Inhibition of bronchoconstriction by pituitary adenylate cyclase activating polypeptide (PACAP 1-27) in guinea-pigs in vivo.

1. We studied the inhibitory effect of pituitary adenylate cyclase activating polypeptide (PACAP 1-27) on the increase in total pulmonary resistance (RL) caused either by allergen or histamine in anaesthetized, ventilated guinea-pigs. 2. PACAP 1-27 given via i.v. infusion (0.045-4.5 nmol kg-1 min-1) dose-dependently reduced the increase in RL caused by inhaled ovalbumin and histamine. At the highest dose, PACAP 1-27 prevented the increase in RL caused by ovalbumin and histamine completely. Infusion of PACAP 1-27 and the beta 2-adrenoceptor agonist, salbutamol (0.045-4.5 nmol kg-1 min-1) inhibited the increase in RL similarly, but salbutamol increased the heart rate more than PACAP 1-27. 3. PACAP 1-27 and salbutamol given via inhaled aerosol (0.1 mM, 20 breaths) significantly reduced the increase in RL caused by histamine infused i.v., whereas aerosolised sterile saline did not. Both PACAP 1-27 and salbutamol caused bronchodilator effects within 1 min of drug inhalation and these effects remained throughout the 20 min of study. 4. Because PACAP 1-27 produced significant bronchodilatation and rapid onset of sustained action in vivo and without pronounced cardiovascular side effects, we conclude that this peptide may have therapeutic potential as a bronchodilator.     

Effects of a potassium channel opener (SDZ PCO 400) on guinea-pig and human pulmonary airways.

1. SDZ PCO 400 evoked dose-related relaxation of isolated airway smooth muscle. For human bronchus precontracted by endogenous tone or addition of carbachol (10(-5) M), IC50 values were 1.74 microM and 1.82 microM respectively. With guinea-pig trachea contracted by endogenous tone, a comparable IC50 (1.79 microM) was observed, but no IC50 (less than 100 microM) could be determined following contraction by carbachol (10(-6) M). 2. Airway obstruction induced by intravenous bombesin in the anaesthetized ventilated guinea-pig was diminished by intravenous injection of SDZ PCO 400 (ID50 54 micrograms kg-1) or by introduction into the duodenum (ID50 1.0 mg kg-1). Inhalation of nebulized SDZ PCO 400 (0.1 mg kg-1) diminished airway obstruction due to intravenous injection of histamine (3.2-5.6 micrograms kg-1) for up to 20 min. 3. Increased bronchoconstrictor responses to bombesin (180-240 ng kg-1) following intravenous infusion of platelet activating factor (PAF) or (+/-)-isoprenaline, or to histamine (1.0-3.2 micrograms kg-1) following intravenous injections of immune complexes, were suppressed following concomitant intravenous infusion of SDZ PCO 400 (ID50 0.3 mg kg-1 h-1, 1.0 mg kg-1 h-1 and 0.1 mg kg-1 h-1 respectively). 4. Intravenous injection of SDZ PCO 400 (0.1 mg kg-1) effected transient (less than 10 min) inhibition of histamine-induced bronchospasm, yet diminished, for prolonged periods [up to 40 min] the enhanced bronchoconstrictor responses to histamine that followed intravenous injections of immune complexes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pulmonary effects of type V cyclic GMP specific phosphodiesterase inhibition in the anaesthetized guinea-pig.

