Effects of bufetolol and propranolol, adrenergic β-receptor blocking and anti-arrhythmic drugs, on active and passive membrane properties of the dog papillary muscle were investigated with microelectrode and sucrose-gap methods. Bufetolol (10^-5 to 10^-4 g/ml) and propranolol (10^-5 g/ml) significantly decreased the maximum rate of rise of the action potential. The maximum responsive frequency to driving stimulus was decreased in the presence of bufetolol (3 × 10^-5 g/ml) and propranolol (10^-5 g/ml), whereas the effective refractory period was not affected. The critical threshold potential was shifted to more positive potential in the presence of the drugs. The passive membrane property, the space constant (λ), the time constant (τ) and the current-voltage relations of the muscle membrane were not significantly altered by the drugs. It is concluded that bufetolol and propranolol suppress the excitability of the muscle membrane and this action may be ascribed to the decrease in the sodium conductance (g_Na) and to the rise of g_Na onset potential without alteration in the passive membrane property.

View full abstract

A simple and sensitive fluorometric assay method for taurine (2-aminoethanesulfonic acid) has been developed. For the separation of taurine, high voltage paper electrophoresis subsequent to column chromatographic procedures was employed. Fluorescent product of taurine was yielded by spraying fluorescamine (4-phenylspiro [furan-2(3H), 1'-phthalan]-3, 3'-dione) and borate buffer on the paper, and the fluorescence was assayed spectro-fluorometrically after eluting with 50% ethanol. The linear relationship between the concentration of taurine and fluorescence developed was achieved over the concentration ranges of 0.5-10 nmoles, and the recoveries obtained were 90-100%. The specificity of this method for taurine was satisfactory and structural analogues involved in the metabolic pathway of taurine did not interfere with the assay. Examples for tissue levels of taurine in various organs of the rat as determined by this new method are also presented.

View full abstract

Effects of metabolic inhibitors and ouabain on the rate of afferent discharges from isolated muscle spindle of the bullfrog were examined in vitro to elucidate the mechanism for generating afferent action potentials. Dinitrophenol, NaCN, iodoacetic acid, and ouabain gradually reduced the rate of discharges. These drugs were without direct effect on the nerve axon. The rate of discharges was also reduced by Li⁺, which is known to be minimally extruded from the interior of cells by an active transport mechanism. The rate of discharges remained approximately 50% in the presence of NaCN or in the absence of oxygen, suggesting that the energy required for the maintenance of the Na⁺-pump can be supplied to some extent in an anaerobic condition. It appears that the metabolic inhibitors and ouabain reduce the afferent discharges from the frog muscle spindle by affecting the Na⁺-pump in fibers of nerve terminals.

View full abstract

The influence of histamine releasing agents on gastric acid secretion was studied in isolated bullfrog gastric mucosa preparations. Maximum acid secretory responses in our preparations were obtained by stimulation with tetragastrin (5×10^-7 g/ml), histamine (1×10^-5 g/ml) and bethanechol (1×10^-6 g/ml). Compound 48/80 (1×10^-4 g/ml) showed a transient stimulatory action which was followed by a gradual depression of basal acid secretion. The stimulatory phase of compound 48/80 was completely antagonized by burimamide (1×10^-5 g/ml), a histamine H₂-receptor antagonist. In gastric mucosa preincubated with compound 48/80, the secretagogue action of tetragastrin or bethanechol was not exerted, although this preparation continued to respond to histamine. The effects of Triton X-100, decylamine and polymixin B were quite similar to those of compound 48/80. After pretreatment with compound 48/80, the gastric mucosa preparation became refractory to the stimulatory action of compound 48/80 or Triton X-100. It is thus suggested that endogenous histamine may play an important role in the secretagogue action of tetragastrin and bethanechol.

View full abstract

The contractile response of the isolated canine tracheal muscle to the transmural nerve stimulation was depressed by atropine and augmented by physostigmine, indicating that the response was predominantly mediated via the parasympathetic nerve. The contractile response to the transmural nerve stimulation was inhibited by prostaglandin E₁ (PGE₁) and E₂ (PGE₂) (10^-7 to 10^-6 g/ml) and the inhibitory action of PGE₁ was more potent than that of PGE₂. On the other hand, the contractile response of the tracheal muscle to exogenously administered ACh was unaffected by 10^-6 g/ml of PGE₁ and PGE₂. These findings lend support to the hypothesis that the PGE series, in a manner similar to adrenergic transmission, are involved in a negative feed-back control mechanism for the transmitter release in cholinergic transmission.

View full abstract

Following dietary administration of strontium carbonate, histological and radiographic changes in the epiphyseal cartilage plate of the rat tibiae were examined in the present study. The weight gain of the rat fed a strontium diet was less than that of the control rats. Longitudinal growth of tibiae and endochondral ossification were inhibited by strontium administration. The widths of both proximal and distal cartilage plates increased enormously as has also been shown by other investigators. Sizes of chondroblasts in columns of proximal cartilage plate in rats fed a strontium diet were smaller than those of the control rats and were not different between upper and lower parts. It is suggested that strontium inhibits bone growth through the inhibitory action on the maturation process of chondroblasts and the succeeding endochondral ossification.

