Procaine (1×10-5-1×10-4 M), dibucaine (1×10-5-1×10-4 M) and tetracaine (1×10-6-1×10-5 M) caused an increase followed by a decrease in the rate of spontaneous afferent (A) discharges (D) accompanied with a decrease in the flow rate of perfusion solution from the pulmonary vein in the isolated lung of the bullfrog, but these local anesthetics only decreased the rate of A.D. synchronized with lung inflation. The stimulatory effects of these drugs on the rate of spontaneous A.D. were studied. In the presence of TTX (1×10-7 M), the increase in the rate of spontaneous A.D. by local anesthetics was inhibited, but the decrease in the flow rate of perfusion solution by these drugs was not inhibited. Papaverine (1×10-5 M), which inhibited the decrease in the flow rate of perfusion solution by these local anesthetics, inhibited the increase in the rate of spontaneous A.D. by dibucaine, but not those by procaine and tetracaine. The inhibitory effects on the increase in the rate of spontaneous A.D. by these local anesthetics could be seen with verapamil in a concentration (1×10-4 M) which significantly inhibited the rate of spontaneous A.D., like TTX (1×10-7 M). Verapamil could not reverse the decrease in the flow rate of perfusion solution by these local anesthetics. From these results, the increase in the rate of spontaneous A.D. by procaine and tetracaine is due to not only the contractile effects of the drugs on the pulmonary vessel but also the direct stimulatory effects on the receptors which generate spontaneous A.D., and the increase in the rate of spontaneous A.D. by dibucaine may result from the contraction of the pulmonary vessel, and the stimulatory effect of dibucaine on the receptors would be weaker than that of procaine and tetracaine, since dibucaine could cause the increase in the rate of spontaneous A.D. only when dibucaine decreased the flow rate of perfusion solution.
The following disulfide compounds: 2-hydroxyethyldisulfide (2-MEOX), 2-aminoethyldisulfide (cystamine) and oxidized dithiothreitol (DTTOX) were found to augment the in vitro antibody response to sheep erythrocytes in murine lymphocytes as effectively as their reduced forms when they were added to the culture medium. We, however, found out that the mode of action of DTTOX was greatly different from that of 2-MEOX or cystamine. 2-MEOX and cystamine showed augmenting effects on the proliferative response to lipopolysaccharide and on the uptake of (35S)-cystine by the lymphocytes. In contrast to these intermolecular disulfides, DTTOX, an intramolecular disulfide compound, was found to be inactive in these systems. 2-MEOX and cystamine, but not DTTOX, were reduced to thiol forms by the intact lymphocytes or by the cell homogenate. Thus, it is likely that DTTOX did not behave as the reduced form in the lymphocyte culture in contrast to 2-MEOX and cystamine, suggesting that the disulfide form itself plays an important role in augmenting effects of DTTOX.
Intracerebrove ntricular (i.c.v.) injection of 19 pmol/rat or more of salmon calcitonin (sCT) or iodinated sCT suppressed spontaneous intake of food and water in a dose-dependent manner. Tail-whipping was a peculiar behavior which concomitantly developed, but no analgesia ensued from the doses tested (up to 62 pmol/rat). It was examined how the rise and fall pattern of these behavioral effects would correlate with the dispositional pattern of 125I-sCT. When the radioactive peptide was injected in anorectic doses via the i.c.v. route, the radioactivity was found to distribute throughout the brain, but not uniformly. In rats which showed a marked anorexia and tail-whipping behavior, distribution occurred in such a manner that it could be interpreted to reflect the regional and subcellular distribution pattern of sCT-specific binding sites. Even 3 hr after injection, the hypothalamus, the smallest region, retained the highest radioactivity corresponding to about 1 % of the dose and at least one half of which was identified as the intact iodo-sCT. To be noted is the finding that sCT injected centrally will quickly enter the systemic circulation and peripherally induced long-lasting hypocalcemia, since the anorectic dose of sCT is considerably higher than the dose needed for the peripheral effect. It is concluded that most of the sCT after i.c.v. injection leaks into the systemic circulation, but the rest is retained rather selectively around the receptor in hypothalamic nuclei for a long time, leading to day-long suppression of feeding and drinking behavior.
The vascular bed in a murine dermal tissue responded to inoculated tumor cells by two-phased changes in the vascular permeability. The initial increase in the vascular permeability was seen in an early stage (1 to 3 day post tumor cells inoculation), and the inflammation was sensitive to glutathione (GSH). Glucocorticoids reduced the increased vascular permeability, but neither acetylsalicylic acid nor indomethacin did. The later vascular response was produced by a growing solid tumor in a continuous mode beginning at 5th to 10th day post inoculation. The degree of the increased vascular permeability in this chronic phase was in direct proportion to the wet weight of the solid tumor, and the inflammation was insensitive to glutathione. Glucocorticoids reduced the increased vascular permeability, but neither acetylsalicylic acid nor indomethacin did. The action of glucocorticoids on the tumor-induced vascular hyper-permeability was discussed in connection with a tumor factor possibly responsible for the vasoexudation.
