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Biomedical subjects

M Otsuka

Publications and source records attributed to M Otsuka.

At least 469 records · Page 26Linked to original sources
PubMed1981

Actions of vasopressin, gastrin releasing peptide and other peptides on neurons on newborn rat spinal cord in vitro.

The actions of various peptides were studied using isolated spinal cord preparation of newborn rat. Vasopressin, substance P, thyrotropin releasing hormone, bombesin, gastrin releasing peptide, oxytocin, neurotensin, cholecystokinin-octapeptide and angiotensin II produced marked depolarizing responses of motoneurons with threshold concentrations of 5 X 10(-10)--8 X 10(-9) M. After the elimination of transsynaptic action by tetrodotoxin, the actions of these peptides were depressed to various extents, the former 5 peptides producing relatively large responses. Somatostatin and enkephalin depressed the dorsal root potential and produced slight hyperpolarization of dorsal root fibers. It is suggested that many of these peptides play important roles in synaptic transmission in mammalian spinal cord.

Animals↗
PubMed1981

[A device for the drug-capsule administration into the rat stomach and its pharmacological application (author's transl)].

To assess the absorption of drugs given in capsule form to rats, the method of administration was studied using gastric-cannulated rats. The body weight of these rats remained the same as even when given casein hydrolysate and vitamins in addition to the usual chow diet. Indomethacin (IM) capsule (2 mg/capsule) was given and the plasma concentration and anti-inflammatory action of IM were studied. The maximum plasma concentration was seen at 2 hr after administration of one capsule. The carrageenin-induced edema of rat hind paw was inhibited with the ingestion of only one capsule. In addition, the time course of the plasma concentration of IM correlated with that of the inhibitory effect of carrageenin-induced edema. In the case of administration of a barium sulfate capsule to the cannulated rats, the transfer of the barium sulfate was clearly observed on the X-rays. Our findings suggest that this approach to the estimation of drugs is feasible, at least in experimental animals.

Animals↗
PubMed1981

Separative determination of ascorbic acid and erythorbic acid by high-performance liquid chromatography.

High-performance liquid chromatography (HPLC) was applied to the determination of ascorbic acid (AsA) and erythorbic acid (ErA). The apparatus was a Shimadzu model LC-2P Liquid Chromatograph equipped with a UV detector set at 254 nm. The separation was achieved on a LiChrosorb-NH2 column which was pre-treated with 0.1 M ammonium monophosphate solution using a mixture of acetonitrile, acetic acid and water (87:2:11, v/v) as an eluant. The HPLC method has the following advantages: AsA and ErA are quantitated after being distinctly separated, analysis time per one sample is short, and AsA or ErA levels as low as 1.0 X 10(-2) microgram are detectable. Recovery experiments with dehydro-AsA and dehydro-ErA, involving reduction with H2S, give satisfactory results.

Antioxidants↗
PubMed1981

Separative determination of ascorbic acid and erythorbic acid in animal tissues by high-performance liquid chromatography.

A method for the separation and determination of ascorbic acid (AsA) and erythorbic acid (ErA) in animal tissues is described. It employs high-performance liquid chromatography on a LiChrosorb-NH2 column in conjunction with a mixture of acetonitrile, acetic acid and water as an eluant. Application of the method, which is sensitive, rapid and simple, to the analyses of AsA and ErA in animal tissues such as liver, adrenals, spleen, kidneys and heart gave satisfactory results. Dehydro-AsA and dehydro-ErA in rat liver could be determined after reduction with H2S. The method was shown to be useful for the routine analyses.

Adrenal Glands↗
PubMed1980

Identification by high-performance liquid chromatography of immunoreactive substance P released from isolated rat spinal cord.

An attempt was made to identify the immunoreactive substance P (SP) released from isolated rat spinal cords using reversed-phase high-performance liquid chromatography (HPLC) combined with radioimmunoassay (RIA) for SP. Soaking the spinal cords of newborn rats in Krebs solution containing 90 mM K+ evoked a release of immunoreactive SP as well as of GABA and glycine in a calcium-dependent manner. Capsaicin also evoked a release of immunoreactive SP but not of GABA and glycine. The immunoreactive SP released from rat spinal cords by high K+ or capsaicin was analyzed by HPLC. A single peak was detected by RIA whose elution position coincided with that of synthetic SP.

Animals↗
PubMed1980

The effects of substance P and baclofen on motoneurones of isolated spinal cord of the newborn rat.

The effects of substance P (SP) and baclofen were studied in the isolated spinal cord of newborn rats. Potential changes generated in motoneurones were recorded extracellularly from the ventral root (L3-L5). When SP (8 X 10(-5) M) was introduced into the bath, the depolarization of motoneurones began with a delay of 1.1 s. A large part of this delay can be explained as a time needed for SP to reach the site of action on spinal neurones. When the preparation was perfused with artificial cerebrospinal fluid (CSF) containing low Ca (0.1 mM) and high Mg (1.6-3.5 mM), the spinal reflexes induced by dorsal root stimulation and recorded from the corresponding ventral root were completely abolished. The depolarizing action of SP (10(-7) M) on the motoneurones was potentiated in the low-Ca medium, suggesting that SP acts directly on the motoneurones. Baclofen at 10(-6) M depressed the monosynaptic reflex by about 75%. The SP-induced depolarization of motoneurones was greatly depressed by baclofen in both normal and 0.1 mM-Ca mediums. The effects of baclofen (10(-6) M) on the responses to various depolarizing agents were compared with that on the response to SP in artificial CSF containing 0.1 mM-Ca and 1.6-2 mM-Mg. The SP response was reduced by about 80%, whereas the responses to acetylcholine and glycine were not appreciably affected, and those to L-glutamate, GABA and noradrenaline were depressed by 10-22% by baclofen. The results suggest that baclofen blocks transmission at certain primary afferent synapses by antagonizing the action of SP that is released as a transmitter.

Action Potentials↗