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Biomedical subjects

I Oye

Publications and source records attributed to I Oye.

At least 19 recordsLinked to original sources
PubMed1992

Naloxone counteracts the fast development of tolerance to morphine in guinea-pig ileum.

The ability of naloxone to inhibit the fast development of tolerance to morphine was examined in the guinea-pig ileum preparation. Dose-response curves were obtained either non-cumulatively with morphine alone or cumulatively with morphine alone and in combination with different concentrations of naloxone. We present some theoretical considerations concerning the competitive interaction between agonist and antagonist on a receptor. According to these theories, it is possible to perform dose-response experiments for an agonist in combination with different concentrations of antagonist and extrapolate to the dose-response curve for agonist alone and to the dissociation constant for the antagonist. EC50 values for morphine alone obtained either non-cumulatively or by extrapolation are almost identical and are significantly lower than those obtained cumulatively. The results indicate that tolerance develops very quickly when dose-response curves are obtained cumulatively with morphine alone and that low concentrations of naloxone counteract the development of tolerance.

Animals↗
PubMed1992

Effects of ketamine on sensory perception: evidence for a role of N-methyl-D-aspartate receptors.

The chiral forms of ketamine were applied as probes for N-methyl-D-aspartate receptor-mediated neurotransmission in humans. Both enantiomers, in clinically relevant concentrations, displaced [3H]dizocilpine (MK 801) from specific binding sites (phencyclidine sites) in membrane fractions of brain homogenates. (S)-Ketamine was at least 4 times as potent as (R)-ketamine in this respect. In healthy volunteers, the most obvious effect of subanesthetic doses of both enantiomers was altered sensory perception. (S)-Ketamine was 4 times as potent as (R)-ketamine in reducing pain perception and in causing auditory and visual disturbances. Both enantiomers caused proprioceptive disturbances (feelings of detachment from the body) and slightly reduced the ability to recall objects seen after administration of the drugs. The ability to recall objects seen immediately before drug exposure was unaffected. The results are in accordance with the hypothesis that inhibition of sensory perception by ketamine in subanesthetic concentrations is due to N-methyl-D-aspartate receptor blockade. It is suggested that N-methyl-D-aspartate receptor-mediated transmission is involved in the processing of sensory information in the human brain.

Adult↗
PubMed1991

A new version of the ischemic tourniquet pain test.

A new method of producing ischemic tourniquet pain is presented. The present test model showed a sex difference in the pain recordings. Sum pain intensity (SPI) for a 5 min trial period of ischemic pain was lower for males than for females (p less than 0.0001). The observed variability between male test subjects was greater than between female subjects, while the variation in pain scores within subjects was lower for males compared to females. The differences between sexes as a group with respect to variability of pain recordings were not statistically significant. Due to the observed sex differences in pain recording it is recommended to use test subjects of the same sex when restricting the test procedure to a limited number of subjects. The present version of the tourniquet pain test, used according to the recommended criteria, allows discriminating between i.v. administered placebo, opioid analgesics (pethidine) and ketamine.

Adult↗
PubMed1990

Evidence of a role for NMDA receptors in pain perception.

Both chiral forms of ketamine caused analgesia when administered in subanesthetic doses to human volunteers suffering acute, experimentally induced ischemic pain. S-Ketamine was 4 times more potent than R-ketamine as an analgesic agent in this model system. The relative order of analgesic potency of the two enantiomers was compared to their relative affinity for phencyclidine (PCP) binding sites (associated with the NMDA receptor-operated ion channel) and for sigma binding sites (which are not associated with the NMDA receptor complex). The relative analgesic potency of the enantiomers correlated positively with their relative affinity for PCP sites and negatively with their relative affinity for sigma sites. The results strongly indicate that PCP sites, but not sigma sites, are functional receptors mediating the analgesic effect of ketamine. This is consistent with the hypothesis that NMDA receptors are essential for pain perception in humans. Disturbances of other sensory modalities, in particular somatosensory perception, vision and hearing, were the main side-effects observed. These effects were qualitatively similar for both enantiomers and were closely associated with their analgesic action. The NMDA type of excitatory amino acid receptor thus appears to be widely involved in the processing of sensory afferent signals in the human brain.