View full abstract

Palytoxin (PTX), the most potent marine toxin isolated from the Zoanthid, Palythoa tuberculosa, was studied to determine the effect on isolated smooth muscles. In guinea pig taenia coli PTX at above 3×10^-10 g/ml caused a contraction which slowly subsided under isotonic recording. Under isometric recording PTX at above 1×10^-10 g/ml caused a contraction which depended on the spontaneous activity. The PTX-induced contraction was not affected by atropine, tripelennamine or tetrodotoxin but was inhibited by 5 mM Mg, norepinephrine, isoprenaline or papaverine. PTX at above 1×10^-9 g/ml induced an increase in spike frequency and a slight depolarization accompanied with a contraction when measured using a sucrose gap method. In some cases the spike generation was almost abolished after a long exposure to higher dose of PTX and the developed tension gradually decreased. Under isometric recording, PTX caused a sustained contraction in rabbit aorta, dog mesenteric and coronary arteries at above 1×10^-10, 1×10^-10 and 1×10^-11 g/ml, respectively, in a dosedependent manner. The coronary artery was most sensitive among the preparations used. PTX-induced contraction in aorta was irreversible, was not influenced by phentolamine but diminished with 5 mM Mg and disappeared in a D-600 or Ca-free medium. PTX is thus an extremely potent and direct stimulant which acts on smooth muscles.

View full abstract

Penfluridol, a long-acting neuroleptic drug, was repeatedly given to rats well trained on the discriminated avoidance schedule (intertrial interval, 25 sec; warning duration, 5 sec), and accumulation of the effects were investigated by observing the behavioral changes. When penfluridol was orally given in a dose of 2-8 mg/kg once daily for 10 consecutive days, the suppression of avoidance response was progressively enhanced until the 3rd-4th day. But from the 4th day, the maximum level of suppression was maintained during the later medication. On its withdrawal, the avoidance response was gradually restored, returning to the initial level in 3-4 days. When 8 mg/kg was given at 1-2 weeks after the withdrawal, the same suppression was observed as after the single administration of the same dose. The progressive enhancement of suppression in the early half of the medication period evidently indicated the cumulative effect. The degree of suppression during the plateau showed a linear correlation with the dosage, and was estimated to be about 3.5 times as high as in the corresponding single administration.

View full abstract

Effects of L-glutamine on acetylsalicylic acid (ASA)-induced gastric mucosal lesions were studied in mongrel dogs. It was confirmed that when oral ASA at 1.0 or 2.0 g per dog is given in two divided doses, there is severe and consistent dose-dependent mucosal damage in the glandular portion of the stomach in fasted dogs. However, when L-glutamine 2.0 or 4.0 g per dog in two divided doses is given concomitantly with ASA 2.0 g per dog orally, the gastric irritation is significantly inhibited. Instillation of 20 mM of ASA in 100 mM HCl solution into the Heidenhain pouch of Beagle dogs produced a significant loss of H⁺ from the pouch and a gain of Na⁺ in the lumen compared with ASA-free controls. When L-glutamine (100 mM) was given concomitantly with ASA (20mM) into the pouch, changes of electrolyte fluxes in response to ASA alone were significantly suppressed. However, 50 mM of L-glutamine had no appreciable effect on acid back diffusion caused by ASA 20 mM. The amino acid itself had little effect on the ionic movement in the pouch. Gross bleeding from the pouch treated with ASA was never observed with the concomitant dosing of ASA and L-glutamine 50 or 100 mM.

View full abstract

Effects of various chemical agents eliciting the catecholamine-release on the adenylate cyclase-cyclic AMP generating system have been studied in the secretory process of the bovine adrenal medulla slices. Cyclic AMP levels were not affected at the interval of the maximal increase of the catecholamine-release by acetylcholine, but increased gradually some time after the end of the release/or at the beginning of the restoration of catecholamine in the medulla tissue. This delayed increase in the medullary cyclic AMP is not attributed to a direct involvement in ‘stimulus-secretion coupling process’ of the medullary secretion, but rather may be caused by release of intracellular catecholamine.

View full abstract

Tissue distribution and levels of allopurinol oxidizing enzyme and xanthine oxidase with hypoxanthine as a substrate were compared with supernatant fractions from various tissues of mice and from liver of mice, rats, guinea pigs and rabbits. The allopurinol oxidizing enzyme activities in liver were quite different among the species and the sex difference of the enzyme activity existed only in mouse liver. In mice, the highest activity of allopurinol oxidizing enzyme was found in the liver with a trace value in lung, but the enzyme activity was not detected in brain, small intestine and kidney, while the highest activity of xanthine oxidase was detected in small intestine, lung, liver and kidney in that sequence. The allopurinol oxidizing enzyme activity in mouse liver supernatant fraction did not change after storage at -20°C or dialysis against 0.1 M Tris-HCl containing 1.15 % KCl, but the activity markedly decreased after dialysis against 0.1 M Tris-HCl. On the contrary, the xanthine oxidase was activated 2 to 3 times the usual activity after storage at -20°C or dialysis of the enzyme preparation. These results indicated that allopurinol was hydroxylated to oxipurinol mainly by the enzyme which is not identical to xanthine oxidase in vivo. A possible role of aldehyde oxidase involved in the allopurinol oxidation in liver supernatant fraction was discussed.

