Effects of Sophora flavescens Ait. on haemodynamics and ventricular fibrillation threshold in anaesthetized dogs

The effects of an ethanol extract of the plant Sophora flavescens Ait. on haemodynamics and ventricular fibrillation threshold were studied in pentobarbitone-anaesthetized dogs. It was found that intravenous injection of the extract, 120 mg/kg, caused transient but significant depression in systolic and diastolic blood pressure, heart rate, left ventricular pressure and dLVP/dtmax, as well as elevation of ventricular fibrillation threshold. These preliminary findings suggest that the ethanol extract of Sophora flavescens Ait. possesses pharmacological activities resembling those of antiarrhythmic agents, but the mechanisms of action are unclear.

Effects of acute and chronic morphine administration on glucose tolerance in mice

The effects of acute and chronic morphine treatment on glucose tolerance were investigated in mice. In acute experiments, a single dose of morphine (20 mg/kg i.p.) increased the serum and muscle glucose level. After glucose loading (1.5 g/kg), the rate of increase and the peak of serum glucose concentration were significantly lowered in morphine-treated mice, while the availability and the half-life of glucose were similar to those of controls. In morphine-dependent mice, the fasting serum and muscle glucose levels were similar to those of control but the liver glucose was significantly greater. After glucose loading the rate of increase in serum glucose level was faster and the availability of glucose was 10% greater than that in naive mice. Again, there was no difference in the half-life of serum glucose between naive and morphine-dependent mice.

Effects of hypoxaemia and hyperoxaemia on some cardiovascular responses of rats to adrenaline

Systemic blood pressure and pulse rate responses to intravenously administered adrenaline during hypoxaemia or hyperoxaemia were studied in urethane-anaesthetized rats. Hypoxaemia or hyperoxaemia was induced by ventilating the animals with 15% O2/85% N2 or with 100% O2, respectively. Hypoxaemia significantly decreased the diastolic blood pressure and elevated the pulse rate; the reflex falls in pulse rate in response to adrenaline were significantly reduced. Hyperoxaemia, on the other hand, did not cause remarkable changes in blood pressure or pulse rate, but significantly depressed diastolic blood pressure to adrenaline. It is suggested that the compensatory cardiovascular reflexes may be impaired by hypoxaemia, and that hyperoxaemia reduces vasoconstrictor response to catecholamine possibly by lessening or enhancing the sensitivities of the vascular alpha 1- or beta 2-adrenoceptors, respectively.

Production of physical dependence in rats by drinking a morphine solution

The plasma concentrations of morphine and glucose, the body weight, and the severity of the naloxone-precipitated withdrawal syndrome were studied in female rats in which morphine dependence was induced by administration of the opiate, with or without sucrose, in their drinking water. It was found that sucrose encouraged the animals to consume more morphine and that the initial plasma concentrations of the opiate, as well as the rate of development of physical dependence, were higher than the group not given sucrose. Plasma glucose concentrations, maximum plasma morphine levels and the maximum severity of the naloxone-precipitated withdrawal syndrome were, however, not significantly different between the two groups. The findings suggest that both regimens of administering the opiate in drinking fluid are effective in inducing morphine dependence in rats; the addition of sucrose tends to speed up the development of physical dependence, probably by increasing intake of the opiate through consuming more sucrose solution.

Cardiovascular effects of ranitidine and cimetidine during acute myocardial ischaemia in anaesthetized dogs

The effects of ranitidine and cimetidine on ventricular fibrillation threshold and haemodynamics were studied in pentobarbitone-anaesthetized dogs subjected to acute coronary artery ligation. These drugs did not significantly change the ventricular fibrillation threshold nor haemodynamics before coronary artery ligation, except for remarkable haemodynamic depression by ranitidine 1 mg/kg. Ligation of the left anterior descending coronary artery reduced the ventricular fibrillation threshold, decreased systemic and left ventricular pressures and myocardial contractility, and slightly increased heart rate. Pretreatment with ranitidine 0.25 or 1 mg/kg, or with cimetidine 2 mg/kg, significantly abolished the reductions in ventricular fibrillation threshold, but did not noticeably alter the haemodynamic changes. These findings further support the hypothesis that histamine release may contribute to the increased ventricular vulnerability resulting from acute myocardial ischaemia. However, the role of histamine in the haemodynamic responses to coronary artery ligation remains obscure.

Gastric acid secretory responses to cholinergic and histaminergic stimulation in chronic morphine-treated rats

The effects of chronic morphine administration on cholinergic and histaminergic activities were evaluated in rats by observing their gastric acid secretory responses to secretagogues. The responses of in-vivo perfused stomachs to 2-deoxy-D-glucose or pentagastrin, and of the isolated gastric mucosa to histamine or bethanechol, were not significantly different between naive and chronic morphine-treated animals. It is suggested that the chronic morphine-treated rats exhibit normal cholinergic and histaminergic activities as well as receptor sensitivities to acetylcholine and histamine.