Humans↗
PubMed1990

[Ketamine: clinically useful--pharmacologically interesting].

Ketamine has been employed as an anesthetic for 25 years. It is the only PCP-like dissociative anesthetic in clinical use. Favourable experience with ketamine in combat situations and at accidents, together with its ability to block the effect of the excitatory neurotransmitter glutamate on NMDA-receptor mediated neurotransmission, has attracted greater attention to this drug in recent years. The indications for and the use of ketamine as an anesthetic is described, and its various side-effects discussed. Combination with benzodiazepines greatly reduces these side-effects. Several pharmacological mechanisms may contribute to the effects of ketamine, in particular when large (anesthetic) doses are given. Recent investigations indicate that the analgesic and anesthetic effects as well as the "dissociative" phenomena seen after analgesic doses are due to PCP receptor mediated inhibition of excitatory amino acid transmission at NMDA synapses. The excitatory effect observed at higher doses, however, may be mediated by the haloperidol sensitive sigma-receptor. The enantiomers of ketamine (R- and S-ketamine) differ in pharmacological profile and may enable improvement of ketamine as a drug.

Analgesia↗
PubMed1978

Effect of prostaglandins and hormones on cyclic AMP formation in rat hepatomas and liver tissue.

The formation of cyclic AMP was studied in normal liver, subcutaneous hepatomas derived from MH1C1 cells, and premalignant liver and primary hepatomas induced by the carcinogens 2-acetylaminofluorene (AAF) and 4-dimethylamino-azobenzene (DAB). While only very slight effects of prostaglandins (PG) were seen in slices of normal liver, all the hepatomas responded strongly to PGE1 and PGE2. The hepatomas also had increase PGE1-sensitive adenylate-cyclase activity. PGF1alpha and PGF2alpha did not increase the cAMP level significantly either in the liver or in the hepatomas. During AAF carcinogenesis the response to PGE1 increased slightly during the carcinogen feeding, and was greatly elevated only in the fully developed hepatomas. This is in contrast to the increase in adrenalin response seen during carcinogenesis, which starts much earlier, and reaches a peak value within 8--10 weeks. It is concluded that various hepatomas have elevated responsiveness to PGE1 and PGE2 as well as to adrenalin, but the course of change in the tissues' ability to respond to these agents during carcinogenesis is very different.

Adenylyl Cyclases↗
PubMed1978

Qualitative differences between beta-adrenergic and alpha-adrenergic inotropic effects in rat heart muscle.

If beta- and alpha-adrenergic inotropic effects are cyclic AMP dependent and cyclic AMP independent, respectively, they may be qualitatively different. The inotropic effects of beta-receptor stimulation (isoprenaline) and alpha-receptor stimulation (phenylephrine combined with propranolol) were characterized in isolated perfused rat hearts, rat atria and rat papillary muscles. The beta-effect reached its maximum before the alpha-effect. The alpha-effect followed a three-phasic time-course indicating both stimulatory and inhibitory components. The aortic pressure wave (perfused heart) indicated a shorter contraction phase after beta-stimulation than after alpha-stimulation. The time to peak tension (atrium, papillary muscle) was relatively shorter after isoprenaline than after alpha-stimulation, which tended to prolong it. The contraction-relaxation cycles (atrium, papillary muscle) were examined by recording the isometric tension (T), its first (T') and second (T'') deri derivatives. alpha and beta-stimulation both increased Tmax, T'max (maximal rate of tension rise), T'min (maximal rate of tension decline) and T''min (maximal rate of transition from rise to decline of tension). Isoprenaline increased T'min (papillary muscle) and T''min (atrium, papillary muscle) relatively more than did alpha-stimulation, i.e. the relaxing processes were activated relatively more by beta-stimulation. The results indicate different mechanisms for the two adrenergic inotropic effects. The relatively larger activation of relaxation by beta-stimulation is assumed to be caused by clic AMP.