View full abstract

Adult male albino rats of three strains—Wistar, Sprague-Dawley and Holtzman—were trained to press a lever to avoid electric shocks under Sidman-type (R-S interval=20 sec; S-S interval=5 sec) and discriminated avoidance (ITI=15 sec; warning duration=5 sec) schedules, and the acquisition processes of avoidance responses, and the properties of behavioral baselines were investigated. Under both schedules, Wistar strain rats, though showing poorer results than the other two in the beginning, rapidly progressed with the repetitive training, and finally displayed excellent and stable performances. Sprague-Dawley strain rats were poorer in performances, with delayed acquisition and prolonged warm-up effect in the within-session performance. The results of Holtzman strain rats ranked between the two. After the establishment of stable behavioral baselines under both schedules, 0.5, 1.0 and 2.0 mg/kg of diazepam were given subcutaneously, and it was found that in Wistar and Holtzman strain rats, the avoidance responses were inhibited together with increase of delivered shocks in parallel to the doses. In Sprague-Dawley strain rats, however, the avoidance responses were conversely improved with 0.5 and 1.0 mg/kg, while such tended to be inhibited with 2.0 mg/kg, with marked concomitant ataxia. As definite strain differences in avoidance response were demonstrated herein, selection of the most appropriate strain should be made when designing behavioral experiments.

View full abstract

Effect of atropine sulfate (atropine) on the contractile responses to acetylcholine chloride (ACh), potassium chloride (K) and barium chloride (Ba) was investigated in isolated rabbit ileum. Tension of the strips suspended in the bath medium (Locke solution, 30°C) was isotonically recorded. The K(ED50)- and Ba(ED50)-induced contractions were not affected by atropine at 3.0×10^-4 mM, which reversibly abolished the ACh(ED100)-contraction. After washout of 6.0×10^-4 mM atropine, the phasic, but not the tonic, component of ACh(ED50)-, K(ED50)- and Ba(ED50)-contractions was to some extent inhibited irreversibly. On the contrary, such irreversible inhibition of the phasic component was not produced by atropine methylbromide even in the high concentration of 3.0×10^-3 mM. The irreversible inhibitions by atropine of 6.0×10^-4 mM on the phasic component of ACh- and K-contractions were protected by pretreatment with a high concentration of ACh or K. Further, these irreversible inhibitions by atropine were potentiated by the absence of Ca and were abolished by the increase of Ca content in bath media. These results suggest that the irreversible inhibition of the contractile responses to drugs by atropine in high concentration may be due to the interference with the mobilization of Ca in the deep layer of the membrane, rather than by a blockade of muscarinic receptor sites.

View full abstract

Effects of aminophylline and the reduction in external Na on the antispasmodic action of isoproterenol were investigated in relation to the mobilization of Ca in the isolated rat rectum. The antispasmodic action of isoproterenol on the phasic contractions by acetylcholine and K both in Ca-free and in Ca-free and Na-poor media was potentiated by treatment with aminophylline, however the antispasmodic action was attenuated by reducing Na in the Ca-free medium. Dibutyryl cyclic AMP inhibited acetylcholine and K-induced phasic contractions in Ca-free and in Ca-free and Na-poor media and the inhibitory action was also potentiated by treatment with aminophylline, while the inhibitory action of dibutyryl cyclic AMP was attenuated by reducing Na in the Ca-free medium. From these findings, it appears that isoproterenol inhibits the release of Ca from storage sites induced by acetylcholine and K via the increase of intracellular cyclic AMP content and that the external Na may play an important role in the Ca release-inhibiting effect of cyclic AMP.

View full abstract

In a previous experiment, fetopathic effects of caffeine were significantly reduced by pretreatment with propranolol at dosage levels of 2.5 to 10 mg/kg. The present experiments were undertaken to investigate the relation between time intervals of propranolol pretreatment and its effect on reducing fetopathy. Furthermore, the effect of timolol, another β-adrenergic blocking agent, on reducing fetopathy was compared with that of propranolol. Propranolol (5 mg/kg) administered 15, 30 or 60 minutes before caffeine treatment significantly reduced the caffeine-induced fetopathy. The optimal effect was found when propranolol was given 30 minutes before caffine. The reduction in fetopathy by timolol pretreatment was comparable to that of propranolol. The results lend support to the hypothesis that the fetopathic effect of caffeine is linked with released catecholamines in maternal or fetal tissues of mice.

View full abstract