1. We have investigated the bronchodilator potential of type V phosphodiesterase (PDE V) inhibitors in anaesthetized ventilated guinea-pigs using the potent and selective PDE V inhibitor, SK&F 96231. We have compared its activity to that of salbutamol, the PDE III inhibitors, siguazodan and SK&F 95654 and to the PDE IV inhibitor rolipram. 2. Administered as an i.v. infusion SK&F 96231 (0.6 and 1 mg kg-1 min-1, i.v.) caused a slowly developing inhibition of histamine (100 nmol kg-1, i.v.)-induced bronchoconstriction and elevated tracheal cyclic GMP levels in the anaesthetized guinea-pig. SK&F 96231 (0.1 and 0.3 mg kg-1 min-1, i.v.) was without effect on histamine-induced bronchoconstriction. In the presence of a sub-threshold infusion of SNP (0.1 mumol kg-1 min-1, i.v.) there was a marked enhancement of SK&F 96231-induced inhibition of histamine responses such that at infusion rates that were ineffective alone, SK&F 96231 caused a > 50% inhibition of histamine responses. The stimulation of tracheal cyclic GMP accumulation by SK&F 96231 was also potentiated. 3. Administered directly into the airway, SK&F 96231 (300 micrograms in 5 mg lactose carrier) was largely without effect on histamine-induced bronchoconstriction (4.9 +/- 1.9% inhibition). In the presence of SNP (0.1 mumol kg-1 min-1, i.v.) or isosorbide dinitrate (200 micrograms administered by insufflation into the trachea) there was a marked potentiation of the inhibitory activity of SK&F 96231 (40 +/- 4% and 62 +/- 1.8% respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Airways hyperreactivity and bronchoconstriction induced by vanadate in the guinea-pig.

1 The characteristics of vanadate-induced bronchoconstriction and airways hyperreactivity were observed in spontaneously breathing anaesthetized guinea-pigs by measurement of airways resistance (Raw) and dynamic lung compliance (Cdyn). Vanadate (0.3-3 mg kg-1 i.v. over 25 min) increased Raw and decreased Cdyn in a reversible, dose-related manner. This action (1 mg kg-1 vanadate) was not inhibited by atropine (1 mg kg-1 i.v.), propranolol (1 mg kg-1 i.v.) or bilateral vagotomy, suggesting a direct effect on the airways smooth muscle. 2 An aerosol of vanadate (10% w/v in H2O) for 3 min decreased Cdyn by 19.5% (P less than 0.05, n = 6) but caused no change in Raw. 3 Histamine (3 micrograms kg-1 i.v.) caused a bronchoconstriction which was enhanced by vanadate in a dose-related manner. This hyperreactivity (after 1 mg kg-1 i.v. vanadate) was unchanged after propranolol or bilateral vagotomy, but was partly blocked by atropine (enhancement by vanadate of the Cdyn change to histamine was diminished, P less than 0.02, n = 3). 4 Bronchoconstrictor responses to acetylcholine (6 micrograms kg-1 i.v.) and 5-hydroxytryptamine (6 micrograms kg-1 i.v.) were also enhanced by vanadate (1 mg kg-1 i.v.) Hyperreactivity after vanadate to the three bronchoconstrictors tested continued during vanadate infusion and was reversed 45 min after cessation of infusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

The antinociceptive action of some beta-adrenoceptor agonists in mice.

The antinociceptive actions of several beta-adrenoceptor agonist drugs have been studied in mice by use of a modified abdominal constriction test. All the drugs studied had high antinociceptive activity, with ID50 values in the nmol kg-1 range. (-)-Isoprenaline and (+/-)-isoxsuprine were the most potent, being about ten times more active than salbutamol, the least potent drug studied. All these drugs produced their action very rapidly and appear to act within the peritoneum. (-)-Isoprenaline had about six times the potency of the (+)-isomer. (+/-)-Propranolol caused rightward shifts, usually parallel, of the dose-response curves for (-)-isoprenaline. (+)-Propranolol was more than ten times less potent than the racemic drug. Practolol also caused parallel, rightward shifts of the dose-response curves for (-)-isoprenaline, and was about twice as potent as (+/-)-propranolol, whether given by subcutaneous or intraperitoneal injection. Atenolol and ICI 118551 had intermediate potencies. Propranolol, practolol and ICI 118551 were all considerably less potent in antagonizing the antinociceptive actions of fenoterol and RO363, than (-)-isoprenaline. None of these antagonist drugs showed more than a slight ability to discriminate between the beta 1- and beta 2-selective agonist drugs. No evidence was found for the involvement of opioid, dopamine, or alpha-adrenoceptors in the antinociceptive action of the beta-adrenoceptor agonist drugs. Evidence for and against the involvement of beta-adrenoceptors is discussed, and it is concluded that if these receptors do mediate the antinociceptive action they appear to be atypical.     

