-opioid receptor agonist, deltorphin II, on extracellular levels of dopamine in the rat nucleus accumbens were investigated in awake animals by in vivo brain microdialysis. In agreement with previous studies, perfusion of deltorphin II (50.0 nmol) into the nucleus accumbens significantly increased the extracellular amount of accumbal dopamine. The effect of deltorphin II (50.0 nmol) was not altered by the selective delta2-opioid receptor antagonist, naltriben (1.5 nmol), which alone did not significantly affect the basal levels of dopamine. Selective antagonists of neither the mu-opioid receptors, D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Phe-Thr-NH2 (0.15 nmol), nor the delta1-opioid receptors, (E)-7-benzylidenenaltrexone tartrate (0.15 nmol), failed to significantly alter the effects of deltorphin II. The nonselective opioid receptor antagonist, naloxone (0.75 and 1.5 nmol), which alone did not significantly affect the basal levels of dopamine, also failed to affect the effects of deltorphin II. Moreover, under the condition that the sodium channel blocker, tetrodotoxin (0.1 nmol), was perfused continuously into the nucleus accumbens, the deltorphin II-induced increase in extracellular levels of dopamine was reduced by 72%. These results suggest that deltorphin II enhances extracellular dopamine in the nucleus accumbens via opioid receptor-independent, tetrodotoxin-sensitive mechanisms.

Analysis of Variance↗

PubMed2004

Molecular mechanism of changes in the morphine-induced pharmacological actions under chronic pain-like state: suppression of dopaminergic transmission in the brain.

In the present study, we demonstrated whether a neuropathic pain-like state induced by sciatic nerve ligation in rodents could cause a long-lasting change in intracellular signaling in both supraspinal and spinal cord related to the suppression of morphine's effect. Mice with sciatic nerve ligation exhibited a significant suppression of the morphine-induced antinociception. Under this condition, phosphorylated-conventional protein kinase C-like immunoreactivity (p-cPKC-IR) and phosphorylated-micro-opioid receptor (p-MOR)-IR were clearly increased on the ipsilateral side in the dorsal horn of the spinal cord of nerve-ligated mice. It is of interest to note that astroglial hypertrophy as well as its proliferation was also noted in this area of sciatic nerve-ligated mice. Like nerve injury, the increase in cPKC activities and astroglial hypertrophy/proliferation in this region was observed by repeated morphine treatment. These findings suggest that the phosphorylation of both cPKC and MOR in the dorsal horn of the spinal cord by sciatic nerve ligation may play a substantial role in the suppression of morphine-induced antinociception under a neuropathic pain-like state. Sciatic nerve injury also caused a significant inhibition of MOR-mediated G-protein activation onto GABAergic neurons and a dramatic reduction in ERK activities onto dopaminergic neurons in the ventral tegmental area (VTA) regulating the rewarding effect of opioids. Furthermore, we found that the inhibition of ERK cascade in the VTA by treatment with specific inhibitors suppressed the morphine-induced rewarding effect in normal mice. These findings provide evidence that the direct reduction in MOR function and the persistent decrease in ERK activity of dopaminergic neurons in the VTA may contribute to the suppression of the morphine-induced rewarding effect under a neuropathic pain-like state. Conclusively, our recent findings provide novel evidences for the mechanism underlying the less sensitivity to opioids under a neuropathic pain-like state.

Analgesics, Opioid↗

PubMed2004

Enhancement of dopamine-induced signaling responses in the forebrain of mice lacking dopamine D3 receptor.

It is well known that the dopamine D(3) receptor plays a critical role in several psychological disorders, such as drug dependence. The present study was designed to investigate the influence of lacking dopamine D(3) receptors in dopamine-induced G-protein activation and Ca(2+) influx in the mouse forebrain. The deletion of dopamine D(3) receptor gene caused the enhancement of dopamine-induced G-protein activation in the limbic forebrain of dopamine D(3) receptor knockout (D(3)KO) mice. Furthermore, the dopamine-induced Ca(2+) influx was enhanced in the coculture of neuron/glia cells obtained from the forebrain of D(3)KO mice. The present data provide direct evidence that a deletion of central dopamine D(3) receptor enhances the dopamine D(1)/D(2) receptor-mediated intracellular signaling.

Animals↗

PubMed2004

Functional compatibility of elongation factors between mammalian mitochondrial and bacterial ribosomes: characterization of GTPase activity and translation elongation by hybrid ribosomes bearing heterologous L7/12 proteins.