Inhibition of rat liver microsomal carboxylesterase(CEase) by O-ethyl O-p-nitrophenyl phenylphosphonothioate (EPN) and binding of EPN oxygen analog to microsomal CEase were enhanced by addition of NAD or NADP. This was more prominent in addition of NAD than NADP. No potentiation of anti-CEase action of EPN by NAD was seen when pure esterase (E.C. 22.214.171.124) instead of liver microsomes was used as an enzyme source. This effect of NAD in microsomal CEase was significantly decreased when N-ethylmaleimide or p-chloromercuribenzoic acid was added. From these findings, it is strongly suggested that NAD-mediated potentiation of the anti-CEase action of EPN might be attributed to the increase in formation of NADH from NAD by microsomal dehydrogenase(s) containing a sulfhydryl group, leading to a subsequent increase in formation of the EPN oxygen analog from EPN, and in turn, CEase inhibition was enhanced.
Effects of calcium hopantenate (HOPA) on neurotransmitter and neuropeptide receptors in the central nervous system (CNS) were investigated. In the radioreceptor assay (RRA), HOPA inhibited the [3H]-γ-aminobutylic acid (GABA) receptor binding in a dose-dependent manner with a cross-reactive potency of 0.2%. On the other hand, radiolabeled ligand binding to CNS receptors in the benzodiazepine (BDZ)-, musucarinic cholinergic (mACh)-, methionine-enkephalin (ENK)- and thyrotropin releasing hormone (TRH)-RRA systems was not inhibited even by the addition of HOPA up to 100 μM. Repeated Injection of HOPA (250 mg/kg/day for 7 consecutive days) increased GABA receptor binding by 53% in the cerebral cortex, while GABA binding in the rest of the forebrain did not change. The increased GABA receptor binding in the cerebral cortex of HOPA treated rats was due to the increased affinity of the binding sites. BDZ-, mACh-, ENK- and TRH-receptor bindings were not affected in either the cerebral cortex or the rest of the forebrain by repeated injection of HOPA. These results suggest that at least a part of the therapeutic efficacy of HOPA is due to sensitization of the GABA receptor in the cerebral cortex.
A possible role of prostaglandin E2 (PGE2) in the regulation of blood pressure in spontaneously hypertensive rats (SHR) was investigated. The inhibition of PG synthesis by chronic indomethacin treatment accelerated the elevation of blood pressure with the tendency to decrease renal PGE2. We, therefore, confirmed that PGE2 in SHR may play a role in the antihypertensive mechanism. In this connection, the participation of renal PGE2 in the retardation of the development of hypertension in male SHR induced by orchiectomy was examined. Urinary PGE2 which reflects the renal PGE2 level tended to keep a higher level in the castrated group. Urinary electrolytes excretion also inclined to augment in the castrated group throughout the experiment. These results indicate that renal PGE2 may participate in the gonads-mediated blood pressure regulation system, although the mechanism of the retardation of spontaneous hypertension induced by orchiectomy remains obscure.
In Ca-deficient smooth muscle of guinea-pig taenia coli, repeated application of high-K solution (45.4 mM) containing Ca induced contractions of similar shape and magnitude. In muscle treated by a Ca- and Mg-deficient solution, however, addition of Ca and K either did not induce contraction or induced only a delayed contraction. Ouabain (1×10-3 M) also inhibited Ca- and K-induced contraction. Na content of taenia coli smooth muscle increased and K content decreased during incubation in Ca- and Mg-deficient solution. Ouabain produced similar, but smaller, changes in Na and K contents. Contractility of Ca- and Mg-deficient taenia partially recovered if the muscle was treated with Na-deficient solution which resulted in a large decrease in Na content. Similar treatment produced only a small decrease in Na content in ouabain-treated taenia, and contractility did not recover in these muscles. Application of hyperosmotic NaCl (160 mM) decreased tissue weight in both control and ouabain-treated taenia. In muscle treated with Ca- and Mg-deficient solution, however, hyperosmotic NaCl application had little effect on tissue weight. Following pretreatment of muscle with Ca- and Mg-deficient solution (containing 2 mM EDTA) for 2 hr, graded contractions were induced by cumulative application of Ca between 10-7 to 10-6 M in the presence of Mg and ATP. It is concluded that Ca- and Mg-deficient solution increases membrane permeability and also abolishes transmembrane gradients of Na and K in guinea pig taenia coll.