Effects of short-term exposure to noradrenaline and adrenaline on adrenoceptor responses

Adrenaline (0.05 and 1.5 mumol/kg per h) and noradrenaline (0.09 and 0.5 mumol/kg per h) were infused i.v. into conscious rabbits. Pressor responses to bolus doses of phenylephrine, alpha-methylnoradrenaline and chronotropic responses to isoprenaline were studied before and during infusion. Plasma adrenaline levels rose from 1.4 +/- 0.5 to 13 +/- 2 and 31 +/- 9 nM during the 0.05 and 1.5 mumol/kg per h infusions respectively while noradrenaline levels rose from 2.0 +/- 0.9 to 16 +/- 7 and 29 +/- 11 nM during the 0.09 and 0.5 mumol/kg per h noradrenaline infusions. Pressor responses to alpha-methylnoradrenaline were attenuated within 2.5 and 60 min during the higher and lower rates of adrenaline infusion respectively. Attenuation occurred within 10 min with the higher rate infusion of noradrenaline but no change was seen during the lower noradrenaline infusion. Chronotropic responses to isoprenaline were also reduced during the adrenaline infusions but not during noradrenaline infusion. In contrast no change was observed in phenylephrine pressor responses. These results suggest that short-term elevation in the levels of the endogenous catecholamines, noradrenaline and adrenaline, can cause desensitisation of alpha 2- and beta-adrenoceptors but not of alpha 1-adrenoceptors.     

Lack of cardiac or bronchodilator tachyphylaxis to isoprenaline in the dog.

1. Tachyphylaxis to heart rate and bronchodilator effects of (plus or minus)-isoprenaline was studied in anaesthetized open-chest dogs by 5 procedures. 2. Heart rate responses to a series of intravenous injections of isoprenaline were essentially unchanged before and after a 15 min infusion of isoprenaline (at 3 doses). 3. Heart rate and bronchodilator responses in the same animal to an intravenous injection of isoprenaline were not significantly different before and after a 30 min infusion of isoprenaline (at 2 doses). 4. Heart rate responses were relatively constant to an isoprenaline injection given every 30 min during a 4 h infusion of isoprenaline (at 3 doses), but the magnitude of the response was smallest for the largest infusion dose (highest background heart rate) and greatest for the smallest infusion dose (lowest background heart rate). 5. Heart rate and bronchodilator responses in the same animal to isoprenaline were relatively constant during a 5 h infusion of isoprenaline (at 2 doses). 6. Bronchodilator responses to intratracheally administered isoprenaline aerosol were essentially unchanged during a 4-5 h period using various doses and procedures. 7. Tachyphylaxis to the heart rate of bronchodilator effects of isoprenaline was not observed. The present data give no support to the hypothesis that tachyphylaxis to isoprenaline aerosols is an important mechanism in asthma mortality.     

The effect of catecholamines on the in vivo and in vitro responses of the cat lung during anaphylaxis.