Effects of morphine, hypoxaemia and hypercapnia on the rat stomach

The effects of morphine, hypoxaemia or hypercapnia on gastric acid secretion, gastric mucus synthesis and the gastric mucosa were studied in conscious rats with pyloric occlusion. Hypoxaemia and hypercapnia were induced by morphine 32 mg/kg given i.p., or each condition was produced separately by adjusting the composition of respired air in the chamber where the animals were kept during the experimental period. Hypoxia significantly enhanced gastric mucus synthesis whereas hypercapnia significantly reduced gastric acid secretion. These effects were significantly alleviated by atropine pretreatment. Morphine-treated rats exhibited decreased gastric acid secretion, increased gastric mucus synthesis and a higher mean ulcer index but only the reduced gastric acid output was significantly prevented by atropine. It is suggested that the effect of morphine on gastric acid secretion may result from its respiratory depressant action and consequent acute stress production. However, the mechanisms by which morphine can increase mucus synthesis and produce ulceration remain obscure.

Cardiovascular responses to sympathetic nerve stimulation in morphine-treated rats

The effects of morphine on the responses of blood pressure and pulse rate to stimulation of sympathetic nerves or to intravenous administration of noradrenaline were studied in female rats which had been treated with either an increasing concentration of morphine sulphate in their drinking fluid (5% sucrose solution), or an acute intraperitoneal injection of morphine. Sympathetic nerve excitation was effected by electrical stimulation of the thoracic segments of the spinal cord in pithed rats. Both sympathetic nerve stimulation and noradrenaline produced dose-dependent changes in blood pressure and pulse rate in naive rats and in the sucrose-drinking controls. Animals which had been chronically treated with morphine in their drinking fluid for 21 days showed significantly less intense responses to sympathetic nerve stimulation. However, these decreased responses were not observed in rats given acute treatment with morphine. Chronic treatment with morphine did not significantly influence the changes in blood pressure or pulse rate induced by noradrenaline. These findings suggest that chronic treatment with morphine lessens the cardiovascular responses to stimulation of peripheral sympathetic nerves in rats. The mechanism is not clear, but it seems unlikely to be due to changes in the sensitivity, or perhaps the number, of adrenoceptors.

Morphine enhances gastric mucus synthesis in rats

The effect of morphine on gastric mucus synthesis was studied in conscious rats, using the method of staining mucus with alcian blue then destaining it with magnesium chloride. It was found that morphine significantly enhanced gastric mucus synthesis, as did fentanyl, a non-histamine-liberating opioid. The effects of the opioids on mucus synthesis were significantly attenuated by pretreatment with naloxone 8 mg/kg or cimetidine 100 mg/kg. Cimetidine itself significantly suppressed gastric mucus production in saline-treated rats. These findings suggest that the increased gastric mucus synthesis caused by morphine is due to activation of opiate receptors and not to histamine release. It appears that cimetidine may counteract rather than block the receptor effects of the opioids by a direct action on the mucus-secreting glands.

Effects of ranitidine and cimetidine on experimentally induced ventricular arrhythmias in anaesthetized rats

The effects of two histamine H2-receptor antagonists, ranitidine and cimetidine, on ventricular arrhythmias induced by acute coronary artery ligation and by aconitine infusion were studied in pentobarbitone-anaesthetized rats. The changes in arterial blood pressure and heart rate were also observed. It was found that both drugs significantly reduced the incidence, and prolonged the time of onset, of ventricular tachycardia and ventricular fibrillation following acute coronary artery ligation; however, they did not significantly alter the incidence or time of onset of ventricular dysrhythmias caused by aconitine infusion. These findings further support the hypothesis that histamine release may contribute to the genesis of early ventricular arrhythmias resulting from acute myocardial ischaemia. Since the decreased blood pressure induced by coronary artery ligation was not significantly prevented by pretreatment with either histamine H2-receptor blocker, this suggests that histamine may not be responsible for the blood pressure changes during acute myocardial ischaemia.

Rapid induction of dependence to morphine in rats

The rate of development of dependence to morphine was studied in female rats which were given increasing concentrations of morphine sulphate in their drinking fluid (5% sucrose solution). The occurrence of physical dependence was determined by the naloxone-precipitated withdrawal syndrome at various times during the 3-week experimental period. It was found that a significant degree of the withdrawal syndrome precipitated by naloxone was evident at 24 hr after starting administration of morphine; the syndrome reached its greatest intensity after the rats had received the opiate for 7 days. This study shows that dependence on morphine can be induced in rats by administration of the opiate in drinking fluid for a period shorter than 7 days.

