Biomedical subjects

Tsutomu Tanabe

Publications and source records attributed to Tsutomu Tanabe.

14 recordsLinked to original sources

PubMed2004

Leukemia inhibitory factor activates cardiac L-Type Ca2+ channels via phosphorylation of serine 1829 in the rabbit Cav1.2 subunit.

We have previously reported that leukemia inhibitory factor (LIF) gradually increased cardiac L-type Ca2+ channel current (I(CaL)), which peaked at 15 minutes in both adult and neonatal rat cardiomyocytes, and this increase was blocked by the mitogen-activated protein kinase kinase inhibitor PD98059. This study investigated the molecular basis of LIF-induced augmentation of I(CaL) in rodent cardiomyocytes. LIF induced phosphorylation of a serine residue in the alpha(1c) subunit (Ca(v)1.2) of L-type Ca2+ channels in cultured rat cardiomyocytes, and this phosphorylation was inhibited by PD98059. When constructs encoding either a wild-type or a carboxyl-terminal-truncated rabbit Ca(v)1.2 subunit were transfected into HEK293 cells, LIF induced phosphorylation of the resultant wild-type protein but not the mutant protein. Cotransfection of constitutively active mitogen-activated protein kinase kinase also resulted in phosphorylation of the Ca(v)1.2 subunit in the absence of LIF stimulation. In in-gel kinase assays, extracellular signal-regulated kinase phosphorylated a glutathione S-transferase fusion protein of the carboxyl-terminal region of Ca(v)1.2 (residues 1700 through 1923), which contains the consensus sequence Pro-Leu-Ser-Pro. A point mutation within this consensus sequence, which results in a substitution of alanine for serine at residue 1829 (S1829A), was sufficient to abolish the LIF-induced phosphorylation. LIF increased I(CaL) in HEK cells transfected with wild-type Ca(v)1.2 but not with the mutated version. These results provide direct evidence that LIF phosphorylates the serine residue at position 1829 of the Ca(v)1.2 subunit via the actions of extracellular signal-regulated kinase and that this phosphorylation increases I(CaL) in cardiomyocytes.

Amino Acid Substitution↗

PubMed2003

Increased sensitivity to halothane but decreased sensitivity to propofol in mice lacking the N-type Ca2+ channel.

Volatile anesthetics are known to depress excitatory synaptic transmission. Inhibition of voltage-dependent Ca2+ channels is speculated to underlie this mechanism, which remains to be clarified in vivo. We examined the sensitivity to halothane in mice lacking the N-type Ca2+ channel, a major contributor of presynaptic neurotransmitter release. Sensitivity to halothane was significantly increased in the knockout mice compared with the wild-type littermates. Halothane also depressed field excitatory postsynaptic potentials recorded from the Schaffer collateral-CA1 hippocampal synapses more greatly in the knockout mice. We further examined sleep time induced by injection of propofol, an intravenous anesthetic that mainly affects inhibitory synaptic transmission. In contrast, sensitivity to propofol was significantly decreased in the knockout mice. We suggest that inhibition of the N-type Ca2+ channel underlies mechanisms of halothane anesthesia but counteracts propofol anesthesia.

Anesthetics, Inhalation↗

PubMed2003

Acetic acid conditioning stimulus induces long-lasting antinociception of somatic inflammatory pain.

A wide variety of noxious stimuli are known to induce a powerful inhibition of pain sensation evoked at a remote region of the body. Here we show that an intraperitoneal acetic acid (AA) conditioning stimulus produces long-lasting inhibition of formalin-evoked somatic inflammatory pain behavior in mice. This novel long-lasting antinociception was completely blocked by the 5-hydroxytryptamine type 2A/2C (5-HT(2A/2C)) receptor antagonists, ketanserin and ritanserin, but not by the opioid receptor antagonist, naloxone, and alpha-adrenergic receptor antagonists, phentolamine and yohimbine. In contrast, the 5-HT(3/4) receptor antagonist, tropisetron, significantly potentiated this long-lasting antinociception. The conditioning stimulus significantly upregulated the levels of both tryptophan hydroxylase immunoreactivity in the medulla oblongata and the 5-HT(2A/2C) receptor mRNA level in the spinal cord. These results suggested that the visceral noxious stimulus caused a long-lasting augmentation of the serotonergic inhibitory system and downregulated the somatic inflammatory nociceptive transmission.

