Effects of aromatic nitrocompounds and phenolderivatives on the cholinergic nerve ending of smooth muscle and skeletal muscle.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
I Takayanagi
Publications and source records attributed to I Takayanagi.
Responses of the isolated ileum of the morphine-tolerant guinea pig.
Explore the source record for details and available documents.
Acetylcholine↗
Endothelin-1 induced contraction of rat aorta: contributions made by Ca2+ influx and activation of contractile apparatus associated with no change in cytoplasmic Ca2+ level.
The modes by which endothelin-1 (ET) induces Ca2(+)-influx and the relative functional importance of the different sources of Ca2+ for ET-induced contraction were studied using fura 2-loaded and unloaded rat aortic strips. ET caused an increase in the cytosolic free Ca2+ level ([Ca2+]i) followed by a tonic contraction in Ca2(+)-containing solution, and produced a transient elevation of [Ca2+]i followed by a small sustained contraction in Ca2(+)-free medium. ET also stimulated 45Ca influx into La3(+)-inaccessible fraction significantly. With the same change of [Ca2+]i, ET caused a larger tension than that induced by high K. ET-induced contraction and [Ca2+]i elevation were not significantly inhibited by 0.1-0.3 microM nicardipine which nearly abolished the contraction and [Ca2+]i elevation produced by high K. During treatment of the strips with high K, addition of ET induced further increases in [Ca2+]i and muscle tension, and vice versa. In Ca2(+)-free medium, ET-induced contraction was influenced neither by ryanodine-treatment nor by high K-treatment, although the former attenuated and the latter potentiated the [Ca2+]i transient induced by ET. Further, the ET-induced sustained contraction under Ca2(+)-free conditions began to develop after the [Ca2+]i level returned to the baseline. Thus, it seems that the Ca2+ released from the ryanodine-sensitive and -insensitive Ca2+ stores by ET may provide only a minor or indirect contribution, if any, to the tension development. ET might cause a contraction mainly by stimulating Ca2(+)-influx through Ca2+ channel(s) other than voltage-dependent Ca2+ channels in character, and by increasing the sensitivity of the contractile filaments to Ca2+ or activating them Ca2(+)-independently.
Animals↗
Irreversible blockade of the kappa-receptor by a newly synthesized dynorphin derivative containing a 3-nitro-2-pyridinesulfenyl group.
The interactions of the dynorphin derivative containing a 3-nitro-2-pyridinesulfenyl group (dynorphin derivative) with kappa-receptors were studied. The dynorphin derivative inhibited, in a concentration-dependent manner, the twitch response to electrical stimulation of the longitudinal muscle of the guinea-pig ileum which contains both mu- and kappa-receptors. It also inhibited the twitch response to electrical stimulation of the rabbit vas deferens, reported to contain only kappa-receptors; its pD2 value was 11.57 +/- 0.09, suggesting that the agonistic activity of the dynorphin derivative is mainly mediated through kappa-receptors. The KD and Bmax values of [3H]U-69593 were calculated from a Scatchard plot of the specific binding. After a 30 min treatment with 10(-5) M of this dynorphin derivative, the KD value did not alter but the Bmax value decreased. However, this decrease recovered after treatment with 2 x 10(-3) M of dithiothreitol. These results suggest that the dynorphin derivative binds to kappa-receptors through the disulfide bound. The dissociation constant of nalorphine-7,8-oxide (nalorphine-epoxide) was determined according to the method of Furchgott, by irreversibly binding a fraction of the kappa-receptors with the dynorphin derivative. The negative logarithms of the dissociation constants (pKA values) for nalorphine-epoxide did not differ in the guinea-pig ileum and rabbit vas deferens, suggesting that the kappa-receptors in the two preparations are identical. However, the pD2 value and efficacy for nalorphine-epoxide in the guinea-pig ileum were significantly greater than those in the rabbit vas deferens. These results indicate that the kappa-receptor reserve in the longitudinal muscle of the guinea-pig ileum is greater than in the rabbit vas deferens. It is thought that the dynorphin derivative, containing a 3-nitro-2-pyridinesulfenyl group, is useful to clarify the kappa-receptor mechanisms.
Amino Acid Sequence↗
Mechanism of action of nicotine in isolated urinary bladder of guinea-pig: involvement of tachykinin(s) released by nicotine in the drug's sympathomimetic effect.