The mammalian mitochondrial (mt) ribosome (mitoribosome) is a bacterial-type ribosome but has a highly protein-rich composition. Almost half of the rRNA contained in the bacterial ribosome is replaced with proteins in the mitoribosome. Escherichia coli elongation factor G (EF-G Ec) has no translocase activity on the mitoribosome but EF-G mt is functional on the E.coli ribosome. To investigate the functional equivalency of the mt and E.coli ribosomes, we prepared hybrid mt and E.coli ribosomes. The hybrid mitoribosome containing E.coli L7/12 (L7/12 Ec) instead of L7/12 mt clearly activated the GTPase of EF-G Ec and efficiently promoted its translocase activity in an in vitro translation system. Thus, the mitoribosome is functionally equivalent to the E.coli ribosome despite their distinct compositions. The mt EF-Tu-dependent translation activity of the E.coli ribosome was also clearly enhanced by replacing the C-terminal domain (CTD) of L7/12 Ec with the mt counterpart (the hybrid E.coli ribosome). This strongly indicates that the CTD of L7/12 is responsible for EF-Tu function. These results demonstrate that functional compatibility between elongation factors and the L7/12 protein in the ribosome governs its translational specificity.

Amino Acid Sequence↗

PubMed2004

Region-dependent G-protein activation by kappa-opioid receptor agonists in the mouse brain.

The G-protein activations induced by kappa-opioid receptor agonists, (-)U50,488H, U69,593 and TRK-820 in the mouse lower midbrain, striatum and limbic forebrain were determined by monitoring guanosine-5'-o-(3-[35S]thio)triphosphate ([35S]GTP gamma S) binding. All kappa-opioid receptor agonists produced approximately 40, 20 and 10% increases of [35S]GTP gamma S binding over baseline in the lower midbrain, striatum and limbic forebrain, respectively. The increases of [35S]GTP gamma S binding induced by kappa-opioid receptor agonists were completely reversed by the selective kappa-opioid receptor antagonist, norbinaltorphimine (norBNI), in all brain regions. The intrinsic activities of kappa-opioid receptor agonists for G-protein activation in brain regions observed in the present study are not correlated with densities of kappa-opioid receptor binding sites from previous reports. The present results suggest that the catalytic efficiency of kappa-opioid receptor-G-protein coupling may be variable in different brain regions.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed2004

Prenatal and neonatal exposure to bisphenol-A affects the morphine-induced rewarding effect and hyperlocomotion in mice.

Bisphenol-A (BPA), one of the most common environmental endocrine disrupters, has been extensively evaluated for toxicity and carcinogenicity. However, little is still known about its action on the CNS. Here we found that prenatal and neonatal exposure to BPA resulted in the enhancement of the rewarding effect and hyperlocomotion induced by morphine in mice. Under these conditions, no change in the G-protein activation by morphine and mu-opioid receptor expression in the lower midbrain was observed by prenatal and neonatal exposure to BPA. These results suggest that chronic exposure to BPA produces the supersensitivity of the morphine-induced rewarding effect and hyperlocomotion without direct changes in mu-opioid receptor function in the lower midbrain. The present data provide further evidence that prenatal and neonatal exposure to BPA can directly influence the development of the central dopaminergic system.

Air Pollutants, Occupational↗

PubMed2004

Yeast Nfs1p is involved in thio-modification of both mitochondrial and cytoplasmic tRNAs.

The IscS protein is a pyridoxal phosphate-containing cysteine desulfurase involved in iron-sulfur cluster biogenesis. In prokaryotes, IscS is also involved in various metabolic functions, including thio-modification of tRNA. By contrast, the eukaryotic ortholog of IscS (Nfs1) has thus far been shown to be functional only in mitochondrial iron-sulfur cluster biogenesis. We demonstrate here that yeast Nfs1p is also required for the post-transcriptional thio-modification of both mitochondrial (mt) and cytoplasmic (cy) tRNAs in vivo. Depletion of Nfs1p resulted in an immediate impairment of the 2-thio-modification of 5-carboxymethylaminomethyl-2-thiouridine at the wobble positions of mt-tRNA(UUU)(Lys) and mt-tRNA(UUG)(Gln). In addition, we observed a severe reduction in the 2-thio-modification of 5-methoxycarbonylmethyl-2-thiouridine (mcm(5)s(2)U) of cy-tRNA(UUU)(Lys2) and cy-tRNA(UUC)(Glu3), although the effect was somewhat delayed compared with that seen in mt-tRNAs. Mass spectrometry analysis revealed an increase in 5-methoxycarbonylmethyluridine concomitant with a decrease in mcm(5)s(2)U in cy-tRNAs that were prepared from Nfs1p-depleted cells. These results suggest that Nfs1p is involved in the 2-thio-modification of both 5-carboxymethylaminomethyl-2-thiouridine in mt-tRNAs and mcm(5)s(2)U in cy-tRNAs.