Acetic Acid↗

PubMed2003

Plastic change of N-type Ca channel expression after preconditioning is responsible for prostaglandin E2-induced long-lasting allodynia.

BACKGROUND: Although considerable evidence indicates neuronal Ca channels play significant roles in pain perception, their possible importance in hypersensitization after acute inflammation has not been investigated. METHODS: Using carrageenan for inducing hypersensitization, the authors investigated the analgesic effects of intrathecally administered N- and P/Q-type channel blockers, omega-conotoxin GVIA and omega-agatoxin IVA, respectively, and also examined the level of N-type channel expression. RESULTS: Acute inflammation, produced by carrageenan injection in a rat hind paw, caused mechanical hypersensitivity that resolved within several days. Injection of prostaglandin E2 into the same hind paw after resolution caused a markedly prolonged mechanical allodynia lasting more than 4 h. Similar but less potent prolonged allodynia was also induced in the contralateral hind paws. Intrathecal administration of omega-conotoxin GVIA (0.03-0.3 microg) produced dose-dependent inhibition of the allodynia in both control and carrageenan-preconditioned rats. However, the potency of omega-conotoxin GVIA was significantly lower in carrageenan-preconditioned paws than in those in the contralateral and saline-preconditioned paws. In contrast, omega-agatoxin IVA (0.01-0.1 microg) did not reduce the allodynia. Significant up-regulation of N-type channel expression was observed in both dorsal root ganglia and the spinal cord ipsilateral to the carrageenan-preconditioned hind paw. CONCLUSIONS: The results suggest an aggravating role of the N-type channel in pain sensation and a selective plastic change of this channel expression that could underlie the mechanism of hypersensitization after acute inflammation.

Animals↗

PubMed2003

Anesthetic sensitivities to propofol and halothane in mice lacking the R-type (Cav2.3) Ca2+ channel.

UNLABELLED: Because inhibition of voltage-dependent Ca(2+) channels can be a mechanism underlying general anesthesia, we examined sensitivities to propofol and halothane in mice lacking the R-type (Ca(v)2.3) channel widely expressed in neurons. Sleep time after propofol injection (26 mg/kg IV) and halothane MAC(RR) and MAC (50% effective concentrations for the loss of the righting reflex and for the tail pinch/withdrawal response, respectively) were determined. Significantly shorter propofol-induced sleep time (291.6 +/- 16.8 s versus 344.4 +/- 12.1 s) and larger halothane MAC(RR) (1.11% +/- 0.04% versus 0.98% +/- 0.03%) were observed in Ca(v)2.3 channel knockouts (Ca(v)2.3(-/-)) than in wild-type (Ca(v)2.3(+/+)) litter mates. To investigate the basis of the decreased anesthetic sensitivities in vivo, field excitatory postsynaptic potentials and population spikes (PSs) were recorded from Schaffer collateral CA1 synapses in hippocampal slices. Propofol (10-30 micro M) inhibited PSs by potentiating gamma-aminobutyric acid-ergic inhibition, and this potentiation was markedly smaller at 30 micro M in Ca(v)2.3(-/-) mice, possibly accounting for the decreased propofol sensitivity in vivo. Halothane (1.4%-2.2%) inhibited field excitatory postsynaptic potentials similarly in both genotypes, whereas 1%-2% halothane depressed PSs more in Ca(v)2.3(-/-) mice, suggesting the postsynaptic role of the R-type channel in the propagation of excitation and other mechanisms underlying the increased halothane MAC(RR) in Ca(v)2.3(-/-) mice. IMPLICATIONS: Because inhibition of neuronal Ca(2+) currents can be a mechanism underlying general anesthesia, we examined anesthetic sensitivities in mice lacking the R-type (Ca(v)2.3) Ca(2+) channels both in vivo and in hippocampal slices. Decreased sensitivities in mutant mice imply a possibility that agents blocking this channel may increase the requirements of anesthetics/hypnotics.