A sympathetic neurone blocking drug, guanethidine, and a tachykinin antagonist, [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-substance P (rpwwL-SP), partially inhibited the contractile response to nicotine to the same degree in the isolated detrusor strips of guinea-pig urinary bladder. Application of rpwwL-SP completely abolished the inhibitory effect of guanethidine on the nicotine-induced contraction, suggesting that the tachykinin(s)-ergic transmission might be involved in the sympathomimetic effect of nicotine. Conversely, when the preparation was treated with guanethidine to block release of a mediator from the sympathetic nerve, the inhibitory effect of rpwwL-SP was diminished, suggesting an exclusive contribution of the sympathetic nerve communications to the action of the tachykinin(s). We previously suggested that nicotine may release acetylcholine and ATP to contract the detrusor strips, and that acetylcholine output may be increased by an unknown substance released from the sympathetic nerve by nicotine. In preparations treated with atropine, rpwwl-SP had no effect on the nicotine-induced contraction. The concentration-response curves for carbachol and ATP were not influenced by rpwwl-SP. After tachyphylaxis to capsaicin developed, the nicotine-induced contraction was not affected. It is suggested that in guinea-pig detrusor, tachykinin(s) from capsaicin-insensitive sites is (are) involved in the excitatory sympathomimetic effect of nicotine, and that the tachykinin(s) behave(s) as a modulator finally to increase the acetylcholine output from the parasympathetic cholinergic nerve.
Adenosine Triphosphate↗
Interactions of R(+) and S(-) isomers of befunolol, a partial agonist with high and low affinity sites of beta-adrenoceptors in guinea-pig taenia caecum.
The beta-adrenomimetic and beta-adrenolytic activities of R(+) and S(-) isomers of befunolol, a beta-adrenergic partial agonist, were studied in the guinea-pig taenia caecum. The pA2 value (9.38) of the S(-) isomer against S(-) isoprenaline was significantly different from that (7.94) of the R(+) isomer, while the pD2 values and intrinsic activities of R(+) and S(-) isomers were not significantly different from each other. The competitive inhibition curves of the specific binding of [3H]befunolol (50 nM) to the microsomal fraction from the guinea-pig taenia caecum by S(-) and R(+) isomers were biphasic, suggesting two different affinity binding sites. The affinity ratio of the R(+) isomer against the S(-) isomer to the high affinity site was 0.081 while the affinities of R(+) and S(-) isomers to the low affinity site were not significantly different from each other. The affinity ratio of the R(+) isomer against the S(-) isomer to the high affinity site resembled their potency ratio in beta-adrenergic blocking action. These findings suggest that beta-adrenoceptors contain two different affinity binding sites and that the high affinity binding site for isoprenaline is more stereoselective than the low affinity binding site.
Adrenergic beta-Antagonists↗
Relationship between the contractile responses and their coupling second messenger systems for muscarinic drugs in the guinea-pig ileal longitudinal muscle.
The relationship between the contractile responses and their coupling second messenger systems such as IPs formation, release of intracellular Ca2+ and Ca2+ influx in the presence of muscarinic agonists and antagonists in guinea-pig ileal longitudinal muscles was examined by using several pharmacological methods. The pD2 for carbachol-induced contraction in the presence of extracellular Ca2+ was greater than that obtained for carbachol in the absence of extracellular Ca2+, which was, in turn, greater than that for carbachol-induced stimulation of IP formation. The pD2-values of oxotremorine and pilocarpine were also higher for the contraction occurring in the presence of extracellular Ca2+ and for the normal contractions than for those of the contraction occurring when Ca2+ was deleted from medium and the IPs formation. In normal contraction and in contraction occurring in the presence of extracellular Ca2+, pilocarpine and oxotremorine were full agonists or highly efficacious partial agonists, while in contraction occurring when Ca2+ was removed from the medium and in IPs formations, they behaved as partial agonists with lower efficacy. However, the dissociation constants for muscarinic agonists and selective or non-selective antagonists were similar under the experimental conditions used. These results suggest that the muscarinic receptors, coupled to each of the different second messenger systems in the ileum, are of the same type.
Animals↗
Propylbenzilylcholine mustard discriminates between two subtypes of muscarinic cholinoceptors in guinea-pig taenia caecum.
A 10-min treatment of isolated guinea-pig taenia caecum with propylbenzilylcholine mustard (PrBCM; 3 x 10(-7) M) inhibited concentration-response curves of 5 full agonists used. A 50-min treatment with PrBCM produced a further inhibition of their curves. However, a 90-min treatment with PrBCM had no further significant inhibitory effect on their curves. Concentration-response curves of 5 partial agonists were completely inhibited by the 50-min treatment with PrBCM (3 x 10(-7) M). The limiting effect of PrBCM observed on the concentration-response curves of the full agonists was not found on the curves of the partial agonists. These results suggest that there are 2 subtypes of muscarinic cholinoceptors, PrBCM-sensitive and -resistant muscarinic receptors, which are discriminated by PrBCM but not by atropine, pirenzepine or AF-DX 116. The pKA value (a negative logarithm of dissociation constant) of carbachol to PrBCM-sensitive receptors is smaller than that to PrBCM-resistant ones, suggesting that the full agonists may be more sensitive to PrBCM-resistant receptors than to PrBCM-sensitive ones. The partial agonists produced contractions of the taenia caecum predominantly through an activation of PrBCM-sensitive receptors, while the full agonists contracted the taenia caecum through the interaction of two subtypes. The responses to nicotine and to electrical stimulation were inhibited by the 50-min treatment with PrBCM, suggesting that PrBCM-sensitive receptors might play a physiological role.