Blotting, Northern↗

PubMed2004

Increased phosphorylated-mu-opioid receptor immunoreactivity in the mouse spinal cord following sciatic nerve ligation.

The present study was designed to determine whether a state of neuropathic pain induced by sciatic nerve ligation could alter phosphorylated-mu-opioid receptor-like immunoreactivity in the superficial dorsal horn of the mouse spinal cord. Mice with sciatic nerve ligation exhibited a significant suppression of the morphine-induced antinociception. Under this condition, phosphorylated-mu-opioid receptor-like immunoreactivity was clearly increased on the ipsilateral side in the superficial laminae of the L5 lumbar spinal dorsal horn in nerve-ligated mice. These findings suggest that the phosphorylation of the mu-opioid receptor in the spinal cord under a neuropathic pain-like state may, at least in part, contribute to the reduction in the antinociceptive effect produced by morphine in the mouse.

Afferent Pathways↗

PubMed2004

Recurrence pattern of squamous cell carcinoma of the thoracic esophagus after extended radical esophagectomy with three-field lymphadenectomy.

BACKGROUND: Extended radical esophagectomy with three-field lymphadenectomy for patients with thoracic esophageal cancer has been shown to be effective. But even if this operation is performed, some patients still experience relapse of the disease. The purpose of this study was to clarify the pattern and timing of recurrence after extended radical esophagectomy. STUDY DESIGN: Recurrence of esophageal squamous cell carcinoma was examined in 171 of 174 patients who underwent extended radical esophagectomy with three-field lymphadenectomy. Recurrence patterns were classified as locoregional (at the site of the primary tumor, the anastomotic site, or the lymph nodes), hematogenous, and other (pleura or site of gastrostomy). Factors associated with recurrence were identified using univariate and multivariate statistical methods for survival analysis. RESULTS: The overall 5-year survival rate was 55.6%. Recurrence was recognized in 74 patients (43.3%). The median disease-free interval until recurrence was 11 months. Thirty patients (17.5%) developed a locoregional recurrence, and 24 (14.0%) developed a hematogenous recurrence. Five patients (2.9%) developed both recurrences simultaneously and were classified as hematogenous recurrences. Of 30 patients with cervical lymph node metastasis, recurrent disease was recognized in 19 patients (63.3%). In multivariate analysis of 160 patients, the depth of invasion and pM-lym (cervical or celiac lymph node metastasis) were significant factors for locoregional recurrence; the depth of invasion and number of lymph node metastases at operation were significant factors for hematogenous recurrence. Survival time for patients with hematogenous recurrence (median 16 months) was significantly shorter than that of patients with locoregional recurrence (median 25.5 months). CONCLUSIONS: Locoregional recurrence is associated mainly with the extent of the local tumor and lymph node metastasis; hematogenous recurrence is not only associated with tumor stage but also with the tumor's oncologic behavior.

Aged↗

PubMed2004

Functional interaction among opioid receptor types: up-regulation of mu- and delta-opioid receptor functions after repeated stimulation of kappa-opioid receptors.

It has been widely accepted that repeated administration of kappa-opioid receptor agonists leads to the development of antinociceptive tolerance. The present study was designed to investigate the effect of repeated administration of a selective kappa-opioid receptor agonist (1S-trans)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-benzeneacetamide hydrochloride ((-)U-50,488H) on the mu- and delta-opioid receptor agonist-induced antinociception and G-protein activation in mice. The mice were injected either subcutaneously (s.c.) or intracerebroventricularly (i.c.v.) pretreated with saline or (-)U-50,488H once a day for seven consecutive days. Two hours after the last injection, the mice were challenged by either mu- or delta-opioid receptor agonist for the antinociceptive assay. Repeated treatment with (-)U-50,488H (s.c. or i.c.v.) significantly enhanced antinociceptive effect of both mu-opioid receptor agonist (morphine) and delta-opioid receptor agonists ([d-Ala2]deltorphin (DELT) and (+)-4-[(alphaR)-alpha-((2S,5R)-4-allyl-2,5-dime thyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC-80) compared to saline-treated groups. Under these conditions, repeated s.c. injection of (-)U-50,488H significantly enhanced both mu- and delta-opioid receptor agonist-stimulated [35S]GTPgammaS binding in the membrane of the thalamus. On the contrary, either repeated administration of morphine (s.c. or i.c.v.) or SNC-80 failed to affect the kappa-opioid receptor agonist-induced antinociception and G-protein activation. Taken together, these results suggest that repeated stimulation of kappa-opioid receptor markedly increases the functional mu- and delta-opioid receptors, whereas repeated stimulation of either mu- or delta-opioid receptor had no direct effect on kappa-opioidergic function in mice.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed2004

Role of mu- and delta-opioid receptors in the nucleus accumbens in turning behaviour of rats.

