共查询到20条相似文献，搜索用时 31 毫秒
1.
Radioactive dopamine was injected into the blood that was perfusing an isolated heart preparation. Analysis of the norepinephrine obtained from the heart 1 hour later demonstrated that it contained radioactivity. Between 1.4 and 10.8 percent of the norepinephrine present had been formed from the dopamine. The turnover of norepinephrine was substantially higher in the ventricles than in the atria. 相似文献
2.
Proportional release of norepinephrine and dopamine- -hydroxylase from sympathetic nerves 总被引：13，自引：0，他引：13
R M Weinshilboum N B Thoa D G Johnson I J Kopin J Axelrod 《Science (New York, N.Y.)》1971,174(16):1349-1351
Dopamine-beta-hydroxylase(DBH), the enzyme that catalyzes the conversion of dopamine to norepinephrine, is localized in the vesicles containing catecholamine in sympathetic nerves. This enzyme is released with norepinephrine when the nerves to the guinea pig vas deferens are stimulated in vitro, and the amount of enzyme discharged increases as the length of stimulation periods increases. The amount of DBH released is proportional to the amount of norepinephrine released, and the ratio of norepinephrine to DBH discharged into the incubation medium is similar to that in the soluble portion of the contents of the synaptic vesicles from the vas deferens. These data are compatible with the release of the neurotransmitter norepinephrine and DBH from symnpathetic nerves by a process of exocytosis. 相似文献
3.
The rate of disappearance of intracisternally administered [(3)H]norepinephrine from rat brain gradually declines as a multiphasic exponential function of time. Conversion to [(3)H]normetanephrine accounts for a larger fraction of the [(3)H]norepinephrine released in the brain shortly after its intracisternal injection than that released at later times. Pools of norepinephrine in the brain thus appear to differ in their turnover rates and pathways of metabolism. The pool of norepinephrine with a rapid rate of turnover and an appreciable conversion to normetanephrine, identified by the techniques reported here, may correspond to a pool of newly synthesized norepinephrine in the brain. 相似文献
4.
Desipramine, a tricyclic antidepressant drug, almost completely prevents the accumulation of tritiated norepinephrine by sympathetic neurons of the rat heart after the injection of a tracer dose of the labeled amine. However, desipramine does not alter the accumulation of norepinephrine after the injection of a large dose of the neurohormone. Despite the failure of desipramine to block the neuronal uptake of norepinephrine, it still prevents exogenous norepinephrine from displacing the endogenous neurohormone (previously labeled with H(3)-norepinephrine) from intraneuronal storage sites. 相似文献
5.
Slices of cat cerebral cortex, heart, and spleen that have been incubated in media containing approximately 5 to 25 mmicrog of dl-norepinephrine-7H(8) per milliliter contain levels of isotopic amine greater than those in the medium. The effects of norepinephrine concentration, reserpine, and ouabain on the uptake suggest that the amine enters cells both by diffusion and by a concentrating miechanism that is saturated at low levels of norepinephrine. The drugs inhibit the latter. 相似文献
6.
Epinephrine and norepinephrine condensed with acetaldehyde or with formaldehyde in dilute aqueous solution at neutral pH and room temperature to form 1,2,3,4-tetrahydroiso-quinoline alkaloids. Similar condensation reactions occurred in cow adrenal glands perfused with dilute aldehyde solutions at 37 degrees C. Biosynthesis of these alkaloids in vivo could play a role in altering an individual's behavior during and after the ingestion of alcohol. 相似文献
7.
Severe depletion of endogenous norepinephrine was observed in the brain, heart, liver, and spleen of albino rabbits in which hemorrhagic shock had been induced. On the other hand, the epinephrine content of these tissues was significantly elevated above the levels in tissues of control animals. The norepinephrine and epinephrine levels of skeletal muscle in shocked animals remained unaffected. 相似文献
8.