Adrenergic alpha-Agonists↗
PubMed1977

Increased level of cAMP in the rat intestinal mucosa caused by sodium lauryl sulphate.

The level of cyclic AMP in the jejunal mucosa from tied loops of anaesthetized rats was found to be significantly increased (27-50%) when sodium lauryl sulphate (SLS) was added to the loop fluid (2-27 mM). Imidazole (25 mM) did not significantly alter the resting level of cyclic AMP, but reduced the increase caused by SLS (17 mM). Theophylline (25 mM) significantly increased the intestinal level of cyclic AMP, and potentiated the increase caused by SLS. Ouabain (2.5 mM) did not alter the level of cyclic AMP in the presence or in the absence of SLS. The results of previous experiments on the increases in intestinal absorption caused by SLS or by dibutyryl cyclic AMP (Briseid et al., 1974, 1976) are discussed in light of the present data. It is concluded that the SLS-effect on absorption can only partly by ascribed to its effect on the intestinal level of cyclic AMP.

Animals↗
PubMed1976

Cyclic AMP formation and morphology of myocardial cells isolated from adult heart: effect of Ca2+ and Mg2+.

Adult rat heart cells were isolated by perfusion with a calcium-free phosphate buffer containing collagenase. Optimal conditions gave a high proportion of elongated cells. Isoprenaline increased cydic AMP content linearly, with ED50 (dose effective in 50% of the population) about 10(-7) M. Ca2+ made the cells spherical, and it nearly abolished cyclic AMP response as did lack of Mg2+.

Animals↗
PubMed1976

Pseudohypoparathyroidism: a difficult diagnosis in early childhood.

We have studied one adult and three children with pseudohypoparathyroidism and observed that the physical character of short metacarpal bones is not evident in the first 4-5 years of life, that hypocalcaemia and hyperphosphataemia may be absent in the first years of life, but that the renal unresponsiveness to parathyroid hormone can still be demonstrated. Our data confirm earlier observation that in evaluating the renal responsiveness to parathyroid hormone, urinary cyclic AMP is a better parameter than urinary phosphorus. Thus in early childhood, it may be difficult to differentiate between a normal child, a child with pseudohypoparathyroidism and a child with pseudo-pseudohypoparathyroidism unless the renal parathyroid hormone responsiveness is studied.

Adult↗
PubMed1976

Basal and hormone-induced urinary cyclic AMP in children with renal disorders.

The excretion of cyclic AMP in urine has been examined in normal children and in children with nephrogenic diabetes insipidus or moderate renal failure (predominantly defective concentrating ability) under basal conditions and in response to antidiuretic hormone (ADH) and parathyroid hormone (PTH). In contrast to other reported data, we could not confirm an ADH- and (PTH-unresponsiveness in hereditary, congenital nephrogenic diabetes insipidus, but our patients with structural renal disorders characterized by a defective urine concentrating ability did have reduced hormonal responses. It seems necessary to define nephrogenic diabetes insipidus very carefully, and until more data are collected, there appears to be no value in the measurement of urinary cyclic AMP level in the individual patient in the differential diagnosis of disorders due to renal concentrating defects.

Adolescent↗
PubMed1976

Adenosine 3',5'-cyclic monophosphate in perfused rat hearts exposed to isoprenaline and dopamine.

