Takeo Fukuda

Ketamine-induced anesthesia involves the N-methyl-d-aspartate receptor-channel complex in mice

The role of the N-methyl-D-aspartate (NMDA) receptor-channel complex in ketamine-induced anesthesia was examined in mice. General anesthetic potencies were evaluated on a rating scale, which provided the data for anesthetic scores, loss of righting reflex, sleeping time and recovery time. All drugs were administered intraperitoneally. NMDA (60-300 mg/kg), an NMDA receptor agonist, dose-dependently antagonized the general anesthetic potencies of ketamine at a dose of 100 mg/kg which produced loss of righting reflex in more than 90% of the mice. On the other hand, a high dose of N-methyl-L-aspartate (400 mg/kg), a stereoisomer of NMDA, did not. A dose of 300 mg/kg of NMDA significantly shifted the dose-response curve of ketamine for loss of righting reflex to the right. A high dose of D-cycloserine (200 mg/kg), an agonist at the glycine site on the NMDA receptor complex, slightly but significantly shortened the sleeping time caused by ketamine (100 mg/kg). However, neither a critical subconvulsive dose of kainate (15 mg/kg), a kainate receptor agonist, nor a subconvulsive dose of quisqualate (120 mg/kg), an alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor agonist, reversed general anesthesia induced by 100 mg/kg of ketamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Extracellular high mobility group box chromosomal protein 1 is a coupling factor for hypoxia and inflammation in arthritis

OBJECTIVE Tissue hypoxia is closely associated with arthritis pathogenesis, and extracellular high mobility group box chromosomal protein 1 (HMGB-1) released from injured cells also has a role in arthritis development. This study was thus undertaken to investigate the hypothesis that extracellular HMGB-1 may be a coupling factor between hypoxia and inflammation in arthritis. METHODS Concentrations of tumor necrosis factor alpha, interleukin-6, vascular endothelial growth factor, lactic acid, lactate dehydrogenase, and HMGB-1 were measured in synovial fluid (SF) samples from patients with inflammatory arthropathy (rheumatoid arthritis and pseudogout) and patients with noninflammatory arthropathy (osteoarthritis). The localization of tissue hypoxia and HMGB-1 was also examined in animal models of collagen-induced arthritis (CIA). In cell-based experiments, the effects of hypoxia on HMGB-1 release and its associated cellular events (i.e., protein distribution and cell viability) were studied. RESULTS In SF samples from patients with HMGB-1-associated inflammatory arthropathy (i.e., samples with HMGB-1 levels >2 SD above the mean level in samples from patients with noninflammatory arthropathy), concentrations of HMGB-1 were significantly correlated with those of lactic acid, a marker of tissue hypoxia. In CIA models in which the pathologic phenotype could be attenuated by HMGB-1 neutralization, colocalization of HMGB-1 with tissue hypoxia in arthritis lesions was also observed. In cell-based experiments, hypoxia induced significantly increased levels of extracellular HMGB-1 by the cellular processes of secretion and/or apoptosis-associated release, which was much more prominent than the protein release in necrotic cell injury potentiated by oxidative stress. CONCLUSION These findings indicate that tissue hypoxia and its resultant extracellular HMGB-1 might play an important role in the development of arthritis.

Involvement of N-methyl-D-aspartate (NMDA) receptors in noncompetitive NMDA receptor antagonist-induced hyperlocomotion in mice

The role of the N-methyl-D-aspartate (NMDA) receptors in hyperlocomotion induced by (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801), a potent and selective noncompetitive NMDA receptor antagonist, was examined in male ddY mice. A low dose of MK-801 [0.2 mg/kg, intraperitoneally (IP)] produced a marked increase in locomotor activity without obvious staggering gait. In contrast, a high dose (1 mg/kg, IP) induced a typical motor syndrome characterized by increased locomotor activity, stereotyped behavior, and severe ataxia. NMDA (60-120 mg/kg, IP), an NMDA receptor agonist, dose dependently antagonized hyperlocomotion induced by a low dose of MK-801 (0.2 mg/kg). However, even a high convulsive dose of NMDA (240 mg/kg, IP) could not completely antagonize the hyperactivity induced by MK-801. On the other hand, neither a high dose of N-methyl-L-aspartate (400 mg/kg, IP), a stereoisomer of NMDA, nor a critical subconvulsive dose of kainate (10 mg/kg, IP), a non-NMDA receptor agonist, reversed MK-801-induced hyperlocomotion. The activity induced by MK-801 was potently suppressed by low doses of haloperidol (0.05-0.1 mg/kg, IP), a dopamine (DA) receptor antagonist, in a dose-dependent manner. These data for MK-801 were similar to those for phencyclidine and ketamine, other noncompetitive NMDA receptor antagonists. These results suggest that noncompetitive NMDA receptor antagonist-induced hyperlocomotion is mediated, at least in part, by NMDA receptor antagonism, although this hyperactivity may also involve dopaminergic mechanisms through indirect (perhaps by reducing NMDA receptor-mediated neurotransmission) and/or direct (by inhibiting DA uptake) effects on DA neurons.