1. Anaphylaxis in the lung of cats actively sensitized to Ascaris antigen has been investigated in vivo and in vitro. 2. In vivo there was a 100% increase in airways resistance and a 50% decrease in dynamic lung compliance following intravenous challenge with Ascaris antigen. Prostaglandin F2alpha induced similar changes but with histamine only dynamic lung compliance was affected. (-)-Isoprenaline prevented these prostaglandin F2alpha- and histamine-induced changes and caused a delay of about 2 min in the onset of the mechanical changes following anaphylactic challenge. 3. In vitro the isolated lung strip contracted within seconds of challenge whereas there was a delay of 2 to 3 min in the onset of the tracheal anaphylactic response. (-)-Isoprenaline, (-)-adrenaline and (+/-)-noradrenaline reduced the magnitude of anaphylactic contractions of the isolated trachea but did not significantly affect those of the isolated lung strip. This indicated lack of inhibition of mediator release from the lung parenchyma. 4. Histamine was released from sensitized lung fragments following challenge with the Ascaris extract. This release constituted 6.3% of the total tissue histamine and was not inhibited by (-)-isoprenaline (1 micrometer). 5. (-)-Isoprenaline abolished 5-hydroxytryptamine (5-HT)-induced contractions of the isolated trachea but not those elicited in response to acetylcholine. The isolated lung strip responses to histamine, prostaglandin F2alpha and 5-HT were highly resistant to inhibition by (-)-isoprenaline.     

The handling of five catecholamines by the extraneuronal O-methylating system of the rat heart

In a comparative study, the handling of five catecholamines by the extraneuronal O-methylating system of the rat heart was determined; all rats were pretreated with reserpine, monoamine oxidase and neuronal uptake were inhibited in all experiments. Hearts were perfused for 7 min with a tracer concentration of 3H-(+/-)-isoprenaline, either in the absence or in the presence of unlabelled catecholamines (which reduced the O-methylation of the tracer amine). IC50's were determined for unlabelled catecholamines and then converted to "half-saturating outside concentrations", i.e., to those concentrations in the perfusion fluid that half-saturate the intracellular catechol-O-methyl transferase (COMT). The values for the (-)-isomers of dobutamine, isoprenaline, adrenaline and noradrenaline and that for dopamine were low and rather similar (between 0.67 and 2.7 mumol/l). Stereoselectivity for isoprenaline probably reflected the preference of uptake2 for the (-)-isomer. The effects of (-)- and (+)-dobutamine indicated that both isomers are a) transported by uptake2 and b) good substrates of COMT. The Vmax for O-methylation [determined for 3H-(+/-)-isoprenaline, 3H-(+/-)-adrenaline, 3H-(+/-)-noradrenaline and 3H-dopamine] was rather similar for all four catecholamines. It is concluded that the extraneuronal O-methylating system of the rat heart handles the five catecholamines in a similar manner, although the Km for uptake2 had been found to increase substantially in the order: dobutamine less than isoprenaline less than adrenaline less than noradrenaline less than dopamine (Grohmann and Trendelenburg 1984b).     

Comparison of the beta2-adrenoceptor selectivity of rimiterol, salbutamol and isoprenaline by the intravenous route in man.

1 The bronchodilating efficacy and the degree of beta2-adrenoceptor selectivity of rimiterol, salbutamol and isoprenaline were determined in seven subjects who exhibited histamine-induced bronchoconstriction. 2 Rimiterol, 0.5 (high dose) and 0.05 (low dose) mug kg-1 min-1, salbutamol, 0.3 and 0.03 mug kg-1 min-1, isoprenaline, 0.05 and 0.005 mug kg-1 min-1 and placebo were administered by a single intravenous injection over 6 min, and the protection against histamine-induced bronchoconstriction, changes in heart rate, pulse pressure and skeletal muscle tremor were measured. 3 Rimiterol (98%), salbutamol (96%) and isoprenaline (69%) protected against histamine-induced bronchoconstriction. For these ventilatory responses, there was a heart rate increase of 31.9, 24.7 and 44.3 beats/min for rimiterol, salbutamol and isoprenaline respectively. The three drugs produced similar increases in pulse pressure and tremor. 4 Significant dose-responses were obtained for all the parameters with each drug. 5 Isoprenaline was approximately 7 and 5 times as potent as rimiterol and salbutamol respectively in bronchodilator action when equimolar doses were compared. Similarly, isoprenaline was approximately 14 and 10 times as potent in increasing the heart rate as rimiterol and salbutamol respectively. 6 Rimiterol, a new beta-adrenoceptor stimulating drug, is an effective bronchodilator and has similar beta2-adrenoceptor selectivity to salbutamol when administered intravenously. The relative potencies and degrees of beta2-adrenoceptor selectivity of these drugs depend partly on their route of administration.     

