The chicken rectum receives a powerful excitatory innervation of non-adrenergic, non-cholinergic (NANC) nerves via the Remak nerve which is a ganglionated nerve trunk in the fowl vicera. To extract a smooth muscle excitatory material from the Remak nerve, tissue samples were boiled in 0.01 N HCI at 100°C for 5-7 min, homogenized, and centrifuged. Aliquots of supernatant were defatted with petroleum ether and lyophilized. The lyophilized residue dissolved in water (ERN) was bioassayed for contracting activity on the longitudinal muscle of the guinea-pig ileum and, if needed, the isolated whole chick rectum. Approximately half of the contacting activity of ERN was attributable to acetylcholine. The remainder was found to be mediated by neither histamine, serotonin, angiotensin II nor prostaglandins (E1, E2 and F2α). The ERN activity was abolished by 2-3 min boiling in alkali and 30 min incubation at 37°C with pepsin, but sustained after boiling in acid, indicating that the mediator of the contracting activity is probably a peptide. Active fractions were obtained with one peak after gel filtration with Sephadex G-50. They were pooled and applied to a Sephadex G-25 column. The Ve/Vo values for the active material ranged from 1.69 to 1.85, indicating that it has a molecular weight of 1000-1300 by comparison with Ve/Vo, values for peptides of known molecular weights applied to the same column.
Effects of Ca2+ and calmodulin antagonists on the oxygen uptake induced by acetylcholine (ACh) or substance P (SP) were investigated in rat submandibular gland slices. The oxygen uptake induced by ACh or SP was significantly inhibited by removing Ca2+ from the medium and the slices. The oxygen uptake by ACh in the Ca2+-deficient slices was almost completely recovered by the addition of 3.0 and 5.0 mM Ca2+, whereas that by SP was not recovered by the addition of 3.0 mM Ca2+, but recovered by 5.0 mM Ca2+. Ca2+ antagonists, diltiazem, verapamil and La3+, significantly inhibited the ACh-induced oxygen uptake. On the other hand, the SP-induced oxygen uptake was inhibited by diltiazem and La3+, but not by verapamil. Calmodulin antagonists, trifluoperazine, chlorpromazine and W-7, had no inhibitory effects on the ACh-induced oxygen uptake. The SP-induced oxygen uptake was not affected by trifluoperazine, chlorpromazine and low concentrations of W-7, but was inhibited by high concentrations of W-7. These results suggest that the ACh- or SP-induced oxygen uptake is dependent on the presence and permeability of Ca2+ with a subtle difference between the ACh and the SP mechanisms and that the oxygen uptake is independent of calmodulin.
The delayed type hypersensitivity (DTH) response of spontaneously hypertensive rats (SHR) was compared with that of Wistar Kyoto rats (WKY), a normotensive strain. SHR showed a lower DTH response to Bordetella pertussis than WKY, especially 48 to 72 hr after antigenic challenge. These results were observed before appearance of abnormality of antibody formation or blood pressure. The reduced DTH responses of SHR were partially restored by either transfer of WKY thymocytes or treatment with levamisole. Conversely, the transfer of SHR thymocytes into WKY rats tended to diminish the DTH response. These findings suggest that SHR have a disfunction of T lymphocytes involved in DTH response (e.g., increase of suppressor cells and/or decrease of helper cells).
The receptor binding profile, composed of the Ki-values measured in eight different receptor binding models using rat brain membranes, is reported for the new tricyclic antidepressant quinupramine, 10, 11-dihydro-5-(3-quinuclidinyl)-5H-dibenz[b, f]azepine, and three reference compounds with a tertiaryamine side chain. Quinupramine was found to possess high affinity for muscarinic cholinergic and histamine H1 receptor binding sites in rat brain, whereas its affinity for imipramine binding sites was only one seventieth that of imipramine. Receptor binding profiles of the reference compounds were almost similar to that of quinupramine, except in the case of imipramine binding sites.
The effects of brotizolam, a new thieno-triazolo-diazepine derivative, on the central nervous system were analyzed in mice, rats and rabbits. Diazepam, estazolam and triazolam were used as control drugs. Brotizolam inhibited spontaneous motor activities; performances in the rotarod test, staircase test, and maximal electroshock seizure test; and pentetrazol- or bemegride-induced convulsion. Moreover, catalepsy inducing action and potentiating effect on sleep elicited by pentobarbital or ethanol were observed. Following intraperitoneal or oral administration of brotizolam to rabbits with chronically implanted electrodes, the electroencephalographic profile in spontaneous EEG was characterized by slow waves with high amplitudes in the neocortex. The arousal responses by stimulation of the midbrain reticular formation and posterior hypothalamus were slightly inhibited, but the recruiting responses induced by stimulation of the diffuse thalamic projecting system were not inhibited, and seizure discharges induced by stimulation of the dorsal hippocampus were inhibited markedly. When motor activities and pentetrazol-induced convulsions were observed as indices of tolerance for brotizolam, tolerance was not developed by repeated administration of brotizolam up to 14 days. These results suggested that brotizolam, a new thieno-triazolo-diazepine derivative, is judged to be a safer and stronger sleep inducer than diazepam and estazolam.