The antiulcer action of elcatonin, an analogue of natural eel calcitonin, was compared with that of cimetidine, secretin and solcoseryl. Elcatonin (3 to 10 u/kg, s.c.) inhibited the development of gastric ulcers induced by pylorus ligation, water-immersion stress, aspirin and reserpine and duodenal ulcers induced by cysteamine in rats. Moreover, once daily injections of elcatonin (1 to 10 u/kg/day, s.c.) promoted the healing of acetic acid-induced chronic gastric ulcers not only in rats but in dogs. The healing effect persisted after the cessation of administrations. Cimetidine (30 to 100 mg/kg, p.o.) inhibited the development of gastric ulcers induced by water-immersion stress, aspirin and reserpine and duodenal ulcers induced by cysteamine in rats. However, once daily administrations of cimetidine (30 to 100 mg/kg/day, p.o.) did not show significant effect on acetic acid-induced chronic gastric ulcers in rats. Secretin (30 to 100 u/kg, s.c.) inhibited the development of gastric ulcers induced by pylorus ligation, water-immersion stress, aspirin and reserpine in rats, but was not effective on cysteamine-induced duodenal ulcers and acetic acid-induced chronic gastric ulcers in rats. Solcoseryl (2 ml/kg, s.c.) inhibited only the development of water-immersion stress-induced gastric ulcers in rats. These results suggest that elcatonin is different from these reference drugs in its properties of action on experimental ulcers. Mechanisms of the antiulcer action of elcatonin which has a superior effect on experimental ulcers are discussed.
The effects of insulin, glucagon, isoproterenol and carbachol on the regeneration of injured liver were investigated in rats treated with carbon tetrachloride (CCl4). These agents effectively potentiated hepatic DNA synthesis in rats both at 48 and at 72 hr after CCl4 intoxication. The maximal stimulatory effects of the agents on the synthesis coincided in time with the peak of elevation in basal DNA synthesis following the intoxication. Plasma levels of insulin and triiodothyronine were decreased before the elevation of basal DNA synthesis in CCl4-treated rats. The possible relationship of these changes in plasma hormones to the potentiated effects of the agents on DNA synthesis was examined in rats treated with streptozotocin (STZ) or methylthiouracil (MTU). The agents caused no potentiation in STZ-treated rats. On the other hand, in MTU-treated rats, isoproterenol and carbachol significantly stimulated DNA synthesis, but this was not the case with insulin and glucagon. These results suggest that the pancreatic hormonal, β-adrenergic and cholinergic stimulations play positive roles in regulating liver regeneration after CCl4 intoxication. Furthermore, the hypothyroid state developed in CCl4-treated rats may provide favorable conditions for the stimulation of DNA synthesis by isoproterenol and carbachol. It is unlikely, however, that insulin deficiency contributes to potentiations in the regenerative responses of the injured liver.
The effects of an antirheumatic agent, N-(2-mercapto-2-methyl-propanoyl)-L-cysteine (SA96), were investigated on allergic reactions in rats and guinea pigs. The effects of SA96 were compared with those of D-penicillamine (D-Pc). SA96 given twice orally at the doses of 10 to 50 mg/kg significantly caused inhibitions of 28%, 29% and 44% against passive cutaneous anaphylaxis (PCA), reversed cutaneous anaphylaxis (RCA) and reversed passive Arthus (RPA) reactions, which are classified as Type I, Type II and Type III allergic reactions, respectively. D-Pc also showed inhibitions of 30%, 23% and 18% on Type I, Type II and Type III reactions, respectively, and inhibitions on Type II and Type III reactions were not significant. On the other hand, SA96 (10 to 50 mg/kg twice) had no influence on the Type IV allergic reaction, delayed hypersensitivity, while D-Pc (20 mg/kg twice) showed an enhancement of 27% on the Type IV reaction. In the in vitro study, SA96 inhibited the hemolytic complement activity at 10-4 to 10-2M and the macrophage migration at 1×10-4 to 5×10-3 M in a dose-dependent manner. These in vitro activities of SA96 were more potent than those of D-Pc. These results showed that SA96 had some different immunopharmacological properties on experimental allergic reactions as compared with those of D-Pc.
Effects of several non-steroidal anti-inflammatory drugs (NSAI Ds) such as aspirin (ASA), indomethacin (IM), flurbiprofen (FP), Ibuprofen (IP), phenylbutazone (PBZ) and flufenamic acid (FA) were studied on the gastric ulceration and gastric acid secretion induced by restraint and water-immersion stress (RWIS) or various secretagogues in rats. These drugs significantly increased ulcer formation. IM (1, 3 and 10 mg/kg, s.c.) reduced gastric mucosal prostaglandin (PG) content dose-dependently. There was an appreciable correlation between this decrease in the PG content of gastric tissue and associated ulceration. The gastric acid secretion induced by the peripheral secretagogues, methacholine, gastrin and histamine, was not significantly influenced by IM pretreatment. In contrast, the gastric acid secretion induced by the vagal mediated secretagogues, insulin, 2-deoxy-D-glucose (2-D-G) and RWIS, was markedly increased by IM pretreatment. These effects were not observed in vagotomized rats. By intracerebroventricular (i.c.v.) injection of IM, no influence was observed on the gastric acid secretion and ulcer formation induced by 2-D-G or RWIS. These results suggest that acidic NSAIDs potentiate the gastric acid output induced by stimulation of vagus nerve activity, and prostaglandins (PGs) may influence gastric acid output by regulating vagus nerve activity.
