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Biomedical subjects

I Takayanagi

Publications and source records attributed to I Takayanagi.

At least 271 records · Page 15Linked to original sources
PubMed1976

Mechanism of morphine block of electrical activity in ganglia of Auerbach's plexus.

A study was made of the effect of morphine on electrical activity within single ganglia of Auerbach's plexus of guinea pig longitudinal muscle-myenteric plexus as monitored by means of external electrodes. Morphine produces a concentration dependent block of single spike activity. This effect is competitively antagonized by naloxone. The ED50 for morphine effect is about 7 X 10(-7) M. Naloxone and dextrorphan have no effect on electrical activity. Acetylcholine in the concentration range of 10(-7)--10(-5) M augments electrical activity of ganglia. Morphine has little if any effect on the enhanced stimulation produced by acetylcholine thus indicating that the drug does not act directly upon the ganglion. Our results suggest that a specific opiate receptor is present on the preganglionic nerve terminals and that morphine and other opiates block ganglionic transmission by inhibiting the release of preganglionic acetylcholine.

Acetylcholine↗
PubMed1976

Effect of a cholinergic stimulant on interaction of isoprenaline with beta-adrenoceptors.

The maximum contraction induced in taenia from the guninea pig caecum by a cholinergic stimulant, butyltrimethylammonium (BuTMA) was relaxed by papaverine (10(-4) M) but not by l-isoprenaline (5 X 10(-7) M). The concentrations used relaxed the taenia completely in the absence of BuTMA. BuTMA (10(-4) M) decreased the increase of cyclic AMP caused by isoprenaline but not that due to papaverine. Futhermore, photoinactivation of the beta-adrenoceptors by l-isoprenaline was not observed on the taenia contracted by BuTMA (10(-4) M). These results suggest that l-isoprenaline does nto interact with the beta-adrenoceptors in the taenie contracted by the high concentration of BuTMA.

Animals↗
PubMed1976

Photoaffinity labeling of the beta-adrenergic receptors and receptor reserve for isoprenaline.

The beta-adrenergic receptors in the taenia isolated from the guinea pig caecum were irreversibly inactivated by photoaffinity labeling with 1-isoprenaline and 2-(2-hydroxy-3-isopropylaminopropoxy)iodobenzene. The photoinactivation was eliminated in the presence of protectors of the receptors. Photoinactivation caused a considerable parallel shift in the concentration-action curve of 1-isoprenaline. The results possibly point to a certain receptor reserve for 1-isoprenaline.

Affinity Labels↗
PubMed1976

Relationship between the levels of intracellular cyclic nucleotides and mechanical responses induced by drugs.

The tracheal smooth muscle dissected free from connective tissues was used as a test preparation, since isoprenaline caused a decrease in cyclic GMP in the muscle while it caused an increase in cyclic GMP in the remaining tracheal tissue. Acetylcholine, histamine and papaverine increased both cyclic AMP and cyclic GMP levels in the tracheal muscle. Isoprenaline increased the cyclic AMP level but decreased the cyclic GMP level. However, when tracheal muscle was incubated with isoprenaline in the presence of acetylcholine, isoprenaline did not cause a decrease in cyclic GMP but rather a significant increase in cyclic AMP after only 1 min incubation. These results indicate that the relaxation of the tracheal muscle by isoprenaline is initiated by the increase in cyclic AMP but is not associated with the change in cyclic GMP.

Acetylcholine↗
PubMed1976

Effects of 5-hydroxytryptamine and morphine on the stomach motility in situ.

The effects of 5-hydroxytryptamine and morphine on the stomach motility were determined in in situ experiments. 5-Hydroxytryptamine and morphine inhibited stomach motility of unanaesthetized cats but did produce a slight contraction of the stomach of anaesthetized cats. In unanaesthetized rabbits, 5-hydroxytryptamine caused a contraction, followed by an inhibition of motility, and morphine depressed motility. The 5-hydroxytryptamine-induced contraction is a direct action on smooth muscle and the inhibition of spontaneous movement due to 5-hydroxytryptamine may be, in part, mediated through catecholamine-release and in part, result from paralysis of the receptors for 5-hydroxytryptamine in the cholinergic nerves in the stomach. In anaesthetized rabbits, 5-hydroxytryptamine produced contraction and morphine had no effect. In unanaesthetized guinea pigs, 5-hydroxytryptamine caused a contraction and morphine abolished spontaneous movement of the stomach. In anaestetized guinea-pigs, 5-hydroxytryptamine caused contraction and morphine produced no effect. The 5-hydroxytryptamine-induced contraction of the guinea pig stomach is indirect. From these results it is concluded that the differences in the modes of actions of 5-hydroxytryptamine and morphine on gastric motility are related to differences in species and experimental conditions such as anaesthesia.

Acetylcholine↗
PubMed1975

Actions of bile salts and of papaverine and intracellular cyclic AMP in isolated rat uterus.

Both antioxytocin and antiphosphodiesterase activities of desoxycholate were potentiated by lowering the pH of the medium. The results suggest the possibility that it is the bile salt in the non-ionized form which exerts the antioxytocin and antiphosphodiesterase action. The concentration of tissue cyclic AMP was measured at different times during relaxation of the uterus. The results show a significant increase in tissue cyclic AMP concentration at a time when the muscle was just beginning to relax in response to papaverine, but not in response to chenodesoxycholate. The intracellular level of cyclic AMP during relaxation of the uterus produced by papaverine or chenodesoxycholate was, however, significantly increased when relaxation was about 90% complete. The difference between the mode of action of papaverine and that of the bile salts is discussed.

Animals↗
PubMed1975

Antiphosphodiesterase activity and nonspecific smooth muscle relaxation tested on intestinal smooth muscles.

Mitochondrial, microsomal and soluble fractions separated from the guinea pig taenia and from the dog longitudinal smooth muscle were used as phosphodiesterase preparation. Each preparation had low and high Km values, indicating the existence of at least two kinds of phosphodiesterase. Papaverine and Aspaminol (1, 1-diphenyl-3-piperidinobutanol hydrochloride), hydralazine, caffeine Na benzoate and aminophylline were used at test drugs. Aspaminol had little inhibitory effect on phosphodiesterase. Ki value of papaverine almost equalled the concentration (M) which was necessary to produce 50% relaxation. Relaxation of the guinea pig taenia by papaverine was preceded by an increase of intracellular cyclic AMP,. Therefore, the action of papaverine is likely to be mediated by an increase in cyclic AMP, which is caused by inhibition of the phosphodiesterase-catalyzed breakdown of cyclic AMP. There was little correlation between relaxing activities of the drugs used and their antiphosphodiesterase activities. Relaxation of the smooth muscle induced by the smooth muscle relaxants excepting papaverine is not due to inhibition of phosphodiesterase.

Animals↗