Isoprenaline and dopamine increased cyclic AMP (cAMP) content and contractile activity of isolated perfused rat hearts. The changes of cAMP levels depended on the mode of drug administration. Isoprenaline (4 x 10(-10) mol) administered to the perfused heart as a relatively concentrated bolus, caused a substantial, rapid and transient increase of cAMP. Isoprenaline (2 x 10(-10) mol and 4 x 10(-10) mol) and dopamine (10(-7) mol) diluted in 40 ml of perfusate which was continuously recirculated through the heart, caused a gradual increase of cAMP content which approached an apparent steady state. cAMP accumulation occurred at isoprenaline concentrations above 10(-9) M and at dopamine concentrations above 10(-6) M. Both agents also increased cAMP labelling from 14C-adenine in the perfusate, probably indicating increased cAMP synthesis. Isoprenaline at 2 x 10(-8) M and 10(-7) M increased labelling more than content of cAMP. Isoprenaline and dopamine also increased phosphorylase a activity. An association between increased cAMP contents and increased contractile activity was revealed by both the time-response and the dose-response curves of hearts exposed to isoprenaline and dopamine. Since both agents stimulate adrenergic beta-receptors in cardiac muscle, the results are concordant with the hypothesis that cAMP is involved as a mediator of the inotropic response to adrenergic beta-stimulation.

Adenine↗
PubMed1975

Role of cyclic adenosine 3',5'-monophosphate in the isoprenaline-induced relaxation of the oestrogen dominated rabbit uterus.

1. The role of cyclic adenosine 3',5'-monophosphate (cyclic AMP) in the relaxation produced by isoprenaline in muscle strips from the oestrogen dominated rabbit uterus has been investigated. 2. Isoprenaline 2 times 10- minus 8 M produced an inhibition of the mechanical activity but no increase in cyclic AMP. Isoprenaline 2 times 10- minus 6 M produced both inhibition of mechanical activity and increase in cyclic AMP. 3. The increase in cyclic AMP, but not the inhibition of mechanical activity, was blocked by propranolol 3.4 X 10-MINUS 6 M. 4. Dibutyryl-ccylic AMP produced a relaxation which mimicked that produced by isoprenaline, in that the longitudinal strips were more sensitive than the circular ones. 5. It is concluded that cyclic AMP may be a mediator of the beta-adrenergic effect in the oestrogen dominated rabbit myometrium. However, it seems not to be an obligatory link between stimulation of beta-adrenoceptors and relaxation. Other mechanisms may also exist.

Animals↗
PubMed1975

Relationship between cyclic AMP metabolism and inotropic response of perfused rat hearts to phenylephrine and other adrenergic amines.

A positive correlation between inotropic response and increment of cyclic AMP levels and labeling (from 14-C-adenine in the perfusate) was found after isoprenaline, dopamine, and phenylephrine alone, and after isoprenaline in the presence of chlorpromazine. 2. a lack of correlation between contractile activity and cyclic AMP levels and labeling was found when the hearts were exposed to phenylephrine in the presence of propranolol. The contractile activity increased, but the parameters for cyclic AMP did not change. These resuls together with findings by other workers indicate that the inotropic response to beta-stimulation always is associated with cyclic AMP accumulation, while the inotropic response to alpha-stimulation (when present) is not correlated to cyclic AMP elevation. Other differences between alpha- and beta-adrenergic effects on heart (course of development of the inotropic response, effect of theophylline on the response, effects on relaxing processes, action potential, and on refractory period) also indicate different mechanisms of action. On the basis of the available data we suggest as a conclusion that the inotropic response after alpha-adrenergic stimulation does not involve cyclic AMP as a mediator whereas beta-adrenergic effects are mediated by cyclic AMP. This means that the naturally occurring adrenergic amines norepinephrine and epinephrine, both of which are able to stimulate both alpha and beta myocardial receptors (twenzel and Su, 1966), elicit the inotropic response through two different mechanisms. Usually the beta-adrenergic effect on the heart is the more important. The contribution from alpha-stimulation, however, may increase under certain conditions: hypothyroidism or proplythiouracil treatment per se (Nakashima et al., 1971) or hypothermia (Kunos and Szentiványi, 1968; Buckley and Jordan. 1970; Benfey et al., 1973; Kunos, Yong, and Nickerson, 1973; Nickerson, 1973). Thus a single physiologic response may be mediated by more than one mechanism. Multiple mechanisms of action for one agent might have more general biologic significance; e.g., they may serve to maintain the responsiveness of a tissue under various conditions.

Animals↗