Differential effects of (+/-)-dobutamine and human alpha-CGRP on cardiac and on regional haemodynamics in conscious Long Evans rats.

1. Comparisons were made of the full haemodynamic profiles of the known cardiostimulant, (+/-)-dobutamine, and the putative inotropic peptide, human alpha-calcitonin gene-related peptide (human alpha-CGRP), in conscious, chronically-instrumented Long Evans rats. Both substances were administered continuously i.v. for 60 min at two doses ((+/-)-dobutamine, 2 and 10 mumol kg-1 h-1; human alpha-CGRP, 0.15 and 1.5 nmol kg-1 h-1). 2. In spite of their similar (small) effects on mean arterial blood pressure, the low doses of (+/-)-dobutamine and human alpha-CGRP influenced cardiac haemodynamics differently. Thus, (+/-)-dobutamine caused an increase in cardiac index (due to a tachycardia), accompanied by rises in peak aortic flow, maximum rate of rise of aortic flow (dF/dtmax) and total peripheral conductance. However, the latter waned during the infusion, and after the infusion there was a significant systemic vasoconstriction and reductions in peak aortic flow, dF/dtmax and stroke index. Such 'off' effects following dobutamine infusion have not been described previously. The infusion of the lower dose of human alpha-CGRP caused only a transient fall in central venous pressure. 3. The rise in total peripheral conductance during infusion of the lower dose of (+/-)-dobutamine was associated with increases in hindquarters and common and internal carotid vascular conductances. The fall in total peripheral conductance after infusion was associated with renal vasoconstriction. Although there was no significant change in total peripheral conductance during the infusion of the lower dose of human alpha-CGRP there were hindquarters and carotid vasodilatations together with mesenteric vasoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of blockade of extraneuronal uptake on responses to isoprenaline in perfused rat heart

1. Isolated rat hearts accumulated 102 pmol/g wet wt/min of isoprenaline when perfused for 5 min with 0-6 muM (+/-)-3H-isoprenaline. 2. The 3-methoxy derivative of isoprenaline ('methoxy isoprenaline') (10 muM) significantly inhibited this uptake by 57%, metanephrine (10 muM) by 29% and normetanephrine (10 muM) by 21%. 3. (+/-)-Isoprenaline (0-6 muM) infused into isolated perfused rat hearts for 5 min activated glycogen phosphorylase 2-4-fold. Normetanephrine (10 muM) or metanephrine (10 muM included in the perfusate significantly potentiated this activation, but 3-0-methyl isoprenaline (10 muM significantly reduced it. However, 3-0-methyl isoprenaline potentiated the ability of 4-8 muM isoprenaline to stimulate phosphorylase. 4. Neither metanephrine (10 muM) nor normetanephrine (10 muM) altered peak inotropic responses to injections of (+/-)-isoprenaline into the solution perfusing isolated rat hearts. 3-0-methyl isoprenaline (10 muM) shifted the isoprenaline dose-response curve to the right, but did not affect the inotropic responses to CaCl2, confirming that 3-0-methyl isoprenaline possess beta-adrenoceptor antagonist activity. 5. Inotropic responses to isoprenaline were significantly prolonged by both 3-0-methyl isoprenaline and normetanephrine (10 muM). 6. These results indicate that blockade of extraneuronal accumulation of catecholamines causes potentiation of both metabolic and mechanical beta-adrenoceptor-mediated responses of the heart to isoprenaline. It is suggested that Uptake2 and the cardiac beta-adrenoceptor are separate entities, and that the beta-adrenoceptor is localized in the sarcolemma. The physiological function of Uptake2 may be to help clear the sympathetic synaptic gap of liberated neurotransmitter.     