Pretreatment with two doses of reserpine (each 0.1 mg/kg, intraperitoneally) sensitizes the heart to the positive chronotropic action of norepinephrine and reduces the response to stimulation of the accelerans nerve. Ganglionic transmission remains unaffected. The results indicate that the presence of certain stores of peripheral sympathetic transmitter is essential for the production of tachycardia by stimulation of the accelerans nerve. 相似文献
9.
Thermoregulation: effects of environmental temperature on turnover of hypothalamic norepinephrine 总被引：2，自引：0，他引：2
The hypothesis that norepinephrine is a transmitter in the temperature regulating center of the hypothalamus is based on observations of changes in the rectal temperatures of animals after injections of norepinephrine into the hypothalamus. By introducing tritiated norepinephrine as a label into the endogenous norepinephrine stores in the brain and then measuring the disappearance of tritiated norepinephrine from discrete areas, one can monitor the activity of norepinephrine-containing neurons in those areas. In the rat exposed to heat, the turnover of endogenous norepinephrine appears to be increased selectively in the hypothalamus, whereas exposure to cold has no effect. 相似文献
10.
The heart of Boltenia ovifera (the sea potato) is a tubular structure formed by a single layer of myocardial cells. Electron microscopic studies show that each cell contains a single myofibril located adjacent to the luminal surface of the cell. Electrical and mechanical measurement of a cannulated perfused heart demonstrate that only the luminal membrane is excitabble and elicits contraction on depolarization. Calcium and magnesium exert antagonistic effects on tension, and potassium depolarizes the myocardium and produces contractures when the luminal membrane is exposed to various concentrations of these ions. The extraluminl membrane does not respond electrically or mechanically to calcium magnesium or potassium, and its potential seems to be effectively "clamped" by the luminal membrane. Functionaly, therefore, this heart consists of a single active membrane with the adjacent contractile apparatus. 相似文献
11.
Physiological variation in alpha-adrenoceptor-mediated arterial sensitivity: relation to agonist affinity 总被引：3，自引：0，他引：3
Vascular smooth muscle from different arteries of the rabbit varies in sensitivity to norepinephrine, even when factors known to contribute to this variation are excluded. Sensitivity to norepinephrine mediated through the alpha-adrenoceptor is linearly related to the agonist dissociation constant, but is not significantly related to receptor reserve. These results suggest that agonist affinity is the primary determinant of sensitivity to norepinephrine, at least in these arteries, and that this is a locally regulated characteristic which may account for regional sensitivity changes. 相似文献
12.
Calcium-induced activation of phosphorylase in rat hearts 总被引：1，自引：0，他引：1
Isolated perfused rat hearts exposed to increased calcium concentrations demonstrated a marked activation of phosphorylase, the maximum occurring about 15 seconds after the peak of the positive inotropic response. These observations provide an explanation for the failure of earlier investigations to demonstrate a significant calcium-induced increase in the active form of phosphorylase in the intact heart. 相似文献
13.
NELSON CV 《Science (New York, N.Y.)》1961,133(3467):1831-1832
The spatial dipole moment of a perfused animal heart suspended at the center of a fluid-filled sphere can be found in magnitude and direction to a good approximation by three sets of bipolar measurements. The method has been applied in finding the vectorcardiograms of turtle and rabbit hearts. 相似文献
14.
Hypoxic dilation of coronary arteries is mediated by ATP-sensitive potassium channels 总被引：44，自引：0，他引：44
J Daut W Maier-Rudolph N von Beckerath G Mehrke K Günther L Goedel-Meinen 《Science (New York, N.Y.)》1990,247(4948):1341-1344
The function of the heart depends critically on an adequate oxygen supply through the coronary arteries. Coronary arteries dilate when the intravascular oxygen tension decreases. Hypoxic vasodilation in isolated, perfused guinea pig hearts can be prevented by glibenclamide, a blocker of adenosine triphosphate (ATP)-sensitive potassium channels, and can be mimicked by cromakalim, which opens ATP-sensitive potassium channels. Opening of potassium channels in coronary smooth muscle cells and the subsequent drop in intracellular calcium is probably the major cause of hypoxic and ischemic vasodilation in the mammalian heart. 相似文献
15.