Ritodrine hydrochloride (ritodrine) has been effectively prescribed for the prevention of premature labor. The present study was carried out to investigate the mode of action of ritodrine on the uterus and heart in comparison with those of isoxsuprine and isoproterenol. 1) Ritodrine (10-8-10-6 M) suppressed the spontaneous motility of pregnant rat uterus and showed positive chronotropic action at the doses of 10-6-10-4 Min guinea-pig atria. 2) In the Ca2+-free, K+-rich Tyrode solution, ritodrine suppressed the Ca2+ induced contracture of pregnant rat uterus, while it potentiated the carbachol induced contraction. 3) Ritodrine increased the amount of cyclic AMP in the uterus but not in heart. This action of ritodrine was suppressed by pretereatment with propranolol (10-6 M). 4) These results suggest that ritodrine causes actions through activation of cyclic AMP production, as in the case of isoproterenol, and it acts more selectively on β2-adrenoceptors than on β1-adrenoceptors.
N, N-Diallyl derivatives of enkephalin analogues were chemically synthesized, and their biological activities were estimated in in vitro isolated preparations. N, N-Diallyl-[D-Ala2, D-Leu5]-enkephalin [test compound I] at doses up to 10 μM did not inhibit the electrically-evoked contractions of guinea-pig ileum, which had been suggested to contain opioid mu- and kappa-receptors, but it significantly depressed the contractions of mouse vas deferens, which had been indicated to contain mu-, kappa- and delta-receptors, suggesting that test compound I did not act on both mu- and kappa-receptors, but acted on delta-receptors. Additionally, the Ke (equilibrium dissociation constant) values againsttest compound I of naloxone were approximately 30 nM and similar to those of Mr 2266, also indicating that test compound I acted as a delta agonist. Moreover, the Ke values of ICI 154129 against compound I were approximately 340 nM, strongly suggesting that test compound I acted as a delta agonist. The Ke values of bis-[N, N-diallyl-[D-Ala2, Leu5]-enkephalyl]-cystine [test compound II] against [D-Ala2, D-Leu5]-enkephalin in mouse vas deferens and morphine or ethylketocyclazocine in guinea-pig ileum were 44.9 nM and 5.00 or 11.3 μM, respectively, showing that test compound II was a potent selective opioid delta antagonist. In conclusion, among compounds synthesized, two new opioid delta-receptor ligands, one being a highly selective agonist and the other being a potent selective antagonist in in vitro isolated preparations, were found in the present study.
In this study, we investigated the effect of 6-aminonicotinamide (6-AN), a typical potent inhibitor of the pentose phosphate pathway, on the renal transport of para-aminohippurate (PAH) in the rat. The contents of adenosine-triphosphate (ATP) and 6-phosphogluconate (6-PG) in the kidney were measured at intervals of 2 hours after the administration of 6-AN (75 mg/kg body weight, i.p.). It was found that the 6-PG content in the kidney rapidly increased and reached a plateau at the fourth hour after the administration, with this level being maintained up to the eighth hour. In contrast, the ATP content was found to remain normal up to the sixth hour, after which it significantly decreased as time elapsed. Furthermore, additional experiments were carried out by loading the rat with a high concentration of PAH solution at 6 hours after the administration of 6-AN. The renal tubular secretion maximum for PAH was significantly depressed in the 6-AN group in comparison to the control. These results suggest that this depression in renal PAH secretion capacity was partially due to the inhibition of the pentose phosphate pathway in the kidney, but not due to the change of renal ATP level.