Mechanisms of captopril-induced potentiation of the depressor responses to arachidonic acid in rats

The mechanisms underlying potentiation by captopril of the depressor responses to arachidonic acid were studied in chloralose-anaesthetized rats. Captopril, in a dose (0.5 mg/kg, i.v.) which inhibited the pressor responses to angiotensin I (0.03-1 microgram/kg, i.v.), enhanced the depressor responses to bradykinin (3-300 micrograms/kg, i.v.) and potentiated the hypotensive action of arachidonic acid (3 mg/kg, intravenously). This phenomenon was observed not only when captopril and arachidonic acid were administered intravenously, but also when these compounds were injected directly into the aortic arch. The enhancement of arachidonic acid-induced hypotension by captopril was not significantly affected by pretreatment with a low dose of aprotinin (3 mg/kg, i.v.), but was abolished by bilateral nephrectomy or by pretreatment with a higher dose of aprotinin (6 mg/kg, i.v.). It is suggested that captopril augments the depressor responses to arachidonic acid by inhibiting angiotensin converting enzyme. This results in accumulation of bradykinin which in turn increases release of vasodilator prostaglandins, originating most probably, from the kidneys. The possibility that blockade of angiotensin II formation by captopril may leave the vasodilator action of prostaglandin unopposed cannot be excluded.

Effects of carbenoxolone sodium on gastric and duodenal mucus synthesis in mice

Using the method of staining mucus with Alcian blue and destaining it with magnesium chloride, it was found that intragastric administration of carbenoxolone in mice did not significantly affect duodenal mucus synthesis at doses which remarkably increased gastric mucus synthesis. However, in vitro study showed that carbenoxolone significantly stimulated both gastric and duodenal mucus synthesis. It is suggested that carbenoxolone may also effectively increase mucus synthesis and probably accelerate ulcer healing in the duodenum if sufficient amounts can escape gastric absorption and reach this region.

The antiarrhythmic effects of Sophora flavescens Ait. in rats and mice

The effects of an ethanol extract of the plant Sophora flavescens Ait. on cardiac arrhythmias induced by coronary artery ligation in rats, and by aconitine infusion in mice, were studied. Pretreatment with intravenous injection of the extract, 120 mg/kg, significantly reduced the incidence and delayed the onset of ventricular tachycardia in rats subjected to ligation of the left coronary artery. The time of onset of both initial cardiac arrhythmias and persistent ventricular tachycardia induced by aconitine infusion in mice was also significantly prolonged. These preliminary findings suggest that the ethanol extract of Sophora flavescens Ait. possesses antiarrhythmic activity.

Sulphasalazine and experimental stress ulcers

The effects of sulphasalazine on gastric ulceration induced by restraint at 4 degrees C (stress) for 2 h were studied in rats. Doses of 63 or 125 mg/kg s.c., which had no effect on stomach wall prostaglandin E2 (PGE2) levels, prevented stress ulceration but not the lesions produced by indomethacin. Stress significantly increased gastric glandular mucosal PGE2 levels. Indomethacin pretreatment (20 mg/kg, p.o.) markedly reduced PGE2 levels in the same region of the stomachs, and worsened stress-induced lesion formation. Pretreatment with sulphasalazine of animals given indomethacin and then subjected to stress did not appear to affect the indomethacin component of indomethacin-stress ulceration. Oral administration of PGE2 200 micrograms/kg significantly elevated gastric PGE2 levels, but had no effect on stress ulceration. It appears that neither the antiulcer activity of sulphasalazine nor stress-induced ulceration is associated with gastric tissue PGE2 increase or decrease, respectively. The protective mechanism may result from the ability of sulphasalazine to inhibit lipoxygenase activity.

A study on the aetiology of reserpine ulceration and the antiulcer action of solcoseryl in rat stomach

The aetiology of reserpine-induced gastric ulcer formation and the antiulcer effects of solcoseryl were studied in rats. Intraperitoneal injection of reserpine produced severe ulceration, as well as mast cell and histamine depletion, in the gastric glandular mucosa. Mepyramine and cimetidine markedly antagonized the gastric lesions, but did not influence the reduced mast cell count; atropine pretreatment significantly inhibited both parameters. Intramuscular injection of solcoseryl lessened ulcer severity and prevented the decreased mast cell counts and histamine levels in reserpine-treated rats. However, the same dose of solcoseryl injected intraperitoneally was ineffective. Solcoseryl, irrespective of the route of administration, did not influence the gastric secretory activities of reserpine. It is concluded that reserpine ulceration is both cholinergic- and histamine-mediated, and that the antiulcer effects of solcoseryl appear to be due to prevention of histamine depletion in the gastric mucosa.