Intraperitoneally administered benzodiazepines, chlordiazepoxide (2-5 mg/kg), diazepam (1 mg/kg), flurazepam (1 mg/kg) and a benzodiazepine antagonist, Ro 15-1788 (0.5 mg/kg), reversed the antinociceptive effect in mice which was induced by intracisternal administration of 1 μg of sulfated cholecystokinin octapeptide. The antinociceptive effect of cholecystokinin was reversed by naloxone, suggesting that the antinociceptive action involves endogenous opioid peptides in its production. On the other hand, morphine-induced analgesia was not reversed by diazepam and Ro 15-1788. These facts rule out opioid receptors as the site of the antagonism between the benzodiazepines or Ro 15-1788 and cholecystokinin on the antinociceptive effect. Benzodiazepines and Bo 15-1788 seem to inhibit the release of opioid peptides induced by cholecystokinin.
Studies were performed to determine the effects of an immunopotentiating agent, lentinan, on the hepatic drug-metabolizing enzymes in mice. Lentinan was injected twice a day for two days, and the enzyme activities were determined 12 hr after the last injection of lentinan. A lentinan dose of over 0.25 mg/kg was required to cause a significant decrease (20-40%) in the hepatic microsomal aminopyrine N-demethylase and aniline hydroxylase activities. The loss of drug-metabolizing activity by the treatment with lentinan agreed with the loss of cytochrome P-450 content in many cases. Strain and substrate differences concerning the effect of lentinan on the metabolism of drug were also observed. That is to say, the loss of cytochrome P-450 content by the treatment with lentinan was observed in the ddY, C57BL/6 and BDF1 strain mice, but was not observed in the DBA/2, C3H/He and C57BL/10 strain mice. The decrease in the activities of 7-ethoxycoumarin O-deethylase and biphenyl 2-hydroxylase by the treatment with lentinan was considerably less than that of aminopyrine N-demethylase and aniline hydroxylase in ddY mice.
Met-Enkephalin injected i.c.v. attenuated stress-induced increases in levels of 3-methoxy-4-hydroxyphenylethyleneglycol sulfate, the major metabolite of brain noradrenaline, in the hypothalamus, amygdala, hippocampus, thalamus, midbrain and LC region in rats. The data suggest that Met-enkephalin acts to attenuate stress-induced increases in noradrenaline turnover in these brain regions in rats.
2, 4, 6-Trinitrophenol (PA) evoked a prolonged catecholamine (CA) secretion from perfused bovine adrenal glands. The PA-evoked CA secretion was concentration-dependent, required the presence of extracellular calcium and resulted from a direct action of PA on the chromaffin cells. Furthermore, PA reduced Mg2+-ATPase activities in the plasma membrane-rich microsome and granule-rich fraction from the adrenal medulla. These results indicate that PA evokes CA secretion through the actions on both the chromaffin cell membranes and Granule membranes.
In anesthetized rats, intra-carotid injections of arachidonate·Na (20 mg/kg) elicited a marked pressor response, producing death within 10 min in untreated rats. The antianginal agents (nicorandil, nitroglycerin and diltiazem) and cyclooxygenase inhibitors (indomethacin and aspirin), applied i.v. or p.o., effectively protected the rats from death. In the surviving rats, these drugs significantly prevented intravascular thrombosis in cerebral vessels and the marked pressor response to arachidonate·Na. The protective mechanism of the antianginal agents tested seems to be different from that of cyclooxygenase inhibitors.
In rat parotid tissue, amylase secretion and accumulation of cyclic AMP were not selective responses to the different β-subtypes, β1 and β2. However, the supersensitivity of the amylase secretory response induced by brief pretreatment with β-agonist was due specifically to a β2-adrenergic response.
The change in responsiveness to α-adrenergic stimulation and to calcium ions in amylase release from parotid glands of hypothyroid rats was compared with that in euthyroid rats. Calcium depletion and addition of verapamil or W-7 in the medium caused a decrease in methoxamine-induced amylase release in both eu- and hypothyroid rats. Moreover, addition of calcium ions to Ca2+-free medium markedly increased the methoxamine-induced amylase release in proportion to its concentration in hypothyroid rats. These results suggest that calcium ions play an important role in methoxamine-induced amylase release from parotid glands of hypothyroid rats as well as those of the euthyroid ones.