Antinociceptive mechanism of l-DOPA

&NA; The mechanism of l‐DOPA for antinociception was investigated. Nociceptive behaviors in mice after an intrathecal (i.t.) administration of substance P were evaluated. l‐DOPA (i.t.) dose‐dependently attenuated the substance P‐induced nociceptive behaviors. Co‐administration of benserazide (i.t.), a DOPA decarboxylase inhibitor, abolished the antinociceptive effect of l‐DOPA. The l‐DOPA‐induced antinociception was antagonized by sulpiride, a D2 blocker, but not by SCH 23390, a D1 blocker. These results suggest that l‐DOPA relieves pain after conversion to dopamine, with the dopamine sedating pain transmission by way of the dopamine D2 receptor.

Capsaicin-induced neuroparalytic keratitis-like corneal changes in the mouse

A single subcutaneous injection of 12.5-100 mg kg-1 capsaicin to newborn mice produced gross corneal changes. The changes were manifest about three weeks after capsaicin treatment and progressed dose-dependently from slight punctate vesiculations in the epithelium to diffuse edematous opacities and vascularizations in the stroma, followed by recovery in several weeks with or without residual scars. Control newborn mice with vehicle solution did not show any corneal abnormality. The most prominent histopathological feature of the affected corneas was a marked loss of nerve axons in the epithelium with associated disorganization of the epithelium. Similar corneal changes were observed with systemic capsaicin treatment to young or adult mice. The pathogenesis of the capsaicin-induced corneal changes was discussed with reference to the trophic action of the trigeminal nerve.

Effects of ketamine on dopamine metabolism during anesthesia in discrete brain regions in mice: comparison with the effects during the recovery and subanesthetic phases

The effects of ketamine on the levels of dopamine (DA), norepinephrine (NE), 5-hydroxytryptamine (5-HT, serotonin) and their metabolites were examined in discrete brain regions in mice. A high dose of ketamine (150 mg/kg, i.p.) did not change DA metabolism in the frontal cortex, nucleus accumbens, striatum and hippocampus, but did decrease it in the brainstem during anesthesia. In contrast, during recovery from the ketamine anesthesia, the high dose increased the level of homovanillic acid (HVA) in all brain regions. A low subanesthetic dose of ketamine (30 mg/kg, i.p.) increased the concentrations of both 3,4-dihydroxyphenylacetic acid (DOPAC) and HVA only in the nucleus accumbens. The DA level was not affected by any ketamine treatment. During ketamine anesthesia, the content of 3-methoxy-4-hydroxy-phenylglycol (MHPG) was decreased in the brainstem, whereas during recovery from anesthesia, the MHPG level was increased in the frontal cortex, nucleus accumbens and brainstem. The NE content was not altered in any region by ketamine treatment. The concentration of 5-hydroxyindoleacetic acid (5-HIAA) was reduced in the frontal cortex, striatum, hippocampus and brainstem during ketamine anesthesia. The 5-HT level was unaltered in all regions except the brainstem where it was reduced. In contrast, after anesthesia, the concentrations of both 5-HT and 5-HIAA were increased in the striatum. During the subanesthetic phase, however, the levels of NE, 5-HT and their metabolites were unchanged. These neurochemical results are consistent with the electrophysiological findings that a high dose of ketamine does not change the basal firing rates of nigrostriatal DA neurons during anesthesia, while low subanesthetic doses significantly increase those of ventral tegmental DA neurons.

Corneal lesions induced by the systemic administration of capsaicin in neonatal mice and rats

SummaryFollowing a single subeutaneous injection of capsaicin to neonatal mice, a high incidence of corneal lesions with opacity developed after a long latency. The intensity of the lesions progressed for about 1 month in animals which had received a high dose (50 or 100 mg/kg) of capsaicin. Although the intensity gradually decreased thereafter, 50% of animals still exhibited a visible opacity 6 months after treatment. Similar corneal lesions were also produced in neonatal rats which had been injected with capsaicin. It is suggested that the corneal lesions induced by capsaicin may be due to destruction of the trigeminal nerve.