Norepinephrine turnover and metabolism in rat brain after long-term administration of imipramine 总被引：3，自引：0，他引：3
The rate of disappearance of intracisternally administered tritiated norepinephrine from rat brain is decreased after a single dose of the tricyclic antidepressant imipramine. During long-term administration of imipramine, however, the rate of disappearance of tritiated norepinephrine from brain gradually increases, and there is a concurrent decrease in the content of endogenous norepinephrine in brain. These findings may help to explain why antidepressant effects are observed clinically only after long-termn treatment with imipramine. 相似文献
16.
An intramuscular injection of alpha-methyl-m-tyrosine ( 100 mg/ kg), which differentially depletes serotonin and norepinephrine in both brain and heart, was given to two groups of pigeons trained to peck at a key for food. The first group received an injection 12 hours before the daily session and showed no behavioral effect. Response rates of birds in the second group, which were injected 30 minutes after the start of the daily session, decreased and returned to normal within 9 hours after injection. Preliminary data on brain serotonin of pigeons indicate that the disruption of the behavior follows the same time course as the change in serotonin. 相似文献
17.
Coronary vasoconstrictor effects of atriopeptin II 总被引：1，自引：0，他引：1
R D Wangler B A Breuhaus H O Otero D A Hastings M D Holzman H H Saneii H V Sparks J E Chimoskey 《Science (New York, N.Y.)》1985,230(4725):558-561
Atrial natriuretic peptides lower arterial pressure, cardiac filling pressure, and cardiac output. In isolated, Langendorff-perfused guinea pig hearts, atriopeptin II, the 23-amino acid atrial natriuretic peptide, is also a potent coronary vasoconstrictor. The median effective dose for atriopeptin II in guinea pig hearts is 26 nanomoles, the threshold constrictor dose is 5 nanomoles, and flow nearly ceases at a dose of 100 nanomoles in perfused hearts at constant pressure. Similar concentrations of atriopeptin II also cause coronary vasoconstriction in rat and dog heart preparations. The disulfide bridge is necessary for vasoconstrictor activity; reduction of this bridge abolishes the activity, as it does the other biological activities of atrial natriuretic peptides. 相似文献
18.
Inhibition of insulin release by norepinephrine in man 总被引：11，自引：0，他引：11
Normal subjects were given glucose (300 mg/ min) or tolbutamide (1 g, intravenously), alone and during intravenous infusions of norepi-nephrine (6 lg/ min). Immunoreactive insulin concentration was less than expected during the infusions of norepinephrine, but returned to higher values after the norepinephrine infusions. From these data it is concluded that norepinephrine inhibits the release of insulin from pancreatic beta cells. 相似文献
19.
Brain norepinephrine: enhanced turnover after rubidium treatment 总被引：4，自引：0，他引：4
After biosynthesis of norepinephrine was inhibited, treatment of rats for 10 days with rubidium chloride (0.6 milliequivalent per kilogram of body weight) caused an increase in the rate of disappearance of norepinephrine in the brainstem but not in the telencephalon. Also the utilization of intracisternally injected tritiated norepinephrine was increased and was accompanied by a shift in the pattern of norepinephrine metabolism to normetanephrine. These data suggest that greater amounts of neuronally stored norepinephrine were released to central adrenergic receptors. 相似文献
20.
The rat hypothalamus contains thermally insensitive, normally sensisitive, and highly thermosensitive cells. The responses of thermosensitive neurons to microelectrophoretically applied acetylcholine, norepinephrine, and 5-hydroxy-tryptamine were the same in both rats and cats. The firing rate of warm-sensitive interneurons was accelerated by acetylcholine and inhibited by norepinephrine. The firing rate of cool-sensitive interneurons was accelerated by norepinephrine and, in one case, was inhibited by 5-hydroxytryptamine. Thermodetector cells were relatively insensitive to these amines, but were sensitive to current flow. These results from the rat, but not from the cat, agree with the data for thermoregulatory responses following microinjection of these amines into the hypothalamus. 相似文献