The role of mu-, delta1- and delta2-opioid receptors in the nucleus accumbens in pivoting was investigated in freely moving rats. Unilateral injections of the mu-opioid receptor agonist, [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO, 1 and 2 microg) and the delta2-opioid receptor agonist, deltorphin II (1 and 2 microg), but not the delta1-opioid receptor agonist, [D-Pen(2,5)]-enkephalin (DPDPE, 1-4 microg), into the shell or the core of the nucleus accumbens significantly induced contraversive pivoting. The pivoting induced by DAMGO (2 microg) and deltorphin II (2 microg) was inhibited significantly by the mu-opioid receptor antagonist, D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Phe-Thr-NH2 (CTOP, 0.1 and 1 microg), and the delta2-opioid receptor antagonist, naltriben (NTB, 0.1 and 1 mg/kg, i.p.), respectively. The DAMGO (2 microg)- or deltorphin II (2 microg)-induced pivoting was also inhibited significantly by co-administration of the dopamine D1/D2 receptor antagonist, cis(Z)-flupentixol (1 and 10 microg). The pivoting induced by unilateral injections of a mixture of dopamine D1 (SKF 38393, 5 microg) and D2 (quinpirole, 10 microg) receptor agonists into the shell was significantly inhibited by cis(Z)-flupentixol (1 and 10 microg) or NTB (1 and 3 mg/kg, i.p.), but not CTOP (1 microg) or delta1-opioid receptor antagonist, (E)-7-benzylidenenaltrexone (1 mg/kg, i.p.). The contraversive pivoting elicited by the cholinergic agonist, carbachol (5 microg), into the core was inhibited by co-administration of the muscarinic M1 antagonist, pirenzepine (1 microg), but not cis(Z)-flupentixol (1 microg). The results suggest that unilateral activation of mu- or delta2-opioid, but not delta1-opioid, receptors in the core and/or shell of the nucleus accumbens elicits contraversive pivoting that requires intact dopamine D1/D2 receptors in the shell, but not intact muscarinic M1 mechanism in the core. The study also shows that delta2-opioid, but not mu- and delta1-opioid, receptors in the core and/or shell modulate the shell-specific, dopamine D1/D2 receptor mechanisms involved in the production of pivoting.

Animals↗

PubMed2004

Role of extracellular signal-regulated kinase in the ventral tegmental area in the suppression of the morphine-induced rewarding effect in mice with sciatic nerve ligation.

We recently reported that micro-opioid receptor agonist morphine failed to induce its rewarding effects in rodents with sciatic nerve injury. In the present study, we investigated whether a state of neuropathic pain induced by sciatic nerve ligation could change the activities of the extracellular signal-regulated kinase (ERK) and p38 in the mouse lower midbrain area including the ventral tegmental area (VTA), and these changes could directly affect the development of the morphine-induced rewarding effect in mice. The sciatic nerve ligation caused a long-lasting and profound thermal hyperalgesia. A dose-dependent place preference induced by s.c. administration of morphine was observed in sham-operated mice, but not in sciatic nerve-ligated mice. We found here for the first time that nerve injury produces a sustained and significant reduction in protein levels of phosphorylated-ERK and -p38 in cytosolic preparations of the mouse lower midbrain. The inhibition of ERK activity by i.c.v. pre-treatment with either PD98059 or U0126 impaired the morphine-induced place preference. In contrast, i.c.v. treatment with a specific inhibitor of p38, SB203580, did not interfere with the morphine-induced rewarding effect. Immunohistochemical study showed a drastic reduction in phosphorylated-ERK immunoreactivity within tyrosine hydroxylase-positive cells of the VTA. These results suggest that a sustained reduction in the ERK-dependent signalling pathway in dopamine cells of the VTA may be implicated in the suppression of the morphine-induced rewarding effect under neuropathic pain.

Analgesics, Opioid↗

PubMed2004

Neuronal protein kinase C gamma-dependent proliferation and hypertrophy of spinal cord astrocytes following repeated in vivo administration of morphine.

