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K Fujibayashi

Publications and source records attributed to K Fujibayashi.

12 recordsLinked to original sources
PubMed1998

Enhancing effect of dimethyl sulfoxide on nociceptive transmission in isolated spinal cord of newborn rat.

The effect of dimethyl sulfoxide (DMSO) on the slow ventral root potential, which is related to nociceptive transmission, was investigated in the isolated spinal cord of a newborn rat. DMSO at 0.3-1% (v/v) enhanced the slow ventral root potential, but not mono- and polysynaptic reflex discharges. DMSO at 1% also enhanced the depolarization induced by substance P or capsaicin. In the presence of tetrodotoxin (0.3 microM), DMSO at 1% did not influence the substance P-induced depolarization but enhanced the acetylcholine-induced depolarization. Edrophonium at 10 microM also enhanced the slow ventral root potential, and the magnitude of the effect was comparable to that of 1% DMSO. In the presence of atropine (0.3 microM) and hexamethonium (30 microM), the effect of edrophonium disappeared, but half of the effect of DMSO remained. Artificial cerebrospinal fluid containing either 0.87% (w/v) urea or 4.6% (w/v) sucrose, which has the same osmotic pressure as that containing 1% DMSO, did not have the same effect as DMSO on the slow ventral root potential. In the saphenous nerve-dorsal root preparation, the compound action potential was enhanced by 4-aminopyridine (10 microM), but was not affected by DMSO up to 3%. The results suggest that DMSO enhances the slow ventral root potential through mechanisms based on the inhibition of cholinesterase activity and other action(s) involved in increasing transmitter release from nerve endings in nociceptive transmission pathways in the isolated spinal cord of the newborn rat. Neither the blockade of K+ channels nor hyperosmotic effects are likely mechanisms of DMSO action.

Animals↗
PubMed1998

Effects of R-84760, a selective kappa-opioid receptor agonist, on nociceptive reflex in isolated neonatal rat spinal cord.

We tested the effects of (3 R)-3-(1-pyrrolidinylmethyl)-4-[(1S)-5,6-dichloro-1-indancarbony l]-2,3,5,6-tetrahydro-1,4-thiazine hydrochloride (R-84760), a selective kappa-opioid receptor agonist, on the slow ventral root potential in the isolated spinal cord of neonatal rats. R-84760 at 10 nM decreased the slow ventral root potential to 35% of the control, leaving the monosynaptic reflex unaffected. The depressant effect of R-84760 progressed slowly for 60 min to the maximum and recovered slightly after removal of the drug from the perfusing solution. This contrasts with [D-Ala2, MePhe4, Gly-ol5]enkephalin (DAMGO) or [MeTyr1, MeArg7, D-Leu-NHEt8]dynorphin A-(1-8) (E-2078) which attained their maximum depressant effect within 15 min with recovery immediately after washout. Reversibility of the R-84760 effect was observed in vivo in antinociceptive tests in mice. R-84760 reduced the depolarization induced by substance P or L-glutamate in the normal solution, but not in the presence of tetrodotoxin at 0.3 microM. Naloxone inhibited the effect of R-84760 at a higher concentration (1 microM) than that (0.1 microM) needed to antagonize the effect of DAMGO. In contrast, R-84760 was more sensitive to nor-binaltorphimine than was DAMGO. The results show that R-84760 selectively inhibits the nociceptive response presynaptically through kappa-opioid receptors and that the inhibitory effect is characteristic, with long duration, in the neonatal rat spinal cord.

Analgesics↗
PubMed1995

Profiles of the antinociceptive effect of R-84760, a selective kappa-opioid receptor agonist, in the formalin test in mice.

The antinociceptive effect of a selective kappa-opioid receptor agonist R-84760, (3R)-3-(1-pyrrolidinylmethyl)-4-[(1S)-5,6-dichloro-1-indancarbo nyl]- tetrahydro-1,4-thiazine hydrochloride, in the second phase of the formalin test, a model of tonic pain, was examined in mice. R-84760 had a 2700 times more potent antinociceptive effect than morphine. The effect of R-84760 was antagonized by subcutaneously administered nor-binaltorphimine, a kappa-selective opioid receptor antagonist. Both intracerebroventricularly and intrathecally administered nor-binaltorphimine partially antagonized the antinociceptive effect of R-84760. Intrathecally administered phentolamine, an alpha-adrenoceptor antagonist, attenuated and desipramine, a noradrenaline reuptake inhibitor, augmented the antinociceptive effect of R-84760. Intrathecally administered noradrenaline attenuated the nociceptive response in the second phase of the formalin test. Intrathecally administered (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), an N-methyl-D-aspartate (NMDA)-receptor antagonist, reduced and threo-beta-hydroxyaspartate, a reuptake inhibitor of glutamate, augmented the second phase nociceptive response. However, R-84760 did not influence the intrathecally injected NMDA-induced nociceptive response. These results suggest the following: R-84760 produces an extremely potent antinociceptive effect against tonic pain through the kappa-opioid receptors; the sites of action of subcutaneously administered R-84760 are the supraspinal and spinal loci in the central nervous system; and a part of the mechanism of the antinociceptive effect of R-84760 is activation of the descending noradrenergic pathway.

