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Biomedical subjects

K W Oh

Publications and source records attributed to K W Oh.

31 records · Page 2Linked to original sources
PubMed1997

Vasodilating and hypotensive effects of fangchinoline and tetrandrine on the rat aorta and the stroke-prone spontaneously hypertensive rat.

Comparative studies of the effects of tetrandrine (TET) and fangchinoline (FAN), two major components of the Radix of Stephannia tetrandrae, on vasodilations and on calcium movement in vascular smooth muscle, and studies of hypotensive effects on stroke-prone spontaneously hypertensive rats (SHRSP) were performed in the following experiments. TET and FAN inhibited high K+ (65.4 mM) and induced sustained contraction in the rat aorta smooth muscle strips. IC50 values for TET and FAN were 0.27 +/- 0.05 microM (n = 6) and 9.53 +/- 1.57 microM (n = 6), respectively, and this inhibition was antagonized by increasing the Ca2+ concentration in the medium. The IC50 of TET for norepinephrine (NE)-induced contraction (0.86 +/- 0.04 g) was 3.08 +/- 0.05 microM (n = 4), and the IC50 of FAN for NE-induced contraction (0.88 +/- 0.07 g) was 14.20 +/- 0.40 microM (n = 4). At the molecular level, radiolabelled 45Ca2+ uptake tests revealed that TET and FAN also inhibited high K+ (65.4 mM) and 1 microM NE-stimulated Ca2+ influx in rat aorta strips at the maximal concentration was needed to inhibit the contraction. TET (3 mg/kg) and FAN (30 mg/kg) administered by intravenous (i.v.) bolus injection also lowered the mean arterial pressure (MAP) significantly during the period of observation in conscious SHRSP, respectively. These results showed that TET was more potent than FAN in blocking calcium channels and antihypertensive activity.

Alkaloids↗
PubMed1996

Blockade by ginseng total saponin of methamphetamine-induced hyperactivity and conditioned place preference in mice.

Ginseng total saponin (GTS) inhibited methamphetamine-induced hyperactivity and conditioned place preference (CPP). Dopamine (DA) receptor supersensitivity was developed in methamphetamine-induced CPP mice and it was inhibited by GTS. GTS also inhibited apomorphine-induced climbing behavior, showing the antidopaminergic activity of GTS. These results suggest that GTS inhibition of the methamphetamine-induced hyperactivity and CPP may be closely related with the inhibition of dopaminergic activation induced by methamphetamine.

Animals↗
PubMed1995

Blockade by ginseng total saponin of the development of cocaine induced reverse tolerance and dopamine receptor supersensitivity in mice.

Daily repeated administration of cocaine (15 mg/kg, over a 7-day period) developed reverse tolerance to the ambulation-accelerating effect of cocaine. Intraperitoneal administration of ginseng total saponin (GTS, 100 and 200 mg/kg of body weight) prior to and during chronic administration of cocaine inhibited the development of reverse tolerance. Dopamine receptor supersensitivity was also developed in reverse tolerant mice that had received the same cocaine. The development of dopamine receptor supersensitivity was evidenced by the enhanced hypothermic response to apomorphine (1 mg/kg) and the enhanced ambulatory activity of apomorphine (4 mg/kg). GTS also prevented the development of dopamine receptor supersensitivity induced by the chronic administration of cocaine. These results provide that GTS may be useful for the prevention and therapy of the adverse action of cocaine. It is concluded that the development of reverse tolerance to the ambulation-accelerating effect of cocaine may be associated with the enhanced dopamine receptor sensitivity because both phenomena were blocked by GTS.

Animals↗
PubMed1995

Inhibition by ginseng total saponin of the development of morphine reverse tolerance and dopamine receptor supersensitivity in mice.

1. Ginseng total saponin (GTS), 200 mg/kg i.p. 3 hr prior to morphine, inhibited the development of reverse tolerance to the ambulatory-accelerating effect of morphine. 2. GTS, 200 mg/kg, also prevented the development of dopamine receptor supersensitivity induced by the chronic administration of morphine, 10 mg/kg a day for 7 days. 3. These results suggest that GTS may be useful for the prevention and therapy of the adverse action of morphine.

Animals↗
PubMed1995

Blockade by ginseng total saponin of the development of methamphetamine reverse tolerance and dopamine receptor supersensitivity in mice.