The β-adrenoceptor density and the activities of adenylate cyclase and cyclic AMP phosphodiesterase were examined to compare AH13 cells having lower β-adrenergic responsiveness with other rat ascites hepatoma cells and normal rat liver cells. Normal rat liver cells used were cultured for 24 hr after the collagenase digestion of liver. The density of binding sites of 3H-dihydroalprenolol in AH13 cell plasma membrane was very similar to the density in AH44 and normal liver cell membrane, but that in AH130 cell plasma membrane was about 10-fold greater than those in the other three cell lines. The activity of cyclic AMP phosphodiesterase was about 2.5 to 7-fold higher in hepatoma cells than in rat liver cells, but this enzyme activity of AH13 cells was not especially high among the hepatoma cells examined. The basal adenylate cyclase activity was lower in AH44 cells, but was higher in AH13 and AH130 cells than in rat liver cells. However, adenylate cyclase of AH13 cells was hardly activated by isoproterenol, while the enzyme of the other cells was activated 3 to 5-fold. On the other hand, adenylate cyclase of each cell line including AH13 was activated 4 to 14-fold by NaF. From these results, it is suggested that AH13 cells can hardly produce cyclic AMP by the β-adrenergic stimulation because of the disordered interaction of β-adrenoceptors with adenylate cyclase.
Direct cardiodepressant potency of nadolol was determined by comparing its effect with those of alprenolol, propranolol and pindolol, in both heart-lung preparation and blood-perfused papillary muscle preparation of the dog. In the heart-lung preparation, mean 50% β-blocking doses of the β-blockers to inhibit the positive chronotropic action of isoproterenol were 3.75 μg for nadolol, 12.5 μg for alprenolol, 9.6 μg for propranolol and 1.6 μg for pindolol. Alprenolol and propranolol in a dose of 10 mg shifted the cardiac function curves rightward and downward, while nadolol and pindolol in the dose of 10 mg did not shift the cardiac function curves. In the blood-perfused papillary muscle preparation, mean 50% β-blocking doses of the β-blockers, administered i.v. to the donor dog, to inhibit the positive inotropic action of isoproterenol were 9.1 μg/kg for nadolol, 56.6 μg/kg for alprenolol, 68.3 μg/kg for propranolol and 8.1 μg/kg for pindolol. Nadolol did not depress the contractile force in doses up to 1 mg/kg given i.v. or doses up to 10 mg given intra-arterially (i.a.) close to the preparation. Alprenolol and propranolol exerted the dose-related negative inotropic effects, when larger doses (30-300 μg) were injected i.a. Thus, it is confirmed that nadolol virtually possesses no direct cardiodepressant activity and also that the depressant activity is exerted only by large doses of the other β-blockers.
Effects of prizidilol and nipradilol (K-351), β-adrenoceptor antagonists with vasodilator action, on blood pressure and heart rate were studied in normotensive conscious rabbits after i.v. administration. In addition, we investigated relationships between plasma drug concentrations and β-adrenoceptor blocking activity as estimated by the inhibition of isoproterenol-induced tachycardia and vasodilator activity as assessed by the inhibition of pressor response to angiotensin II (ANG II). Prizidilol (4 mg/kg) produced a significant and sustained fall in blood pressure and a slight increase in heart rate, while hydralazine (2 mg/kg) caused the same degree of hypotension and a marked tachycardia. Nipradilol (1 mg/kg) caused a significant reduction of resting heart rate, but had no significant effect on blood pressure. Propranolol (1 mg/kg) did not affect resting blood pressure and heart rate. Hypertensive response to ANG II was significantly attenuated only by hydralazine. Isoproterenol -induced tachycardia was significantly suppressed by prizidilol, nipradilol and propranolol. Good correlations were observed between β-adrenoceptor blocking activity and plasma drug concentrations. These data suggest that prizidilol has an advantage over hydralazine to induce less tachycardia, but still may cause a certain degree of increase in heart rate. Nipradilol has a more potent β-adrenoceptor blocking action than propranolol, while its vasodilator action is not obvious, at least in rabbits. Plasma concentrations of prizidilol and nipradilol are good indicators for β-adrenoceptor blocking activity, but not for vasodilator activity.
A study was undertaken on the antiulcer effect of some active ingredients present in the lipid part of the fruits of M. azedarach administered p.o. to male rats. Acute gastric ulcers were induced by gipsing the rats for 22 hr preceded by 24 hr starvation to obtain the maximum stress. The free HCI, total HCI and total acidity were also measured. The total lipid (TLP), 1.0, 2.5 and 5.0 g/kg, reduced the ulcer index by 25-41.8% and 50-58% when given daily for 5 and 10 days, respectively. The saponifiable fraction (SP), 0.85, 2.0 and 4.0 g/kg, given for 10 days reduced the ulcer index by 41.8-50%, while the nonsaponifiable (NSP), 0.075, 0.150 and 0.50 g/kg, for 10 days reduced it by 50-83.5%. The 70% ethanol extract of the defatted residue showed no antiulcer effect. Analysis of the gastric juice showed a significant decrease in free HCI (P<0.001) induced by TLP; the total HCI and total acidity were reduced only at 5 g/kg. The results revealed the antiulcer effect of the lipid components of M. azedarach fruits which is mainly due to the phytosterol fraction.