Anesthetics, Inhalation↗

PubMed2003

N-type Ca2+ channel.

Ca(2+) entry through voltage-dependent Ca(2+) channels (VDCCs) regulates various aspects of physiological function, including neurotransmitter release, regulation of cell membrane excitability, and control of gene expression. VDCCs are classified into several sub-types (L-, N-, P/Q-, R-, and T-types) based on electrophysiological and pharmacological properties. Each type of channels except the T-type is composed of at least four subunits, designated alpha(1), alpha(2), beta, and delta. During the past decade, a number of genes encoding these subunits have been cloned, and cDNA expression studies using heterologous expression systems have revealed the intricate nature of subunit interaction and many biophysical aspects of channel function. In recent years, an entirely new strategy has been introduced in attempts to clarify the physiological role of each of the VDCCs, and this has proven to be very useful in defining previously unknown in vivo functions of VDCCs. In this article, we briefly review the recent advances in our understanding of VDCCs with special emphasis on the N-type channel, which is mainly expressed in neural tissues and is the essential component of neurotransmitter release. We will mainly discuss the subunit composition, channel regulation by G proteins and exocytotic proteins, and the mouse phenotypes in which N-type channel subunits have been deleted by gene targeting technology.

Animals↗

PubMed2002

Altered cocaine effects in mice lacking Ca(v)2.3 (alpha(1E)) calcium channel.

Much evidence indicates that calcium channel plays a role in cocaine-induced behavioral responses. We assessed the contributions of Ca(v)2.3 (alpha(1E)) calcium channel to cocaine effects using Ca(v)2.3 knockout mice (Ca(v)2.3-/-). Acute administration of cocaine enhanced the locomotor activity in wild-type mice (Ca(v)2.3+/+), but failed to produce any response in Ca(v)2.3-/- mice. Repeated exposure to cocaine induced the behavioral sensitization and conditioned place preference in both genotypes. Pretreatment with a D1-receptor antagonist, SCH23390, blocked the cocaine-induced place preference in Ca(v)2.3+/+ mice; however, it had no significant effect in Ca(v)2.3-/- mice. Microdialysis and RT-PCR analysis revealed that the levels of extracellular dopamine and dopamine D1 and D2 receptor mRNAs were not altered in Ca(v)2.3-/- mice. These data indicate that Ca(v)2.3 channel contributes to the locomotor-stimulating effect of cocaine, and the deletion of Ca(v)2.3 channel reveals the presence of a novel pathway leading to cocaine rewarding which is insensitive to D1 receptor antagonist.

Animals↗

PubMed2002

Changes in expression of voltage-dependent ion channel subunits in dorsal root ganglia of rats with radicular injury and pain.