Repeated administration of methamphetamine (2 mg/kg) developed reverse tolerance to the ambulation-accelerating effect. Intraperitoneal administration of ginseng total saponin (GTS, 200 mg/kg of body weight) prior to and during chronic administration of methamphetamine inhibited the development of reverse tolerance. Dopamine receptor supersensitivity was also developed in reverse tolerant mice which had received the same methamphetamine. The development of dopamine receptor supersensitivity was evidenced by the enhanced hypothermic response to apomorphine (1 mg/kg) and the enhanced ambulatory activity of apomorphine (4 mg/kg). GTS also prevented the development of dopamine receptor supersensitivity induced by the chronic administration of methamphetamine. These results show that GTS may be useful for the prevention of and therapy for the adverse action of methamphetamine. It is concluded that the development of reverse tolerance to methamphetamine may be associated with the enhanced dopamine receptor supersensitivity since both phenomena were blocked by GTS.

Animals↗
PubMed1994

Involvement of kappa-opioid receptors in opioid dependence/withdrawal: studies using butorphanol.

The dependence liability of a class of opioid agonist/antagonist analgesics, e.g. pentazocine, butorphanol, and buprenorphine, is widely recognized. However, the relative involvement of mu-, delta-, and kappa-opioid receptors mediating physical dependence on these compounds is not completely known. In the present study, butorphanol dependence was produced by continuous intracerebroventricular (i.c.v.) infusion of butorphanol (26 nmol/h) for 3 days in male Sprague-Dawley rats. Nor-binaltorphimine, a long-acting kappa-opioid receptor antagonist, and naloxone, a nonspecific antagonist, were administered i.c.v. to precipitate withdrawal in butorphanol-dependent animals, so as to investigate the involvement of central kappa-opioid receptors in opioid dependence. ED50 ratios (naloxone/nor-binaltorphimine) for eliciting withdrawal signs were: teeth-chattering (1.25), yawning (2.13), and ejaculation (0.72). Our data indicate that nor-binaltorphimine precipitated withdrawal behaviors similar to those precipitated by naloxone. It appears that central kappa-opioid receptors may play a major role in the development of butorphanol dependence in rats.

Animals↗
PubMed1994

Interactions of ginsenosides with ligand-bindings of GABA(A) and GABA(B) receptors.

1. Total saponin fraction decreased the affinity of specific [3H]muscimol binding without changes in Bmax. Ginsenoside Rb1 Rb2, Rc, Re, Rf and Rg1 inhibited the specific [3H]muscimol binding to the high-affinity site. 2. Total saponin fraction increased the affinity of specific [3H]flunitrazepam binding. Ginsenoside Re and Rf enhanced specific [3H]flunitrazepam binding. 3. Total saponin fraction decreased the affinity of specific [35S]TBPS binding without changes in Bmax. Ginsenosides did not affect specific or non-specific [35S]TBPS binding. 4. Total saponin fraction decreased the affinity of specific [3H]baclofen binding without changes in Bmax. Ginsenoside Rc inhibited specific [3H]baclofen binding.

Animals↗
PubMed1992

Antagonism of U-50,488H-induced antinociception by ginseng total saponins is dependent on serotonergic mechanisms.

Morphine-induced antinociception was prevented by pretreatment with ginseng total saponins in the tail-pinch and tail-flick tests carried out in mice. The antinociceptive effect of U-50,488H, a selective kappa-opioid receptor agonist, was prevented by naloxone, a nonselective opioid receptor antagonist, in the tail-pinch but not in the tail-flick test. However, U-50,488H-induced antinociception was prevented by ginseng total saponins in the tail-flick but not in the tail-pinch test. These results indicate that nonopioid mechanisms are involved in the antagonism of U-50,488H-induced antinociception by ginseng total saponins. In addition, the antagonism of U-50,488H-induced antinociception in mice pretreated with ginseng total saponins was abolished by pretreatment with a serotonin precursor, 5-hydroxytryptophan, but not by a noradrenaline precursor, L-dihydroxyphenylalanine, in the tail-flick test. Therefore, it appears that the antagonism of U-50,488H-induced antinociception by ginseng total saponins is dependent on serotonergic mechanisms.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1992

Effects of beta-funaltrexamine on butorphanol dependence.

The present experiments were performed to investigate the effects of the selective mu opioid receptor antagonist, beta-funaltrexamine (beta-FNA), on the physical dependence liability of butorphanol (a mixed agonist/antagonist opioid analgesic). Butorphanol (26 nmol/microliter/h) was continuously infused via osmotic minipumps into the lateral cerebral ventricle of male Sprague-Dawley rats for 72 h. beta-FNA (12, 24, and 48 nmol/5 microliter/rat) was administered ICV 3 h prior to and 48 h after initiation of the butorphanol infusion. Treatment with beta-FNA significantly diminished naloxone-induced escape behavior, hypothermia, and loss of body weight in a dose-dependent manner, while naloxone-induced teeth-chattering, forepaw tremors, and urination were also reduced, but in a dose-independent manner. These results suggest that the mu opioid receptor is partially involved in the development of physical dependence upon butorphanol.