Hyperlocomotion during Recovery from Isoflurane Anesthesia Is Associated with Increased Dopamine Turnover in the Nucleus Accumbens and Striatum in Mice

Background It was recently reported that isoflurane increases dopamine release in the striatum in rats both in vivo and in vitro, and that isoflurane inhibits uptake of dopamine in the rat brain synaptosomes. However, the functional role of these effects of isoflurane on dopamine neurons is uncertain. Dopaminergic mechanisms within the nucleus accumbens and striatum play an important role in the control of locomotor activity, and a change in dopamine turnover depends essentially on a change in impulse flow in the dopamine neurons. In this study, the effects of isoflurane on locomotor activity and on dopamine turnover were investigated in discrete brain regions in mice. Methods Mice were placed in individual airtight clear plastic chambers and spontaneously breathed isoflurane in 25% oxygen and 75% nitrogen (fresh gas flow, 4 l/min). Locomotor activity was measured with an Animex activity meter. Animals were decapitated after treatments with or without isoflurane, and the concentrations of monoamines and their metabolites in different brain areas were measured by high‐performance liquid chromatography. Results During the 10 min after the cessation of the 20‐min exposure to isoflurane, there was a significant increase in locomotor activity in animals breathing 1.5% isoflurane but not 0.7% isoflurane. This increase in locomotor activity produced by 1.5% isoflurane was abolished by a low dose of haloperidol (0.1 mg/kg), a dopamine receptor antagonist. Regional brain monoamine assays revealed that 1.5% isoflurane significantly increased the 3,4‐dihydroxyphenylacetic acid:dopamine ratio (one indicator of transmitter turnover) in the nucleus accumbens and striatum, but a concentration of 0.7% did not. This significant increase in dopamine turnover in these regions continued during 20 min after the cessation of the administration of 1.5% isoflurane. Conclusions These results suggest that isoflurane‐induced hyperlocomotion during emergence may be associated with increased dopamine turnover in the nucleus accumbens and striatum.

The metabolic rate and vulnerability of dopaminergic neurons, and adenosine dynamics in the cerebral cortex, nucleus accumbens, caudate nucleus, and putamen of the common marmoset.

Abstract The pathophysiology of the striatum and cerebral cortex were studied from the pharmacological aspect.Investigation of the dopamine content in the cerebral cortex revealed that the premotor and motor area showed the highest level (61±6.2 ng/g). Intravenous injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at a dose of 10 mg/kg reduced the dopamine content in the caudate nucleus and putamen to 2–3% of the control level in common marmosets, while it fell to 60% in the nucleus accumbens. There was no alteration of the dopamine content in the cerebral cortex. Immunohistochemical staining for tyrosine hydroxylase in the midbrains of MPTP-treated marmosets showed almost complete disappearance of dopaminergic cells from the substantia nigra and good preservation of cells in the ventrotegmental area. Dopaminergic cells projecting to the caudate/putamen, nucleus accumbens, and cerebral cortex showed marked, moderate, and no vulnerability to MPTP, respectively.After systemic administration of MPTP, dopaminergic neurons projecting to the caudate nucleus and putamen were damaged equally. However, the compensatory increase of dopamine turnover was more prominent in the putamen than in the caudate nucleus. Thus, nigroputaminal dopaminergic neurons may have a higher level of activity than neuron in the caudate. The neural connections and functions of the caudate nucleus and putamen have already been differentiated anatomically or physiologically. This compensatory increase of the dopamine turnover rate is another aspect of functional differences between the caudate nucleus and putamen.Investigation of the dopamine content in the heat, body, and tail of the caudate nucleus showed no differences in the concentration of dopamine. However, a study of the metabolic rate of dopamine using α-methyl-p-tyrosine, a tyrosine hydoxylase inhibitor, showed higher metabolism of dopamine in the head of the caudate nucleus in common marmosets. Thus, dopaminergic neurons projecting to the caudate nucleus may show topographical differences in their firing rates.A microdialysis study indicated an increase in the metabolism of adenosine in the striatum of MPTP-treated animals. Cholinergic neurons are interneurons and are one of the main sources of adenosine in the striatum. Dopaminergic input from the substantia nigra acting on cholinergic neurons was decreased following MPTP treatment. The increase of adenosine metabolism suggested that cholinergic neurons in the striatum receive inhibitory inputs from nigrostriatal dopaminergic neurons.

Effects of methysergide and naloxone on analgesia induced by the peripheral electric stimulation in mice

We investigated the antinociceptive effects produced by peripheral electric stimulation (PES) in mice and the influence of administration of L-5-hydroxytryptophan (5-HTP), methysergide and naloxone on the antinociceptive effect of the PES. Administration of 5-HTP enhanced antinociceptive effects induced by PES, while methysergide and naloxone abolished this antinociception. The mechanisms of analgesia produced by PES involve both endogenous opiate systems and central serotonergic mechanisms.