STUDY DESIGN: Changes in expression of voltage-dependent ion channel subunits were examined in the radicular pain state. Furthermore, antinociceptive effects of gabapentin on radicular pain were compared with effects on peripheral neuropathic pain. OBJECTIVES: To clarify molecular substrates involved in the development of radicular pain, and to investigate the responsiveness of radicular pain to gabapentin. SUMMARY OF BACKGROUND DATA: Peripheral nerve injuries are known to induce dynamic changes of voltage-dependent Na+ and Ca2+ channel subunits expression in dorsal root ganglion neurons. However, the expression profiles of Na+ and Ca2+ channel subunits in the radicular pain state have not been examined. METHODS: Two radicular pain models and one peripheral neuropathic pain model were prepared. By using semiquantitative reverse transcriptase-polymerase chain reaction, the expression levels of several Na+ and Ca2+ channel subunits in the dorsal root ganglions of these pain model rats were investigated. The antinociceptive effects of gabapentin were examined in a behavioral study using the aforementioned pain models. RESULTS: All three neuropathic pain operations induced comparable mechanical allodynia and thermal hyperalgesia. The upregulation of the Na(v)1.3 Na+ channel and Ca(v)alpha2delta Ca2+ channel subunits was observed only in the peripheral nerve injury model. A downregulation of the Na(v)1.9 channel was observed in all three pain model rats. A lower dose of gabapentin was significantly more effective in alleviating the mechanical allodynia of rats with radicular pain. CONCLUSIONS: The reduction of Na(v)1.9 found in all three models may link to the neuropathic pain state, including radicular pain. The lower sensitivity to gabapentin in rats with peripheral neuropathic pain might be partly explained by the marked upregulation of Ca(v)alpha2delta in the dorsal root ganglions, suggesting that gabapentin may be more effective in radicular pain treatment.

Acetates↗

PubMed2002

Ca(v)2.3 (alpha1E) Ca2+ channel participates in the control of sperm function.

To know the function of the Ca2+ channel containing alpha(1)2.3 (alpha1E) subunit (Ca(v)2.3 channel) in spermatozoa, we analyzed Ca2+ transients and sperm motility using a mouse strain lacking Ca(v)2.3 channel. The averaged rising rates of Ca2+ transients induced by alpha-D-mannose-bovine serum albumin in the head region of Ca(v)2.3-/- sperm were significantly lower than those of Ca(v)2.3+/+ sperm. A computer-assisted sperm motility assay revealed that straight-line velocity and linearity were greater in Ca(v)2.3-/- sperm than those in Ca(v)2.3+/+ sperm. These results suggest that the Ca(v)2.3 channel plays some roles in Ca2+ transients and the control of flagellar movement.

Animals↗

PubMed2002

Role of Ca(v) 2.3 (alpha1E ) Ca2+ channel in ischemic neuronal injury.

We investigated the role of the Ca(v)2.3 (alpha1E) channel in ischemic neuronal injury using Ca(v)2.3 mutant mice. In focal ischemia model with a complete occlusion of the middle cerebral artery in vivo, infarct at 24 h was significantly larger in Ca(v)2.3 mutant mice compared with that in wild-type controls. In vitro Ca2+ imaging studies using hippocampal slices revealed that oxygen-glucose deprivation induced a [Ca2+]i increase in the hippocampal CA1 region more vigorously in Ca(v)2.3 mutant mice than in wild-type controls, and that tetrodotoxin or bicuculline application abolished the difference between the genotypes. These results suggest that the Ca(v)2.3 channel plays a protective role in ischemic neuronal injury by a mechanism in which GABAergic neuronal actions are involved.

Animals↗

PubMed2002

2-Nitroethenylbenzenes as natural products in millipede defense secretions.

The white millipede Eucondylodesmus elegans Miyosi (Polydesmida: Doratodesmidae) secretes odoriferous droplets from the glands on both lateral surfaces of its body segments. The secretion was shown to be composed of a mixture of (1E)- and (1Z)-2-nitroethenylbenzenes (2-3 microg per millipede), identified by GC/MS analyses and synthesis. This is the first identification of these compounds as natural products. A granulated sugar block baited with the synthetic compound (more than 0.71 microg) demonstrated repellent activity against foraging wild ants, indicating that the compound functioned as a defense substance against potential predators. alpha,beta,2,3,4,5,6-d7-(1E)-2-Nitroethenylbenzene was detected by GC/MS analysis in the millipede secretion after feeding with alpha,beta,beta,2,3,4,5,6-d8-L-phenylalanine, indicating that L-phenylalanine is the precursor of these compounds.