Analgesics↗
PubMed1994

Pharmacological properties of R-84760, a novel kappa-opioid receptor agonist.

The pharmacological properties of a structurally novel kappa-opioid receptor agonist, (3R)-3-(1-pyrrolidinylmethyl)-4-[(1S)-5,6-dichloro-1-indancarbo nyl]- tetrahydro-1,4-thiazine hydrochloride (R-84760), were examined. In an opioid receptor binding assay with a guinea pig brain membrane fraction, R-84760 showed a 5 times higher affinity for the kappa-opioid receptor than CI-977, the most potent reference kappa-opioid receptor agonist, and selectivity of R-84760 for the kappa-opioid receptor was higher than that of U-69593, a highly selective kappa-opioid receptor agonist. R-84760 was functionally 2.5 times more potent than CI-977 as a kappa-opioid receptor agonist in rabbit vas deferens. Subcutaneously administered R-84760 had an antinociceptive effect in the phenylquinone writhing test in mice and its potency was 5-846 times higher than those of CI-977, U-50488, morphine, pentazocine and butorphanol. On oral administration, R-84760 was 20-2077 times more potent than the same reference drugs. The antinociceptive effect of R-84760 was not antagonized by naloxone in a dose at which naloxone antagonized the effect of morphine, but on the other hand nor-binaltorphimine antagonized the effect of R-84760 at a dose which did not affect the effect of morphine. R-84760 and the reference kappa-opioid receptor agonists produced sedative and diuretic effects in mice with the same order of potency as for the antinociceptive effect. Tolerance to the antinociceptive effect of R-84760 barely developed, and naloxone-induced jumping tests for morphine-like physical dependence of R-84760 gave negative results.

Amino Acid Sequence↗
PubMed1988

Effect of flunarizine on experimentally induced facial nerve injury.

The effect of flunarizine, a calcium antagonist, on experimentally induced facial nerve injury in guinea pigs was studied electron microscopically. In flunarizine-untreated animals, intra-axonal accumulation of cell organelles and degradation of myelin sheaths were observed. In flunarizine-treated animals, these changes were not observed, but a knob-like protrusion of myelin sheaths and a structure resembling the myelin sheath in Schwann cell cytoplasm was occasionally observed.

Animals↗
PubMed1983

Comparison of analgesic potencies of mu, delta and kappa agonists locally applied to various CNS regions relevant to analgesia in rats.

Analgesic potencies of relatively selective agonists for mu, delta and kappa subtypes of opioid receptors, morphine, [D-Ala2,D-Leu5]-enkephalin (DADL) and ethylketocyclazocine (EKC), respectively, were examined with the tail-pinch test in the rat, when microinjected into the brain stem regions relevant to analgesia such as the nucleus reticularis paragigantocellularis (NRPG), nucleus raphe magnus (NRM) and periaqueductal gray matter (PAG), and into the lumbar subarachnoid space (LSS). Morphine, DADL and EKC produced dose-dependent analgesic effects at the NRPG, NRM, PAG and LSS. The ED50 values indicated that morphine was more potent than DADL at the NRPG and LSS but less at the NRM and PAG. EKC was the weakest at all the injection sites. Further, naloxone (0.1 mg/kg, s.c.) significantly antagonized the analgesic effect of morphine but not that of DADL or EKC at the NRPG. These findings suggest that mu, delta and kappa subtypes of opioid receptors mediate analgesia, and that the extent of contribution of each subtype to the production of analgesia differs among the CNS sites examined in this study.

Analgesics, Opioid↗
PubMedDate not supplied

Effects of R-84760, a selective kappa-opioid receptor agonist, on nociception, locomotion and respiration in rats.

The effects of R-84760 [(3R)-3-(1-pyrrolidinylmethyl)-4-[(1S)-5,6-dichloro-l-indancarb onyl] tetrahydro-1,4-thiazine hydrochloride] on nociception, locomotion and respiration were examined in rats. R-84760 induced a potent antinociceptive effect in the formalin test. The potency was 930 and 1500 times higher than that of U-50488 and morphine, respectively, when injected subcutaneously. Intracerebroventricular and intrathecal injection, as well as subcutaneous administration of naloxone antagonized the antinociceptive effect of R-84760, suggesting the sites of action of R-84760 were at the spinal and supraspinal levels. R-84760 disturbed the rotarod performance at doses 16 times higher than those needed for antinociception. R-84760 did not affect the arterial blood Pco2, Po2 and pH at a supramaximal dose for antinociception.

Analgesia↗