Animals↗
PubMed1992

Blockade by ginseng extract of the development of reverse tolerance to the ambulation-accelerating effect of methamphetamine in mice.

Daily repeated administration of methamphetamine (MAP) developed reverse tolerance to its ambulation-accelerating effect. After pretreatment of mice daily with ginseng extract (GE) for 5 days, concomitant injections of MAP and GE suppressed the development of reverse tolerance to the effect of MAP, although GE itself did not affect the spontaneous motor activity of the naive mice. These results provide evidence that GE may be useful for prevention and therapy of the adverse action of MAP.

Animals↗
PubMed1988

A non-opioid mechanism in the inhibitory effect of ginseng saponins on electrically evoked contractions of guinea-pig ileum and mouse vas deferens.

Both ginseng total saponins (GTS) and one of its constituents, protopanaxatriol saponins (PT), inhibited the electrically evoked contractions of guinea-pig ileum (GPI) in a concentration dependent manner in a range of 1-100 micrograms/ml, and this effect was irreversible at high concentrations of the saponins. Protopanaxadiol saponins (PD) had a transient and weak effect. On the other hand, in mouse vas deferens (MVD), the contractions were increased by PT and PD, however, GTS was almost without effect. The inhibitory effect of morphine was arithmetically increased by pretreatment with 100 micrograms/ml of these saponins in GPI preparations, while the inhibitory effect of the contractions was potentiated in MVD preparations. Neither the inhibition of contractions in the GPI preparation nor the facilitation of contractions in the MVD preparation by these ginseng saponins was reversed by 1 microM naloxone, in contrast to naloxone antagonism of morphine-induced contractions in both preparations. GTS and PT caused a dose-dependent inhibition of BaCl2-induced contraction of GPI. It is concluded that the mechanism on the inhibitory or facilitated effect of ginseng saponins on electrically evoked contractions in GPI and MVD preparations may be separated from the effect of opioids, and the mechanism may be based on the direct action of the saponins on smooth muscles preparations.

Animals↗
PubMedDate not supplied

Relationship between polymorphisms G395A in promoter and C1818T in exon 4 of the KLOTHO gene with glucose metabolism and cardiovascular risk factors in Korean women.

BACKGROUND: Recently, klotho has been proposed as a link between cardiovascular diseases and premature aging, but the relationship between KLOTHO genes and cardiovascular risk factors, especially glucose metabolism, in humans is unclear. OBJECTIVES: We investigate the relationship between polymorphisms G395A in promoter and C1818T in exon 4 of the KLOTHO gene with glucose metabolism and cardiovascular risk factors in Korean women. MATERIAL AND METHODS: In 251 women (mean age 51.3+/-6.9 yr), body mass index (BMI), waist circumference, blood pressure, fasting plasma glucose, insulin and lipid profiles were measured. The genotyping of polymorphisms G395A in promoter and C1818T in exon 4 of the KLOTHO gene was performed by allelic discrimination using a 5' nuclease polymerase chain reaction assay. RESULTS: Allele frequencies of G395A polymorphism was 0.829 for the G allele and 0.171 for the A allele and allele frequencies of C1818T polymorphism were 0.804 for the C allele and 0.196 for the T allele, both of which were in compliance with Hardy-Weinberg equilibrium and the two polymorphisms were in linkage disequilibrium (D'=0.43, p<0.01). Mean systolic blood pressure was significantly higher in A allele carriers of G395A polymorphism compared with non-carriers, and the significance was persistent even after adjustment for age and BMI. Mean fasting plasma glucose was significantly higher in T allele carriers of C1818T polymorphism compared with non-carriers, and the significance was persistent even after adjustment for age and BMI. Subjects without any minor allele from either single nucleotide polymorphisms (SNP) had significantly lower mean values for systolic, diastolic blood pressure and fasting plasma glucose levels compared with subjects with both minor allele from either SNP. CONCLUSIONS: We observed that KLOTHO G395A polymorphism was associated with blood pressure and KLOTHO C1818T polymorphism was associated with glucose metabolism in Korean women. Further studies are needed to clarify this relationship.

Adult↗