Animals↗
A regional difference in alpha 1-adrenoceptors in canine arteries.
Noradrenaline sensitivity (pD2-value) and agonist dissociation constant (pKA-value) were determined in the following 4 canine arteries: thoracic and abdominal aorta, mesenteric and renal. The experiments were done in the presence of beta- and alpha 2-adrenoceptor blockers, and inhibitors of neuronal and non-neuronal uptake of catecholamine. A positive correlation was found in the pD2- and pKA-values for noradrenaline (r = 0.976, P less than 0.05). The slope (0.92) was not significantly different from 1. The pD2- and pKp (negative log of dissociation constant of partial agonist)-values of clonidine, an alpha 1-adrenergic partial agonist, were also determined. There was a positive correlation between the pD2- and pKp-values (r = 0.974, P less than 0.05). Again, the slope (1.39) was not significantly different from 1. These results indicate that the regional difference in the pD2-values for noradrenaline and clonidine in canine arteries is due to the affinities to alpha 1-adrenoceptors and that there is a qualitative difference between alpha 1-adrenoceptor mechanisms in the arteries and veins. However, no positive correlation between the pD2-values for noradrenaline and clonidine was observed (r = 0.182, P greater than 0.05). Thus, it may be suggested that either the recognition sites for noradrenaline, clonidine and prazosin are different or else their mode of attachment to the same recognition site is not identical.
Animals↗
Comparison of beta-adrenoceptors in single smooth muscle cells and in isolated smooth muscle preparations from the guinea-pig taenia caecum.
Single smooth muscle cells were prepared from guinea-pig taenia caecum. To study the beta-adrenoceptors in the single cells, we observed mechanical responses of the single cells to beta-adrenergic drugs and also tested the binding of a [3H]-labelled drug to the single cells. The single cells showed a graded relaxing response to isoprenaline. The concentration-response curve was shifted in a parallel fashion by propranolol, indicating a competitive antagonism. The pA2 value of propranolol was in agreement with that estimated using the intact tissue. The dissociation constant of [3H]-dihydroalprenolol was similar to the value estimated in the microsomal fractions. The apparent dissociation constants of isoprenaline and propranolol estimated from inhibition of the specific binding of [3H]-dihydroalprenolol to the single cells were also in agreement with the values in the microsomal fractions. The results suggest that there is no change in the beta-adrenoceptor mechanism in single smooth muscle cells by isolating the cells.
Animals↗
Some pharmacological properties of a newly synthesized morphine derivative, (-)-6 beta-acetylthiomorphine.
Some pharmacological properties of a newly synthesized morphine derivative, (-)-6 beta-acetylthiomorphine (AcS-morphine) were studied. AcS-morphine was about twice as potent as morphine in the inhibitory action of the twitch response of the guinea-pig ileal preparation to electrical stimulation. AcS-morphine, however, was 5 times as potent as morphine in the analgesic action in the rats. Both the effects of AcS-morphine were inhibited by naloxone, suggesting that the site of action of AcS-morphine is mu-receptors. It is interesting that 6 beta-isomer of AcS-morphine is 5 times as potent as 6 alpha-OH isomer of morphine in the analgesic action, because 6 alpha-OH isomer of morphine is much more potent than that of 6 beta-OH isomer. The effects of AcS-morphine on the specific binding of [3H]-naloxone, [3H]-ethylketocyclazocine and [3H]-D-Ala2-D-Leu5-enkephalin to the membrane fractions from the rat brain were tested. AcS-morphine was about 5 times as potent as morphine in its interactions with opioid receptors, as determined by the binding assay. AcS-morphine, as well as morphine, had a selectively high affinity to mu-receptors. The "sodium effect" and the "GTP effect" of AcS-morphine were almost the same as those of morphine. The dependence liability of AcS-morphine was preliminary tested in the guinea-pig ileal preparations treated with a high concentration of AcS-morphine for 24 hr. Results suggested that AcS-morphine is weaker than morphine in its dependence liability, though it seems almost certain that AcS-morphine does have this liability.
Analgesics↗
Age-related alteration of alpha(1)-adrenoceptor mechanisms and Ca2+ inhibitory effects of isradipine.