Inhibitory effect of sodium cromoglycate on pulmonary responses to histamine administered after indomethacin in anaesthetized guinea-pigs.

1. Histamine (2-4 micrograms kg-1 i.v.) increased airways resistance (Raw) and decreased dynamic lung compliance (Cdyn) in urethane-anaesthetized guinea-pigs. The effects on Raw were almost abolished by atropine (0.1 mg kg-1 i.v.) and reduced by vagal cooling (11-16 degrees C). 2. Histamine-induced changes in Raw and Cdyn were significantly (P less than 0.05) enhanced by indomethacin (1 mg kg-1 i.v.). 3. In animals not treated with indomethacin, exposure to an aerosol containing sodium cromoglycate (0.01-2% for 30 s) failed to affect subsequent (3 min) histamine-induced bronchoconstriction. 4. Administration of an aerosol containing low (0.01-0.2%) concentrations of sodium cromoglycate had no effect on the enhanced responses (i.e. hyperreactivity) seen after indomethacin. However, more concentrated sodium cromoglycate aerosols (greater than 0.2%) reduced or abolished the hyperreactivity to histamine seen after indomethacin. 5. It was concluded that sodium cromoglycate can prevent the development of hyperreactivity to histamine, possibly by interacting with some mechanism utilized by both histamine and indomethacin in this model.     

Role of kinins in anaphylactic-induced bronchoconstriction mediated by tachykinins in guinea-pigs.

1. In the present study, we have investigated the role of kinins in allergen-induced bronchoconstriction. 2. Anaesthetized guinea-pigs were sensitized to ovalbumin, ventilated artificially, pretreated with atropine (1.4 mumol kg-1, i.v.) and total pulmonary resistance (RL) measured. In preliminary studies in the presence of the neutral endopeptidase inhibitor, phosphoramidon (4.5 mumol kg-1, i.v.), the bradykinin B2 receptor antagonist Hoe 140 (0.1 mumol kg-1, i.v.) completely abolished the increase in RL following aerosolized bradykinin (1 mM, 40 breaths), but had no effect on the increase in RL following aerosolized neurokinin A (NKA, 10 microM, 40 breaths). On the other hand, a combination of the NK1 (CP-96,345, 2 mumol kg-1, i.v.) and NK2 (SR 48968, 0.3 mumol kg-1, i.v.) tachykinin receptor antagonists abolished completely the increase in RL produced by NKA and partially inhibited the increase in RL produced by bradykinin. These results confirm previous studies that suggest that bradykinin induces the release of tachykinins from sensory nerves in guinea-pig airways. 3. Aerosolized ovalbumin (0.5%, 5 breaths) increased RL in sensitized guinea-pigs pretreated with atropine (1.4 mmol kg-1, i.v.), an effect that began within 2 min and reached a maximum within 5 min; RL remained above baseline at 20 min. Pretreatment with the bradykinin B2 receptor antagonist, Hoe 140, decreased the bronchoconstrictor effect of ovalbumin markedly at 10 to 20 min. In the presence of phosphoramidon (4.5 mumol kg-1, i.v.) the inhibition induced by Hoe 140 was apparent earlier and remained over the 20 min period of study.(ABSTRACT TRUNCATED AT 250 WORDS)     

班布特罗对豚鼠支气管收缩反应的扩张作用

观察班布特罗对豚鼠支气管收缩反应的影响。方法：用哮喘发作潜伏期,肺机械功能及离体气管平滑肌松弛试验观察班布特罗的支气管扩张作用。结果：班布特罗ｉｇ后１ｈ,４ｈ和２４ｈ均能延长组胺诱导的豚鼠哮喘潜伏期,ＥＤ５０分别为０．７４,０．７５,１．００ｍｇ．ｋｇ＾－１,其作用持续时间明显长于特布他林。     

The cat lung strip as an in vitro preparation of peripheral airways: a comparison of beta-adrenoceptor agonists, autacoids and anaphylactic challenge on the lung strip and trachea.