Animals↗

PubMed2002

Effects of ablation of N- and R-type Ca(2+) channels on pain transmission.

Recently several mutant mouse lines lacking neuronal voltage-dependent Ca(2+) channels (VDCCs) have been established by the use of gene targeting in embryonic stem cells. Pain-related behaviors in Ca(v)2.2 (alpha(1B)) and Ca(v)2.3 (alpha(1E)) knockout mice were studied to gain further insight into the mechanism of pain transmission, where VDCCs are thought to play important roles. We review here the data from these recent studies. Ca(v)2.3-/- mice showed normal responses to acute painful stimuli, and reduced responses to the somatic inflammatory pain stimuli. Ca(v)2.3+/- mice exhibited reduced symptoms of visceral inflammatory pain. Ca(v)2.3-/- mice showed abnormal behavior related to the descending antinociceptive mechanism activated by the intraperitoneal injection of acetic acid. Ca(v)2.2-/- mice showed variable acute nociceptive responses depending on the mutant lines. However, all the lines of Ca(v)2.2-/- mice exhibited reduced responses in the phase 2 of the formalin test, suggesting a suppression of inflammatory pain. Furthermore Ca(v)2.2-/- mice showed markedly reduced neuropathic pain symptoms after spinal nerve ligation. Impaired antinociception, similar to that seen in the Ca(v)2.3-/- mice, was also observed in the Ca(v)2.2-/- mice. Therefore, it is suggested that these mutant mice could provide novel models to delineate the nociceptive and antinociceptive mechanisms.

Acetic Acid↗

PubMed2002

1-Octen-3-ol together with geosmin: new secretion compounds from a polydesmid millipede, Niponia nodulosa.

The small millipede Niponia nodulosa (Polydesmida: Cryptodesmidae) emits an earthy smell when disturbed. This smell was obtained from hexane extracts from both sexes at the sixth and seventh instars and adult stages, and was found by GC/MS analyses to be composed of two compounds, 1-octen-3-ol as the major component and geosmin as the minor component. This is the first report of these compounds in secreted substances from millipedes. As they showed little repellent activity against foraging ants in bioassays, their biological function as defensive allomones was not clearly elucidated. However, both compounds provoked negative chemotaxis of conspecific millipedes in a Y-tube olfactometer, especially 1-octen-3-ol, which was active at a dose equivalent to the content of a single millipede. Such biological activity suggests that this compound is involved in intraspecific communication in this millipede and may play a role as an alarm pheromone.

Animal Communication↗

PubMed2001

Novel Cav2.1 splice variants isolated from Purkinje cells do not generate P-type Ca2+ current.

The alpha(1)2.1 (alpha(1A)) subunits of P-type and Q-type Ca(2+) channels are encoded by a single gene, Cacna1a. Although these channels differ in the inactivation kinetics and sensitivity to omega-agatoxin IVA, the mechanism underlying these differences remains to be clarified. Alternative splicings of the Cacna1a transcript have been postulated to contribute to the respective properties, however, the splice variants responsible for P-type Ca(2+) channels have not been identified. To explore P-type-specific splice variants, we aimed at cloning alpha(1)2.1 from isolated mouse Purkinje cells using single-cell reverse transcription-PCR, because in Purkinje cells P-type currents dominate over the whole currents (>95%) with Q-type currents undetected. As a result, two novel splice variants were cloned. Compared with the previously cloned mouse alpha(1)2.1, two novel variants had additional 48 amino acids at the amino termini, six single amino acid changes, and splicing variations at the exon 46/47 boundary, which produced different carboxyl termini. Furthermore, one variant had one RNA editing site. However, electrophysiological and pharmacological studies indicated that these variants did not generate P-type current in cultured cells. These results suggest that P-type-specific splice variants may exist but that post-translational processing or modification by uncharacterized interacting proteins is also required for generating the P-type current.

Alternative Splicing↗