Repeated administration of morphine induced a time-dependent inhibition of the morphine-induced antinociceptive action, indicating the development of tolerance to morphine. We demonstrated that mice tolerant to morphine exhibited a significant increase in the level of protein kinase Cgamma-like immunoreactivity (PKCgamma-IR) in the dorsal horn of the spinal cord. The PKCgamma-IR was exclusively colocalized with the neuron-specific markers neuronal nuclei (NeuN) and microtubule associated protein 2ab (MAP2ab). Here we found a dramatic increase in reactive astrocytes in the dorsal horn of the spinal cord following repeated treatment with morphine, as characterized by the increase and morphological changes in glial fibrillary acidic protein (GFAP)-positive cells. Furthermore, transgenic mice that express enhanced green fluorescent protein (EGFP) under the control of the mouse GFAP promoter displayed enhanced levels of EGFP expression after repeated treatment with morphine. Under these conditions, mice lacking the PKCgamma gene failed to show any changes in astroglial hypertrophy or proliferation after repeated treatment with morphine. These findings strongly support the idea that the sustained activation of neuronal PKCgamma is implicated in the increased levels of reactive astrocytes in the dorsal horn of the spinal cord following repeated treatment with morphine. This neuron-glia communication may lead to the development of tolerance to morphine-induced antinociception.

Animals↗

PubMed2004

The pathogenic A4269G mutation in human mitochondrial tRNA(Ile) alters the T-stem structure and decreases the binding affinity for elongation factor Tu.

The A4269G mutation in the human mitochondrial (mt) tRNA(Ile) gene is associated with fatal cardiomyopathy. This mutation completely inhibits protein synthesis in mitochondria, thereby significantly reducing their respiratory activity. The steady-state amount of tRNA(Ile) in cells bearing the A4269G mutation is almost half that of control cells. We previously reported that this mutation causes tRNA(Ile) to be unstable both in vivo and in vitro. To investigate whether the instability of the mutant tRNA(Ile) is due to structural alterations, a nuclease-probing experiment was performed with a mitochondrial enzymatic extract, which showed that the A4269G mutation destabilizes the T-stem of the mutant tRNA(Ile). In addition, measurements of the binding affinity of the aminoacylated mutant tRNA(Ile) for mt elongation factor Tu (EF-Tu) showed that the mutant tRNA(Ile) binds mt EF-Tu less efficiently than the wild-type does. This observation provides insight into the molecular pathology associated with tRNA dysfunction caused by this pathogenic point mutation.

Base Sequence↗

PubMed2003

Change in the expression of c-fos in the rat brain following sciatic nerve ligation.

A little or none is known about the direct evidence for the possible change in the expression of c-fos at the supraspinal level after nerve injury. Therefore, the present study was designed to investigate the level of c-fos in some brain regions following sciatic nerve ligation in the rat. Immunoblot analysis clearly showed that the levels of c-fos in the rat frontal cortex, thalamus and periaqueductal gray matter were significantly increased, whereas it was significantly decreased in the nucleus accumbens and ventral tegmental area. Under these conditions, the levels of c-fos in the rat amygdala, hippocampus and hypothalamus were not changed. These results provide direct evidence that the neuropathic pain-like state causes a substantial change in the expression of c-fos in the rat brain.

Animals↗

PubMed2003

Differential involvement of spinal protein kinase C and protein kinase A in neuropathic and inflammatory pain in mice.

In the present study, we demonstrated the differential role of spinal protein kinases in neuropathic and inflammatory pain. Mice with sciatic nerve ligation exhibited a spinal protein kinase C (PKC)-dependent neuropathic pain-like state. In contrast, an intraplanter injection of inflammatory agent caused a protein kinase A (PKA)-related thermal hyperalgesia. These findings suggest that the substantial activation of spinal PKC and PKA may differentially contribute to the development of respective chronic pain-like state in mice.

Animals↗

PubMed2003

Quick two-step RNA ligation employing periodate oxidation.

The introduction of modified or labeled nucleotides into RNA is a powerful RNA engineering tool as it enables us to investigate how native RNA modifications affect RNA function and structure. It also helps in the structural analysis of RNA. A modified nucleotide can be introduced into a specific position of RNA by the method of two-step enzymatic ligation of RNA fragments. However, this method requires a complicated purification step between the two ligation steps that results in low yields of the ligation product. Here we have developed a new ligation technique employing periodate oxide that eliminates this purification step. This increases the total yield of the ligation product and makes it a faster procedure.

Anticodon↗