1 A new in vitro preparation, the isolated lung strip of the cat, is described for investigating the direct effect of drugs on the smooth muscle of the peripheral airways of the lung. The preparation comprises a thin strip of lung parenchyma which can be mounted in a conventional organ bath for isometric tension recording. Its pharmacological responses have been characterized and compared with the isolated tracheal preparation of the cat. 2 The lung strip exhibited an intrinsic tone which was relaxed by catecholamines, aminophylline and flufenamate. It was contracted strongly by histamine, prostaglandin F2alpha, acetylcholine, compound 48/80, potassium depolarizing solution and alternating current field stimulation. In contrast, the cat trachea was unresponsive to histamine and prostaglandin F2alpha and did not exhibit an intrinsic tone. 3 (-)-Isoprenaline and (-)-adrenaline were much more potent in relaxing the lung strip than the trachea. The potency order of relaxation responses to isoprenaline, adrenaline and (+/-)-noradrenaline in the lung strip was isoprenaline greater than adrenaline greater than noradrenaline but in the trachea was isoprenaline greater than noradrenaline greater than or equal to adrenaline. 4 beta2-Adrenoceptor selective agonists salbutamol and terbutaline were more potent in the lung strip than the trachea, suggesting beta2-adrenoceptors predominated in the lung strip. Propranolol was equipotent in inhibiting isoprenaline relexations of the lung strip and trachea, whereas practolol was much less effective in inhibiting lung strip than trachea, further supporting a predominance of beta2-adrenoceptors in lung strip and beta1-adrenoceptors in trachea. 5 Strong Schultz-Dale type contractions were elicited in both lung strips and trachea by Ascaris lumbricoides antigen in actively sensitized cats. The initial phase of the contractile response of the lung strip following challenge was shown to be due to histamine release and was absent in the trachea. The delayed phase of the contraction which took several minutes to develop in both the mepyramine-treated lung strip and trachea was not due to prostaglandins E1, F2alpha or bradykinin, the probable mediator being slow reacting substance of anaphylaxis (SRS-A). 6 It is concluded that the isolated lung strip of the cat is useful as an in vitro model for investigating the effect of drugs on the smooth muscle of the peripheral airways of the lungs.     

Effect of the glucocorticosteroid budesonide and a novel phosphodiesterase type 4 inhibitor CDP840 on antigen-induced airway responses in neonatally immunised rabbits.

1. The effects of the inhaled corticosteroid budesonide and a novel PDE 4 inhibitor CDP840 given systematically, were evaluated in a model of antigen-induced airway inflammation in the rabbit. 2. Adult litter-matched NZW rabbits (2.4-3.5 kg) immunised within 24 h of birth with Alternaria tenuis antigen were pretreated with budesonide (total dose 100 micrograms, inhaled over 2 days) or CDP840 (total dose 7 mg kg-1, i.p. over 3 days), before antigen challenge. For each drug-treated group a parallel group of rabbits was pretreated with the appropriate vehicle. In all groups airway responsiveness to inhaled histamine was assessed and bronchoalveolar lavage (BAL) performed 24 h before and after antigen challenge. 3. Basal lung function in terms of total lung resistance (RL; cmH2O l 1s-1) and dynamic compliance (Cdyn; ml cmH2O-1) were unaltered by pretreatment with budesonide or CDP840 compared to their respective vehicles 24 h before or after antigen challenge. 4. The RL component of the acute bronchoconstriction induced by inhaled Alternaria tenuis aerosol was unaffected by pretreatment with budesonide. However, budesonide prevented the fall in Cdyn due to antigen. Treatment with CDP840 significantly reduced antigen-induced acute bronchoconstriction in terms of both RL and Cdyn. 5. Airway hyperresponsiveness (AHR) to inhaled histamine was indicated by reduced RL PC50 (2.4-4.5 fold) and Cdyn PC35 (2.1-3.9 fold) values 24 h after antigen challenge. Treatment with either budesonide or CDP840 abolished the antigen-induced increase in responsiveness to inhaled histamine. 6. Total cells recovered per ml of BAL fluid increased 24 h after antigen challenge. Antigen-induced pulmonary eosinophilia was reduced (93%) in budesonide and (85%) in CDP840 treated rabbits. Antigen-induced increases in neutrophil numbers were reduced (76%) with budesonide but not CDP840 pretreatment. 7. Inhalation of Alternaria tenuis aerosol elicited an acute bronchoconstriction, followed 24 hours later by an increased responsiveness to inhaled histamine and pulmonary neutrophil and eosinophil recruitment. CDP840 was more effective than budesonide in preventing the antigen-induced increase in total lung resistance (RL); however, both drugs prevented the antigen-induced reduction in dynamic compliance (Cdyn). CDP840 and budesonide also prevented antigen-induced AHR and eosinophilia in the immunised rabbit.     