Human milk-derived growth factor prevents duodenal ulcer formation

Human milk was fractionated to obtain a partially purified growth factor preparation. The growth factor in this fraction, designated as human milk growth factor III, exhibits chromatographic and biological characteristics similar to epidermal growth factor-urogastrone. Pretreatment of mice with human milk growth factor III significantly reduces the incidence, number, total length, and severity score of cysteamine-induced duodenal ulcers.

The influence of morphine on acid secretion by the isolated rat gastric mucosa

The influence of morphine on acid secretion by the isolated gastric mucosa was studied in adult rats. A wide range of morphine concentrations (1 X 10(-4) to 1.6 X 10(-3) M) was found to have no effect on basal acid output, or on acid secretion maximally stimulated by bethanechol or histamine. It is suggested that the opiate receptors in the rat gastric mucosa, if there are any, are not involved in modulating acid secretion.

Gastric secretion and mucosal lesions in morphine-dependent rats

The gastric mucosa and basal gastric secretion of morphine-dependent rats with pyloric occlusion were examined. Morphine tolerance and dependence were induced by administering increasing concentrations of morphine sulphate in the drinking water for 3 weeks, and were confirmed by a decreased analgesic response to morphine in the tail-immersion test and by occurrence of a naloxone-precipitated withdrawal syndrome, respectively. It was found that although the basal gastric secretion of morphine-dependent rats was not significantly different from that of naive animals, the former group showed a significantly higher gastric glandular mucosal ulcer index. Intraperitoneal injection of naloxone induced significant withdrawal effects but did not produce significant changes in gastric secretion or in ulcer index.

Effects of hypoventilation on the cardiovascular responses of rats to adrenaline and acetylcholine

Blood pressure and pulse rate in response to administered adrenaline and acetylcholine during hypoventilation were studied in urethane-anaesthetized rats. Hypoventilation was induced by decreasing the stroke volume of artificial ventilation from 1 ml/100 g to 0.3 ml/100 g. There was a significant rise in pulse rate accompanied by minimal changes in blood pressure during hypoventilation. The blood pressure and pulse rate in response to adrenaline were significantly reduced. The depressant effect of acetylcholine on pulse rate was intensified, but that on blood pressure was not significantly affected. These findings suggest that the compensatory cardiovascular reflexes may be impaired during hypoventilation.

Potentiation of depressor responses to arachidonic acid by angiotensin converting enzyme inhibitors in the rat

In chloralose anaesthetized rats, intravenous administration of captopril, SQ 20881, SA 446 or MK 421 (0.5 mg/kg) potentiated the depressor responses to arachidonic acid 3 mg/kg given intravenously. Same doses of the above angiotensin converting enzyme inhibitors caused an approximately 100-fold decrease in sensitivity to the pressor effects of angiotensin I, with a concomitant similar increase in sensitivity to the depressor effects of bradykinin. Depressor responses to arachidonic acid, both before and after administering the converting enzyme inhibitors, were abolished by intravenous indomethacin (5 mg/kg). These results suggest that increased synthesis of prostaglandins in the circulation may contribute to the hypotensive effect of the angiotensin converting enzyme inhibitors, a group of newly developed antihypertensive agents.

Effects of SK&F 93479 on experimentally induced ventricular arrhythmias in dogs, rats and mice

The effects of SK&F 93479, a potent histamine H2-receptor antagonist, on ventricular arrhythmias induced by coronary artery ligation in dogs and rats, and by aconitine infusion in mice were investigated. It was found that SK&F 93479 in large doses, significantly prevented the occurrence of spontaneous ventricular fibrillation and the changes in ventricular fibrillation threshold following coronary artery ligation in dogs. In rats subjected to ligation of the main left coronary artery, it significantly reduced the incidence of ventricular fibrillation, and significantly prolonged the time of onset of ventricular tachycardia and ventricular fibrillation. On the contrary, SK&F 93479 did not significantly alter the incidence or the time of onset of cardiac dysrhythmias caused by aconitine infusion in mice. These findings suggest that SK&F 93479 lacks non-specific antiarrhythmic activity and that its protective effects against coronary artery ligation may be mediated by its histamine H2-receptor antagonizing action. They also support the hypothesis that histamine may contribute to the genesis of ventricular arrhythmias resulting from acute myocardial ischaemia.

Protection by SK&F 93479 against the haemodynamic effects of coronary artery ligation in dogs

The effects of SK&F 93479, a potent histamine H2-receptor antagonist, on the changes in haemodynamics induced by coronary artery ligation were investigated in anaesthetized dogs. Intravenous bolus injection of SK&F 93479 1 mg/kg followed by 1 mg/kg/h infusion caused transient decreases in systemic blood pressure, left ventricular pressure, and dLVP/dtmax, but did not significantly alter heart rate. Coronary artery ligation produced haemodynamic depression, and this was significantly prevented by pretreatment of the animals with SK&F 93479. These findings suggest that histamine may contribute to the haemodynamic changes arising from acute myocardial ischaemia.