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Biomedical subjects

W K Schmidt

Publications and source records attributed to W K Schmidt.

30 records · Page 2Linked to original sources
PubMed1990

Anti-inflammatory and safety profile of DuP 697, a novel orally effective prostaglandin synthesis inhibitor.

DuP 697 (5-bromo-2[4-fluorophenyl]-3-[4-methylsulfonylphenyl]-thiophene) is a potent inhibitor of paw swelling in nonestablished and established adjuvant arthritis in rats (ED50 = 0.03 and 0.18 mg/kg/day, respectively). DuP 697 had no effect on phenylquinone writhing in rats (ED50 greater than 100 mg/kg), but was analgetic against inflammation-related pain in the Randall-Selitto assay (ED30 = 3.5 mg/kg) and was a very potent antipyretic agent (ED50 = 0.05 mg/kg). The drug was not ulcerogenic in rats at single doses up to 400 mg/kg. DuP 697 (5 mg/kg i.v.) did not alter renal blood flow or the renal vascular response to angiotensin II in furosemide-pretreated, volume-depleted rats. In contrast, indomethacin (5 mg/kg i.v.) decreased renal blood flow and potentiated the renal vascular response to angiotensin II in these animals. DuP 697 was a moderate inhibitor of bull seminal vesicle prostaglandin (PG) synthesis (IC50 = 2.4 X 10(-5) M) and a potent inhibitor of rat brain PG synthesis (IC50 = 4.5 X 10(-6) M) but was ineffective against rat kidney PG synthesis (IC50 7.5 X 10(-5) M). These differential effects of DuP 697 on PG synthesis by various tissues may account for its high potency as an anti-inflammatory and antipyretic agent and its minimal toxicity profile.

Administration, Oral↗
PubMed1988

Nalbuphine: an autoradiographic opioid receptor binding profile in the central nervous system of an agonist/antagonist analgesic.

Nalbuphine is a potent agonist/antagonist analgesic with a low side effect profile and low abuse potential. Previous studies have shown that nalbuphine produces predominantly agonist (analgesic) effects at kappa receptors and antagonist (morphine-reversal) effects at mu receptors in vivo. The present study was designed to localize the sites of nalbuphine binding to mu, delta and kappa opioid receptors in the central nervous system (CNS) using in vitro labeling light microscopic autoradiography. Mu, delta and kappa opioid receptors were labeled selectively using [3H]dihydromorphine, D-[3H]Ala2-D-Leu5-enkephalin and (-)-[3H]ethylketocyclazocine, respectively. In displacement studies in rat brain homogenates, nalbuphine had the highest affinity (Ki) for mu receptors (0.5 nM) with progressively lower affinities for kappa (29 nM) and delta (60 nM) opioid receptors. In autoradiographic studies in slide-mounted sections of guinea pig brain and monkey spinal cord, nalbuphine (300 nM) displaced completely the binding at mu and kappa receptors without significantly altering the binding at delta receptors. The binding of [3H]nalbuphine in slide-mounted sections of guinea pig forebrain was saturable and showed a curvilinear profile indicating the presence of two binding sites with apparent dissociation constant (Kd) values of 0.5 and 12 nM. Morphine and U-50,488H, which have high affinities for mu and kappa opioid receptors, respectively, inhibited [3H]nalbuphine binding with IC50 values of 0.9 and 10 nM, respectively. In saturation studies, morphine (50 nM) and U-50,488H (100 nM) selectively blocked the high and low affinity components of [3H]nalbuphine binding, respectively. The autoradiographic distribution of [3H]nalbuphine binding sites in the CNS corresponds well to the distribution of mu and kappa opioid receptors. In addition, CNS areas (deep layers of the cerebral cortex, laminae I and II of the spinal cord, substantia gelatinosa of the trigeminal nerve, periaqueductal gray and thalamic nuclei) that mediate analgesia contain high concentrations of [3H]nalbuphine binding sites. In summary, these data demonstrate that nalbuphine acts on mu and kappa opioid receptors and identify anatomical loci in the CNS in which nalbuphine may produce its actions.

Analgesia↗
PubMed1985

Nalbuphine.