Inhibitory effect of isoprenaline on gastric acid secretion in the rat. The role of endogenous histamine

In dogs beta-adrenoreceptor agonists inhibit gastric acid secretion stimulated by exogenous gastrin to a much greater extent than acid secretion stimulated by exogenous histamine. One possible explanation for this observation is that endogenous histamine is important in gastrin-mediated acid secretion and that isoprenaline and related beta-adrenoreceptor agonists block gastric mucosal histamine release. This possibility was tested in the present study in gastric lumen-perfused anaesthetized rats. Intravenous infusion of isoprenaline (12 microgram kg-1 h-1) inhibited maximal, pentagastrin-stimulated acid output by 50-70% (P less than 0.01), but had no significant inhibitory effect on the maximal acid secretory response to histamine. In contrast to its inhibitory effect on gastrin-stimulated acid output, isoproterenol had no effect on gastric histamine output during pentagastrin infusion. We conclude that isoprenaline selectively inhibits gastrin-stimulated acid secretion in the rat, as in the dog, and by a mechanism other than inhibiting gastric histamine release.     

The effect of (-)-isoprenaline and (+/-)-salbutamol on pepsinogen and acid secretion in the dog.

1 The beta-adrenoceptor agonists, (-)-isoprenaline and (+/-)-salbutamol, reduced pepsinogen secretion induced by pentagastrin in conscious dogs with Heidenhaim pouches. 2 (-)-Isoprenaline and (+/-)-salbutamol also reduced gastric acid secretion while producing a moderate tachycardia.     

Actions of some sympathomimetic bronchodilator and beta-adrenoceptor blocking drugs on contractions of the cat soleus muscle

1. (-)-Isoprenaline, salbutamol, orciprenaline and quinterenol injected intravenously decreased the tension and degree of fusion of incomplete tetanic contractions of the soleus muscle of the anaesthetized cat.2. Under the most sensitive conditions, the smallest effective dose of (-)-isoprenaline was of the order of 0.01 mug/kg intravenously. Salbutamol was usually 6-10 times, orciprenaline 20-30 times and quinterenol about 35 times less potent than isoprenaline. The effects of salbutamol were about 1.6 times, of orciprenaline about 1.8 times and of quinterenol more than 20 times as long lasting as those of (-)-isoprenaline.3. The effects of the sympathomimetic amines were blocked by propranolol, H56/28, H35/25 and butoxamine but not by ICI 50172. The combined results with agonists and antagonists indicate that the receptors involved can be classified as of the beta(2) type.4. The effect of the amines on the cat soleus muscle appears to be analogous to that causing enhancement of physiological tremor in man, which suggests that skeletal muscle tremor may be an occasional unwanted side effect of the use of these bronchodilators.