The effects of age on alpha1-adrenoceptor and Ca2+ channel-mediated contractile mechanisms in the thoracic aorta, isolated from rats of 3, 6, 10, 18 and 40 weeks old, were studied. The potency (pD(2) value) of norepinephrine increased with age from 3 to 10 weeks, but decreased thereafter from 10 to 40 weeks. The change in pD(2) value of norepinephrine was proportional to the logarithm of the maximum number of binding sites (B(max)), obtained in the [(3)H]prazosin binding study. The inhibitory effect of a potent Ca(2)+ channel blocker, israpidine, on the norepinephrine-induced contraction decreased with age from 3 to 10 weeks, but increased in rats aged 10 to 40 weeks. An inverse relationship between the change in isradipine inhibition, the maximum reduction of isradipine on norepinephrine-induced contraction and the logarithm of B(max) was found. The inhibitory effect of a nonselective Ca2+ channel blocker, SKF96365, on the norepinephrine-induced contraction did not change with age. The amplitude of the Ca2+-induced sustained contraction, after pretreatment with isradipine (10(-7) M) in the presence of norepinephrine (10(-6) M), increased with age from 3 to 10 weeks, but decreased thereafter in rats aged 10 to 40 weeks. There was no significant difference in the slope of the regression lines between the cytosolic Ca(2)+ level ([Ca2+]i) and the tension in the presence of norepinephrine at different ages. These results suggest that the changes in alpha(1)-adrenoceptor mechanisms and the reduction by isradipine with age are due to changes in the alpha1-adrenoceptor density and the population of Ca2+ channels, but not to changes in the affinity of drugs to the alpha1-adrenoceptor or Ca2+ sensitivity of contractile elements of aortic smooth muscles.
Adrenergic alpha-Agonists↗
Some pharmacological properties of a newly synthesized 3-acetoxy-6 beta-acetylthio-10-oxo-N-cyclopropylmethyl-dihydronormorphine (KT-95).
The pharmacological properties of a newly synthesized 3-acetoxy-6 beta-acetylthio-10-oxo-N-cyclopropylmethyl-dihydronormorphine (KT-95) were examined. This compound, as well as (-)-3-acetyl-6 beta-acetylthio-N-cyclopropylmethylnormorphine (KT-90) and morphine, inhibited the twitch response to electrical stimulation of the guinea-pig ileal preparation that contains mu- and kappa-receptors. The inhibitory effect of KT-95 was about 17 times more potent than morphine, and about 4 times more potent than KT-90. In the guinea-pig ileal preparation, KT-95 behaved as a mu-antagonist against morphine in the presence of norbinaltorphimine (3 x 10(-8) M). In the rabbit vas deferens, containing kappa-opioid receptors, KT-95 inhibited the twitch response to electrical stimulation in a concentration-dependent manner. Norbinaltorphimine concentration-dependently caused parallel rightward shifts of the concentration-response curves to KT-95 in the guinea-pig ileum and in the rabbit vas deferens after electrical stimulation, suggesting that KT-95 behaved as an agonist for the kappa-opioid receptor. In the mouse vas deferens, that contains delta-receptors. KT-95 behaved also as a delta-antagonist against Leu-enkephalin in the presence of norbinaltorphimine. KT-95, KT-90 and morphine were examined for their potencies in displacing the specific binding of [3H]naloxone (mu-selective ligand), [3H]U69593 (kappa-selective ligand), and [3H]D-Ala2-D-Leu5-enkephalin (delta-selective ligand) to synaptosomal fractions from rat brain. Although KT-95 had a higher nonselective affinity to mu-receptors than KT-90 and morphine, the affinity of KT-95 to kappa-receptors was about 18 times higher than that of morphine, and about 5 times higher than that of KT-90. In the acetic acid-induced writhing test, subcutaneously injected KT-95 was more potent than morphine. Furthermore, the analgesic effect, induced by KT-95 (0.062 mumol/kg, s.c.), was abolished by simultaneous administration of norbinaltorphimine (0.020 mumol/mouse, s.c.), suggesting that the analgesic action of KT-95 is mediated through the kappa-opioid receptor. In the pressure test, KT-95 was 20.17 times more potent than morphine. The analgesic action, induced by KT-95 (2.05 mumol/kg, s.c.), was also in this test abolished by simultaneous administration of norbinaltorphimine (0.14 mumol/rat, s.c.), suggesting that this action of KT-95 is mediated through the kappa-opioid receptor. These results indicate that KT-95 behaves as a kappa-agonist with mu- and delta-antagonistic activities, and suggest that analgesia, induced by KT-95, is mainly mediated through kappa-receptors.
Analgesia↗