Nalbuphine is a potent analgesic with a low side effect and dependence profile in animals and man. Nalbuphine is distinguished from other agonist/antagonist analgesics in having greater antagonist activity and fewer behavioral effects at analgesic doses than pentazocine, butorphanol or buprenorphine. At equi-analgesic doses, nalbuphine is quantitatively similar to nalorphine in regard to its large ratio of antagonist to analgetic activity. Clinical studies have confirmed this balance of strong antagonist to analgesic activity. Nalbuphine has been shown to effectively antagonize the respiratory depressant activity of narcotic analgesics while concomitantly adding to their analgetic responses. Unlike nalorphine or pentazocine, nalbuphine produces few overt behavioral or autonomic effects in animals at doses over 300 times its analgesic range. These findings are confirmed by clinical results which show that nalbuphine produces few psychotomimetic effects, even at elevated dose levels, in contrast to nalorphine or pentazocine. Nalbuphine produces limited respiratory depression in animals and in man. Significant cardiovascular effects have not been found. Nalbuphine was found to produce significantly less inhibition of gastrointestinal activity than any of the clinically useful narcotic or agonist/antagonist analgesics tested in animals. Nalbuphine's analgetic effects are reversed by naloxone doses similar to those which reverse nalorphine's agonist effects. Results in this and other tests suggest that nalbuphine is primarily a kappa-agonist/mu-antagonist analgesic. Unlike pentazocine or buprenorphine, nalbuphine does not suppress the narcotic abstinence syndrome in partly-withdrawn morphine-dependent animals or man. Rather, due to nalbuphine's strong antagonist activity, analgesic-range doses of nalbuphine severely exacerbate the withdrawal syndrome in partly-withdrawn mice, monkeys and humans. Nalbuphine also precipitates a strong abstinence response in non-withdrawn morphine-dependent animals and man. In post-addict humans, analgesic-range doses of nalbuphine are perceived as minimally morphine-like, but higher doses are judged to be progressively more nalorphine-like (i.e. dysphoric), which further limits nalbuphine's abuse potential in drug-seeking individuals. Primary dependence studies have demonstrated that physical dependence is possible at high dose levels that produce marked side effects. Other studies show that dependence is unlikely to be of significance within nalbuphine's usual analgesic range. Six-month studies in patients with chronic pain have confirmed that analgesic tolerance or physical dependence is uncommon.(ABSTRACT TRUNCATED AT 400 WORDS)

Analgesics↗
PubMed1980

Effect of a calcium chelator on morphine tolerance development.

To assess the effects of calcium ion chelation on narcotic tolerance development, adult Sprague-Dawley rats were implanted with i.c.v. cannulae connected to osmotic minipumps for continuous infusions of saline or EGTA (2 mumol/24 h) during chronic morphinization by s.c. pellet implantation. Additional rats receiving the same morphine pellet treatment but without minipumps served as non-surgical controls. After 64 h the minipumps and pellets were removed and narcotic tolerance was assessed by the tail-flick technique. A positive analgetic response to an 8.50 mg/kg s.c. dose of morphine sulfate was noted in 6/12 no-minipump controls and 4/9 saline-infused controls. In placebo-treated rats caused no alteration of either baseline tail-flick latencies or in analgetic responsiveness to lower doses of morphine. It is concluded that the enhancement of morphine tolerance by EGTA (a calcium-specific chelator) results from a facilitation of certain adaptive changes of calcium ion disposition that are related to the neurochemical mechanisms of narcotic tolerance and dependence development.

Analgesics↗
PubMed1980

Hyperalgesic effects of divalent cations and antinociceptive effects of a calcium chelator in naive and morphine-dependent mice.

Using a modified tail-flick procedure we have found a highly significant hyperalgesic response in narcotic dependent mice peaking 12 hr following the removal of chronically implanted morphine pellets. Withdrawal-induced hyperalgesia correlated well with other signs of opiate withdrawal behavior. Intracerebroventricular injections of CaCl2, MnCl2 further enhanced the hyperalgesic response in morphine-dependent mice; morphine-dependent mice were more than twice as sensitive to calcium-induced hyperalgesia as placebo-treated controls. On the other hand, i.c.v. injections of the calcium-specific chelator EGTA produced highly significant, dose-dependent antinociceptive responses in both morphine-dependent and control mice, but morphine dependent mice were only half as sensitive to EGTA-induced analgesia as controls. Withdrawal hyperalgesia and EGTA analgesia may be directly related to changes in brain localization of calcium that have been reported previously; it is concluded that morphine and EGTA-induced analgesia may be associated with a calcium depleted state within a relatively small calcium pool of the nerve cell and that opiate withdrawal hyperalgesia is a sensitive measure of narcotic dependency that is likely associated with an increased Ca++ content in the same region.

Animals↗
PubMed1977

The pharmacology of drug abuse--a novel approach to drug education at San Quentin.

A novel and successful undergraduate-level course in pharmacology has been established as part of the drug education program at California's San Quentin State Prison. The program was designed to create a two-way teaching--learning experience between former drug abusers and their teachers, all of whom were doctoral candidates and post-doctoral scholars in pharmacology at a nearby university medical center. In reviewing the pharmacology of psychoactive drugs, the emphasis was on the principles of drug action in the central nervous system, with additional attention to those factors that contribute a potential for abuse. An attempt was made to present information in a strictly objective and non-prejudical manner. An initial analysis has shown a possible change in attitude among the student-inmates toward drugs of abuse. It is likely that courses following a similar design would be well received and successful in any type of undergraduate program that addresses the subject of drug abuse.

Adult↗
PubMedDate not supplied

Cyclic nucleotides and ethanol tolerance and dependence.

Acute ethanol administration decreases cyclic AMP levels in brains of some animal strains. The ethanol-induced decrease of cyclic GMP levels cannot be blocked by intraventricular infusion of calcium but it can be prevented by pretreatment with pyrazole. Although cyclic AMP levels in the cerebral cortex change reciprocally after acute ethanol administration and during withdrawal, the increase observed during withdrawal is probably secondary to some withdrawal processes. Ethanol decreases cerebellar GABA levels only in rats which are stressed prior to sacrifice. Chronic intraventricular infusion of calcium increased the intensity of an acoustic startle response during ethanol withdrawal while EGTA infusion delayed the development of tolerance to the hypothermic effect of ethanol. The ratio of cyclic GMP to GABA levels is postulated to be important for expression of the withdrawal syndrome.

Animals↗